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IV. LIGHT

IV. LIGHT. A. Importance to Greenhouse Crops temperature CO 2 water fertilization timing spacing retardant. B. Natural Light Properties 1. Quality -electromagnetic spectrum 2. Intensity -range summer --max-- 10,000 ft-cds 2000 umols/m 2 /sec winter --max-- 800 ft-cds

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IV. LIGHT

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  1. IV. LIGHT A. Importance to Greenhouse Crops • temperature • CO2 • water • fertilization • timing • spacing • retardant

  2. B. Natural Light Properties 1. Quality -electromagnetic spectrum 2. Intensity -range summer --max-- 10,000 ft-cds 2000 umols/m2/sec winter --max-- 800 ft-cds 60 umols/m2/sec

  3. 3. Duration -range 0-24 hrs -Kentucky 9-15 hrs 4. Accumulated light daily a. range summer ----- moles/day/m2 winter ----- moles/day/m2

  4. Factors • Cloud • Smog • Trees, buildings c. Daily accumulated radiant energy in greenhouse - type of covering - shadows in greenhouses

  5. C. Plant Response to Light 1. Quality a. photosynthesis 400-700 A (visible spectrum) b. photoperiod 700-800 A (red/farred)

  6. 2. Intensity a. photosynthesis 50-10000 ft-cds 2-2000 umol/m2/sec temp. & CO2 dependent increase intensity -- increase photosynthesis

  7. b. photoperiod 5-15 ft-cds 1-2 umols/m2/sec c. greenhouse 40-60% external intensity

  8. 3. Duration a. photosynthesis increase duration -- increase photosynthesis (9-20+ hrs) b. photoperiodic short (1-4 hrs/night)

  9. 4. Accumulated - correlates with increased photosynthesis/growth 20-30 moles/day - range low - slow growth - poor quality excess - chlorophyll destruction dessication fading of flower

  10. January February March April

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