Plant Physiology for Environmental and Agricultural Sciences

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 • Transpirationis 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?