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Photosynthesis, Physiology and Growth of Orchids

國立嘉義大學 古森本

Maurice S. B. KuNational Chiayi University

Photosynthetic Pathways in Higher Plants

C3: temperate, without CO2 concentrating mechanism

C4: tropical origin, with CO2 concentrating mechanism

CAM: arid, with CO2 concentrating mechanism

Evolution and Diversity of Photosynthetic Mechanism Evolution and Diversity of Photosynthetic Mechanism among Higher Plantsamong Higher Plants

CC33 (~90%)CC33

CC44 (~3%)

CAMCAM (~5%)

HCOHCO33-- pumppump (aquatic, facultative)

CC33--CC44

?

CC33--CAMCAM (aquatic, facultative)

Low CO2 , warm climate

Low CO2 , warm and dry climate

Low CO2, aquatic environments

(aquatic, ancestral)

(terrestrial, facultative or obligate)

(aquatic or terrestrial, obligate)

(terrestrial, obligate)

Decreasing CO2

Evolution of Cyanobacterial, Algal and Terrestrial Plant CO2Concentrating Mechanisms (CCMs)

Modified from Badger et al. 2002. FPB 29:61

Start ofterrestrial CCMs?

3500 3000 2500 2000 1500 1000 600 500 400 300 200 100 0Millions of Years Before Present

ARCHAEAN PROTEROZOIC PHANEROZOIC

BryophytaPteridophytes

GymnospermsAngiosperms

Embryophyta

Cyanobacteria

O2 evolving photosynthesis

Eukaryotic algaeRhodophyta

Chlorophyceae

40

20

10

0

RCO2(past/present)

CARB IIImodel

30

O2 %

Start of cyanobacterialand algal CCMs ?

Unicellularphotosynthesis

Multicellular photosynthesisLand plants

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Rice: C3 plantTemperate or subtropical origin

One photosynthetic cell

Photosynthesis is not saturated by atm. CO2 levels, with high photorespiration

Maize: C4 plantTropical origin

Two photosynthetic cells (Kranz anatomy)

Photosynthesis is saturated at atm. CO2 levels, with low photorespiration

CAM Plants

succulent,

thick leaf,

central H2O

storage cells,

one photosynthetic mesophyll cell type,

fix CO2 in the night, few stomates

Opuntia

Paphiopedilum

Leaf anatomy – C3, C4

C4 - Kranz anatomy

Mesophyll cells Bundle sheath cells

C3 -

Mesophyll cells

Maize: Kranz

Rice: non-Kranz(Surridge, 2002)

MCBSC

MCUndifferentiated

BSC

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C4 plants are more efficient in utilizing low atm CO2

Ku et al. (1999)

Atm. CO2

C4 plants have a higher photosynthetic capacity, especially under high light and warm temperature conditions

Sage (2000)

C4 plants have a higher nitrogen use efficiency

Evans & Caemmerer

(2000)Maize

Sorghum

Rice, Wheat

Higher photosynthetic rates lead to higher growth rates

Sharkey et al. (2000)

Maize

Bean

Castor bean

Sunflower

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C4 and CAM plants have a higher water use efficiency than C3

C3: 550-850 g H2O/g DM

C4: 250-350 g H2O/g DM

CAM: 150-250 g H2O/g DM

C4: high photosynthetic rate, lower stomatal frequencyhigher stomatal resistance to CO2 diffusion.

CAM: thick leaf, lowest stomatal frequency, open in the night whentemperature is low, fix CO2 in the night

C3 pathway:Photorespiration and CO2/O2 ratio

CO2 - Carboxylase

O2 - Oxygenase

Photorespiration – CO2 lossRubisco

The CThe C44 Pathway in NADPPathway in NADP--ME SubtypeME Subtype

NADP-ME

(Buchanan et al. 2000)(Buchanan et al. 2000)

C4: Carboxylation phase

Regeneration phase

C4: Decarboxylation phase

C3: Refixation of CO2

Unstacked (PSI) Stacked (PSII)

Unstacked (PSI)

MC BSC

CO2

CO2

CO2CA

NADP-MDH

PPDK

PEPC

Borszczowia aralocaspica,a C4 Species Without Kranz Anatomy (Freitag and Stichler 2000)

This succulent dicot species from Central Asia has dimorphic chloroplasts located in different positions within one single chlorencyhma cell. Its mechanism for C4photosynthesis remains to be elucidated.

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Intracellular Intracellular compartmentationcompartmentation of the of the

CC44 pathway in pathway in BorszczowiaBorszczowia

(Vozesenskaya, et al., 2001)

Proximal region:Proximal region:

C4-acid decarboxylation enzyme

Rubisco

Distal region:Distal region:

PEP carboxylase

Pyruvate, Pi dikinase

CAM pathwayCAM pathway

(Taiz and Zeigler, 2003)

Rubisco

The Four Phases in a Typical CAM

Night - PEPCDay - Rubisco

Criteria to identify C3, C4, CAM Plants

Leaf anatomy or morphology

Enzyme activity

CO2 gas exchange pattern

CO2 compensation point14CO2 labeling

Discrimination again 13CO2 during photosynthesis

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Good criteria for identification of CAM Plants

Succulence

Night CO2 fixation

Night accumulation in acidity (malate)

Day decrease in acidity (malate)

Discrimination against 13CO2

CO2 Composition in Atmorsphere

98.892% 12CO2

1.108% 13CO2

Trace 14CO2

1.116% 13CO2 in PBD stone (standard)

Heavier isotopes rich in low elevation

Major Factors Related to 13CO2

Diffusion of CO2 in air (C3, C4, CAM) : + 4 per mil (discrimination)

Equailibrium of CO2 to HCO3- (C4, CAM) : - 8 per mil (enrichment)

PEPC (C4, CAM) : + 2 per mil

Rubisco (C3) : + 34 per mil

Expected values for C3, C4 and CAM

C3: (+4) + (+34) + (-7) = +31

C4: (+4) + (+2) + (-7) + (+8) = +7

CAM: between C3 and C4 values depending on the degree of CAM (C4)

Why Rubisco is not a factor for C4 ?

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Identification of C3, C4, CAM plants by 13C content Anatomical, Physiological and Biochemical Characteristics – C3, C4, CAM

Anatomical, Physiological and Biochemical Characteristics – C3, C4, CAM CAM in Aranda

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CAM in Arachnis

Very young leaf is not capable of performing CAM.

Aerial roots, not terrestrial roots, perform CAM.

CAM activity in Encyclia tampensis

CAM in the roots of shootlessorchid Chilochista usneoides

CAM activity in Encyclia tampensis

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The genus Oncidium– C3, weak and strong CAM

If leaf thickness >2.5 mm: CAM (weak and strong)

Strong CAM are mostly epiphates in warm regions

Mutiple origins of CAM in the genusO. carthagenense – strong CAM ( no C3)

O. ampliatum – CAM (C3/CAM)

O. sphacelatum – weak CAM (more C3)

O. ornithorrhyncham – C3

(Cushman and Winter, 2008)

Oncidium goldiana may be a weak CAM

Effect of leaf age on CAM in Phalaenopsis

Mature leaves display a higher night fixation (CAM).

Effect of Drought on CAM in Phalaenopsis

Severe drought lowers its CAM activity.

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執行成果 Effect of contineouslight on CAM in Phalaenopsis at different temperatures

It is an obligate CAM with an optimal temperature at 25

oC.

Effect of Different Day/Night Temperatures on CAM in Phalaenopsis

Optimum temeratureregime: 25/15-20oC.

Lower or higher day/night temperatures lowers CAM activity.

Low temperature favor C3.

Effect of Developmental Stageon CAM in Phalaenopsis

Flowering promotes CAM activity.

Initial Photosynthetic Productsin Bromeheadia finlaysonia and Arundina graminifolia

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Changes in Day/night TitratableAcidity in Some Orchids

Thick-leaved orchids tend to be CAM and vice versa.

Leaf thickness and Leaf thickness and 1313C content on some orchidsC content on some orchids

A good correlation exists between leaf thickness (succulence) and CAM in orchids.

Carbon Fixation in Non-foliar Organs of Some Orchids

In orchids, leaf, stem, flower stalk, pseudobulb and aerial root are all capable of fixing atmospheric CO2 by the same photosynthetic mode.

Carbon Fixation in Non-foliar Organs of Some Orchids

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Effect of day length on CAM activity in Phalaenopsisamabilis

Long day promotes C3photosynthesis.

Short day promotes CAM.

12-14 h of photoperiod appears to be optimum for photosynthesis in Phalaenopsis.

(李哖, 2002)

Effect of light on CAM activity in Phalaenopsisamabilis

400-500 μmol/m2/s (20% of full sunlight) appears to be optimum for photosynthesis in Palaneopsis.

(李哖, 2002)

Effect of Light Intensity on Photosynthesis in Palaenopsisamabilis

Too much light cause photoinhibition.

Phalaenopsis is adapted to low light conditions, presumably due to a low photosynthetic capacity.

Fv/Fm = e transport efficiency via PSII

(李哖, 2002)

Photosynthetic Response of Orchids to Light

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Effect of CO2 enrichment on Photosynthesis and Growth of

Orchids

1. CO2 enrichment suppresses photorespiration, enhances photosynthesisand promotes growth of C3 plants due to increased CO2/O2 ratio. Water use efficient is also increased.

2. Its effect on photosynthesis and growth of C4 plants is less significant, but WSU is also increased.

3. Therefore, C3 orchids will benefit most from CO2 enrichment and weak CAM with C3 photosynthesis will also benefit to some extent. Inflorescence growth and size of Oncidium goldiana were increased by elevated CO2 (1% and 10%).

Effect of virus on CAM activity in Epidendrum elongatum

Phaleanopsisformosum– CAM

(薛聰賢, 1995)

Pleione bulbocodioides – likely a C3

(薛聰賢, 1995)

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Cattleya –

CAM

(薛聰賢, 1995)

Phalaenopsis - CAM

(薛聰賢, 1995)

Dendrobium - CAM

(薛聰賢, 1995)

Vanda and Ascocenda - CAM

(薛聰賢, 1995)

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Oncidium ampliatum – Likely CAM

(薛聰賢, 1995)

Paphiopedium paarishii - CAM

(薛聰賢, 1995)

Cymbidium – C3, CAM

(薛聰賢, 1995)