| In northwest of China,due to the influence of low temperature,the daylighting time of solar greenhouse is only about 7 hours in deep winter and early spring.Short illumination time is an important factor affecting the growth and yield formation of greenhouse crops.Light supplementation in greenhouse has become an important way to improve the yield and quality of horticultural crops in greenhouse.However,the application of supplementary light in greenhouses in China is still in its infancy,and there is still a lack of systematic research on the effects of supplementary light on crops.There are many studies on the effects of light intensity and light quality on crop growth and development,but few studies have been conducted on the effects of different light supplementation time on crop growth and development.The effects of light supplementation time(7h + 1H(T1),7h + 3H(T2),7h + 5h(T3)on growth physiology and differential gene expression of transcriptome in pepper seedlings were studied by using LED light supplementation and simulating 7h daily light as control(CK),and the molecular mechanism of different light supplementation time affecting growth physiology of pepper was revealed.The main results are as follows:1.The accumulation of dry matter in hot pepper seedlings was significantly increased by supplementing light for 1 h,3 h and 5 h after 7 hours of light per day.The plant height,root surface area,root projection area and root volume of pepper seedlings were significantly increased after 3 and 5 hours of light supplementation.Compared with 1 h and 5 h of light supplementation,3 h of light supplementation could significantly increase the total root length and root tip number of seedlings.Light supplementation for 1 h and 3 h could significantly promote the leaf morphological development of pepper seedlings.Compared with 3 h and 5 h light supplementation,the leaf area of 5 h light supplementation was significantly smaller than that of 3 h light supplementation.The content of chlorophyll a increased significantly after 3 hours and 5 hours of light supplementation compared with 1 hour and CK supplementation.The net photosynthetic rate and stomatal conductance at 5 h after light supplementation were significantly lower than that at 3 h after light supplementation.2.The ultrastructure of chloroplasts showed that the number of chloroplasts in mesophyll cells increased after 3 hours of light supplementation.The shape of chloroplasts was mainly ellipsoid,which was close to the membrane of mesophyll cells.The chloroplasts were closely distributed but not overlapped.The grana lamellae of chloroplasts were stacked tightly.It was obvious that the starch volume was cumulative,the number of chloroplasts increased significantly,and the photosynthetic capacity was enhanced.The maximum quantum efficiency(Fv/Fm)and actual quantum yield(ps II)of photosystem II of seedling leaves treated with light supplementation for 3 hours were significantly higher than those treated with light supplementation for 5 hours.Compared with light supplementation for 5 hours and CK,the regulatory energy dissipation(Y(II)of light supplementation for 3 hours was significantly lower than that of light supplementation for 5 hours and CK.3.RNA-Seq sequencing showed 124 differentially expressed genes between T1 and CK,82 of which were significantly up-regulated and 42 significantly down-regulated;1283 differentially expressed genes between T2 and CK,705 of which were significantly up-regulated and 578 significantly down-regulated;1091 differentially expressed genes between T3 and CK,553 of which were significantly up-regulated and 538 significantly down-regulated.4.Compared with T3,T2 significantly upregulated 347 genes and downregulated 590 genes.GO annotation analysis showed that these genes were significantly enriched in 15 GO terms,including xyloglucosyl transferase activity,apoplastic,cellular polysaccharide metabolism,which were closely related to cell carbohydrate metabolic process and plant photoresponse.CPRF2,Paggis,HLIPS,GIGANTEA,LSH1 and FTSH genes related to plant photoresponse were significantly different in different treatments.5.KEGG Pathway enrichment analysis showed that 19 genes were significantly enriched in plant-pathogen interaction,9 genes were significantly enriched in zeatin biosynthesis and 24 genes were significantly enriched in plant hormone signal transduction and other metabolic pathways in T2 vs.CK(P < 0.05).In the comparison group of T2 vs.T3(P < 0.05),20 genes were significantly enriched in plant-pathogen interaction,5 genes were significantly enriched in sesquiterpenoid and triterpenoid biosynthesis,6 genes were significantly enriched in zeatin biosynthesis,and 4 genes were significantly enriched in Flavonoid biosynthesis.In metabolic pathways such as synthesis.6.Quantitative protein analysis showed that the expression of Csp41 b,PGM,ASP1,CAP family,CHLM and MPEC genes(proteins)in different treatments of seedling leaves was significantly different between control group and T1,T2 and T3 treatments,and the expression trend was consistent at the protein and gene levels,and the correlation was high. |
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