Research On The Response Difference And Mechanism Of LED Supplementary Light Period In Tomato

Tomato is the main type of vegetable for winter in facilities in northern my country,but the problem of short sunshine time and weak intensity in winter facilities has become a key factor affecting the growth and development of crops and restricting the efficient development of facility agriculture.LED supplementary light is an effective solution to this problem.In this study,LED plant growth lamp(7R2B)was used to supplement light in the morning(5:00-8:00)and evening(18:00-21:00)to study the effects of light supplementation on tomato growth and development,leaf photosynthetic characteristics and key fruit quality.At the same time,the expression rules and differences of genes and metabolites in leaves of red and blue light LED in different periods were analyzed from the aspects of transcriptome and metabolic group.The differential response characteristics and physiological and molecular mechanism of tomato to LED supplementary light period were elucidated preliminarily,and the main results were as follows:(1)Red and blue light LED supplementation in different periods could promote the growth morphology,root growth and dry matter accumulation of tomato,increase the content of endogenous hormones in tomato leaves,induce early flowering,and increase the number of fruit set and yield of tomato.Among them,supplementary light in the morning is beneficial to the vegetative growth of tomato,while supplementary light in the evening is beneficial to the reproductive growth of tomato.(2)Red and blue LED supplementary light at different time periods significantly increased the content of photosynthetic pigments,net photosynthetic rate and photosynthetic products in tomato leaves.Supplemental light in the morning increased the content and relative electron transfer rate of chlorophyll synthesis precursors in tomato leaves.Supplementary light in the evening increased the opening degree of the reaction center of photosystem II in tomato leaves,and the conversion efficiency and utilization of light energy.Red and blue light supplementation at different time periods increased the activities of Calvin cycle and glucose metabolism-related enzymes and gene expression in tomato leaves,and up-regulated the expression of photoreceptors and downstream light signal regulator HY5.The improvement effect of supplemental light in the morning was more obvious.Red and blue LED light supplementation at different time periods may activate the expression of phytochrome and cryptochrome in tomato leaves,and then regulate the transcription and accumulation of the downstream light signal regulator HY5,thereby activating the transcription of genes encoding Calvin cycle and glucose metabolism-related enzymes.,to improve the photosynthetic capacity of tomato,increase the synthesis and accumulation of photosynthetic products,and ultimately promote the growth and development of tomato seedlings.(3)Full-length transcriptome sequencing was performed on tomato leaves treated with LED supplementary light at different periods.The clean data produced by sequencing all reached 10.14 GB,and the full-length sequences ranged from 6178129 to 8663951,and57663 transcript sequences were obtained.955,245 and 463 differential genes were found in the CK vs T1,CK vs T2 and T1 vs T2 comparison groups,respectively,and 904,227 and441 differential genes were annotated,respectively.Differential gene GO annotation and enrichment analysis showed that supplemental light in the morning significantly regulated the lipid metabolism process of tomato,and supplemental light in the evening significantly regulated the response of tomato to abiotic stimuli.Annotation and enrichment analysis of the differential gene KEGG database showed that supplemental light in the morning significantly regulated the plant circadian rhythm of tomato,and supplemental light in the evening significantly regulated the zeatin biosynthesis pathway of tomato.Through gene structure analysis and prediction,a total of 19124 SSRs,3445 new gene loci,23659 new transcripts,6117 transcription factors and 1316 lnc RNAs were obtained.(4)A total of 1098 metabolites were detected by wide target metabonomics of tomato leaves treated with LED in different periods.62,69 and 18 differential metabolites were screened in CK vs T1,CK vs T2 and T1 vs T2 groups,respectively.The number of differential metabolites up-regulated by supplementary light in the morning was the largest,while that down-regulated in the evening was the largest.KEGG enrichment analysis of differential metabolites showed that light supplementation in the morning significantly regulated the carbon metabolism pathway of tomato,while light supplementation in the evening significantly regulated the amino acid biosynthesis pathway.The correlation analysis between metabolic group and transcriptome showed that light supplementation in the morning significantly regulated phenylpropanoid biosynthesis pathway,flavonoid biosynthesis pathway and carbon metabolism pathway in tomato,while light supplementation in the evening significantly regulated phenylpropanoid biosynthesis pathway and amino acid biosynthesis pathway.(5)Light supplementation in the morning significantly increased the contents of VC,total organic acids,amino acids,carotenoids and ammonia aromatic substances in tomato fruits,while decreased the contents of flavonoids and some minerals.Compared with evening supplemental light,morning supplemental light is more conducive to the accumulation of health-promoting substances such as VC,amino acids and carotenoids in tomato fruit,and is conducive to improving the nutritional quality of tomato fruit.Light supplementation in the evening significantly increased the contents of sugars,amino acids,flavonoids and benzene aromatic substances in tomato fruit,and decreased the content of minerals.LED supplementary light in the evening is beneficial to improve the flavor quality of tomato fruit.In conclusion,To sum up,supplemental light in the morning is beneficial to promote the vegetative growth of tomato,the accumulation of photosynthetic pigments,the photosynthetic ability and the nutritional quality of fruit,and regulates the lipid metabolism process of tomato leaves,plant circadian rhythm,carbon metabolism pathway,phenylpropanoid Biosynthetic pathways of flavonoids and flavonoids.Supplemental light in the evening was beneficial to promote the reproductive growth of tomato,the opening degree of photosystem II reaction center and the flavor quality of fruit,and regulated the zeatin biosynthesis pathway,phenylpropanoid biosynthesis pathway and amino acid biosynthesis pathway in tomato leaves.