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Nghiên cứu ảnh hưởng của ánh sáng đến sinh trưởng cây trồng
1 Light in horticulture Light spectrum 2 Perception of light Human eye Plant 3 Measuring light • Photosynthetic active radiation (PPFD, PAR) – 400 – 700 nm – PAR-sensor : µmol/m².s – Is hardly used in horticultural entreprises • Short wave irradiation – 300 – 3000 nm – Pyranometer (Kipp & Zonen); solarimeter • W/m²: instant short wave irradiation per second • MJ/m² or J/cm²: sum over a determined period of time t • Used on nursery scale for operating irrigation, screening and supplementary lighting • Sensitivity of the human eye – 555 nm – Lux-meter – Also used on nursery scale to control lighting and screening Conversion factors for different light sources 3.91 2.80 2.61 4.00 18 14 12 20 Sun light High pressure Na-lamp Fluorescence lamp Incandescent lamp 1000 1000 1000 1000 W.m - ²µmol.m -2 .s -1 Conversion to Light source Unit (lux) 4 Seasonal fluctuations in day length and light intensity jan febr maart apr mei juni juli aug sept okt nov dec Irradiation sum/day (MJ/m²) 0 2 4 6 8 10 12 14 16 18 20 Light absorption by the leaf 5 Light distribution above and beneath the leaves Photoreceptors • Light quantity: counting the number of photons • Light quality: ratio of photons • Direction of the light: photongradients • Duration of light: timing of light-dark transitions • Polarisation: dichromatic photoreceptor-regulation 6 Structure of chlorophyll Absorption spectra of chlorophyll and carotenoids 7 Structure of phytochrome Absorption spectra of phytochrome 8 Hyperbolic relation between φ and the R:FR ratio P fr : the active form of phytochrome • Very low fluence response • Low fluence response • High irradiance response 9 Blue light absorbing pigment (BAP) Cabbaging of the leavesNon-directional Phototropism, phototaxis, intracellular rearrangement of chloroplasts Orientation Flowering, growth inhibition, seed germination, Morphogenesis Enzyme regulation, pigment synthesis, carbon metabolism Metabolism Effects of UV-B receptors Cryptochrome-action-spectrum 10 Interactions among photoreceptors ABC X Y Type I: X and Y have an independent control Interactions among photoreceptors AB X’ Y Type II: the action of X is influenced by Y X Precursor X . Lenghtening the day: SLR-18 Watt lamps – Cyclic lighting: incandescent lamps 18 Control of photoperiod via cyclic lighting incandescent lighting: high. bud blasting in Alstroemeria and Eustoma (photo) 14 Forcing of florist azalea With supplementary lighting Without supplementary lighting Forcing of florist