Effect Of Light Quality On Physiological Characteristics And Quality Of Leaf Lettuce

The effect of different light qualites on leaf lettuce about growth, development, physiological metabolism and quality were studied by two breeds'Yu Hu'and'Da Ye Su Sheng'in order to provide the theory basis of good quality, high yield and the product of special use film.The results indicated:Different light qualites had great effect on the growth of leaf lettuce. Height , the lenght of leaf stalk were heightened in red light, while were diminished in yellow light. Leaf area and dry weight were enhanced in yellow light, while were decreased in red light.Different light quality also had notable effect on quality of leaf lettuce. Red light or yellow light could significantly increase the content ofβ-catotene, improve the content of Vc, and in blue light there was upper content of Cu,Zn,Mn, it showed that different light quality were chosed by different need.The content of NO3- in different light quality in whole growth period increased gradually then came down in the later, and the contents in different leaf positions ranged that: inner leaf >middle leaf> outside leaf, and in different growth positions the contents of NO3- were stem>leaf> root, NR activity and NO3- content become the negative relevance mainly, but in blue light NR activity always high, maybe blue light had a direct effect on NR.The content of solutable protein, free amino acid in different light quality within entire growth all rose firstly and then came down, the content of solutable protein in diffenent light quality ranged from high to low were yellow light, white light ,blue light and red light. While free amino acid were red light, blue light, white light and yellow light.The relationship between solutable protein and free amino acid was negative relevance. The experimentation showed that the relationship between solutable protein and free amino acid was interrelated. In growth period, leaf extent and strongly protein synthesis needed large quanties of amino acid, then leaf become caducity, and intension of metabolism was weaken and the capacity of synthesis reduced, so the contents of solutable protein, free amino acid fallen.Temperature adversity may arouse oxidation adversity, in greenhouse, temperature adversity was one of important limit factors. The result indicated that yellow light could improve the leaf antioxidase activity, reduce EC, and benefit to improving the resistance to adversity.Light quality also had certain effect on photosynthesis. Yellow light improved the chlorophyll content and Pn, CE, Fv/Fm,ΦPSII, ETR and qP, the result showed that it enhanced the photosynthesis ability, so it was benefit to growth and development.The research of different light quality on hormone had been reported long time ago, this experiment indicated that yellow light improved the GA , IAA , ZR contents of leaf, and reduced the content of ABA, the result showed that yellow light were more beneficial to promoting growth and delaying senility.