Effects Of Different Led Light Quality And Photoperiods On Growth And Photosynthetic Characteristics Of P.Baillonii Seedlings

Paramichelia baillonii DC Hu.is an evergreen broad-leaved tree of the Magnoliaceae family,and is a rare,endangered and protected plant in the country.The reproduction rate of para,michelia baillonii seedlings is low and the cycle is relatively long,which is one of the factors restricting the protection and development of para,michelia baillonii.Therefore,it is of great significance to improve the quality of the seedlings,and one of the effective ways to improve the quality of the seedlings is to improve the quality of light source.This article uses Paramichelia baillonii seedlings as research material,using LED to control photoperiod and light quality,setting 2 photoperiods(12 h/d,16 h/d)and 4 light quality ratios(R:B:P:G=8:1:1:1,R:B:P:G=6:1:1:1,R:B=8:1,R:B=6:1,where R,B,P,and G represent red,blue,purple,and green light).The effects of different photoperiods,light quality and their interaction on the growth and photosynthetic characteristics of para,michelia baillonii were studied.The response of paramichelia baillonii to light environment changes was discussed,and the effect of photoperiod × light quality ratio combination on paramichelia baillonii cultivation was evaluated synthetically.New ideas and approaches for para,michelia baillonii Seedling cultivation.The main findings are as follows:(1)Treatment with L7(16 h/d×R:B=8:1)was benefi-cial to increase seedling height,leaf area,and nutrient content(especially Ca and Mg)and promote accumulation of biomass of Paramichelia baillonii seedlings,The effect of promoting the growth of seedlings was the best;followed by L8(16 h/d×R:B=6:1)and L5(16 h/d×R:B:P:G=8:1:1:1)which had a greater effect on the growth of Paramichelia baillonii seedlings.The growth and biomass of Paramichelia baillonii seedlings were significantly correlated with endogenous hormones,and there was also a significant correlation with photosynthesis.(2)At L7 and L8,the content of IAA,GA3,and ZR of seedlings increased,and ABA content decreased,(IAA +GA3+ZR)/ABA and IAA/ABA ratios were higher and the ABA/GA3 was lower.The increase of endogenous hormone level of paramichelia baillonii seedlings and the balance of hormones promote plant growth;the treatment of L5 was less effective.(3)Under L7 treatment,the content of chlorophyll a and carotenoids,chlorophyll a/b,Rubisco enzyme and ATPase activity of Paramichelia baillonii were increased,but chlorophyll b was decreased;followed by Ls and L3(12 h/d×R:B=8:1),The former had higher chlorophyll a content,Rubisco enzyme and ATPase activity,while the latter had higher carotenoid content and chlorophyll a/b.(4)Under L7 and L8 treatments,the photosynthetic rate(Pn),maximum photosynthetic rate(Amax)and stomatal conductance(Gs)were higher than those of other treatments,and the respiration rate(Rday)was lower,the optical saturation point(LSP)was the highest under L7 treatment.These two treatments were beneficial to improve the seedlings photosynthesis;followed by L3 and L5,the seedlings had better photosynthesis,which showed greater Pn,Gs and Amax,and lower LCP.Photosynthesis has a significant correlation with photos-ynthetic enzymes and photosynthetic pigments.In addition,Pn and LSP had a stronger positive correlations with Fv’/Fm’,qP and ETR.(5)L7 treatment can improve the maximum photochemical rate(Fv/Fm),effective photochemical rate Fv’/Fm’,non-photochemical quenching(qP),relative electron transfer rate(ERT),the parameter indicates that the photosynthesis of Paramichelia baillonii seedling under this treatment was strong;Secondly,chlorophyll fluorescence in plants treated with L8 has a certain degree of improvement,qP showed no significant difference with L7,ERT was highest and Fv’/Fm’ only secondary.(6)The effects of light quality and photoperiod interaction on Paramichelia bailonii seedlings were significant.The results of the principal component analysis showed that:L7 and Ls treatments,which was ranked first and second respectively,scored well for growth,plant biomass,endogenous hormones,photosynthetic pigments and photosynthesis;followed by L5;L1(12 h/d× R:B:P:G=6:1:1:1)and L4(12 h/d×R:B=6:1)treatments showed poor effective on Paramichelia baillonii seedlings.