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Light and Temperature Interaction

Light and Temperature Interaction. Fall Leaf Color. cool temps - very bright days. Orange. yellow, reds, purples and browns chlorophyll cells die as temperatures get cooler. Yellow. carotenoids after chlorophyll dies you see the other pigments that are always present. Red-Purple.

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Light and Temperature Interaction

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  1. Light and Temperature Interaction

  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 • tanins • 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 axillary 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 abscision • 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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