The Effects Of Light Intensity And Time On Plant Growth

Light-emitting diodes (LEDs) have been considered as novel light sources for growth and photo-morphogenesis in horticultural plant species because of their small masses, volumes and durability. These attractive characteristics may make LEDs suitable for use in plant production not only in growth chambers but also in greenhouses. In plant production, light intensity and quality play roles in the establishment of photosynthesis, morphogenesis and photochemical of many plant species and are essential factors for plant growth and development under greenhouse, thus the main aim of our study to investigate the effect of light quality and several photoperiodic times on plant growth.The effect of light provided by various light intensities combined with different photoperiods on the growth and morphogenesis of lettuce (Lactuca sativa L.) in growths chamber were evaluated in this study. The role of photoperiodic and irradiance level on growth and development of lettuce was investigated in three parts.In the first part, the plant was exposed to different intensities of light 150μmolm-2s-1, 100μmol m-2s-1, and 75μmol m-2s-1 with same photoperiod 12h light 12h dark. The height and diameter were significantly affected. The best results were obtained at the intensity of light 150μmol m-2s-1 (12h/12h). VC content also affected as well as the CO2 concentration. The Chlorophyll content has affected among the all previous intensities.In the second part, the experiment was conducted under the light intensities of 150μmol m-2s-1 and 100μmol m-2s-1 with photoperiod for each of them 6h light 6 h dark, and the intensity of 75μmol m-2s-1 with 24h light. The morphological parameters, i.e., the height and diameter were observed the greatest under intensity 75μmol -m2s-1 with 24h light. At the same time biochemical content, i.e., sugar and protein were enhanced significantly. Chlorophyll a, b and carotenoid were not strongly affected by light intensity. The respiration and transpiration were improved significantly, but the CO2 concentration was not.In the third part, the plant were illuminated by the intensity of 150μmol m-2s-1 with 3 h light,3 h dark and 1.5 h light,1.5h dark respectively, and the intensity of 112.5μmol m-2s-1 with photoperiod 1h light,0.5h dark.The chlorophyll content was found to be affected significantly. Results demonstrated that the morphology of lettuce growth was shown in high performance as well as the transpiration of photosynthesis. Changes in biochemical VC, protein and sugar content were not found. Based on these results,150μmol m-2s-1 with 1.5 h light,1.5h dark is a recommend light intensity for lettuce production.