Study On The Difference Of Physiological Response Of Different Tomato Varieties To Weak Light

Tomato（Lycopersicon esculentum.Mill）as a hi-light crop,is often under weak light stress in winter and spring protected cultivation,which seriously affects its early morphogenesis.In order to find out the effect of weak light on the growth and development of tomato seedlings and the mechanism of weak light tolerance,in this study,under the condition of artificial climate chamber,the light intensity of 600μmol·m^-2·s^-1 and 100μmol·m^-2·s^-11 were used as control and treatment,respectively.The tomato varieties of weak light tolerance‘YF’and weak light sensitivity‘906’were selected from 15 tomato varieties,and their growth and development characteristics,antioxidant system,photosynthetic electron transport and transcriptome were further studied.The main results are as follows:1.The coefficient of variation of 15 tomato varieties under weak light in plant height,stem diameter,dry and fresh weight,strong seedling index,total chlorophyll content and net photosynthetic rate were between-108.16%and 73.10%,and each indicator has a certain correlation.The principal component analysis method was used to calculate the feature vector and the comprehensive evaluation of 15 tomato varieties value were obtained.Then,the cluster analysis was used to divide 15 varieties into 4 grades to gardes to obtain the weak ligh sensitive variety‘906’and the weak light tolerance variety‘YF’.2.The growth of‘906’and‘YF’was inhibited by weak light stress,which showed that the dry and fresh weight,leaf area,root structure parameters and root activity of tomato seedlings were significantly reduced.The content of N,P and K in the whole plant was significantly increased,while the content of Ca was decreased.The content of H₂O₂ and O₂^-as well as the activity of SOD and CAT was decreased,but the activity of POD increased and no significant difference was found in MDA content.3.Under weak light,the chlorophyll content of‘906’and‘YF’both increased significantly,and the leaf thickness decreased,but the palisade tissue/sponge tissue increased.The absorption ratio of red-orange light and blue-violet light increased by the leaves,which showed that the absorption of light energy per unit reaction center of PSII（ABS/RC）increased.However,the actual quantum yield and electron transfer rate of PSI and PSII decreased,the heat dissipation increased,and the receptor side of PSI was severely inhibited.4.Compared with the weak light sensitive varieties‘906’,the biomass of the weak light tolerance tomato varieties‘YF’changed less,and the leaves were thicker.With the expression of LHCb1 increased,the absorption of red orange light,blue violet light and far red light were also increased in the leaves.The higher PQ size and Fd expression of‘YF’enhanced the efficiency of electron transfer between photosystems,while the increase of CEF reduced the degree of oxidative stress on the receptor side of PSI..5.According to the transcriptome analysis of weak light sensitive and tolerance tomato varieties,the differential genes were mainly enriched in MAPK,hormone signal transduction,phenylpropionic acid biosynthesis and starch sucrose metabolism pathway.Moreover,compared with weak light sensitive varieties,the expression of SlCaM2 and HY5 in weak light tolerance varieties were up-regulated specifically,which had a potential role in improving the ability of weak light tolerance.