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Light. Photosynthesis is the process by which the light energy of the sun is changed by green plants into chemical energy.Chemical Reaction of PhotosynthesisComponents of the Photosynthetic ReactionCarbon Dioxide, Water, Light, Light IntensityLight Quality- (Red and Blue Light Waves). Light. Li
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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.