Effect Of Light Quality On Physiological Characteristics And Quality Of Purple Lettuce(Lactuca Sativa L.)

In order to explore the effect of light quality on the growth and development of purple lettuce and find the best light quality“formula”suitable for the growth of purple lettuce,we used purple lettuce?Lactuca sativa L.cv‘Zhongshu Purple Lettuce'?as material,and LED intelligent light control console as light source to study the effects of supplementing different proportions of red and blue light?1:1,2:1,4:1 and 1:2?to the white light on photosynthetic characteristics and commercial quality of purple lettuce,and the appropriate white-red-blue light quality ratio was preliminarily screened.Then,10,20,30?mol·m^-2·s^-11 UV-A was supplemented on the basis of the above-mentioned light quality ratio.The effects of different doses of UV-A on the growth,antioxidant and anthocyanin synthesis of purple lettuce were studied.Determine the appropriate proportion of UV-A addition,precise precision regulation of light quality,provide theoretical basis and technical parameters for the production of purple leaf lettuce under controlled environmental conditions.The main findings are as follows:1.When the ratio of red and blue light was 4:1,the photosynthetic pigment content of purple lettuce,the light energy conversion efficiency and RuBP carboxylase activity were the highest,which significantly improved the photosynthetic and growth of purple lettuce.Carbohydrate accumulation is promoted by increasing the activity of sucrose metabolism-related enzymes.Nitrite content is significantly inhibited.However,the nutritional quality improvement effects such as vitamin C and secondary metabolites are poor.2.When the ratio of red and blue light was 1:2,the activity of primary nitrogen metabolism enzymes in purple leaf lettuce was promoted,enhanced nitrogen accumulation and increased protein content.The contents of vitamin C,secondary metabolites such as anthocyanins,flavonoids,total phenolic compounds,and the contents of antioxidant capacity were significantly higher than those in the control and other treatments.However,the effect of promoting the growth is not obvious.3.On the basis of WR₄B₁ treatment,the supplementation of 10,20?mol·m^-2·s^-11 UV-A increased the photosynthetic pigment content,but had no significant effect on the light energy conversion efficiency and net photosynthetic rate.The growth is also similar to WR₄B₁treatment,but the dry mass and blade thickness are significantly improved.Under the treatment of 30?mol·m^-2·s^-11 UV-A,the stomatal conductance is significantly decreased,the net photosynthetic rate is decreased,and the growth amount is declined.4.Under all treatments with UV-A irradiation,the activity of antioxidant enzymes was induced by promoting the production of active oxygen;the content of secondary metabolites such as flavonoids and total phenols was significantly improved;for soluble sugar and soluble protein of purple lettuce and the quality indicators such as vitamin C are further improved;by regulating the anthocyanin biosynthesis structural gene and regulating gene expression,the activity of the relevant synthetase is increased,and the anthocyanin biosynthesis is significantly promoted.5.The supplementation of red,blue light and 20?mol·m^-2·s^-11 UV-A?380-400 nm?to white light can significantly improve the quality of purple lettuce,and it has no inhibition on growth,which is in line with the requirements of benign stress and is recommended as a special formula for purple lettuce in the greenhouse horticulture.