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 PHOTOSYNTHESISRESPIRATION 1. Food is produced1. Food is used for plant energy 2. Energy is stored2. Energy is released 3. Occurs in cells containing chloroplasts 3. Occurs in all cells 4. Oxygen is released4. Oxygen is used 5. Water is used5. Water is produced 6. Carbon Dioxide is used6. Carbon Dioxide is produced 7. It occurs in sunlight7. It occurs in light and dark

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?