Effects Of Different Light Quality Ratio And Light Intensity On Growth And Metabolites Of Pepper

Originating from tropical region,pepper plants has a high demand for light,and appropriate light qualities and intensities are important for the growth of pepper.However,how to use the light environment to enhance the growth and development of pepper has notbeen thoroughly studied so far.In view of this,this study uses pepper as the test material,from the perspective of phenotype,physiology and biology,to study characteristics of the growth and development in pepper under different light qualities and intensities.This studyis aimed to provide the theoretical basis for the improvement or innovation of peppercultivation.The results are listed as follows:(1)Through the analysis of different light quality ratio[(control,CK)white,T1(3 red:1 blue:6 white),T2(4 red:1 blue:5 white),T3(5 red:l blue:4 white),T4(7 red:1 blue:2 white)]effects on growth and physiological characteristics of pepper,we found that,at the seedling stage,the number of leaves under T4 treatment was significantly lower than that under CK treatment,and the node spacing was significantly longer than that under T2 treatment at theblooming stage,and results from T1 treatment showed phenotype of obvious dualization,because its plant height was significantly lower than that of CK and other treatments.Thenumber of flowering under T3 treatment was significantly higher than that under CK and other treatments and there were significant differences among them,which is significance for the theoretical research on the regulation of light quality on flowering and fruit setting in pepper.For physiological characteristics,T2 treatment promoted the synthesis of chlorophyll,whose content was significantly higher than that of CK.For anthocyanin content,light treatment seemed to promote anthocyanin synthesis at the seedling stage due to increased anthocyanin content observd in all other treatments except T4 treatment when compared with CK,but the opposite situation occurred at full flowering stage,except T3 treatment,anthocyanin content from all other treatments were significantly reduced compared with CK.The analysis in photosynthetic characteristics showed that excessive red light could significantly inhibit the photosynthetic capacity of pepper under T4 treatment,especially in thecase of intercellular CO2 concentration.Appropriate light quality ratio properly improved the photosynthetic characteristics of pepper.For example,stomatal conductance under T2 treatment was significantly improved compared with CK.In addition,different light quality ratios had significant effects on the activities of antioxidants in pepper,and the levels of ascorbate(APX),superoxide dismutase(SOD),peroxidase(POD)and malondialdehyde(MDA)in each growth stage under T1 treatment were the more higher.Under T2 treatment,the content of ascorbate(APX)and superoxide dismutase(SOD)were significantly increased as comparison to CK,while the content of malondialdehyde was significantly decreased.Throughcomprehensive analysis,it was found that the light quality ratio T2-4 red:1 blue:5 white;T3-5 Red:1 blue:4 white is the best combination,Comprehensive analysis showed that the growth of pepper under T2(4 red:1 blue:5 white)and T3(5 red:1 blue:4 white)treatments was significantly affected.(2)On the basis of result(1),effect of different light intensities[M1(T2-240 μmol·m-2·s-1),M2(T2-310 μmol·m-2·s-1),M3(T3-240 μmol·m-2·s-1),M4(T3-310 μmol·m-2·s-1),CK(White-310μmol·m-2·s-1)]on the growth and physiological characteristics of pepper was anlyzed,and found that compared with the CK,M1 significantly promoted the plant height and leaf area of pepper at full flowering stage,and at seedling and initial flowering stage,M2 significantly promoted the stem diameter,but inhibited the leaf growth in pepper.M3 promoted the stem diameter at the seedling and beginning flowering stages,but inhibited the leaf growth.In addition,M4 inhibited the leaf growth.For anthocyanin,its content at the seedling stage and initial flowering stage was significantly higher under M1 treatment than that in the control group,anthocyanin synthesis at the bud stage was inhibited,and the content of anthocyanin at the full flowering stage was the highest under M3 treatment.M1 significantly promoted the increase of SOD and POD activities at the full flowering stage but these enzyme activities at the bud stage were generally inhibited under each treatment.In the M1 treatment and the control group,MDA content in the pepper plants was accumulated in the seedling stage and the bud stage,while in the M3 treatment group,MDA content was accumulated in the pepper plants at the initial flowering stage and the full flowering stage.Comprehensive analysis showed that the growth indexes of pepper treated with M1(T2240 μ mol·m-2·s-1)and M2(T2-310 μmol·m-2·s-1)were superior to other treatments.(3)Based on the results of(2),the different metabolites of M1 and M3 were further analyzed,and the results showed that anthocyanin,quinate and lutein were accumulated more in M1 treatment,whileother metabolites,such as D-gulose acid-1,4-lactone,4-hydroxy-2,6dimethylaniline etc,accumulated more under M3 treatment.These differential metabolites were mainly related to the biosynthesis of phenylpropanoid biosynthesis ABC transporters and other pathways.