Effects Of Light Quality On Physiological Characteristics And Qualities Of Spinach

With spear and round leaf varieties of spinach as test materials, and under different light conditions, the effects of different light qualities on growth, primary nitrogen assimilation, physiological characteristics, heat tolerance to high temperature stress and qualities of spinach were studied. The main results were as following:1. Leaf blade had more proportion than petiole in fresh weight. The results showed that under red light vigorous vegetative growth, the dry matter accumulation, leaf area, length of petiole, chlorophyll a/b ratio, photosynthetic rate, soluble sugar content and total sugar content were all maximal while the total nitrogen content were lowest compared with the other treatments. It is concluded that red light treatment could accelerate the growth of spinach, and increased the yield.2. Light quality could influence the nitrogen metabolism of plant, and adjust the carbohydrate and protein metabolism. The content of carbohydrate was high under the red light treatment, while the content of protein was high under blue light treatment. Blue light could significantly increase the nitrogen metabolism of spinach leaf, and the contents of total nitrate, protein and free amino acids were increased, while the content of soluble sugar was decreased.3. The activities of SOD, POD, CAT and the content of MDA in Round-leaf spinach were higher than those in the Spear-leaf spinach under the same light quality treatment during the high temperature stress. And it showed the higher heat tolerance to high temperature than Round-leaf spinach. The Spear-leaf spinach under the yellow light was at the higher level of heat tolerance to high temperature, while the Round-leaf spinach under red light had higher heat tolerance to high temperature. There were significant differences between two varieties in heat tolerance to high temperature.4. The results showed that changes of nitrate and oxalate contents were different in petiole and leaf blade among various treatments, while the trends of plant growth increment were the same. Red light was better to the formation and accumulation of dry matter and carbohydrate. Nitrate concentration in petiole was significantly higher than that in leaf blade. The petiole was the dominant place for nitrate accumulation, and the variation of nitrate concentrations in leaf blade was significantly higher than that in petiole. The oxalate content in leaf blade was higher than that in petiole under white light and yellow light treatments, but it was opposite under red light and blue light treatments. The total oxalate content of red light treatment was the lowest. The nitrate content was significantly reduced under red, blue and yellow light. Although spinach biomass was not the highest under red light treatment, the nitrate, nitrite and total oxalate contents could be reduced obviously, and the flavone and mineral content were improved in spinach shoot. The quality of spinach was improved by red light treatment.