Plant Anatomy

and PhysiologyJust the Concepts

Environmental

FactorsOn Plant Growth

Obje

ctiv

es

Describe the functions of water

in plant growth; Explain plant responses to a

shortage or excess of water;

Describe efficient use of water in

plant production; Describe the effects of

temperature on plant growth;

Describe plant responses to

temperature extremes;

Explain the qualities of light that

affect plant growth, including

color, intensity, and duration;

and Explain plant responses to light.

Functio

ns o

f

Wate

rWater covers three-fourths

of the earth’s surface and it

is available for plants in

most areas of the world.

It is a major component of

plants and animals.

Humans are about 70 percent

water and cacti are about 90

percent water

Funct

ions

of

Wate

r

Water Plays an important

role in all plant functions

Needed for turgor – gives

a plant rigidity and shape

Provides internal pressure

to help roots push through

soil Aides in cell division and

growth Used in photosynthesis Release oxygen Use hydrogen to

manufacture carbohydrates

Functio

ns o

f

Wate

r Water Plays an important role in

all plant functions

Transport nutrients and energy

through the plant

Movement of materials through plants

is called Translocation

Transpiration is the process of

evaporating water from the

stomates to pull in new water

through the roots

This process helps stabilize the

temperature of the plant

Resp

onse

to

Short

age a

nd E

xcess

Shortage Transpiration continues

even though water is

not absorbed Wilting occurs due to

loss of turgor Color changes

Resp

onse

to

Shorta

ge a

nd E

xcess

Excess

Root hairs die due to

saturated soil (no

oxygen)

Can no longer absorb

water and nutrients

Usi

ng W

ate

r Effi

cientl

y

What determines the

frequency and the amount of irrigation water that we use? The plant is the factor

Type of soil is next Irrigation is artificial

application of water to

a crop

Usin

g W

ate

r

Effi

ciently

Who is the least

efficient Irrigator?

Why

The home owner

Usi

ng W

ate

r Effi

cientl

y What is the goal of efficient water use? There can be several Greater production

Conservation of water

Conservation of soil

Usin

g W

ate

r

Effi

ciently

Greater Production

Got to have water to make a

good crop.

Conservation of Water

Why?

How?

Conservation of Soil

What does this have to do with

using water efficiently?

Tem

pera

ture

Temperature is one factor that contributes

to plant growth Metabolism: all of the

chemical reactions in a

plant Photosynthesis,

respiration Temperature affects the

speed of metabolism

Tem

pera

ture

Most plants show optimum growth

when night temps are 10˚ -15˚ cooler

than day temps

Photosynthesis occurs mostly during the

day

Cool temperatures slow down respiration

Photosynthesis > Respiration = growth

Most plants will stop photosynthesis at

temps above 86˚

At that time they begin using stored

reserves.

Tem

pera

ture

The daily change in temp. is a thermoperiod When thermoperiod influences plant functions they are called thermoperiodic Begin to flower when the

days get shorter and the

temps are cooler

Tem

pera

ture

Some plants are cool season

crops

Wheat, barley, rye, spinach,

lettuce

They grow best in cooler

weather and are tolerant to

frost

They begin to flower when the

temps get warmer and the

days are longer

Tem

pera

ture

Warm season crops grow best in warmer

temps Cotton, Corn, Soybeans,

Sorghum Tomatoes will absolutely

not flower in cool temps

Tem

pera

ture

Plants like tulips or

winter wheat require

Vernalization

Period of cold

temperatures, often

below freezing, in order

for physiological

processes to occur

Tem

pera

ture

Some seeds will remain

dormant until it has been

subjected to a period of cold

temperatures This is called stratification If a plant is hardy it can

withstand cold weather

There are categories of

hardiness Plants are usually classified

into hardiness categories by

the zone of the country where

they grow best

Light

Light Quality

Color or wavelengths

Wave length range is placed

on the electromagnetic

spectrum

Visible light is a very small

portion of the spectrum

It is what drives

photosynthesis

Light

Red and blue are the

most effective for plant growth Why? Readily absorbed by

chlorophyllGreen is the least effective Why? It gets reflected

Light

What type of lights are best for

plants?

Fluorescent or incandescent

Fluorescent

Blue wave lengths

Cool

Incandescent

Red wave lengths

Hot

Light

Light Quantity Intensity of light More intense at high altitudes

and near the equator The greater the intensity the

more food produced through

photosynthesis What will a plant do if it prefers

full sun but is grown in shady

area? It stretches Internodes become longer to

push the plant towards more

sunlight

Light

Light duration is called

Photoperiod

Many plants respond to

changes in day length

They are called photoperiodic

Usually this affects flowering

Long day, short day, day neutral

Light

Long-day Initiate flowering when

nights grow shorterShort-day Initiate flowering when

nights grow longerDay-neutral Don’t respond to

changes in day length