Environmental Growth Factors in Plants

1. Environmental Growth Factors in Plants

2. Light Photosynthesis is the process by which the light energy of the sun is changed by green plants into chemical energy. Chemical Reaction of Photosynthesis Components of the Photosynthetic Reaction Carbon Dioxide, Water, Light, Light Intensity Light Quality- (Red and Blue Light Waves)

3. Light Light Requirements of Plants Light Compensation Point- This is the point which the amount of food produced by the plant equals the amount used up in respiration. Light Saturation Point As the light intensity gets brighter, there is a point where growth is limited. This is called the light saturation point Point where there is no further increase in photosynthesis with an increase with light. Continuation of intense light might actually damage plant.

4. Effects of Low Light Phototropism Bending of the plant towards light. Photo-Light Tropism-turning Bending is due to the development of growth hormones on the side of the stem away from the light.

5. Effects of Light Photoperiodism Length of time that light shines on a plant each day. 4 dates of the year when day length is really important: March 21 (Spring Equinox) September 21 (Fall Equinox) June 21 (Summer Solstice) December 21 (Winter Solstice)

6. Effect of Day Length The greatest growth takes place on days with the longest light and the shortest night. This effect of light is called photoperiodism and it breaks plants down into three classes Short Day-Flower when the day length is shorter than the critical number of hours. Poinsettia and Chrysanthemums Long Day-flower only if the length of the day is longer than a critical number of hours. Tuberous rooted begonias Day Neutral-Plants that day length does not effect the flowering directly Roses and Violets

7. Controlling Day Length Photosynthesis requires high light intensities. Photoperiodism is controlled by very low light intensity. Poinsettias will remain green if they are exposed to less than 11 Lux Curtains Artificial Light

8. Temperature Ranges in Temperature The Minimum Temperature- Level below when growth does not take place The Optimum Temperature- When growth is the greatest The Maximum Temperature Level above when growth does not take place.

9. Temperature Seeds may survive after very low or very high temps. The same temps that would probably kill seedlings or plants.

10. Temperature Rule of Thumb- Maintain Day temperatures 10�F warmer than night temperatures on cloudy days and 15 �F or more on clear days. DIF (Differential Temperature) Reversing the day and night temperatures Day temps are cooler than the night temperatures Stems do not elongate or stretch as much Negative Diff. Makes for hardier plants and stems.

11. Air Temperature and Respiration and Transpiration Respiration occurs 24/7 Temperature has a direct effect on respiration. High respiration in hot weather Lower respiration in cooler weather Transpiration Greatest effect on leaves Transpiration increases when temperatures increase Radiational Cooling On clear cold winter nights, plants growing close to greenhouse wall will lose heat quicker. This can cause the development of anthocyanin (Red Pigment) in geraniums and marigolds.

12. Gasses Oxygen Humans and animals need it Runs about 78% in atmospheric oxygen Plants take in oxygen during respiration Carbon Dioxide Plants use Carbon Dioxide in Photosynthesis Replenished by ventilation When vents are closed, the plants may use up the gas. May cause a shortage and limit growth. We can add a propane burner.