Plant Physiology

1
Plant Physiology

• Chapter 16
• Introduction to Environmental and Agricultural
  Sciences

2
Introduction

• As plants grow to maturity, the cells are
  produced, divide, grow become specialized
  organs.
• Stems, leaves, roots, flowers, fruits, seeds.
• Physiology study of how these organs function
  and the complex chemical processes that permit
  the plant to live, grow and reproduce.

3
Major Parts of a Plant
4
Photosynthesis

• Most important life-sustaining process
• Without photosynthesis, maintenance of life on
  this planet would not exist
• Plants need carbon dioxide to manufacture food
• Animals need oxygen to live
• Photosynthesis permits animals and plants to live
  and support each other

5
Photosynthesis

• Photosynthesis is a series of processes in which
  solar (light) energy is converted to chemical
  energy in the form of a simple sugar.
• Chlorophyll and chloroplasts are essential to
  this process.
• Chlorophyll is the substance that gives plant
  leaves their green color.

6
Photosynthesis

• Chloroplasts are small membrane bound bodies
  inside the cell that contain the green
  chlorophyll pigment.
• Chloroplasts are the actual site where solar
  (light) energy is converted into stored
  energy-simple sugars.

7
Photosynthesis

• Photosynthesis is the conversion of carbon
  dioxide and water in the presence of light
  (energy) and chlorophyll into glucose, oxygen and
  water.

8
Rate of Photosynthesis

• The rate of photosynthesis varies with the light
  intensity, temperature and concentration of
  carbon dioxide in the atmosphere.
• Light Intensity is the quality of light, or
  brightness of light.
• Photosynthesis occurs best in a temperature range
  of 65-85?F.
• Extreme temperatures slow down or stop the
  process completely.
• A lack of carbon dioxide can be a limiting factor
  in the photosynthesis process.

9
Respiration

• All living cells carry on the process of
  respiration.
• Respiration is the process by which living cells
  (plant or animal) take in oxygen and give off
  carbon dioxide.
• Respiration occurs both day and night.

10
Respiration

• Respiration is a breaking down process
• Uses sugars starches produced by photosynthesis
  and converts them into energy.

11
Photosynthesis vs. Respiration
12
Transpiration

• Transpiration is the process by which a plant
  gives up water vapor to the atmosphere.
• Water loss takes place primarily through the leaf
  stoma.
• A plant transpires 90 of the water that enters
  through the roots.
• About 10 of the water that enters from the roots
  is used in chemical processes and in the plant
  tissues.

13
Transpiration

• Functions of the water include transporting
  minerals through the plant, cooling the plant,
  moving sugars and plant chemicals and maintaining
  turgor pressure.
• Turgor means swollen or stiffened condition as a
  result of being filled with liquid.
• When plants do not have enough water, turgor
  pressure is lost and the plant starts to wilt.

14
Transpiration
15
How is transpiration affected?

• Humidity
• Humidity Transpiration
• Wind Other air movement
• Air Movement Transpiration
• Temperature
• Temperature Transpiration

16
How is transpiration affected?

• During dry weather, transpiration often causes
  the plant to lose water faster than it can be
  replace by the root system.
• When this occurs, the guard cells will close to
  slow down the rate of transpiration.
• Enables the plant to preserve the water it
  contains

17
How is transpiration affected?