Plant Anatomy

and PhysiologyJust the Concepts

Environmental Factors

On Plant Growth

Obje

ctive

s

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.

Functions of W

aterWater 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

Func

tions

of

Wat

er

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

Functions of W

ater 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

Shor

tage

and

Exc

ess

Shortage Transpiration continues even though water is not absorbed Wilting occurs due to

loss of turgor Color changes

Response to Shortage

and Excess

ExcessRoot hairs die due to

saturated soil (no

oxygen)

Can no longer absorb

water and nutrients

Usin

g W

ater

Effi

cient

ly

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

Using Water

Efficiently

Who is the least

efficient Irrigator?

Why

The home owner

Usin

g W

ater

Effi

cient

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

Conservation of water Conservation of soil

Using Water

Efficiently

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

Temperature

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

Temperature

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

Temperature

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

LightLight 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 shorter

Short-day Initiate flowering when nights grow longer

Day-neutral Don’t respond to changes in day length