B gio dc v o to

Trng i hc nng nghip I H ni

GS.TS. Hong Minh Tn (Ch bin)

GS.TS. Nguyn Quang Thch, PGS.TS. V Quang Sng

Gio trnh

Sinh l thc vt

H Ni - 2006

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....3

M u

Sinh l thc vt l g?

Sinh l thc vt l mt khoa hc nghin cu v cc hot ng sinh l xy ra trong c th thc vt, mi quan h gia cc iu kin sinh thi vi cc hot ng sinh l ca cy cho ta kh nng iu chnh thc vt theo hng c li cho con ngi.

i tng v nhim v ca mn hc sinh l thc vt

* Nghin cu cc hot ng sinh l ca cy. Cc hot ng sinh l din ra trong cy rt phc tp. C 5 qu trnh sinh l ring bit xy ra trong cy l:

1. Qu trnh trao i nc ca thc vt bao gm qu trnh ht nc ca r cy, qu trnh vn chuyn nc trong cy v qu trnh thot hi nc trn b mt l...

2. Qu trnh quang hp l qu trnh chuyn ha nng lng nh sng mt tri thnh nng lng ha hc tch ly trong cc hp cht hu c cung cp cho cc hot ng sng ca cy v cc sinh vt khc.

3. Qu trnh vn chuyn v phn b cc cht hu c t ni sn xut trc tin l l n tt c cc c quan cn thit cht dinh dng v cui cng chng c tch ly v cc c quan d tr ca cy to nn nng sut kinh t.

4. Qu trnh h hp l qu trnh phn gii oxi ha cc cht hu c gii phng nng lng cung cp cho cc hot ng sng v to nn cc sn phm trung gian cho cc qu trnh sinh tng hp cc cht hu c khc ca cy.

5. Qu trnh dinh dng cht khong gm qu trnh ht cht khong ca r v ng ha chng trong cy.

Kt qu hot ng tng hp ca 5 qu trnh sinh l trong cy lm cho cy ln ln, m chi, ny lc ri ra hoa, kt qu, gi i v cui cng kt thc chu k sng ca mnh. Hot ng tng hp gi l sinh trng v pht trin ca cy.

Sinh l thc vt cn nghin cu phn ng thch nghi ca cy i vi iu kin ngoi cnh bt li tn ti v pht trin - Sinh l tnh chng chu ca cy.

Tt c cc hot ng sinh l ca cy u din ra trong n v c bn l t bo. nghin cu cc hot ng sinh l ca cy th trc tin chng ta tm hiu cc hot ng sinh l din ra trong t bo.

* Sinh l thc vt nghin cu nh hng ca cc iu kin ngoi cnh (iu kin sinh thi) n cc hot ng sinh l ca cy nh nhit , nh sng, m, cc cht dinh dng trong t, su bnh... nh hng ny c th tc ng ln tng qu trnh sinh l ring r, hoc nh hng tng hp ln ton cy.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....4

* Trn c s nhng hiu bit v cc hot ng sinh l din ra trong cy m con ngi c kh nng iu chnh cy trng theo hng c li cho con ngi.

Nh sinh l hc thc vt ni ting ngi Nga (Timiriadep) c ni: "Sinh l thc vt l c s ca trng trt hp l".

Ni nh vy c ngha l sinh l thc vt nghin cu c s l lun ra cc bin php k thut trng trt hp l nht nhm nng cao nng sut v phm cht nng sn phm. Ni cch khc, tt c cc bin php k thut trng trt c hiu qu th u phi da trn c s l lun ca cc nghin cu sinh l thc vt. V d, cc nghin cu v sinh l s trao i nc ca cy gip ta xut cc phng php ti nc hp l cho cy; cc nghin cu v quang hp l c s cho cc bin php k thut b tr cy trng sao cho cy s dng nh sng mt tri c hiu qu nht hoc cc bin php bn phn hp l v hiu qu cho tng loi cy trng nht nh phi da trn cc nghin cu v nhu cu dinh dng khong ca cy...

V tr ca mn hc Sinh l thc vt

Trong chng trnh hc tp ca ngnh nng hc, sinh l thc vt c xem l mn hc c s nht c quan h trc tip n cc kin thc c s v chuyn mn ca ngnh hc.

Cc kin thc ca mn: Ha sinh hc, cng ngh sinh hc, sinh thi hc, di truyn hc, ti nguyn kh hu, nng ha, th nhng... lm nn tng cho vic nghin cu v tip thu kin thc mn hc sinh l thc vt su sc hn. Ngc li, cc kin thc sinh l thc vt c quan h b tr cho vic tip thu kin thc ca cc mn hc .

Vi cc mn hc chuyn mn ca ngnh, sinh l thc vt c vai tr cc k quan trng. Cc kin thc sinh l thc vt chng nhng gip cho vic tip thu mn hc tt hn m cn lm c s khoa hc cho vic xut cc bin php k thut tc ng ln cy trng tng nng sut v cht lng nng sn phm.

Vic hiu bit su sc bn cht ca cy trng - cc hot ng sinh l din ra trong chng - l cng vic trc tin ca nhng ai mun tc ng ln i tng cy trng, bt chng phc v cho li ch ca con ngi.

Kt cu ca gio trnh Sinh l Thc vt

Gio trnh Sinh l thc vt ny c chng ti trnh by trong 8 chng:

Chng 1: Sinh l t bo thc vt

Chng 2: S trao i nc

Chng 3: Quang hp

Chng 4: H hp

Chng 5: S vn chuyn v phn b cc ch ng ha trong cy

Chng 6: Dinh dng khong

Chng 7: Sinh trng v pht trin

Chng 8: Sinh l tnh chng chu ca cy vi cc iu kin ngoi cnh bt thun.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....5

T chng 2 n chng 6, chng ti trnh by 5 chc nng sinh l c bn xy ra trong cy c tnh c lp tng i. Chng 7 - Sinh trng v pht trin - l kt qu hot ng tng hp ca cc chc nng sinh l c bn trn. Chng 8 trnh by cc hot ng thch nghi v mt sinh l ca cy c th tn ti v pht trin trong cc iu kin ngoi cnh lun lun bin ng vt qu gii hn bnh thng (iu kin stress). Tt nhin, tt c cc hot ng sinh l ca cy u xy ra trong n v c bn l t bo. V vy m chng u tin ca gio trnh Sinh l thc vt (Chng 1) cp n cu trc v chc nng sinh l ca t bo thc vt (Sinh l t bo thc vt).

Cch trnh by ca gio trnh

gip cho sinh vin hc tt mn ny, trong tng chng chng ti c nu ln mc tiu chung ca chng. Sau mi chng, chng ti c tm tt li ni dung c bn ca chng, cc cu hi cn thit trao i v n tp. Phn cui cng ca tng chng, chng ti a ra phn trc nghim kin thc sau khi l hc xong. Phn trc nghim ny s gip cho sinh vin kim tra cui cng kin thc ca mnh.

Chng ti hy vng vi cc kin thc v cch trnh by ca chng ti, cun gio trnh ny s l ti liu hc tp tt v rt b ch cho cc sinh vin ngnh Nng hc (Cy trng, Bo v thc vt, Ging cy trng, Cng ngh sinh hc thc vt...) ca cc Trng i hc Nng nghip. ng thi n cng l ti liu tham kho tt cho cc cn b ging dy v nghin cu c lin quan n cy trng.

Tp th tc gi bin son cun gio trnh ny:

GS.TS. Hong Minh Tn, ch bin v bin son chnh

GS.TS. Nguyn Quang Thch (tham gia bin son chng Sinh l t bo, chng dinh dng khong v chng sinh l tnh chng chu ca cy vi iu kin ngoi cnh bt thun)

PGS.TS. V Quang Sng (tham gia bin son chng quang hp) rt mong nhn c nhiu kin ng gp b ch c th b sung cho cun gio trnh Sinh l thc vt ny cng hon chnh hn, phc v c hiu qu cho vic hc tp v tham kho ca sinh vin ngnh Nng hc...

Xin chn thnh cm n!

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....6

Chng 1

Sinh l t bo

V t bo thc vt l n v c bn v cu trc v thc hin cc chc nng sinh

l ca c th thc vt, nn trc tin sinh vin cn phi nm mt cch khi qut v cu

trc v chc nng ca thnh t bo, cht nguyn sinh v khng bo.

Tt c cc hot ng sng u din ra trong cht nguyn sinh nn cn nm

chc cc c tnh ca cht nguyn sinh.

- V thnh phn ho hc ch yu cu to nn cht nguyn sinh, sinh vin cn

quan tm n ba cht: protein, nc v lipit, c bit l protein.

- Tnh cht vt l ca cht nguyn sinh biu th n va c tnh lng va c c

tnh ca vt cht c cu trc.

- Cc trng thi ho keo ca cht nguyn sinh v ngha ca chng i vi hot

ng sng ca t bo v ca cy.

Cn nm vng cc hot ng sinh l quan trng din ra trong t bo.

- Qu trnh trao i nc ca t bo bng phng thc thm thu v ht trng.

- S xm nhp cht tan vo t bo thc vt bng c ch b ng v c ch ch

ng cn nng lng...

1. i cng v t bo thc vt

Ngy nay, ai cng u bit cc c th sng c xy dng nn t cc t bo. Tuy nhin, cch y vi th k, iu vn cn b n.

Ngi t nn mng cho vic pht hin v nghin cu v t bo l Robert Hooke (1635-1763). ng l ngi u tin pht hin ra knh hin vi phc tp cho php nhn mt vt c phng i rt nhiu ln. Khi quan st lt ct mng lie di knh hin vi, ng nhn thy n khng ng nht m c chia ra nhiu ngn nh m ng gi l "cell" tc l t bo. Sau pht minh ca Robert Hooke, nhiu nh khoa hc l i su vo nghin cu cu trc hin vi ca t bo nh pht hin ra cht nguyn sinh, nhn ca t bo...

Bc nhy vt trong vic nghin cu t bo hc l pht hin ra knh hin vi in t c phn gii cao vi vt liu sinh hc c kch thc v cng nh (0,0015-0,002 m), gp 100 ln so knh hin vi thng. Nh knh hin vi in t m ngi ta c th quan st th gii ni t bo c cu trc rt tinh vi, pht hin ra rt nhiu cu trc siu hin vi m knh hin vi thng khng nhn thy c.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....7

Ngi ta phn ra hai mc t chc t bo: cc t bo nhn nguyn thy gi l cc th procariota (vi khun, to lam...) cha c nhn nh hnh v cc t bo c nhn thc gi l cc th eucariota (t bo ca thc vt, ng vt v nm).

Cc c th khc nhau c cc t bo hon ton khc nhau v hnh dng v cu trc. Ngay trong cng mt c th, cc c quan, b phn khc nhau, cc t bo ca chng cng rt khc nhau.V d nh r, t bo lng ht hon ton khc vi t bo biu b, t bo m dn...Mc d cc t bo c tnh a dng nh vy, nhng chng tun theo nhng nguyn tc cu trc thng nht. Mi mt t bo c tt c c tnh ca h thng sng: Trao i cht v nng lng, sinh trng, pht trin, sinh sn v di truyn cho th h sau...

Hc thuyt t bo khng nh rng t bo l n v cu trc v chc nng ca c th sng. S sng ca mt c th l s kt hp hi ha gia cu trc v chc nng ca tng t bo hp thnh. Theo quan nim v tnh ton nng ca t bo th mi mt t bo cha mt lng thng tin di truyn tng ng vi mt c th hon chnh. Mi t bo tng ng vi mt c th v c kh nng pht trin thnh mt c th hon chnh. S khc nhau t bo ng vt v thc vt l ch kh nng ti sinh ca t bo thc vt ln hn rt nhiu so vi t bo ng vt. V vy, i vi thc vt th vic nui cy t bo in vitro ti sinh cy, nhn bn chng d dng thnh cng vi hu ht tt c i tng thc vt.

2. Khi qut v cu trc v chc nng sinh l ca t bo

thc vt

2.1. S cu trc t bo thc vt

Th gii thc vt v cng a dng, v cng phc tp, nhng chng cng c mt im chung nht, l chng u xy dng t n v c bn l t bo. Vi cc loi thc vt khc nhau, cc m khc nhau th cc t bo cu chng cng khc nhau v hnh dng, kch thc v thc hin cc chc nng khc nhau. Tuy nhin, tt c cc t bo thc vt u ging nhau v m hnh cu trc. Chng c cu trc t ba b phn l thnh t bo, khng bo v cht nguyn sinh. Cht nguyn sinh l thnh phn sng thc hin cc chc nng c bn ca t bo. N bao gm h thng mng, cc bo quan v cht nn c bn (Hnh 1.1)

T bo thc vt khi tch ri ra khi m th thng c dng hnh cu, nhng khi nm trong mt tp hp cc t bo ca m th chng b nn p nn thng c hnh a gic. T bo thc vt c kch thc rt nh. Khong 100 triu t bo to nn c mt hnh khi c th tch 1 cm3. Do , mt cy c th do hng t t bo to nn.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....8

Hnh 1.1. S v cu trc ca t bo thc vt.

2.2. Thnh t bo

c trng khc nhau c bn gia t bo thc vt v ng vt l cu trc thnh t bo. T bo thc vt c cu trc thnh t bo kh vng chc bao bc xung quanh. V ngha ng dng, thnh t bo l nguyn liu chnh ca cc sn phm g, giy v dt may. Thnh t bo cng l thnh phn chnh trong qu, rau ti v cha thnh phn cht x quan trng trong khu phn n hng ngy ca con ngi.

* Chc nng ca thnh t bo

Thnh t bo thc vt c hai chc nng chnh:

- Lm nhim v bao bc, bo v cho cho h thng cht nguyn sinh bn trong.

Thnh t bo Mng sinh cht (plasmalem)

Mng khng bo (tonoplast)

Khng bo

Cc bo quan siu hin vi (riboxom, peroxixom, glyoxixom),

Lysoxom

Ty th

Nhn

Lc lp

Dictioxom

Li ni cht

T bo thc vt

Thnh t bo Cht nguyn sinh Khng bo

H thng mng Cc bo quan Cht nn (Nhn, lc lp, ty th, (Khun t bo cht) cc cu trc siu hin vi )

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....9

- Chng li p lc ca p sut thm thu do khng bo trung tm gy nn.

Khng bo cha dch bo v to nn mt p sut thm thu. T bo ht nc vo khng bo v to nn p lc trng ln hng ln trn cht nguyn sinh. Nu khng c thnh t bo bo v th t bo d b v tung.

* c trng c bn ca thnh t bo

m nhim hai chc nng , thnh t bo cn phi bn vng v c hc nhng cng phi mm do c th sinh trng c. Hai c tnh ny ca thnh t bo c tnh i khng nhau, nhng cn phi c trong t bo thc vt.

- Tnh bn vng v c hc c c l nh vt liu cu trc c tnh n hi v n nh ca cc phn t xelulose.

- Tnh mm do ca thnh t bo l do cc vt liu cu trc mm mi di dng khun v nh hnh ca cc phn t protopectin, hemixelulose... Hai loi vt liu cng cu trc nn thnh t bo mt t l nht nh ty theo giai on pht trin ca t bo. T bo cng trng thnh th tnh bn vng ca thnh cng tng v tnh mm do cng gim.

* Thnh phn ha hc

Cc thnh t bo c cu to t cc polysaccarit, protein v cc hp cht thm.

- Xelulose: y l thnh phn c bn cu trc nn thnh t bo thc vt. Thnh phn cu trc nn phn t xelulose l cc phn t glucose. Mi phn t xeluloza c khong 10 000 gc glucose vi phn t lng gn 2 triu. Cc phn t xelulose lin kt vi nhau to nn cc si xelulose. y l n v cu trc nn thnh t bo.

Thnh t bo c cu to t cc b si xellulose. Cc b si ny c nhng vo mt khi khun mm do v nh hnh c to thnh t hemixellulose, pectin v protein. Thng thng th khong 100 phn t xellulose hp thnh mt mixen, 20 mixen hp thnh mt vi si v 250 vi si to nn mt b si xellulose. Cc b si ny lin kt vi nhau bng lin kt hydro. Cc si xellulose hnh thnh mt dn khung v buc cht vi nhau bi cc glycan ni bc ngang.

Xellulose l thnh phn cu to c bn cu thnh t bo. Hm lng ca n trong thnh t bo thay i theo loi t bo v tui ca t bo.

- Hemixelulose: y l cc polyxacarit gm cc monoxacarit khc nhau lin kt vi nhau to nn: Galactose, manose, xylose, arabinose... (gm 150-300 monome).

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....10

Khng bo

Lp gia

Lp 1

Lp 2

- Cc cht pectin l thnh phn quan trng cu trc nn thnh t bo. Pectin kt dnh cc t bo vi nhau to nn mt khi vng chc ca cc m. c bit quan trng l cc protopectin. N gm chui axit pectinic kt hp vi canxi to nn pectat canxi.

Khi thnh t bo phn hy th thnh phn trc tin b phn gii l pectat canxi. Cc pectin b phn gii lm cho cc t bo tch khi nhau, khng dnh kt vi nhau, nh khi qu chn, hoc lc xut hin tng ri trc khi rng.

* Cu trc ca thnh t bo

Thnh t bo c cu trc ba lp ch yu: lp gia, lp 1 v lp 2 (Hnh 1.3).

Hnh 1.3. S cu trc ca thnh t bo

- Lp gia c hnh thnh khi t bo phn chia. Phn cu trc nm gia ranh gii hai t bo bin i thnh lp gia v c nhim v gn kt cc t bo vi nhau. Thnh phn cu trc ch yu l pectin di dng pectat canxi. Pectat canxi nh l cht xi mng gn cc t bo vi nhau thnh mt khi vng chc. Khi qu chn, pectat canxi b phn hu nn cc t bo ri nhau ra v qu mm i. Trong k thut tch protoplast (t bo trn), ngi ta s dng enzym pectinase phn hu thnh t bo, mt s gn kt cc t bo trong m. to nn cc t bo khng c thnh t bo bao bc gi l cc t bo trn (protoplast).

- Lp thnh th 1 c hnh thnh trong qu trnh sinh trng ca t bo. V lp 1 c hnh thnh trong qu trnh t bo ang dln nn n c cu to t cc vt liu va mm do, va n hi iu tit s sinh trng ca t bo. Lp ny c khong 30% xellulose di dng cc b si xellulose vi d di phn t xelluse tng i ngn (khong 2000 gc glucose) v cc b si c sp xp ln xn. Thnh phn cn li l

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....11

hemixellulose, protopectin v mt s thnh phn khc. Cc b si xellulose c nhng trong khun (gm hemixellulose v protopectin) m khng lin kt vi nhau bng lin kt ho hc, nn chng rt do d thay i, d bin dng.

- Lp thnh th 2 c hnh thnh khi t bo ngng sinh trng. N c hnh thnh do bi p thm vo trong lp 1 lm cho bn vng c hc ca thnh t bo tng ln rt nhiu. V t bo l ngng sinh trng, nn vai tr ca lp 2 l lm tng tnh bn vng c hc ca thnh t bo. V vy, hm lng xellulose ca lp 2 chim n 60% vi di phn t xellulose ln hn ca lp 1 (14000 gc glucoza) v cc b si c xp song song lm mc bn vng tng ln... Vi cu trc nh th ny th thnh t bo mt kh nng sinh trng (dln) nhng nc v cc cht tan vn thm qua thnh t bo d dng.

* Nhng bin i ca thnh t bo

Trong qu trnh pht trin ca t bo, ty theo chc nng m nhim ca t bo m thnh t bo c th c nhng bin i sau:

- Ha g: Mt s m nh m dn truyn c thnh t bo b ha g do cc lp

xelluloza ngm hp cht lignin lm cho thnh t bo rt rn chc. m dn, cc t bo ha g b cht to nn h thng ng dn lm nhim v vn chuyn nc i trong cy. H thng mch g ny thng sut t r n l to nn mch mu lu thng trong ton c th.

- Ha bn: mt s m lm nhim v bo v nh m b, lp v c... th cc t bo u ha bn, nh lp v c khoai ty, khoai lang... Thnh t bo ca chng b ngm cc hp cht suberin v sp lm cho chng khng th thm c nc v kh, ngn cn qu trnh trao i cht v vi sinh vt xm nhp. To lp bn bao bc cng l mt trong nhng nguyn nhn gy nn trng thi ng ngh su ca c, ht. Cc c, ht ny cn c thi gian ng ngh lm tng dn tnh thm ca lp bn ca chng th mi ny mm c.

- Ha cutin: T bo biu b ca l, qu, thn cy... thng c bao ph bng mt lp cutin mng. Thnh t bo ca cc t bo biu b thm thm t hp ca cutin v sp. Lp cutin ny khng thm nc v kh nn c th lm nhim v che ch, hn ch thot hi nc v ngn cn vi sinh vt xm nhp... Tuy nhin, khi t bo cn non, lp cutin cn mng th mt phn hi nc c th thot qua lp cutin mng, nhng t bo trng thnh, khi lp cutin l hnh thnh th thot hi nc qua cutin l khng ng k.

S tng kch thc t bo ph thuc vo hot ng ca enzym endoglycosidase, hoc expansin hoc mt s t hp ca chng. Tuy nhin, hnh dng t bo ch yu do kiu cu trc xellulose quyt nh. S tng kch thc t bo cng km theo mt s thay i trong khun glycan v pectin. Cc protein v cc hp cht thm c kt hp vo thnh t bo khi t bo kt thc sinh trng.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....12

2.3. Khng bo

* Qu trnh hnh thnh khng bo

- ng vt c h thng bi tit nn t bo ca chng khng c khng bo. Thc vt khng c h thng bi tit ring nn trong qu trnh trao i cht ca t bo, mt s sn phm tha s c thi ra v c cha trong cc ti nm trong mi t bo gi l khng bo.

- Khng bo bt u hnh thnh khi t bo bc sang giai on dln tng kch thc ca t bo.

Ban u khng bo xut hin di dng cc ti nh ri rc trong cht nguyn sinh. Sau , cc ti nh lin kt vi nhau to nn cc ti ln hn v cui cng, chng lin kt vi nhau to nn mt khng bo trung tm. Khng bo trung tm ngy cng ln ln v khi t bo gi th khng bo trung tm chim hu ht th tch ca t bo, y nhn v cht nguyn sinh thnh mt lp mng p st thnh t bo.

* Vai tr sinh l ca khng bo

- Khng bo cha cc cht bi tit do qu trnh hot ng trao i cht ca t bo sn sinh ra. Chng gm cc cht hu c v v c. Cc cht hu c bao gm cc axit hu c, ng, vitamin, cc sc t dch bo nh antoxyan, cc cht tanin, alcaloit, cc mui ca cc axit hu c nh oxalat canxi. Cc cht v c gm cc mui ca kim loi nh Na, Ca, K... Cc cht tan ny to nn mt dung dch gi l dch bo. Dch bo c pH trong khong 3,5 - 5,5, c khi thp hn do chng cha nhiu axit hu c; trong khi pH ca t bo cht thng trung tnh (pH = 7). Vic duy tr pH trung tnh ca t bo cht l do cc bm H+ trn mng khng bo (mng tonoplast) l bm ion H+ t t bo cht vo khng bo mt cch thng xuyn.

- Dch bo l mt dung dch cht tan khc nhau c nng thay i nhiu trong khong 0,2-0,8 M. Dch bo c to nn do qu trnh trao i cht nn nng ca n ph thuc vo cng trao i cht ca t bo, ph thuc vo loi t bo v tui ca chng. iu quan trng l dch bo s gy nn mt p sut thm thu. Chnh nh p sut thm thu ny m t bo c th ht nc vo khng bo. y l nguyn nhn cho nc xm nhp vo t bo bng con ng thm thu. Nc i vo khng bo to nn sc trng nc p ln thnh t bo. Nh lc trng ny m t bo trng thi blo ha, trng thi "trng" v do m cy nht l b l thng trng thi ti, mt t thi thun li cho cc hot ng sinh l ca cy. Nu t bo khng ht nc th mt sc trng v t bo trng thi thiu bo ha nc, cy s ho r, hon ton khng thun li cho cc hot ng sinh l ca cy v nng sut cy trng gim. Mc gim nng sut ty thuc vo mc ho ca cy.

- Ngoi ra, khng bo c vai tr nh mt ci kho cha cht bi tit ca t bo. Lng cht bi tit v th tch ca khng bo ngy cng tng ln theo tui, cho n khi chng chim ton b th tch t bo th t bo s cht.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....13

2.4. Cht nguyn sinh (Protoplasm)

Cht nguyn sinh c gii hn gia khng bo v thnh t bo. N l thnh phn sng c bn ca t bo. Cht nguyn sinh cha cc bo quan v mi bo quan thc hin chc nng sinh l c trng ca mnh. C th ni rng cht nguyn sinh t bo l ni thc hin tt c cc hot ng sinh l ca t bo v ca cy. Cht nguyn sinh gm ba b phn hp thnh l h thng mng (membran), cc bo quan v cht nn (khun t bo cht).

2.4.1. H thng mng (Membran)

Membran trong t bo cn gi l mng sinh hc, l t chc c cu trc c trng. Trong cc loi membran th membran bao bc cht nguyn sinh gi l plasmalem l membran quan trng nht. Plasmalem bao quanh t bo ring bit to ra ranh gii gia cc t bo, va to nn va duy tr mt s khc bit v in ha gia bn trong v bn ngoi t bo. Ngoi ra, cn c cc membran khc bao bc quanh cc c quan t nh nhn, lc lp, ty th Membran cng to nn cc khoang ni bo nh mng li ni cht (ER) trong t bo cht v thylacoit trong lc lp. Membran cng c th dng lm cc dn cho mt s protein trong t bo.

* Chc nng ca mng

- Bao bc, bo v cho t bo cht v cc bo quan. Mng ngn cch cc bo quan v cc phn cu trc ca t bo vi nhau, nh hnh cho cc bo quan trnh s trn ln nhau...

- iu chnh tnh thm ca cc cht i ra hoc i vo t bo v cc bo quan. S xm nhp cc cht tan vo t bo v cc bo quan c kim tra rt cht ch v mi mt mng c tnh c hiu ring ca mnh i vi tng cht tan ring bit. Chnh v vy m nng cht tan trong v ngoi mng chnh lch nhau rt nhiu. V d nh nng ion H+ trong khng bo cao hn rt nhiu so vi trong t bo cht. Qu trnh quang hp c c tip tc hay khng c quyt nh bi cc sn phm quang hp c c thm nhanh qua mng lc lp vn chuyn ra khi lc lp v l i n mch dn.

Khi s iu chnh tnh thm ca mng b ri lon, s d r cht tan v ion ra ngoi t bo lm ri lon qu trnh trao i cht, cy c th cht. Chng han, khi gp iu kin ngoi cnh bt thun hoc c t nm bnh..., cu trc nguyn vn ca mng b nh hng v s ri lon tnh thm ca mng...

- Tin hnh qu trnh trao i cht v nng lng. Cc mng n su vo trong lc lp (mng thilacoit) lm nhim v bin quang nng thnh ha nng trong quang hp (Quang phosphoryl ho) v h thng mng trong n su vo trong ty th lm nhim v tng hp ATP cung cp nng lng cho cc hot ng sng ca c th (Phosphoryl ho oxi ho). S sinh tng hp protein c th c tin hnh trn cc riboxom c nh v trm mng li ni cht...

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....14

* Phn loi mng

Ngi ta phn chia mng sinh hc thnh ba loi l mng bao bc, mng trong v mng li ni cht.

- Mng bao bc: V tr ca mng ny l bao bc cc bo quan v t bo cht... Chng gm: Mng sinh cht (plasmalem) bao bc quanh cht nguyn sinh v nm st thnh t bo; mng khng bo (tonoplast) ngn cch cht nguyn sinh v khng bo v cc mng bao bc xung quanh cc bo quan nh mng nhn, lc lp, ty th v cc bo quan siu hin vi... Mng bao bc c th l mng kp gm hai lp mng c s (Mng nhn, lc lp, ty th) v cng c th ch mt lp mng c s m thi (Mng ca cc bo quan siu hin vi nh peroxixom, lysoxom, dictioxom...). Mng bao bc thng lm chc nng bo v v kim tra tnh thm ca cc cht qua mng.

- Mng trong: y l h thng mng n su vo trong mt s c quan. C hai bo quan quan trng c h thng mng trong l lc lp v ty th. H thng mng trong ca lc lp gi l mng quang hp hay thylacoit; cn ty th l h thng mng trong. Chc nng ca mng trong l tin hnh qu trnh trao i cht v nng lng trong t bo.

- Mng li ni cht: y l mt h thng mng chng cht n su vo trong cht nguyn sinh ngn cch cht nguyn sinh thnh cc khoang ring bit, ni lin khng bo vi nhn v cc c quan, xuyn qua cc si lin bo ni lin cc t bo vi nhau... Trn chng c th c nhiu riboxom - c quan tng hp protein.

Chc nng ca h thng mng li ni cht cha hon ton sng t, nhng mt trong nhng vai tr quan trng l lm cu ni lu thng gia cc c quan, cc t bo vi nhau v l ni vn chuyn cc cht bi tit, cc nguyn liu xy dng thnh t bo, ni tng hp protein...

* Cu trc ca mng (membran)

Ton b cc membran sinh hc u c cng t chc phn t c s. Chng u bao gm mt lp kp (bilayer) ca cc phn t phospholipit mng plasmalem hoc l glysosylglyxerit mng ca lc lp v cc lp th. Cc phn t protein c nm chm trong lp kp lipit ny. Mi lp kp nh vy cn c gi l n v membran. Thnh phn lipit v c tnh protein thay i tu loi membran to cho membran c nhng c trng v chc nng nht nh.

Cc phospholipit l thnh phn quan trng nht ca mng sinh hc. Phospholipit l mt loi lipit trong hai axit bo c kt hp vi glyceril. Phn t phospholipit va c tnh a nc (ha tan trong nc v to lin kt hydro vi nc), va c c tnh k nc (khng ha tan trong nc v khng to lin kt hydro vi nc). Chng l cc cht lng cc. Chui hydro cacbon ca axit bo khng phn cc to nn mt vng k nc khng cho nc thm nhp.

Nn tng c bn ca mng sinh hc l tng kp lipit, trong , cc ui khng phn cc k nc ca phospholipit hng vo nhau to nn mt vng khng phn cc bn

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....15

trong tng kp. Do vy n c kh nng y li bt k phn t cht tan no ha tan trong nc i qua mng t bo ging nh mt lp du ngn chn git nc i qua.

Cng nh tt c cc cht bo khc, lipit membran cng tn ti hai trng thi vt l khc nhau l th gel bn tinh th v th lng. Trng thi gel bn tinh th c th chuyn sang th lng khi nhit mi trng tng ln. S thay i trng thi ny gi l s chuyn pha. Mi loi lipit c s chuyn pha mt nhit nht nh gi l nhit

nng chy. nhit thp xy ra s ng kt (gelling) lipit lm mt hot tnh membran v tng cng tnh thm membran. Khi nhit cao, lipit t ra qu linh ng duy tr trng thi ngn chn ca hng ro membran. Nh vy, thc vt s c nhng phn ng thch nghi vi mi trng bng cch iu chnh linh ng ca membran. Membran s c kh nng b sung thnh phn lipit ca membran thch ng vi nhit mi trng. Chnh v th , cc phospholipit thc vt thng c t l cc axit bo cha

no cao nh axit oleic (c mt lin kt i), linoleic (hai lin kt i) v -linoleic (ba lin kt i).

Hnh 1.4. M hnh cu trc ca mng sinh hc c s

(tng kp lipit v protein mng)

a. Cu trc ca phn t phospholipit b. Protein xuyn qua tng kp lipit

a

b

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....16

Cc protein lin kt vi cc lp kp lipit thng c hai loi: Loi ho nhp (xuyn mng) v loi ngoi vi.

Protein ha nhp thng xuyn qua lp kp lipit. Cc protein ny xuyn qua mng nhiu ln to nn cc ng dn qua tng kp hnh thnh nn cc knh cho cc ion xuyn qua. Mt phn protein vn ra ngoi nh l th quan tng tc vi pha ngoi ca mng t bo, phn khc tng tc vi phn a nc c trong membran. Cc protein c chc nng l cc knh ion gm cc protein ha nhp ca membran.

Cc protein ngoi vi thng c gn vo b mt menbran vi cc cu khng ho tr nh cc cu ion hoc lin kt hydro. Cc protein ngoi vi c mt s vai tr trong chc nng ca membran tng tc gia plasmalem v cc thnh phn khc ca t bo.

Protein mng c cc chc nng sau: vn chuyn cc ion, phn t; di tr cc tn hiu qua membran; bin ha thnh phn lipit nh enzym; lp rp cc glycoprotein v polysaccarit, to ra s lin kt c hc gia vng t bo cht v thnh t bo. Thnh phn ca protein trong membran s quyt nh tnh c hiu ca membran. Vi cu trc membran nh trn cho thy ton b cc phn t ca membran c th khuch tn t do cho php membran thay i cu hnh v sp xp li mt cch nhanh chng.

2.4.2. Cc bo quan

Cc c quan nm trong cht nguyn sinh ty theo kch thc ca chng m c th chia ra cc bo quan hin vi gm nhn, lc lp v ty th v cc bo quan siu hin vi gm cc th nh riboxom, peroxixom, lisoxom, glyoxixom... Mi mt c quan m nhim chc nng sinh l c trng cho c th. C ba c quan c cha ADN, ARN v riboxom ring nn c kh nng thc hin di truyn c lp l nhn, lc lp v ty th - di truyn nhn v di truyn t bo cht (qua lc lp v ty th). Ngi ta gi chng l cc yu t cu trc.

2.4.2.1. Nhn

* Hnh thi, cu trc

- Mi t bo c mt nhn hnh cu hay hnh trng vi kch thc 7-8 m.

- Nhn c bao bc bng mt mng kp. Trn b mt ca mng c rt nhiu l cc thng tin di truyn c truyn ra ngoi d dng.

- L nhn l mt cu trc gm hng trm cc protein khc nhau sp xp theo dng bt gic. Trn mng nhn c th c t vi l cho n hng ngn l nhn. Cc i phn t t nhn (k c cc cu phn ca robosom) c th i qua mng nhn vo t bo cht.

- Nhn cha AND ca chromosom (nhim sc th) v ARN ca hch nhn. AND v ARN nhng chm trong khi nucleoplasma cha nhiu protein c hot tnh enzym.

- Thnh phn ha hc ch yu ca nhn l ADN, ARN va protein. ADN cha thng tin di truyn ca c th m dn v di truyn l cc gen. Cc gen xc nh cc tnh

trng ca t bo v ca c th, iu ho cc hot ng ca t bo.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....17

* Vai tr ca nhn

- Duy tr thng tin di truyn c trng cho mi loi. Thng tin di truyn cha ng trong cu trc ca phn t ADN.

- Truyn thng tin di truyn t nhn n t bo cht thng qua vic tng hp cc ARN thng tin mang ton b thng tin di truyn ca ADN ca nhn.

- Truyn thng tin di truyn t t bo ny sang t bo khc bng c ch nhn i ADN ging nhau mt cch tuyt i v tip theo l c ch phn chia i t bo cng ging ht nhau.

2.4.2.2. Lp th

- Lp th l cc bo quan lm nhim v tng hp v tch ly cht hu c. Chng bao gm lc lp (chloroplast) lm nhim v quang hp, sc lp (chromoplast) cha cc sc t nh carotenoit to nn mu sc ca hoa, qu v v sc lp (leucoplast) l trung tm tch ly tinh bt v cc cht khc. Chng cha nhiu enzym tng hp gluxit phc tp t cc ng n.

- Trong ba bo quan th lc lp l quan trng nht v n thc hin chc nng quang hp tng hp nn cc hp cht hu c cung cp cho i sng ca tt c sinh vt. Ngoi ra lc lp cn cha ADN, ARN v riboxom ca ring mnh nn c kh nng thc hin di truyn mt s tnh trng c trng ngoi nhn gi l di truyn t bo cht. (Hnh thi, cu trc v chc nng ca lc lp s c cp trong chng quang hp).

2.4.2.3. Ty th

- Ty th l bo quan quan trng v n gn lin vi hot ng sng, hot ng trao i cht ca t bo v c quan. u c hot ng sng mnh th tp trung nhiu ty th.

(Hnh thi v cu to ca ty th s cp trong chng H hp).

- Chc nng c bn ca n l tin hnh qu trnh h hp trong cy, tc l phn gii oxi ha cc cht hu c gii phng nng lng hu ch cung cp cho cc hot ng sng ca cy. C th ni ty th l cc "trm bin th" nng lng ca t bo.

- Ngoi ra, cng ging nh lc lp, ty th cn c chc nng thc hin di truyn t bo cht mt s tnh trng c trng v chng c ADN, ARN v riboxom c lp ca mnh. (Cu trc v chc nng ca ty th s c trnh by trong chng H hp ca thc vt).

2.4.2.4. Cc bo quan c cu trc siu hin vi

Cc c quan ny c c im chung l chng c kch thc siu hin vi, s lng rt nhiu, c dng hnh cu v c mng bao bc l mng n gm mt mng c s... Mi mt bo quan m nhim mt chc nng c trng ca t bo.

- Riboxom: Riboxom l cc tiu phn ribonucleotit hnh cu, ng knh 15 nm, khng quan st c di knh hin vi thng. Thnh phn ho hc ca n gm ARN

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....18

(60%) v protein (40%). Chng c th tn ti c lp trong t bo cht hoc gn vi li ni cht, hoc nm trong nhn, lc lp v ty th. Riboxom l a im din ra qu trnh tng hp protein ca t bo.

- Peroxixom: y l nhng th hnh ht c mng n bao bc. Chng c s lng rt nhiu trong t bo, c bit l t bo ca thc vt C3, l thc vt c quang h hp mnh. Peroxixom m nhim chc nng quang h hp, tc qu trnh thi CO2 ngoi sng, mt chc nng lm tn hi n nng sut ca cy. Thc ra n ch m nhim mt khu trong quang h hp, oxi ho glycolat thnh glyoxilat v gii phng H2O2.

- Glyoxixom: C quan ny c mt ch yu khi cc ht c cha lipit ny mm. Chng cha rt nhiu enzym ca chu trnh glyoxilic. Chc nng ca glyoxixom l thc hin chu trnh glyoxilic nhm chuyn ha axit bo thnh ng cc ht d tr cht bo phc v cho qu trnh ny mm ca cc ht ny.

- Lysoxom: C quan siu hin vi ny thc hin chc nng tiu ha trong t bo. Chng cha nhiu enzym thy phn nh nucleaza, proteaza, lipaza... phn gii cc vt l khi xm nhp vo t bo. Khi trng thi nguyn vn, cc enzym thu phn ny khng tip xa vi t bo cht v khng hot ng. Nhng khi c vt l xm nhp, mng b thng tn gii phng cc enzym tip xc vi vt l v tin hnh thu phn chng.

- Dictioxom (b my golgi): Chng bao gm mt tp hp mng c 3 - 12 a chng ln nhau. Mi t bo thc vt c ti hng nghn th golgi.

Chc nng ca b my golgi l hnh thnh v tit ra nhng cht bi tit nh cc dch nhy. Chng cn c vai tr trong vic hnh thnh thnh t bo qua vic hnh thnh cc gluxit thnh t bo...

- Oleoxom

Nhiu thc vt tng hp v d tr mt lng ln cc triacylglycerol di dng du thc vt trong qu trnh hnh thnh ht. Cc du ny c tch lu trong cc c quan d tr gi l olexom cn gi l th m hay spheroxom. Khi ht ny mm du trong olexom s b phn gii bi lipase v bin i thnh ng nh glyoxixom.

Ngoi ra cn rt nhiu cc bo quan v cc t chc khc nhau trong t bo c nhim v thc hin cc bin i, cc chc nng rt a dng v phc tp ca t bo.

2.4.3. Khun t bo cht

- Khun t bo cht l cht nn cha tt c cc bo quan v sn phm ca qu trnh trao i cht trong t bo. Khun t bo cht l mt khi na lng, ng nht v quang hc v c th coi l mt dung dch keo protein trong nc. Cc protein phn ln l cc enzym thc hin cc qu trnh bin i trong t bo nh qu trnh ng phn, chu trnh pentozophotphat, ln men, cc phn ng thy phn v tng hp... Khun t bo cht cn cha rt nhiu cc sn phm ca cc phn ng bin i cht xy ra thng xuyn trong t bo.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....19

- Khun t bo cht thng xuyn vn ng v ko theo cc bo quan v cc cu trc trong chng cng vn ng theo. S vn ng ny lm cho cc qu trnh din ra trong t bo c linh hot hn. Ta c th quan st s vn ng ca t bo cht thng qua vn ng ca cc ht lc lp di knh hin vi.

2.4.4. Cc s lin bo (Plasmodesma)

Plasmodes l mt dng mng hnh ng c ng knh 40-50 nm. Chng xuyn qua thnh t bo v ni t bo cht vi t bo bn cnh. Do hu ht cc t bo thc vt lin thng vi nhau theo kiu ny, t bo cht ca chng to nn mt h kt ni lin tc gi l symplast. S vn chuyn ni bo cc cht tan v nc qua cc si lin bo gi l s vn chuyn symplast.

3. Cc c tnh c bn ca cht nguyn sinh

Cht nguyn sinh l thnh phn sng duy nht ca t bo. Mi hot ng sinh l u din ra trong cht nguyn sinh. Chnh v vy m chng ta cn cp n cc c tnh c bn ca cht nguyn sinh gm tnh cht ha hc, ha keo v vt l ca n...

3.1. Thnh phn ha hc ch yu ca cht nguyn sinh

Khi phn tch thnh phn ha hc tng i ca t bo, chng ta thu c cc s liu sau: nc chim 85%, protein 10%, lipit 2%, ADN 0,4%, ARN 0,7%, cc cht hu c khc 0,4%, cc cht khong 1,5%. Axit nucleic s nghin cu trong gio trnh ho sinh v di truyn, cht khong s c cp n trong chng dinh dng khong ca gio trnh ny. Trong phn ny, chng ta s nghin cu ba thnh phn c bn v cng rt quan trng l protein, lipit v nc.

3.1.1. Protein

Theo quan im ca Anghen th s sng chnh l s tn ti v hot ng ca cc th protein. V vy, protein l cu phn quan trng nht ca cht nguyn sinh. Chng tham gia cu to nn h thng cht nguyn sinh, cu to nn mng sinh hc; ng thi chng l thnh phn bt buc ca tt c cc enzym xc tc cho tt c cc phn ng din ra trong cy. C th ni rng protein va l yu t cu trc va l yu t chc nng ca t bo.

Protein l cc i phn t c phn t lng dao ng rt ln t 10 000 n hng triu ty thuc vo loi protein v chc nng ca chng trong t bo. Chng c th dng n gin ch do cc axit amin lin kt thnh, cng c th dng phc tp khi chng lin kt vi cc cht khc nh vi kim loi (metalloprotein), vi lipit (lipoprotein), vi gluxit (glucoprotein), vi axit nucleic (nucleoprotein)...

3.1.1.1. Cu trc ca protein

Cc axit amin lin kt vi nhau bng cc lin kt peptit to nn cc phn t protein.

Tuy nhin, ty theo chc nng ca chng trong t bo m protein co cu trc rt khc nhau v cu trc ca chng quyt nh hot tnh sinh hc ca chng.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....20

C bn loi cu trc ca protein:

* Cu trc bc mt c quy nh bi trnh t sp xp ca cc axit amin trong phn t protein bng cc lin kt peptit. Nu trt t cc axit amin thay i th xut hin protein mi v hot tnh ca chng cng thay i. Do , c th c v s cu trc bc mt. V d mt protein c 1000 gc axit amin to nn m trong ch c 20 axit amin c bn th s kiu cu trc bc mt c kh nng l 201000. S phong ph ca cc cu trc bc mt ca protein lm cho th gii sinh vt ht sc a dng. Cu trc bc mt phn nh c tnh di truyn ca ging loi, nn c th s dng tiu chun ny xc nh mi quan h huyt thng gia cc ging cy trng.

* Cu trc bc hai l cu trc khng gian ca phn t protein. Ngoi lin kt peptit ra, phn t protein cn c b sung thm cc lin kt hydro c hnh thnh gia nguyn t hydro ca nhm -NH- ca mt lin kt peptit vi nguyn t oxi ca nhm =C=O ca mt lin kt khc:

H N

C=O.......H N

C=O

Do cc cu ni hydro m cc chui polypeptit c dng hnh xon theo kiu xon (tng t kiu cu trc xon ca ADN) v xon c dng gp khc. Cc protein dng si l in hnh cho cu trc bc hai.

* Cu trc bc ba l cu trc khng gian ca phn t protein. Chui polypeptit trong protein cun trn lai gn hn nh c 4 lin kt b sung: lin kt hydro, lin kt ion gia cc nhm mang in tch tri du, lin kt k nc gia cc nhm ght nc, lin kt disulfit gia cc nguyn t S trong protein (-S-S-). Tr lin kt disulfit c nng lng lin kt ln hn, cn cc lin kt khc c vai tr quan trng trong n nh cu trc ca protein u l cc lin kt yu, c nng lng lin kt nh nn rt d b ct t. Chc nng ca proten lin quan cht ch n cu trc bc ba. S kt hp bt k mt cht no vi phn t proten u lm thay i cu trc bc bav lm thay hot tnh ca protein.

* Cu trc bc bn l cu trc khng gian gia mt s phn t protein c cu trc bc hai v bc ba to nn mt th protein c kch thc ln hn, cng knh hn. Cc lc lin kt duy tr n nh cu trc bc bn u l cc lin kt yu tng t nh cu trc bc ba.

3.1.1.2. S bin tnh ca protein

* S bin tnh ca phn t protein: Phn t protein ca cht nguyn sinh rt d b bin tnh. S bin tnh ca protein gy nn s bin tnh ca cht nguyn sinh, ph v

cu trc ca cht nguyn sinh v t bo cht.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....21

Khi b bin tnh, protein mt hot tnh sinh hc nh mt sc trng, mt kh nng tch in, gim tnh ha tan v mt hot tnh xc tc... S bin tnh ca protein cng lm thay i kh nng kt hp ca protein vi cc cht khc v gim st hot tnh ca chng.

mc trm trng, s bin tnh ca protein dn n bin tnh cht nguyn sinh v ng ngha vi s cht ca t bo v ca cy.

* Cc iu kin gy bin tnh protein v cht nguyn sinh thng l cc iu kin ngoi cnh bt thun c kh nng lm cht cy nh nhit qu cao hoc qu thp, pH qu cao hay qu thp, c t nm bnh, in th oxi ha kh ca t qu cao, tia t ngoi, sng siu m, cc dung mi hu c...

* Bn cht ca s bin tnh protein

- Cc lin kt vn n nh cu trc ca phn t protein l nhng lin kt yu

v chng rt d dng b ct t khi gp tc nhn gy bin tnh. Chng hn, khi r cy gp in th oxi ha kh ca t thay i nhiu th lin kt disulfit b ph v mc d nng lng lin kt kh ln. Nhit mi trng cao qu s ct cu ni hydro. Cc dung mi hu c nh ru, axeton s ph hy cc lin kt ght nc. Lin kt ion s b ph hy di tc dng ca pH mi trng thay i nhiu...

- Chnh v vy m kh nng chng chu ca cy i vi iu kin ngoi cnh bt thun gn lin vi tnh bn vng ca phn t protein chng li s bin tnh. y l c trng ca cc ging c kh nng chng chu tt vi tc nhn "stress" ca mi trng.

3.1.1.3. Tnh lung tnh v im ng in ca protein

* Tnh lng tnh ca phn t protein

- Cc phn t axit amin cu to nn protein c tnh lng tnh: va c tnh axit (phn t ca n c nhm -COOH) v va c tnh kim (c nhm -OH). Trong mi trng axit (H+) th nhm -COOH b c ch nn axit amin phn ly cho ion mang in dng:

R- CH-COOH + H+ R- CH-COOH

NH2 NH3+

Ngc li, trong mi trng kim (OH-) th nhm -NH2 b c ch nn axit amin phn ly cho ion mang in m:

R- CH-COOH + OH- R- CH-COO- + H2O

NH2 NH2

mt tr s pH nht nh, phn t axit amin trung ha v in tch (R-CH-COO-).

Tr s pH c gi l im ng in ca phn t axit amin (pI). NH3+

- Trong cu trc ca phn t protein th cc nhm -COOH v -NH2 c s dng vo vic hnh thnh nn cc lin kt c bn peptit (-CO-NH-). Tuy nhin, cui cng

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....22

ca mch peptit v cc mch nhnh tn ti rt nhiu cc nhm -COOH v -NH2 t do nn chng cng b phn ly trong mi trng c pH khc nhau. Nu sau khi phn ly m s gc COO- nhiu hn s gc NH3

+ th phn t protein tch in m v ngc li th tch in dng. Kt qu ny hon ton ph thuc vo pH ca mi trng

* im ng in ca protein (pI) v ca cht nguyn sinh

- Ti tr s pH no m ta c s gc mang in dng bng s gc mang in m trong phn t protein th ta c im ng in ca phn t protein .

Nh vy th ngi ta gi tr s pH gy nn trung ha v in ca phn t protein no l im ng in ca n (pI).

- im ng in ph thuc khng nhng vo hng s phn ly ca phn t protein m cn ph thuc rt nhiu n s lng cc nhm axit v kim t do c trong phn t ca chng. V vy, mi protein khc nhau th c im ng in khc nhau. V d pI ca pepxin bng 1, ca globulin i mch l 4,9...

im ng in ca cht nguyn sinh l tr s trung bnh ca tt c cc im ng in ca cc phn t protein c trong cht nguyn sinh v thng bng 5,5. Khi pH mi trng ln hn pI (pH > 5,5) th t bo thc vt tch in m. Ngc lai, pH < pI th cy tch in dng. V vy, trong mi trng trung tnh (pH = 7) th cy thng tch in m.

- Ti im ng in, protein gim trng, ha tan v khng bn, d dng b sa lng. Keo nguyn sinh cht duy tr c cu trc bn vng ca n nh mang in tch nn nu trung ha v in th s b bin tnh v s cht. Thc vt gp im ng in th cng khng tn ti c.

Tuy nhin, thc vt c kh nng t iu chnh trnh im ng in. l mt thuc tnh thch nghi ca thc vt v n phi sng trong mi trng lun c s bin ng v pH.

3.1.2. Lipit

Lipit trong nguyn sinh cht c hai dng: dng d tr v dng tham gia cu trc.

* Thuc v dng d tr tham gia qu trnh trao i cht khai thc nng lng ph bin l cc git du nm trong cht nguyn sinh, cc sn phm trao i cht bo nh cc axit bo...

* Sp, cutin v suberin cng l cc cht bo tham gia kin to nn lp biu b, lp v c, qu... Cc cht ny c tc dng bo v, che ch cho cc b phn bn trong, cng nh gim s thot hi nc v xm nhp ca vi sinh vt.

* Dng lipit c ngha quan trng nht l dng lipit tham gia cu to nn h thng mng sinh hc trong cht nguyn sinh. Lipit cu to nn membran l photpholipit. y l hp cht gia lipit v axit photphoric. S c mt ca photpholipit lm tnh cht mng tr nn bn vng hn, kim tra tnh thm cht ch hn v quyt nh n kh nng chng chu ca cy.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....23

3.1. 3. Nc

Nc c xem l thnh phn quan trng ca cht nguyn sinh. N l vt cht c bit i vi c th sinh vt ni chung v thc vt ni ring. Hm lng nc trong cht nguyn sinh ca t bo thc vt l rt ln, khong 95% khi lng cht nguyn sinh.

* Vai tr ca nc trong t bo thc vt

- Nc l dung mi l tng ha tan cc cht thc hin cc phn ng ha sinh xy ra trong t bo.

- To nn mng nc thy ha bao bc quanh cc phn t keo nguyn sinh cht, nh vy m duy tr c cu trc v hot tnh ca keo nguyn sinh cht.

- N tham gia vo cc phn ng ha sinh trong t bo c bit l cc phn ng trong qu trnh quang hp, h hp v cc phn ng thy phn trong qu trnh trao i cht ca t bo.

- Nc to nn dng vn chuyn vt cht trong ni b t bo v gia cc t bo vi nhau, to nn mch mu lu thng trong cy nh tun hon mu ng vt.

- Hm lng nc lin kt trong cht nguyn sinh quyt nh tnh chng chu ca keo nguyn sinh cht v ca t bo...

* Tnh cht l ho ca nc

Vai tr quan trng ca nc trong t bo c quyt nh bi cc c tnh l ha ca phn t nc.

- Phn t nc c kh nng bay hi bt c nhit no nn cy lun lun thot hi nc, c kh nng cho nh sng xuyn qua nn thc vt thy sinh c th sng c, c kh nng gi nhit cao...

- Mt trong nhng c tnh quan trng nht l tnh phn cc ca phn t nc. Phn t nc gm hai nguyn t hydro v mt nguyn t oxy ni vi nhau nh lin kt cng ha tr. Gc lin kt gia oxy v hai hydro l 105o nn trung tm in dng v in m khng trng nhau, hn na oxy ht in t mnh hn nn hydro thng thiu in t v tch in dng. Kt qu l phn t nc c m men lng cc, mt u l in dng v u kia l in m (Hnh 1.6a).

- Do s phn cc mnh ca lin kt O-- - H+ nn chng d dng tng tc vi nguyn t oxi ca cc phn t khc to nn lin kt hydro. Gia cc phn t nc cng to nn cc lin kt hydro nn chng c th to nn mng lin kt. Khi nc ng bng, cu trc mng lin kt l ln nht. Khi nhit trn 4oC, cc lin kt ca mng b b gy do s vn chuyn ca cc phn t nc tng. Khi nhit trn 100oC, cc lin kt hydro b ph v hon ton v nc si. Cng do tnh phn cc ca phn t nc to nn lin kt hydro m nc c tnh dnh ( nht) v chng c kh nng lin kt vi nhau vn chuyn ln cao trong cy. S phn cc ca nc l to cho chng kh nng thu ho

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....24

mnh trong cht nguyn sinh, mt c tnh v cng quan trng quyt nh n cc hot ng sng ca cy (Hnh 1.6b)...

Hnh 1.6. Cu trc ca phn t nc (a) v kh nng thy ha

trong cht nguyn sinh (b)

* S thy ha trong cht nguyn sinh

- Do phn t nc phn cc v in nn khi gp phn t mang in trong cht nguyn sinh nh cc keo protein mang in trong cht nguyn sinh chng hn th chng b hp dn bng lc tnh in. Kt qu l cc phn t nc quay u tri du in vo nhau to nn mt mng nc bao xung quanh keo mang in gi l hin tng thy ha v lp nc bao xung quanh phn t mang in c gi l lp nc thy ha.

- Mng nc thy ha ny c hai loi nc (Hnh 1.6b). Cc phn t nc gn vi keo mang in b hp dn mt lc ln c th n 1000 atm nn chng sp xp rt trt t v rt kh c th tch ra khi keo mang in, to nn dng nc lin kt. Nc lin kt khng cn cc tnh cht thng thng nh khng bc hi ngay 100oC, khng ng bng 0oC, khng tham gia vo cc phn ng ha hc... Chng bo v cho keo nguyn sinh cht khi dnh kt nhau.

- Cng xa trung tm mang in th lc ht yu hn nn cc phn t nc sp xp khng c trt t v rt linh ng, c th d dng tch ra khi trung tm mang in khi c mt lc no tc ng. Chng to nn dng nc t do. Hm lng nc t do trong cht nguyn sinh rt cao, c th t trn 90% lng nc trong cy.

b

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....25

* Vai tr ca nc t do v nc lin kt

- Nc lin kt trong cht nguyn sinh to nn bn vng ca keo nguyn sinh cht nn n c vai tr quan trng trong vic quyt nh kh nng chng chu ca cy. Hm lng nc lin kt trong cy phn nh tnh chng chu ca cy i vi iu kin ngoi cnh bt thun. Mi cy c mt t l v hm lng nc lin kt nht nh. T l ny cng cao th cy cng chng chu tt. Chng hn cy xng rng sng c trong iu kin rt nng v kh hn ca sa mc ch yu l do t l hm lng nc lin kt rt cao , chim gn 2/3 hm lng nc trong chng. V vy, hm lng nc lin kt trong cy l mt ch tiu nh gi tnh chng hn v nng ca cy trng.

- Dng nc t do l dng nc rt linh ng. N tham gia vo cc phn ng ha sinh trong cy nh cc phn ng trong quang hp, h hp, sinh tng hp... Ngoi ra, nc t do tham gia vo dng vn chuyn, lu thng phn phi trong c th, vo qu trnh thot hi nc... nn n quyt nh hot ng sinh l trong cy.

V vy, cc giai on c hot ng sng mnh nh lc cy cn non, lc ra hoa... th cn c hm lng nc t do cao. Ht ging khi phi kh th nc t do gn nh b tch khi ht nn gim hot ng sng n mc ti thiu v chng ng ngh. Nhng khi ta cho ht tip xc vi nc th nc t do c b sung vo ht v lp tc hot ng sng ca chng tng ln mnh m, chng ny mm...

3.2. c tnh vt l ca cht nguyn sinh

3.2.1. Tnh lng ca cht nguyn sinh

Tnh lng ca cht nguyn sinh th hin hai c im:

* Kh nng vn ng nh mt cht lng. Ta c th quan st s vn ng ca cht nguyn sinh thng qua vn ng ca cc ht lc lp di knh hin vi. Tc vn chuyn ca cht nguyn sinh thay i rt nhiu ty thuc vo cc loi t bo, cc cy khc nhau v iu kin ngoi cnh nh nhit , nh sng, pH ca mi trng... Nh c s vn ng ny m vt cht trong t bo c iu kin lu thng.

* Sc cng b mt c trng cho cht lng. y l mt c tnh ca cht lng. Nh sc cng b mt m cht lng c th co trn li. Bng k thut c bit, ngi ta ph b lp v t bo to ra t bo trn (protoplast). Cc t bo trn cng co trn li nh git nc v chng c sc cng b mt.

3.2.2. nht ca cht nguyn sinh

* Khi nim v nht

nht ( qunh, dnh) l kh nng ngn cn s di chuyn, s i ch ca cc ion, cc phn t, tp hp phn t hay cc tiu th phn tn trong mi trng lng. Lc cn tr ny ph thuc vo sc hp dn tng h gia cc phn t v trng thi cu trc ca chng. N l mt i lng c trng cho cht lng.

* nht ca cht nguyn sinh

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....26

nht ca cht nguyn sinh l kh nng cn tr s vn ng ca cc cht v cc bo quan trong nguyn sinh cht. Cht nguyn sinh l mt h thng keo, nn cc c im cu trc ca h thng keo v cc iu kin nh hng n keo nguyn sinh cht u nh hng n nht ca cht nguyn sinh. nht cht nguyn sinh ca t bo thng bng 10 - 18 centipoi, ngha l bng 10 - 20 ln nht nc, km nht du thu du 80 - 100 ln. iu chng t cht nguyn sinh gn vi cht lng hn.

* nht cu trc

S khc nhau gia nht cht nguyn sinh v cht lng thng thng l ch nht cht nguyn sinh ph thuc nhiu n cu trc rt phc tp ca cht nguyn sinh. Lc tng tc gia cc i phn t, cc tiu th, cc bo quan trong cht nguyn sinh l rt phc tp, nn nht cht nguyn sinh mang tnh cu trc. nht cu trc l trung gian gia cht lng v vt th c cu trc.

* ngha ca nht cht nguyn sinh

- nht cht nguyn sinh cng gim th hot ng sng cng tng v ngc li. nht cht nguyn sinh thay i theo ging loi cy, theo tui cy v hot ng sinh l ca cy. Quy lut bin i nht cht nguyn sinh l theo qu trnh trng thnh v ha gi th nht ca cht nguyn sinh tng dn ln; tuy nhin, vo giai on ra hoa kt qu, do hat ng sng i hi tng ln mnh nn nht gim xung t ngt v sau giai on ra hoa, nht li tip tc tng ln.

- nht ca cy cng cao th cht nguyn sinh cng bn vng nn c kh nng chng chu tt hn vi cc iu kin bt thun ca mi trng nh chu nng, hn, bnh...

- nht ca cht nguyn sinh cn thay i rt nhiu theo cc iu kin ngoi cnh.

+ Nhit cng tng th nht cng gim (cht nguyn sinh lolng ra) v ngc li nn khi gp rt th nht cht nguyn sinh tng ln cn tr cc hot ng sng v cy d b thng tn.

+ Cc ion c mt trong mi trng cng tc ng n thay i nht cht nguyn sinh.

Cc ion c ha tr mt nh Na+, K+, NH4+... lm gim nht v tng hot ng

sinh l; Cn cc ion c ha tr cao nh Ca2+, Al3+, Mg2+... lm c cht nguyn sinh v tng nht, lm gim hot ng sng.

+ Mt trong nhng nguyn nhn cy trng cht rt l do nht tng ln, hot ng sng gim khng c kh nng chng rt. Trong trng hp nu ta tc ng lm gim nht v mc bnh thng ca n th cy c th qua c rt, v d ngi ta thng hay bn tro bp cho m xun chng rt c l do tro bp cha nhiu kali c kh nng lm gim nht v c th hp thu c nhit na...

3.2.3. Tnh n hi ca cht nguyn sinh

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....27

* Tnh n hi ca cht nguyn sinh

Tnh n hi l c tnh ca cht rn, l kh nng quay v trng thi ban u ca vt th l b bin dng khi ngng lc tc dng vo vt. V d nh khi nn v ngng nn ci l xo. Nu ta dng mt kim ko di mng sinh cht ra khi trng thi ban u nhng nu ta thi tc ng lc ko th cht nguyn sinh tr v nh c. iu chng t cht nguyn sinh ca t bo thc vt c tnh n hi. N mang c tnh ca mt vt th c cu trc.

* ngha ca tnh n hi

- Nh c tnh n hi m cht nguyn sinh ca t bo khng tan v khng trn ln vo dung dch nu n khng c thnh t bo. C th s dng k thut enzym phn hy thnh t bo thc vt to ra cc t bo trn (protoplast) mt cch nguyn vn. Sau c th tin hnh dung hp protoplast tao nn con lai soma.

- Tnh n hi ca cht nguyn sinh tng quan thun vi tnh chng chu ca cy v tng quan nghch vi cng qu trnh trao i cht. Do vy, tnh n hi cng cao th cy cng c kh nng chng chu vi cc iu kin bt thun.

3.3. c tnh ha keo ca cht nguyn sinh

3.3.1. Cht nguyn sinh l mt dung dch keo

- Ty thuc vo kch thc ca cht tan m ngi ta phn dung dch thnh ba loi: dung dch tht, dung dch keo v dung dch huyn ph. Nu kch thc cht tan nh hn 1nm, ta c dung dch tht, ln hn 200 nm l dung dch huyn ph v kch thc cht tan t 1 n 200 nm l dung dch keo.

- Cht nguyn sinh c cu to ch yu t cc i phn t nh protein, axit nucleic hoc lipoprotein, nucleoprotein... v rt nhiu cc th, cc bo quan... Tt c cc phn t ny u c kch thc ca ht keo (1 - 200 nm), nn khi chng tan trong nc th to nn mt dung dch keo.

3.3.2. c im ca dung dch keo nguyn sinh cht

- Cht nguyn sinh l mt dung dch keo rt phc tp v n c rt nhiu loi cht tan c kch thc khc nhau, mc phn tn khc nhau v hot tnh cng rt khc nhau.

- Nguyn sinh cht l dung dch keo a nc rt mnh v hu ht cc i phn t tan trong cht nguyn sinh u rt a nc nh protein, axit nucleic... Do , cht nguyn sinh c kh nng ht trng rt mnh v y l mt ng lc quan trng t bo ht nc vo, nht l i vi t bo cha xut hin khng bo.

- C b mt hp ph v phn hp ph ln, to iu kin thun li cho qu trnh trao i cht xy ra trong t bo. Cc phn ng u din ra trn b mt ca keo nguyn sinh cht.

3.3.3. Cc trng thi keo nguyn sinh cht

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....28

Ty theo mc thy ha v kh nng hot ng ca chng m keo nguyn sinh cht c th tn ti di ba dng: sol, coaxecva v gel (Hnh 1.7).

- Trng thi sol

Khi cc ht keo phn tn ng u v lin tc trong nc ta c dung dch keo

trng thi sol. trng thi sol, keo nguyn sinh cht rt linh ng v c hot ng sng rt mnh, cc qu trnh trao i cht xy ra thun li nht. Trong i sng ca cy, cc m, c quan v giai on sinh trng no c hot ng sng mnh nht th cht nguyn sinh trng thi sol. Chnh v vy m giai on cy cn non, hoc lc ra hoa cn hot ng sinh l mnh th keo nguyn sinh trng thi sol.

- Trng thi coaxecva

C th xem coaxecva nh l mt dung dch keo m c. Cc ht keo khng mt hon ton nc m chng cn mt mng nc mng. Ht keo khng dnh nhau thnh khi m tn ti c lp v rt ngn c li gia chng. Kt cu ht keo khng thay i, ch gim mng thy ha. Thng thng th ngoi mng nc thu ho ring, mt s ht keo gn nhau cn chung nhau mt mng nc na to nn cc th coaxecva. Tuy nhin, hot ng sng v cc qu trnh trao i cht din ra trong keo nguyn sinh cht coaxecva gim i nhiu so vi trng thi sol. Do vy, trng thi coaxecva tng ng vi cy tui trng thnh n gi, hot ng sng ca chng gim dn.

- Trng thi gel

+ y l trng thi rn ca dung dch keo. Ht keo trng thi coaxecva c mng thy ha mng i nhng ng u, cn ht keo trng thi gel c mng nc mng i khng u. Ti nhng im c mng thy ha mt i th ht keo c c hi dnh kt vi nhau to thnh chui di to nn kt cu vng lp th. Dung dch c tp trung cc khong trng ca cc mt li v mt i kh nng linh ng ca n. Keo nguyn sinh cht chuyn sang trng thi rn.

+ trng thi gel, cht nguyn sinh gim st n mc ti thiu cc hot ng trao i cht v cc hot ng sinh l ca chng. C th ni, t bo, m v cy trng thi gel l trng thi tim sinh, trng thi ng ngh. Tng ng vi trng thi gel trong cy l cc c quan ang ng ngh nh cc ht ging, c ging, hay chi ng ng...

+ Cht nguyn sinh trng thi gel c kh nng ht nc rt mnh. Lc trng nc ht ging phi kh c th ln n 1000 atm. Khi hp thu nc vo nht l khi c nhit tng ln th cc ht keo trng thi gel c th chuyn v trng thi sol v hot ng sng li tng ln, chng hn nh lc ht ny mm.

- Cc trng thi keo nguyn sinh cht phn nh kh nng hot ng sng ca chng v do chng ng vi cc giai on sinh trng pht trin nht nh ca cy. Ty theo iu kin v hon cnh c th m ba trng thi keo c th chuyn bin cho nhau. V d, giai on cn hot ng sng rt mnh th keo nguyn sinh t coaxecva v thm ch c gel cng c th chuyn sang trng thi sol. Nu c quan hay cy cn bc vo trng thi

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....29

ng ngh th keo nguyn sinh t trng thi sol v coaxecva c th chuyn sang trng thi gel...

Hnh 1.7. Cc trng thi ca keo nguyn sinh cht

S linh hot trong bin i cc trng thi keo nguyn sinh cht lm cho cy c kh nng d dng thch ng hn vi iu kin ngoi cnh...

4. S trao i nc ca t bo thc vt

S trao i nc ca t bo thc vt l mt hot ng sinh l quan trng nht ca t bo. C hai loi t bo kh c nhau c c c c ch trao i nc kh c nhau. Vi c c t bo cha c khng bo nh c c m phn sinh th s xm nhp ca nc vo t bo ch yu c tin hnh theo c ch ht trng ca keo nguyn sinh cht; cn vi t bo l xut hin khng bo ca c c m chuyn ho th s trao i nc ch yu theo c ch thm thu.

4.1. S trao i nc ca t bo theo c ch thm thu

4.1.1. Hin tng thm thu

* Hin tng khuch tn: Phn t ca bt k mt vt cht no cng u c mt ng nng nht nh v nh m n khng ngng vn ng. S vn ng ca cc phn t t ni c nng cao (th ho hc cao) n ni nng thp (th ho hc thp) cho n khi cn bng nng trong ton h thng gi l hin tng khuch tn. V d nh ta ha tan ng vo nc hay s di chuyn ca cc phn t nc hoa trong phng....Tc khuch tn ca cc phn t t l thun vi s chnh lch nng trn mt n v khong cch (gradient nng ), t l thun vi nhit v t l nghch vi kch thc phn t v nht ca mi trng.

* Hin tng thm thu: Hin tng thm thu l mt trng hp c bit ca khuch tn. Tnh c bit l phn t vt cht tham gia khuch tn l nc v cc phn t nc phi vn ng xuyn qua mt mng bn thm. Mng bn thm l mng ch cho nc i qua m khng cho cht tan i qua. Vy, hin tng thm thu l s khuch tn ca cc phn t nc qua mng bn thm. Nc nguyn cht c nng nc cao nht (100%), cn dung dch c nng cng cao th c hm lng nc cng thp. Nu c hai dung dch cch nhau mt mng bn thm th nc s di chuyn t dung dch

a. Trng thi sol: Cc ht keo phn tn ng u trong cht nguyn sinh

b. Trng thi coaxecva: Nhiu ht keo chung nhau mt mng nc

a. Trng thi gel: Cc ht keo to thnh chui c cu trc vng lp th

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....30

lolng (hm lng nc cao hn) n dung dch c hn (c hm lng nc thp hn). y chnh l qu trnh thm thu.

4.1.2 p sut thm thu

* p sut thm thu ca dung dch

Nm 1877, nh Bc hc c Pfeffer l ch to ra mt dng c o p sut thm thu gi l thm thu k (Hnh 1.6a). Thm thu k gm mt ti c to t mt mng bn thm (feroxyanua ng). Bn trong ti cha dung dch ng. Khi nhng ti thm thu ny vo trong mt cc nc th theo qui lut thm thu, nc s i t ngoi vo ti nhanh hn nc i t trong ra ngoi lm ct nc trong ng thu tinh dng cao. Nc cng i vo th p lc thu tnh trong ti cng tng dn v nc trong ti i ra cung tng dn. n mt lc no th trng thi cn bng ng c thit lp (tc

nc i ra bng tc nc i vo). p sut thu tnh ng vi trng thi cn bng ng gi l p sut thm thu ca dung dch trong thm thu k. Chiu cao ca ct nc dng ln trong ng thu tinh t l thun vi nng dung dch ng hay cc cht tan cha trong ti.

Mi mt dung dch bt k u tn ti mt p sut thm thu tim tng ca mnh (mc d khng phi i qua mng bn thm).

p sut thm thu ca dung dch c tnh theo cng thc ca Vant Hoff:

= RTCi

Trong : l p sut thm thu ca dung dch (atm)

T l nhit tuyt i (to + 273)

C l nng dung dch (Mol/lit)

R l hng s kh = 0,082

i l mc in ly v i = 1 + (n - 1)

l h s in ly

n l s ion hnh thnh khi phn t phn ly, v d NaCl c n = 2,

cn dung dch khng in ly nh sacaroza th n = 1.

* p sut thm thu ca t bo

T bo c khng bo th xut hin dch bo. Do p sut thm thu ca t bo chnh l p sut thm thu ca dch bo. V nng dch bo thay i nhiu theo loi t bo v hot ng trao i cht nn p sut thm thu ca t bo cng thay i rt nhiu.

4.1.3. T bo thc vt l mt h thng thm thu sinh hc

* H thng thm thu

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....31

Nu c hai dung dch hay mt dung dch v nc ngn cch vi nhau bng mt mng bn thm th to nn mt h thng thm thu. H thng thm thu ngoi c th l h thng thm thu vt l. Chng hn nh dng c o p sut thm thu gi l thm thu k l mt h thng thm thu vt l.

* T bo thc vt l mt h thng thm thu sinh hc

T bo trng thnh c mt khng bo trung tm v trong dch bo ca n c p sut thm thu nht nh. Bao bc xung quanh khng bo l mt lp nguyn sinh cht mng nh mt mng bn thm. Nu ta so snh t bo vi thm thu k th ta thy (Hnh 1.6): Dch bo tng ng vi dung dch trong thm thu k; Lp nguyn sinh cht tng ng vi mng bn thm bao bc dung dch ca thm thu k v dung dich ngoi thm thu k (nc) tng ng vi dung dch bn ngoi t bo (nu ta nhng t bo vo nc hay t bo r ngm trong dung dch t). Do , c th ni rng t bo thc vt cng l mt h thm thu.

Tuy nhin, t bo thc vt c c tnh ca mt c th sng nn n c xem l mt h thng thm thu sinh hc:

+ Dch bo l sn phm ca qu trnh trao i cht nn nng ca n thay i ty theo cc loi c quan v thc vt khc nhau, ty thuc vo giai on sinh trng v cng trao i cht. T bo cng trng thnh th cng tch ly cc sn phm trong dch bo nhiu hn... Trong khi , dung dch trong thm thu k l dung dch xc nh.

Hnh 1. 8. So snh t bo thc vt vi thm thu k

A. Thm thu k B. T bo thc vt

+ Lp cht nguyn sinh thc hin cc hot ng sng ca t bo nn khng nhng ch cho nc i qua m cn cho cc cht tan cn thit i qua. N c tnh thm chn lc,

Nc 100%

Dung dch ng

Mng bn thm

Khng gian thm thu

Dch bo

A B

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....32

hay cn gi l mng bn thm sng. Nu l mng bn thm n thun nh thm thu k th t bo s cht.

+ H thng thm thu trong t bo l mt h thng thm thu kn hon ton, khng m nh h thng thm thu vt l. Nc qua cht nguyn sinh vo khng bo s lm cho th tch t bo tng ln gy p lc trn thnh t bo, cn tr nc i vo t bo. Do quy lut thm thu xy ra trong t bo phc tp hn nhiu so vi h thng vt l.

4.1.4. Hot ng thm thu ca t bo thc vt

Khi t bo thc vt nm trong mt dung dch th c ba trng hp xy ra:

* Nng dich bo bng nng dung dich ngoi t bo (dung dich ng trng):

Hin tng thm thu xy ra theo hng cn bng ng, tc l s phn t nc xm nhp vo t bo cn bng vi s phn t nc i ra khi t bo. V hnh thi th t bo

khng c thay i g. p sut thm thu ca t bo bng p sut thm thu ca dung dch

* Nng dch bo nh hn nng dung dch (dung dch u trng):

Hnh 1.9. Hin tng co nguyn sinh

Theo qui lut thm thu, nc s i t khng bo ra ngoi dung dch. Kt qu l th tch ca khng bo co li v ko theo cht nguyn sinh cng co theo, nhng thnh t bo c tnh n hi cao nn n khng co theo c m dn dn cht nguyn sinh tch ra khi thnh t bo co trn li gi l hin tng co nguyn sinh (Hnh 1.8). Lc u do mt nc cn t nn cht nguyn sinh ch tch ra khi thnh t bo cc gc gi l co

Thnh t bo

Nguyn sinh cht

b. T bo co nguyn sinh hon ton (li)

a. Bt u co nguyn sinh (lm)

Dung dch m c bn ngoi

c. T bo trng nc

Nguyn sinh cht p ln thnh t bo to nn sc trng P

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....33

nguyn sinh lm, nhng v sau, khi mt nc nhiu th cht nguyn sinh tch hon ton khi thnh t bo gi l co nguyn sinh li.

Nu ta a t bo l co nguyn sinh vo dung dch lolng hn hay nc th nc li xm nhp vo khng bo v t bo dn quay li trng thi ban u gi l phn co nguyn sinh.

ngha ca co nguyn sinh

- Ch c t bo sng mi c kh nng co nguyn sinh. V vy mun xc nh t bo cn sng hay l cht ta ch vic gy co nguyn sinh. iu ny rt c ngha trong vic xc nh kh nng chng chu ca cy vi cc iu kin bt thun ca mi trng. V d, mun xc nh tnh chng chu nng ca cc ging cy trng no , ta ly l ca chng v ngm trong nc nng c nhit khc nhau (40-50oC) trong thi gian nht nh. Sau , ta gy co nguyn sinh v xc nh t l t bo sng (t bo c kh nng co nguyn sinh). Ging no c t l t bo sng cao th c kh nng chng nng tt hn. Cng vi cng vic tng t nh vy, ta c th xc nh kh nng chng chu mn, hn, c t nm bnh...

- S dng co nguyn sinh xc nh nng dch bo v p sut thm thu ca cy. Nng ca dung dch bt u gy co nguyn sinh s tng ng vi nng ca dch bo. Khi bit nng dch bo ta c th tnh c p sut thm thu ca m.

- Thi gian chuyn tip t co nguyn sinh lm sang co nguyn sinh li nhanh hay chm l do nht cht nguyn sinh quyt nh. Do vy, ta c th s dung co nguyn sinh xc nh nht tng i ca t bo (thi gian t co nguyn sinh lm sang co nguyn sinh li). Thi gian t co nguyn sinh lm sang li cng lu th nht cht nguyn sinh cng cao.

nht cht nguyn sinh cng l mt ch tiu nh gi mc chng chu ca cy i vi cc iu kin ngoi cnh bt thun.

* Nng dch bo ln hn nng ca dung dch bn ngoi (dung dch

nhc trng)

- Phng trnh thm thu nc ca t bo thc vt

Theo qui lut thm thu th di tc ng ca p sut thm thu ca dch bo (), nc t ngoi i vo khng bo qua cht nguyn sinh. Kt qu l lm cho th tch khng bo tng ln, p ln cht nguyn sinh v thnh t bo mt lc chng li dng nc i vo t bo. Lc gi l sc trng ca t bo (k hiu l P). Nc cng vo t bo th th tch t bo cng tng v P cng tng ln. P cng tng th cng cn tr dng nc vo t bo, tc xm nhp nc cng chm dn. n mt thi im no khi p sut thm thu pht trin ht thnh sc trng P th nc khng th xm nhp vo t bo c na, t bo trng thi cn bng ng. l trng thi no nc hay blo ha nc ca t bo v ta c = P. Tuy nhin, thc vt trn cn lun c qu trnh bay v thot hi nc t cc b phn ca cy, c bit l b l nn t bo thc vt thng thiu blo ha

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....34

100 110 120 130 140 150

20

15

10

5

0

P

S

pi

Th tch tng i ca t bo (%) Thiu bo ho nc

(atm) S, pi, P

Bo ho nc:

S = 0, pi = P

Ho hon ton: P = 0, S = pi

nc t nhiu. Do vy ta c > P tc - P > 0. Hiu s gia p sut thm thu v sc trng ca t bo quyt nh s xm nhp ca nc vo t bo v ngi ta gi l sc ht nc ca t bo. Sc ht nc ca t bo c k hiu l S (atm).

Ta c phng trnh thm thu nc vo t bo thc vt nh sau:

S = - P

- Cc trng thi nc ca t bo (Hnh 1.9)

C bn trng thi khc nhau ca t bo nh sau:

h T bo blo ha hoc no nc hon ton v lc ta c = P. T bo trng thi rn. Tuy nhin cy blo ha nc hon ton ch xy ra khi gp ma ko di v m khng kh blo ha lm cy khng thot nc c.

h T bo ho hon ton xy ra khi dung dch bn ngoi m c nn t bo mt nhiu nc v t bo khng cn sc trng nc na, thnh t bo xp xung. Lc ny t bo c sc ht nc rt ln v bng p sut thm thu, tc S = v P = 0. y l trng hp rt hln hu, v d khi gp mn, nng dung dch bn ngoi cy qu cao.

h T bo thiu blo ha nc, tc l S > 0 v > P. y l trng thi quan trng nht v thng xuyn xy ra trong cy. Do thiu blo ha nn t bo ht nc t blo ha v l ng lc a nc vo t bo v vo cy. Ty theo mc thiu blo ha nc ca t bo m cy ht nc nhiu hay t.

Hnh 1.10. Mi quan h gia S, v P khi t bo cc trng thi nc khc nhau

h Khi s mt nc ca t bo v ca cy khng phi bng con ng thm thu m bng con ng bay hi nc, th thnh t bo co li v sc trng P hng vo

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....35

trong, ngc chiu vi sc trng trong trng hp thm thu (-P) nn ta c phng trnh thm thu nc trong trng hp ny l: S = - (-P) = + P . Trong trng hp ny, t bo c sc ht nc cc ln nn nu t bo tip xc vi nc, n s ht nc qu mnh c th gy nn thng tn t bo, t bo c th b v v cy cht. Trng hp ny thng xy ra khi s thot hi nc qu mnh, cy mt cn bng nc thng xuyn, lng nc bay hi nhiu hn lng nc ht vo, cy s ho r thng xuyn. V d khi gp nhit khng kh qu cao, m khng kh qu thp v gp hn t th hin tng ho lu di xy ra. Gp trng hp ny ta nn cung cp nc t t trnh lm thng tn cho t bo...

Mi quan h gia cc i lng trong phng trnh thm thu ca t bo c biu th bng s hnh 1.10.

4.1.5. Th nc v phng trnh th nc ca t bo thc vt

* Th nc v cc i lng ca n

- Th nc: Khi xem xt v mt nhit ng hc cu qu trnh xm nhp nc vo t bo thc vt, ngi ta a ra khi nhm v th nc. Mc nng lng ca mt phn t vt cht no c biu th bng tc khuch tn ca n trong dung dch gi l th ho hc ca n. Th ho hc ca mt cht trong iu kin khng i v p sut v nhit ph thuc vo s mol c mt ca cht . Th ho hc ca nc c gi l th nc v c biu th bng k hiu w. Th ho hc ca phn t nc biu th hot tnh ca phn t nc tc l nng lng t do di chuyn cc phn t nc t v tr ny n v tr khc.

Th nc ca dung dch no chnh l s chnh lch gia th ho hc ca nc ti thi im bt k no ca h thng (w) v th ho hc ca nc nguyn cht trong iu kin tiu chun (wo):

w = w - wo = R.T.ln e/eo

Trong : R: hng s kh; T: nhit tuyt i; e: p sut hi nc ca dung dch To v eo: p sut hi nc ca nc nguyn cht cng To.

Vi nc nguyn cht th e = eo nn e/eo = 1 m ln1 = 0, ta c R.T.ln e/eo = 0.

Do vy, w ca nc nguyn cht bng 0.

Vi dung dch th eo> e v e/eo < 1 (s thp phn) nn R.T.ln e/eo < 0. Do vy, th nc ca dung dch lun lun l mt s m. Hay ni cch khc cc phn t nc trong dung dch b cc phn t cht tan khc hp dn, cn tr vn ng lm gim hot tnh ca chng. Dung dch c nng cng cao th th nc cng gim (cng m). Trong qu trnh thm thu th cc phn t nc s c vn chuyn t ni c th nc cao n ni c th nc thp hn (m hn).

n v o th nc cng tng t nh sc ht nc tc atmotpher hay bar (1bar=0,987atm).

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....36

- Cc i lng khc ca th nc

Th thm thu ()c quan h trc tip vi cht tan trong dung dch v ph thuc vo nng cht tan. Th thm thu cng c tr s m nh th nc. Nng cht tan cng cao th th thm thu cng thp (cng m). N l i lng tng ng vi p sut thm thu nhng c gi tr m.

Th trng (p)biu th sc trng ca t bo khi nc xm nhp vo t bo v c gi tr tng ng vi sc trng (P) ca t bo . Th trng lun lun c gia tri dng.

* Phng trnh th nc ca t bo thc vt

Nh trn l trnh by, phng trnh thm thu nc vo t bo l S = - P.

Xt v mt nhit ng hc th qu trnh trao i nc ca t bo c biu th di dng th nng. Khi xem xt cc i lng tng ng th sc ht nc tng ng vi th nc (S = -w), p sut thm thu tng ng vi th thm thu ( = - ) v sc

trng tng ng vi th trng (P = p). T phng trnh thm thu ta suy ra phng trnh th nc nh sau:

-w = - p hay w = + p

Mi quan h gia th nc v cc i lng ca th nc c biu din hnh 1.11

Hnh 1.11. S minh ho th nc v cc i lng ca th nc trong t bo

Trong cy, th nc thay i theo tng loi t bo khc nhau. Theo quy lut chung th cng ln cao, cc c quan c th nc cng thp (cng m). Do vy, w ca r > w

3

2

1

-3

0

-2

-1

0,9 1,0 0,8

Th tch tng i ca t bo

Ho hon ton

Bt u co nguyn sinh

Trng hon ton

Th n

c (a

tm)

p

w = pi + p

pi

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....37

ca thn > w ca l. Chnh v vy m nc i lin tc t r ln l v thot ra ngoi khng kh (khng kh c th nc rt thp). S chnh lch th nc ca cc c quan trong cy theo hng gim dn t gc n ngn l ng lc cho dng nc i lin tc trong cy. Phng trnh th nc c minh ho bng hnh 1.9.

4.2. S trao i nc ca t bo thc vt theo phng thc ht trng

* Khi nim ht trng

Ht trng l s ht nc ca cc cao phn t hoc cc mao qun cha blo ha nc cho n khi t trng thi bo ha.

Cht nguyn sinh c cu to bng cc cao phn t a nc nh protein, axit nucleic, nucleoprotein, photpholipit... Khi chng cha bo ha nc th chng ly nc vo cho t trng thi blo ha. Chnh nh vy m to nn mt ng lc thng xuyn a nc vo t bo. Trong thnh vch t bo, tn ti mt h thng mao qun v chng ht nc bng lc mao qun trng ln.

* S ht trng thng km theo hai hiu ng: hiu ng keo v hiu ng mao qun.

- Hiu ng keo: Cc cao phn t trong t bo thng dng keo a nc. V vy m khi thiu bo ho nc th cc keo ht nc vo gy nn s trng ca cc th keo.

Trong cht nguyn sinh, keo a nc ch yu l keo protein v axit nucleic. Cn trong thnh t bo th hiu ng keo gy ra bi cc keo protopectin, hemixeluloza, pectin cu to nn thnh t bo.

- Hiu ng mao qun: Thnh t bo c cu to bng cc si xeluloza an xen nhau to nn mt mng li cc mao qun chng cht. Nh c lc mao qun m chng ht nc vo thnh t bo lm thnh t bo trng nc.

Nh vy, cht nguyn sinh ch c hiu ng keo m thi, cn thnh t bo tn ti c hai hiu ng keo v mao qun. Tt nhin, khng bo khng c kh nng ht trng m ch ht nc thm thu v khng bo khng tn ti cc th trng.

* Bn cht ca s ht trng

S ht trng v thm thu c bn cht nh nhau. Ta gi p sut ca th trng l J, tng t nh p sut thm thu .Phng trnh ht nc ca th trng l: S = J - P

(tng t trong trng hp thm thu: S = - P). ng vi th thm thu, ta c th trng ca th trng j ( phn bit vi th trng p do sc trng P gy ra ca t bo, ta gi j l th c cht hay th khun do th trng gy ra).

S ht trng ca keo nguyn sinh cht cng chu tc ng ca lc trng ca t bo nh trng hp thm thu. Do vy, ta c phng trnh th nc trong trng hp ht trng ca cht nguyn sinh l: w = j + p.

Tuy nhin, nc i vo t bo c l nh c hai phng thc thm thu v ht trng. Ta c phng trnh th nc tng hp ca t bo l:

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....38

- Vi cc t bo cha xut hin khng bo nh t bo m phn sinh th s xm nhp nc vo t bo ch nh ht trng. Phng trnh th nc ca t bo cha c khng bo l:

w = j + p. - Vi t bo trng thnh l xut hin khng bo nh t bo ca cc m chuyn

ho th chng va c c ht trng v thm thu. Phng trnh th nc ca cc t bo ny l:

w = + j + p. * ngha ca ht trng

- S ht trng ca keo v mao qun l mt ng lc thng xuyn a nc vo t bo. Khi keo v mao qun thiu blo ha nc th chng ht nc ti blo ha v khi cho nc i th li thiu blo ha. Hin tng blo ha v thiu blo ha nc l hot ng thng xuyn xy ra trong t bo...

- Vi cc t bo cha xut hin khng bo nh cc t bo ca m phn sinh v nm cnh m phn sinh th ht trng l phng thc ht nc c trng v quan trng nht nu khng ni l duy nht v cc t bo ny cha xut hin khng bo nn khng c kh nng ht nc thm thu. Ngoi ra, cc bo quan trong t bo cng ly nc bng c ch ht trng ca cc keo.

C th ni rng, vi cc t bo trng thnh c khng bo th chng ht nc theo hai phng thc: thm thu v ht trng, trong , phng thc thm thu l ch yu; Cn vi cc t bo cha c khng bo th ht trng l phng thc ht nc duy nht.

5.1. S xm nhp cht tan th ng vo t bo thc vt

* c trng ca c ch xm nhp cht tan th ng l:

- Qu trnh xm nhp cht khong khng cn cung cp nng lng, khng lin quan n trao i cht v t din ra.

- Ph thuc vo s chnh lch nng ion trong v ngoi t bo (gradient nng ). Nng bn ngoi ln hn bn trong t bo.

- Ch vn chuyn cc ion c tnh thm i vi mng, tc phi c tnh tan trong mng lipit v h thng membran cu to ch yu bng phospholipit.

C rt nhiu quan im gii thch s xm nhp ca cht tan vo t bo thc vt theo c ch b ng.

* S khuch tn cht tan vo trong t bo

Khuch tn l qu trnh vn ng ca cc phn t vt cht t ni c nng cao n ni c nng thp cho n khi cn bng nng trong h thng.

Tc xm nhp ca cht tan (V) vo t bo c xc nh theo cng thc sau:

V = Const. K. M-1/2 (Co Ci )

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....39

Trong : K : h s biu th tnh tan ca ion trong lipit

M: phn t lng ca cht tan khuch tn

Co v Ci l nng ca cht khuch tn bn ngoi v bn trong t bo.

Const. : hng s khuch tn

Nh vy th tc xm nhp cht tan vo t bo ph thuc vo 3 iu kin:

- Tnh ha tan ca ion trong lipit (K) cng cao th xm nhp cng nhanh.

- Phn t lng ca cht tan (M) cng nh th cng d xm nhp

- S chnh lch nng cht khuch tn (gradient nng ) cng ln th ion xm nhp cng nhanh.

y l cc iu kin cn thit cho mt ion c th xm nhp vo t bo bng con ng khuch tn. Nu thiu mt trong cc iu kin trn th s khuch tn s khng din ra. Tuy nhin, cng thc ny ch ng khi M>70 v ng knh ion khuch tn >0,5nm. Cc ion nh hn c th khuch tn qua cc l xuyn mng nhanh hn m khng cn tan trong lipit ca mng, v trn mng c v s l xuyn mng c ng knh l khong 0,5 - 0,8 nm.

Thc t th khi c cc iu kin cho s khuch tn th tc khuch tn t nhin chm hn rt nhiu ln so vi khuch tn ca cht tan trong t bo. Nh vy, trong t bo tn ti mt c ch b tr no cho s khuch tn lm nhanh tc khuch tn. chnh l s khuch tn c xc tc.

* S khuch tn c xc tc

Tn ti mt s c ch b tr c th lm cho tc khuch tn tng nhanh ln rt nhiu gi l khuch tn c xc tc. y cng l c ch xm nhp cht tan th ng v khng tiu tn nng lng ca qu trnh trao i cht.

C th c mt s c ch sau:

- Ionophor: y l cc cht hu c trn mng m chng c th d dng lin kt c chn lc vi ion v a ion qua mng m khng cn nng lng. Ngi ta l nghin cu nhiu cht ng vai tr l cc ionophor v bn cht ha hc v c ch hot ng mang ion ca chng. Cc cht ny thng c chit xut t cc vi sinh vt nh valinomycin t streptomyces, cht nonactin t actinomyces... Khi cc cht ny tc ng ln mng th lm cho tnh thm ca mng tng ln v s xm nhp ca ion qua mng rt d dng. S lin kt gia ionophor vi cc ion mang tnh c hiu cao...

- Knh ion: Trn mng sinh cht v mng khng bo c rt nhiu l xuyn mng c ng knh ln hn kch thc ca ion, to nn cc knh cho cc ion d dng xuyn qua. Tuy nhin cc knh ion cng c tnh c hiu. Mi ion c knh hot ng ring v cng c th chng ng v m ty theo iu kin c th.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....40

- Th xuyn mng: Trong qu trnh vn chuyn ca cc ion i qua mng th dn

n s chnh lch nng ion hai pha ca mng v to nn mt th hiu xuyn mng. Hiu in th c c th t 50 - 200 mV v thng m pha bn trong t bo. Nh th xuyn mng ny m cc cation c th i theo chiu in trng t ngoi vo trong t bo, cn cc anion th c th lin kt vi ion H+ chuyn thnh dng cation vn chuyn vo trong.

5.2. S xm nhp cht khong ch ng

*Trong nhiu trng hp s xm nhp cc cht khong vo cy vn tin hnh c mc d nng ca ion bn trong t bo cao hn bn ngoi t bo (ngc vi gradient nng ). V d nh khi phn tch hm lng cc ion khong trong t bo v ngoi t bo ca 2 loi to Nitella v Valonia ta thy s tch ly cc ion khong trong c th l qu trnh chn lc m khng hon ton ph thuc vo gradient nng trong v ngoi t bo (Hnh 1.11).

Nh vy th quan im khuch tn v khuch tn c xc tc khng th gii thch c trng hp tch ly ion khc nhau trn. Hn na s tch ly ny b c ch khi km hlm hot ng trao i cht ca cy nh gim hm lng oxi trong mi trng hay s dng cht km hlm h hp.

C th ni rng s ht v tch ly ion khong rt cn nng lng ca qu trnh trao i cht, l mt qu trnh chn lc v ch ng. l s vn chuyn tch cc.

Nitella Valonia

Dch t bo Dch t bo

Nc ngt Nc bin

Na K Ca Mg Cl ion Na K Ca Mg Cl ion

Hnh 1.11. Nng ca mt s ion trong dch bo v ngoi dung dch

nui to nc ngt Nitella v to bin Valonia

S vn chuyn ch ng (Active transport) khc vi s vn chuyn th ng (Passive transport) nhng c im sau:

- C s dng nng lng ca qu trnh trao i cht.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....41

- C th vn chuyn ngc chiu gradient nng (t nng thp bn ngoi n nng cao trong t bo).

- C th xm nhp cc ion khong khng thm hay thm t vi mng lipit.

- C tnh cht c hiu cho tng loi t bo v tng cht.

C rt nhiu quan im a ra gii thch s vn chuyn ch ng, nhng quan nim v cht mang c tha nhn rng rli nht.

* Quan nim cht mang

Theo quan im ny th trn mng sinh cht v mng khng bo tn ti cc cht c hiu chuyn lm nhim v mang cc ion i qua mng t ngoi vo trong gi l cc cht mang. Chng c nhim v t hp vi cc ion pha ngoi ca mng v gii phng ion pha trong mng.

iu quan trng l tha nhn mt phc hp trung gian cht mang-ion nh l mt phng tin thun li cho vic vn chuyn ion i qua mng. phc hp ny c hnh thnh th trc tin cht mang phi c hot ha bng nnglng ca ATP v enzym phosphokinase. V vy, y l mt qu trnh vn chuyn tch cc ion lin quan n qu trnh trao i cht ca t bo. Khi cht mang c hot ha th n d dng kt hp vi ion v a ion vo bn trong. Nh enzym photphatase m ion c tch khi phc h gii phng vo bn trong mng.

Qu trnh ny c th chia lm ba giai on:

1) Hot ha cht mang

Kinase

Cht mang Cht mang*

ATP ADP

2) To phc h ion-cht mang

ion (+ hay -)

Cht mang* Phc hp cht mang* - ion

3) Gii phng ion

Photphatase

Cht mang * - ion Cht mang + ion c gii phng

( * Y c hot ha)

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....42

Trong ba giai on th ch c giai on u tin l cn nng lng hot ha cht mang m thi. phng thc kt hp gia cht mang v ion cng tng t nh s kt hp gia enzym v c cht khi tin hnh xc tc phn ng ha hc. Hai phng thc hot ng ny cng ging nhau hai c im:

- Hiu ng bko ha

Khi ta tng nng ion khong no trong mi trng th tc ca s hp thu ion khong ca m tng ln ri s t c blo ha. Sau mt thi gian no th m mi tip tc ht ion . iu c th gii thch l cc cht mang l b chim ch. Hiu ng blo ha ca cc phn ng enzym cng tng t nh vy.

- Tnh c hiu

Cc ion khc nhau s c hp thu v tch ly vi lng khc nhau trong t bo v trong m. S d nh vy l v cc cht mang c tnh c hiu cao. Mi cht mang ch c nhim v mang mt loi ion qua mng, hoc c th mt vi ion c c tnh ha hc rt ging nhau. Tnh c hiu ny rt cht ch vi cc ion khc hn nhau, nhng khng cht ch vi cc ion c tnh cht tng t nhau... Tnh cht c hiu ny cng hon ton ging vi cc phn ng enzym.

Nh vy, s xm nhp cht khong vo t bo c thc hin bi hai c ch: th ng v ch ng. Ty theo trng hp c th, iu kin c th m c ch no l u th. Nhn chung th c hai c ch ny u din ra song song trong cy. Nu mt trong hai phng thc b c ch th cng c ngha l s ht khong b c ch. V d khi cy b ym kh (thiu O2 cho h hp ca r) th s ht khong cng b ngng tr.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....43

Tm tt chng 1

T bo l mt n v cu trc v chc nng ca c th thc vt mang y cc

c tnh v chc nng ca mt h thng sng. Chng gm ba hp phn l thnh t bo, khng bo v cht nguyn sinh. Cht nguyn sinh c t chc cu trc rt phc tp gm

h thng mng, cc bo quan v khun t bo cht, m nhim ton b cc hot ng

sinh l ca t bo v ton cy.

Thnh phn ha hc cu to nn cht nguyn sinh quan trng nht l protein v nc.

Protein rt d b bin tnh do cc lin kt yu n nh cu trc ca phn t protein d b ph v di tc ng ca iu kin bt thun ca mi trng v cng gy

nn s bin tnh ca cht nguyn sinh. Protein c tnh lng tnh do cn cc gc -

COOH v -NH2 t do v chng c im ng in c trng cho tng protein v gy nn im ng in ca cht nguyn sinh.

Phn t nc c tnh lng cc nn trong cht nguyn sinh chng gy nn hin

tng thy ha cc keo mang in to nn tnh n nh cho h thng keo nguyn sinh cht. C hai dng nc trong cht nguyn sinh: nc t do linh ng quyt nh hot ng sinh l ca cy v nc lin kt quyt nh kh nng chng chu ca cy.

Cht nguyn sinh l mt cht na lng. c tnh lng th hin kh nng vn ng, sc cng b mt v nht thp. c tnh ca vt th rn th hin tnh n hi

v nht cu trc ca cht nguyn sinh. Cc c tnh vt l gn lin vi cc hot ng sng ca cy v kh nng chng chu ca cy.

Cht nguyn sinh l mt dung dich keo a nc. Ty theo trng thi tui v mc hot ng sng ca t bo m cht nguyn sinh c th tn ti dng sol, dng

coaxecva hay dng gel. Cctrng thi ca keo nguyn sinh cht ny c th bin i linh ng cho nhau to nn tnh a dng thch nghi ca cy.

T bo thc vt trao i nc nh hai phng thc: Thm thu v ht trng. Vi cc t bo cha xut hin khng bo (m phn sinh) th s ht nc vo t bo nh

kh nng trng nc ca cc cao phn t cha bo ha nc. Vi cc t bo trng thnh c khng bo th nc xm nhp vo t bo nh c hai phng thc: Ht trng

ca cc cao phn t, ht trng ca cc mao qun trong thnh vch t bo v ht nc

bng con ng thm thu, trong phng thc thm thu l ch yu. Hu ht cc m

thc vt u c khng bo (tr m phn sinh) nn phng thc ht nc thm thu i vi thc vt l quan trng nht...

S xm nhp cht tan vo t bo l mt hot ng sinh l quan trng v phc tp gn lin vi cc hot ng trao i cht v sinh l ca cy. Cht tan c th xam nhp

th ng hay ch ng vo t bo. S xm nhp th ng khng cn cung cp nng lng v t din ra c th bng c ch khuch tn. khuch tn c xc tc hay nh th hiu xuyn mng. S xm nhp ch ng lun lun cn nng lng ca h hp cung cp

v c th thc hin theo c ch cht mang.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....44

Hiu bit cc hot ng sinh l ca t bo c ngha quan trng trong vic iu

chnh cy trng mc t bo. C th chn to ging cy trng c kh nng chng

chu vi ngoi cnh bt thun da trn cc ch tiu v sinh l t bo nh tnh bn vng

ca h thng mng, h thng keo nguyn sinh cht, nht v tnh n hi cao, hm

lng nc lin kt ln, kh nng iu chnh thm thu cao... C th s dng t bo vo

vic nui cy in vitro nhn nhanh ging cy trng hoc c th s dng t bo trn

cho mc ch lai ging v tnh bng dung hp protoplast to con lai soma...

Cu hi n tp

1. Hly v s cu trc ca t bo thc vt v:

- Cu trc v chc nng ca thnh t bo thc vt.

- Khng bo v chc nng ca khng bo i vi hot ng sinh l ca chng.

- Cu trc v chc nng ca h thng mng sinh hc.

- Cc bo quan trong cht nguyn sinh v chc nng ca chng.

2. S bin tnh ca cht nguyn sinh: C s ca s bin tnh, iu kin bin tnh v ngha ca s bin tnh.

3. Tnh lng tnh v im ng in ca protein v ca cht nguyn sinh. ngha ca n i vi hot ng sng ca t bo v ca cy?

4. S thy ha trong cht nguyn sinh v ngha ca n n cu trc ca cht nguyn sinh? Vai tr sinh l ca nc t do v nc lin kt i vi hot ng sng ca cy?

5. Ti sao c th ni cht nguyn sinh l mt dung dch keo? c tnh ca keo nguyn sinh cht? c trng ca cc trng thi ha keo ca cht nguyn sinh v ngha ca cc trng thi ny i vi i sng ca cy?

6. Hly trnh by s xm nhp nc ca t bo bng phng thc ht trng v nu ngha ca n trong s trao i nc ca t bo?

7. S trao i nc ca t bo theo phng thc thm thu:

- Khi nim v thm thu v p sut thm thu

- T bo thc vt l mt h thng thm thu sinh hc

- Phng trnh thm thu nc vo t bo thc vt v minh ha bng s .

- Phng trnh th nc v s minh ho.

8. Hin tng co nguyn sinh v ngha ca n?

9. Hly gii thch s xm nhp cht tan vo t bo theo c ch th ng.

10. Hly trnh by s xm nhp cht tan vo t bo nh cc cht mang.

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....45

Cu hi trc nghim 1. Thnh phn ha hc quan trng nht cu to nn thnh t bo l: A. Pectin B. Protopectin C. Hemixelulose D. Xelulose 2. bn vng c hc ca thnh t bo c quyt nh bi thnh phn no? A. Pectin B. Protopectin C. Hemixelulose D. Xelulose 3. Tnh mm do ca thnh t bo c quyt nh bi thnh phn cu to no? A. Protopectin + Xelulose B. Hemixelulose + Protopectin C. Xelulose + Hemixelulose D. Xelulose + Pectin 4. Trong cc chc nng ca thnh t bo thc vt, chc nng no l khng c ngha? A. Cho nc v cht tan i qua C. Chng li s ph v t bo do ht nc thm thu

B. Bao bc v bo v D. Cho t bo c kh nng sinh trng

5. Nhn, lc lp v ty th c gi l cc yu t cu trc v: A. C kch thc hin vi B. C ADN v ARN ring C. C c riboxom D. C kh nng di truyn c lp 6. Cc c quan siu hin vi c c trng chung l: A. Kch thc siu hin vi B. C mng n bao bc C. Thc hin chc nng sinh l c trng D. Quan im khc 7. Thnh phn ha hc cu trc nn mng c s l: A. Gluxit + Protein B. Lipit + Protein C. ARN + Protein D. Photpholipit + Protein 8. Mng no thuc loi mng trong? A. Mng lc lp C. Mng nhn

B. Mng thilacoit D. Mng li ni cht

9. Chc nng no khng thuc h thng mng sinh hoc? A. Kim tra tnh thm C. Kim tra tng hp protein

B. Kim tra tng hp ATP D. Kim tra chuyn vn in t.

10. ngha quan trng nht ca khng bo l: A. Cha cht bi tit B. To nn dch bo C. Cha cc sn phm trao i cht D. To nn p sut thm thu 11. Khng bo c hnh thnh khi: A. T bo ang phn chia B. T bo ang dln C. T bo ang phn ha D. T bo ang ha gi 12. Nguyn nhn chnh gy bin tnh protein: A. Tch in B. Mt mng thy ha C. Ph v lin kt yu D. Kch thc phn t ln 13. Protein trong mi trng pH khc nhau th: A. Mi trng axit th tch in + , mi trng baz th tch in - B. _____________________ _ ______________________ + C. _____________________ _ ______________________ _ D. _____________________ + ______________________ + 14. Dng lipit no l quan trng nht trong t bo thc vt:

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....46

A. Du d tr trong cht nguyn sinh B. Photpholipit trong mng t bo C. Axit bo trong cht nguyn sinh D. Sp + suberin trong thnh t bo 15. c tnh quan trng nht ca phn t nc quyt nh cu trc cht nguyn sinh l: A. Trung ha in B. Phn cc v in C. Bay hi mi nhit D. Ha tan tt cc cht 16. Vai tr quan trng ca nc lin kt i vi cy l: A. Tham gia phn ng ho sinh B. iu ha nhit trong cy C. Quyt nh tnh chng chu D. Quan im khc 17. Vai tr quan trng nht ca nc t do l: A. Cu to nn cht nguyn sinh B. To nn mng thy ha ca keo C. Tham gia hot ng sinh l D. Tham gia vo kh nngchng chu 18. nht cht nguyn sinh cao nht lc no? A. Giai on non B. Ra hoa C. Trng thnh D. Gi chn 19. Ma no c nht ca cy cao nht (hay thp nht)? A. Xun B. H C. Thu D. ng 20. Ion ca nguyn t no lm gim (hat tng) nht cht nguyn sinh nhiu nht? A. Ca B. Na C. Mg D. Al 21. Trng thi keo Sol (hay Coaxecva, Gel) tng ng vi giai on no ca cy: A. Non B. Trng thnh C. Gi D. ang ng ngh 22. T bo thc vt l mt h thng thm thu sinh hc v: A. Cht nguyn sinh nh mt mng bn thm B. Dch bo l sn phm trao i cht C. Mng sinh cht c tnh thm chn lc D. C kin khc 23. Xc nh co nguyn sinh ca t bo khng c ngha trong vic: A. Xc nh t bo sng hay cht B. Xc nh p sut thm thu ca t bo C. Xc nh nng dch bo D. Xc nh mc chng chu ca cy. 24. Trng thi no ca t bo l quan trng v ch yu trong cy? A. S = 0 B. S > 0 C. S = D. S = + P 25. Khi no t bo c sc ht nc ln nht? A. T bo ho hon ton B. T bo thiu blo ha nc C. T bo khng cn sc trng P D. T bo c sc trng m (-P) 26. S ht trng khng xy ra : A. Thnh t bo C. Cc bo quan

B. Khng bo D. Cht nguyn sinh

27. S ht trng xy ra chnh xc : A. M du C. M phn sinh

B. M b D. Nhu m

28. Trong cy, nc i theo hng: A. T bo c S cao n TB c S thp C. TB c w cao n TB c w thp

B. T bo c cao n TB c thp D. C kin khc

29. T bo ca l, hoa, qu ht nc ch yu theo c ch no? A. Ch ng B. B ng C. Ht trng D. Thm thu 0. Phng trnh th nc w = j + p i din cho loi t bo no?

Trng i hc Nng nghip H Ni Gio trnh Sinh l Thc vt ....47

A. T bo non C. M phn sinh

B. Chi ngn D. Chp r

31. Phng trnh th nc w + + j + p i din cho loi t bo no? A. T bo non C. M phn sinh

B. Chi ngn D. L

32. S ht ion khong b ng ph thuc vo: A. Hot ng trao i cht C. Cung cp nng lng

B. Chnh lch nng ion D. Hot ng thm thu

33. S xm nhp cht khong ch ng vo t bo ph thuc vo: A. Gradient nng cht tan C. Trao i cht ca t bo

B. Hot ng thm thu D. Th hiu qua mng

34. Nng lng ATP ca h hp c vai tr g trong vic a ion qua mng? A. Vn chuyn cht mang C. Lin kt cht mang v ion

B. Hot ho cht mang D. Gii phng ion khi cht mang

35. C ch no khng c ngha trong vic a ion qua mng t bo? A. Chui qua l xuyn mng C. Hot ng thm thu ca t bo

B. Lin kt vi cht mang D. Khuch tn qua mng

36. Hai c im quan trng nht phn bit t bo thc vt v ng vt l: A. Thnh t bo + Lc lp

B. Thnh t bo + Khng bo

C. Lc lp + Khng bo

D. Quan im khc

37. Khi t bo ho g th thnh t bo bin i nh th no: A. Ngm cutin B. Ngm suberin C. Ngm sp D. Ngm linhin 38. Khi t bo ho bn (v c khoai ty) th thnh t bo bin i nh th no: A. Ngm cutin B. Ngm suberin C. Ngm sp D. kin khc 39. biu b l, qu..., thnh t bo bin i nh th no: A. Ngm cutin B. Ngm suberin C. Ngm sp D. kin khc 0. Cht no thng khng cha trong dch bo: A. axit hu c B. Mui khong C. Sc t D. Protein 41. T bo m no khng c khng bo: A. M phn sinh B. Nhu m C. M biu b D. M ng ho 42. Chc nng iu chnh thm thu ca khng bo lin quan trc tip n chc nng sinh l no: A. Trao i nc

B. Trao i cht khong

C. Trao i cht D. Trao i nng l-