采前不同比例LED红蓝光连续光照对生菜光合特性及产量和品质的影响

Effects of Different Ratios of LED Red and Blue Continuous Light on the Photosynthetic Characteristics,Yield and Quality of Lettuce Before Harvest

为了探究采前连续光照光质对水培生菜(Lactuca sativa L.)产量和品质的影响,研究了不同红(R)蓝(B)光质比例(1R:4B、1R:2B、1R:1B、2R:1B和4R:1B)对水培生菜生长、光合特性、抗坏血酸(ascorbic acid,AsA)含量和AsA代谢关键酶活性的影响。结果表明:与连续光照前相比,不同比例LED红蓝光连续光照后,生菜地上部鲜重的增幅为38.82%~77.65%,2R:1B处理下的地上部鲜重最大达到30.23 g;根鲜重的增幅为27.43%~73.14%,4R:1B处理下的根鲜重最大为3.03 g。红光比例越高,生菜的叶面积、SPAD和可溶性糖含量越高,硝酸盐含量的变化不显著。与其他处理相比,1R:4B的连续光照处理后,生菜的净光合速率、蒸腾速率、胞间CO_(2)浓度和气孔导度达到最大。提高采前连续光照中的蓝光比例可显著提高生菜AsA含量和单脱氢抗坏血酸还原酶(MDHAR)的酶活性,1R:4B处理下叶片AsA的含量最高达到3.22 mg·g^(-1),1R:4B处理下的生菜叶片MDHAR酶活性显著增加了0.81 U·mg^(-1) FW。综上,降低采前连续光照的蓝光比例,可显著提高生菜的产量和可溶性糖等的含量,而提高采前连续光照蓝光比例可显著提高AsA的含量,这是因为采前连续光照蓝光比例的升高提高了MDHAR的活性。

In order to explore the effect of continuous light quality on the yield and quality of hydroponic lettuce(Lactuca sativa L.),five treatments of different red(R)and blue light(B)quality ratios(1 R:4 B,1 R:2 B,1 R:1 B,2 R:1 B and 4 R:1 B)were set.The growth,photosynthetic characteristics,ascorbic acid(AsA)content and key enzyme activities of AsA metabolism were studied.The results showed that:the shoot fresh weights of lettuce increased by 38.82%~77.65%under different treatments of red and blue LED light,and the maximum shoot fresh weight of lettuce was 30.23 g under 2 R:1 B treatment.The root fresh weights were increased by 27.43%~73.14%,and the maximum root fresh weight was 3.03 g under 4 R:1 B treatment.The higher the ratio of red light,the bigger the leaf area,SPAD value and soluble sugar content of lettuce,but the change of nitrate content was not significant.Compared with other treatments,the net photosynthetic rate,transpiration rate,intercellular CO_(2) concentration and stomatal conductance of lettuce were the highest under 1 R:4 B treatment.The content of AsA and the activity of monodehydroascorbic acid reductase(MDHAR)in lettuce significantly increased with increasing the ratio of blue light to continuous light.Under 1 R:4 B treatment,the content of AsA in leaf was the highest level of 3.22 mg·g^(-1),and the activity of MDHAR in lettuce leaf significantly increased by 0.81 U·mg^(-1) FW.In conclusion,the decrease of the ratio of blue light to continuous light before harvest could significantly improve the yield of lettuce and the content of soluble sugar.Increasing the ratio of continuous light to blue light before harvest could significantly increase the content of AsA and the activity of MDHAR.