Effects Of Different LED Lighting Regimes On The Growth And Photosynthetic Characteristics Of Lettuce Seedlings In Plant Factory

Lettuce(Lactuca sativa L.)is the main type of leafy vegetables production in plant factory,which is rich in nutrition and has large market demand.The quality of lettuce seedlings had significant effects on the production of lettuce.In this paper,we used lettuce as test material,W19 treatment as control(CK).This study invested the effects of different LED lighting regimes(W19,R19,B19,W12B7,W12R7,B12W7,B12R7,R12B7,and R12W7)on the growth,quality and photosynthetic characteristics of lettuce seedlings.To provide reference for lettuce seedlings production in plant factory by using LED light sources.The main results are as follows:1.The effects of different lighting regimes on the shoot dry and fresh weight,leaf area of the two kinds of lettuces were different.The results indicated that the growth index of lettuce seedlings under different lighting regimes had differences between varieties.The shoot dry weight of green leaf lettuce seedlings under R19,W12R7 and B12R7 treatments were significantly higher than that of CK,and there were no significant differences between other treatments and CK.The shoot dry weight of red leaf lettuce seedlings under R19 treatment were significantly higher than that of CK;under B19 treatment were significantly lower than CK,other treatments compared with CK did not exist significant differences.The effects of different treatments on the shoot fresh weight and leaf area of the two several of lettuce seedlings were similar to those of the dry weight,respectively.The stem length of two kinds of lettuce seedlings under R19,R12B7 and R12W7 treatments were significantly higher than that of other treatments,which were not conducive to the further growth of lettuce.Therefore,the growth of green leaf lettuce seedlings which under W12R7 and B12R7 treatments were most appropriate.W12B7,W12R7,B12W7 and B12R7 treatments were suitable for the growth of red leaf lettuce seedlings compared with CK,but the effects were not obvious.2.The contents of chlorophyll,anthocyanin,vitamin C and nitrate in lettuce leaves under different lighting regimes were determined.The nitrate contents of green leaf lettuce seedlings under R19,W12R7 and B12R7 treatments were significantly lower than that of CK,and there were no significant difference among other treatments.The nitrate contents of red leaf lettuce seedlings under R12,W12R7 and B12R7 treatments were significantly lower than that of CK,under B19,W12B7 and R12B7 treatments were significantly higher than that of CK,under R12W7 and B12W7 treatments did not have significant difference with CK.The contents of vitamin C in green leaf lettuce seedlings under R19,W12R7 and B12R7 treatments were significantly lower than that in CK,and there were no significant differences among other treatments.There were no significant differences in the content of vitamin C in red leaf lettuce seedlings between CK and other treatments.Therefore,the contents of vitamin C in different varieties of lettuce seedlings were different under different lighting regimes.The order of chlorophyll a + b content of green leaf lettuce seedlings was B19>R12B7>B12W7>R12W7>W12B7>W19>W12R7>B12R7>R19.The order of chlorophyll a + b content of red leaf lettuce seedlings was R12W7>B19>B12W7>W19>R12B7>W12B7>B12R7>W12R7>R19.The trend of anthocyanin contents of the two kinds of lettuce under different treatments were similar,and the anthocyanin content of red lettuce was higher than that of green lettuce under different treatments.The results showed that the content of anthocyanin was variety difference.3.In this study,the photosynthetic characteristics of lettuce leaves under different lighting regimes were measured by Li-COR photosynthesis system.The differences of single leaf photosynthetic rate under all treatments in red leaf lettuce were less than that of green leaf lettuce.The single leaf photosynthetic rate of green leaf lettuce seedlings under B19,W12B7 and R12B7 treatments were significantly higher than that of CK,and the whole plant photosynthetic rate under R19,W12R7 and B12R7 treatments were significantly higher than that of CK.The single leaf photosynthetic rate of red leaf lettuce seedlings were not significantly different among all treatments;the whole plant photosynthetic rate of red leaf lettuce seedlings under R19 treatment was significantly higher than CK,under B19 treatment was significantly lower than CK,there were no significant differences between other treatments and CK.The changing trends of whole plant photosynthetic rate of green leaf lettuce seedlings and red leaf lettuce seedlings were similar as that of aboveground fresh and dry weight in all treatments.In summary,the effects of different lighting regimes on two kinds of lettuce were different.Green leaf lettuce seedling under W12R7 and B12R7 treatments,had shorter stem length,higher shoot dry weight,leaf area and photosynthetic rate,which were most beneficial to the growth and photosynthesis of lettuce.W12R7,W12B7,B12W7 and B12R7 treatments were suitable for culturing red leaf lettuce seedlings,but the effects were not obvious compared with CK.This study provides some theoretical basis and practical guidance for the management of LED light sources for seedlings production in plant factory.