| Rape(Brassica napus)is one of the four major oil crops in the world,and it occupies an important position in my country’s agricultural production.Rapeseed seedlings indoor nursery can get rid of the influence of harsh natural environment,and can flexibly provide timely and age-appropriate seedlings for field production.Therefore,cultivating healthy strong seedlings becomes the key to indoor seedling cultivation.Light is the primary factor for growing strong seedlings indoors.At present,many studies have pointed out that red and blue composite light is the most important matching spectrum that is beneficial to plant growth.The good effect of red and blue light have also been found in the research on rapeseed,but these studies still cannot provide sufficient support for the regulation of indoor rapeseed seedling light environment.Moreover,the research on the characteristics and mechanisms of light regulation of rapeseed growth and development is not fully documented,and the study of the interaction between spectrum and spectrum is rarely involved.The supplement to these studies is an important basis of the optimal design of indoor rapeseed growing light environment.Therefore,this study used Brassica napus L.var.Njau 4 as the test material,Under the condition of artificial light,investigated that:(1)How light affected the growth of rapeseed seedlings;(2)Effects of supplemental lights to red-blue light on the growth of rapeseed seedlings;(3)Effects of supplemental lights to red-blue light on the differentially expressed genes and metabolic pathways of rapeseed seedlings.(1)The research of rapeseed seedlings growing in different spectra including red-blue light(RB),red-blue-yellow light(RBY),blue-yellow light(BY),blue light(B),red light(R)and yellow light(Y)found that different spectra did not affect the stem thickness,but significantly affect other morphological characteristics and biomass accumulation of rapeseed seedlings.The plant height of Y treatment was the highest,and that of B treatment was the lowest.There was no significant difference in plant height of other spectral treatments.The spectrum significantly regulated the leaf area.The leaf area of the compound light treatment was larger than that of the monochromatic light treatment,and the Y was obviously not conducive to leaf growth,and the leaf number and root length of the Y was significantly less than that of other treatments.In addition,the root length of the RB and RBY treatments was longer than that of other treatments,and there was no significant difference in root length of other treatments.The spectrum also regulated the biomass accumulation of rape.The combined light treatments of RB,RBY and BY were beneficial to the biomass accumulation of rape,while the Y and B treatments were obviously not conducive to the accumulation of biomass of rape.The content of photosynthetic pigments under different spectral conditions was significantly different.The content of chlorophyll and carotenoids of the BY treatment was significantly greater than that of other treatments.The content of chlorophyll a,chlorophyll(a+b)and carotenoids was the smallest in Y treatment,and chlorophyll a/b was value significantly reduced,there was no significant difference in chlorophyll content and chlorophyll a/b value of other treatments.The net photo synthetic rate(Pn)of composite light was significantly greater than that of monochromatic light.The Pn,stomatal conductance(Gs)and transpiration rate(Tr)of Y treatment were always the lowest.The anatomical structure of the leaves was significantly regulated by the spectrum.The leaf thickness,palisade tissue thickness,the number of palisade tissue layers and the ratio of palisade tissue to sponge tissue were the largest in RB treatment.Except for the number of layers,there was no significant difference in leaf development indexes between RBY treatment and RB treatment.Except for the B treatment,the leaf development of the monochromatic light treatment was obviously hindered,and the indexes of the palisade tissue layers and the leaf thickness were small.The results showed that the different morphology and biomass accumulation of rapeseed under different spectra were the results of the spectral control of chlorophyll content,Pn,Gs,leaf thickness,palisade tissue thickness and layer number.Monochromatic light,especially Y,severely restricted the morphogenesis and growth of rapeseed,and the composite spectra RB and RBY were more conducive to the growth of rape.(2)Based on the results of the first experiment,RB,RBY,red-blue-green light(RBG),red-blue-white light(RBW)and white light(W)were set to study the effects of supplemental lights to RB on the growth of rapeseed seedlings.The study found that the spectrum did not significantly affect the plant height,while the stem thickness,leaf area and number of leaves of the RBG treatment were significantly larger than other treatments,and the root length was not significantly different from RBW.The stem thickness and leaf area of W treatment were significantly the smallest,while the stem thickness,leaf area and number of leaves including root length in other treatments had no significant difference.The stem biomass and total biomass of the W treatment were significantly lower than other treatments,while the stem biomass and total biomass accumulation of the RB,RBG,RBW and RBY treatments had no significant difference.Only the root mass of the RBG treatment was significantly higher than other treatments.Compared with W,the content of chlorophyll a,chlorophyll(a+b)and carotenoids in RB,RBG and RBY were significantly reduced,but the photo synthetic pigment content of RBW treatment was higher than that of RB treatment,While the photosynthetic pigment content of RBY treatment was lower than that of RB treatment.The RBG,RBW and RBY did not affect Pn,but the Pn of RBW treatment was significantly greater than that of RBY and W treatment,and the Gs and Tr of RBG treatment was the largest.Adding light to RB did not affect the electron transfer rate(ETR)and non-photochemical quenching coefficient(NPQ),but RBY and RBW significantly reduced the photochemical quenching coefficient(qP)and actual photochemical quantum yield(Fv’/Fm’),And the maximum photochemical quantum yield(Fv/Fm)of RBG treatment was significantly higher than that of RBY treatment.At the same time,the soluble sugar and sucrose of the RBG treatment was higher than other treatments,while the starch content was only lower than W treatment.In addition,compared with other light treatments,leaf thickness,palisade tissue thickness,leaf compactness,the ratio of palisade tissue to sponge tissue and palisade tissue layer number under RBY and W treatment were reduced,while there was no significant difference in leaf anatomical structure indexes under other treatments.The results showed that the effects of supplemental lights to RB on the growth and morphology of rapeseed seedlings were mainly significantly related to the development of leaf structure,chlorophyll fluorescence parameters and photosynthetic products.From the perspective of morphology and biomass comparison,the RBG composite light was more conducive to growth of rapeseed seedlings.(3)In order to analyze the mechanism of compound light affecting photosynthesis and leaf development of rapeseed,this study used RNA-seq technology to analyze differentially expressed genes(DEGs)and their metabolic pathways under different spectral treatments.The study found that compared with RB,214,600,232,517 up-regulated genes and 235,213,135,234 down-regulated genes were identified in RBG,RBW,RBY and W treatments,respectively.The GO and KEGG analysis of DEGs showed that DEGs induced by RBG were significantly enriched in biological processes,and up-regulated genes were significantly enriched in high light intensity,carotenoid catabolism,root hair development and carbohydrate metabolism pathways,and the down-regulated genes were significantly enriched in simple leaf morphogenesis and negative regulation of leaf senescence.The up-regulated genes induced by RBW were significantly enriched in light stimulation,photosynthesis and stomatal movement related pathways,and down-regulated genes were significantly enriched in the pathways related to the negative regulation of auxin transport and abscisic acid biosynthesis at the grassroots level.The up-regulated genes induced by RBY were significantly enriched in pathways such as carbohydrate metabolism,galactose metabolism and other polysaccharide degradation,and down-regulated genes were significantly enriched in cell development,leaf development,cell proliferation regulation,and photoreaction pathways in photosystem II.The up-regulated genes induced by W were significantly enriched in the pathways of oxidative phosphorylation and carotenoid biosynthesis,and the down-regulated genes were significantly enriched in the pathways related to cell growth,leaf development and photosynthesis.The current results suggested that the DEGs induced by supplemental light to RB affect photosynthesis,leaf development,cell differentiation and division,hormones,carbohydrate metabolism and other processes,which in turn affect its morphogenesis and growth,However,the RBY blocked the development of palisade tissue via DEGs which were involved in the processes of cell division,proliferation and growth,and thus the leaves grown under RBY only formed a two-layer palisade tissue. |
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