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Light and Temperature Interaction

Light and Temperature Interaction. Modified by Georgia Agricultural Education Curriculum Office June, 2002. Fall Leaf Color. cool temps - very bright days. Orange. yellow, reds, purples and browns chlorophyll cells die as temperatures get cooler. Yellow. carotenoids

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Light and Temperature Interaction

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  1. Light and Temperature Interaction Modified by Georgia Agricultural Education Curriculum Office June, 2002

  2. Fall Leaf Color • cool temps - very bright days

  3. Orange • yellow, reds, purples and browns • chlorophyll cells die as temperatures get cooler

  4. Yellow • carotenoids • after chlorophyll dies you see the other pigments that are always present

  5. Red-Purple • anthocyanins • not always present • synthesized in cooler temps • made from sugar molecules

  6. Brown • tannins • mask or show up more once chlorophyll dies • produced in the leaves

  7. Leaf Fall • need an abscission layer • leaf can no longer translocate carbohydrates out of the leaf

  8. Bright Days • lots of carbohydrates in the leaf • anthocyanins get brighter color

  9. The Key…… • cool, short days

  10. Greenhouse Effect • short, high energy wave lengths of light from sun enters house • absorbed by structures and plants

  11. Greenhouse Effect • plants re-radiate green light in longer waves • long waves do not have as much energy as the short waves

  12. Greenhouse Effect • longer waves do not have enough energy to escape from the house • result is heat

  13. Greenhouse Effect • this is how the earth is heated • long waves cannot escape through the clouds • cloudy nights are warmer

  14. Light • energy - electromagnetic radiation • wavelengths - distance from peak to peak • measured in nanometers “NM”

  15. Far Red • color plants use

  16. Infra Red • heat energy

  17. Visible light • light quality - color • quantity - intensity, how bright • duration - photoperiod

  18. Quality • blue - 400-510 NM • cell elongation • photosynthesis - chlorophyll absorbs red and blue light

  19. Quality • phototropism - plant tends to grow or bend toward a light source

  20. Red • photosynthesis • stimulates branching • encourage growth of auxiliary buds

  21. Red • phytochrome - light absorbing pigment • seed germination in photoblastic seeds

  22. Red • flowering responses • photoperiod

  23. Far Red

  24. Far red • promotes stem elongation

  25. Yellow - Green • does not effect plants

  26. Intensity • measured in foot candles • amount per unit area on plant

  27. Plants • shade loving • too much sun - leaf burn • dehydrate • kill chlorophyll

  28. Plants • sun loving • low light, pale color • new leaves are small • lack vigor

  29. Plants • don’t flower properly if at all

  30. Light • Light Compensation Point -”LCP” • light intensity where rate of photosynthesis = the rate of respiration

  31. LCP • Lowest intensity you can grow a plat at • If a plant is grown below this level, respiration will be greater than photosynthesis

  32. LCP • plant will die • for a plant to grow photosynthesis must be greater than respiration

  33. Acclimitization • preparing plant for lower light intensity conditions • expose to lower light intensity

  34. Artificial Lights • Incandescent • far red, red - elongation • low blue • 80% of emitted radiation is heat

  35. Incandescent • 20% visible light • 12% utilized by plant

  36. Flourescent • red, blue • 36% heat energy • 22% light used by plant • spectral flexibility

  37. Flourescent • can change the quality of the light by changing the coating on inside of bulbs • Cool White - Ca Halophosphate

  38. “Gro-Lux” • coated with Mg Fluorogerminate • not as long life as cool white, 30X more expensive

  39. Metal Halide • increase light intensity

  40. Low Pressure Sodium • yellow glow • energy efficient • yellow - orange light

  41. High Pressure Sodium • red, blue light • energy efficient

  42. Photoperiod • length or duration of the light period • biological measurement of relative length of light and dark periods

  43. Photoperiod • effects • flowering • leaf abscission • dormancy - acclimate for winter

  44. Effects….. • Sex expression • runner formation • tuber formation • bulb formation

  45. Short Day Plants • flower when day length is shorter • the dark period is critical • it’s dark longer than it is light

  46. Short Day Plants • examples • Chrysanthemum • Christmas Cactus • Poinsettia

  47. Long Day Plants • flower when days are long and nights are short • example: lettuce, radish, petunias

  48. Facilitative Long Day • flower any period • if long day - flowering is enhanced • examples - tomato, begonia

  49. Day Neutral • flower under long or short day lengths • example: African Violet

  50. Poinsettias • use night interrupted lighting • turn on artificial lights from 10 p.m. to 2 a.m. • splits up the dark period

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