| Catalpa bungei,originated in China,is a famous ornamental species and high-quality precious timber species,it is also one of most ancient species and has a long history of over 3000 years of cultivation.At present,in the process of fast-growing and high-yield plantation construction of C.Bungei clones,facing the challenges such as low stand quality,low productivity and lack of scientific management measures.Light and water are major restrictive environment factors in plant growth and development,and plant productivity.Our study focused on the two constrained resources,light and water,and mainly focused on light,based on the method of plant ecophysiology and molecular biology,to reveal the morphophysiological characteristics and bioinformatics.Our results can provide theoretical reference and data support for C.bungei seedlings cultivation,forest light environment management and stand density control etc.,and fill the blank in light response of C.Bungei.At the same time,our results will further enrich the intensive and efficient cultivation technology system of C.Bungei commercial forest,and promote the construction of precious timber commercial forest in central region of China.?1?The experiment of light intensity conversion was carried out to study the response of both new and old leaves in Catalpa bungei clone 9-1 plantlets to the changing light environment.Three fixed light gradients?80%,50%and 30%of natural light intensity?,and four transformation groups of light intensity?80%to 50%,80%to 30%,30%to 50%,30%to80%?,the experiment simulated the process of both increasing and decreasing photon density at lower and middle canopy leaves after pruning and thinning,and canopy closure,respectively.Results showed that:C.Bungei seedlings'growth,photosynthesis,fluorescence parameters were significant different?P<0.05?.With strong ability of using high light,thus,C.bungei seedlings can be cultivated with only mild shading measures.For old leaves,when seedlings were transformed from 30%to 50%and 80%respectively,photoinhibition was observed with sudden increase of light intensity,the seedlings in 50%can recover at30 days,whereas that can not recover in 80%light intensity with the Fv/Fm value was significantly lower than other combinations.For new leaves,the fluorescence parameters of leaves in the same light environment were not significantly different,indicating that the new leaves has been fully accepted to the new light environment.So,some forest management measures,such as pruning and thinning,to obtain canopy light redistribution,thinning and pruning intensity should be considered in plantation management,because great changes in light intensity may cause photoinhibition in shade-adapted leaves,leading to a reduction in canopy photosynthesis,and ultimately,biological yield.?2?Three light gradients and two water gradients were designed to study the drought adaptability of C.bungei clone 9-1 plantlets,to explain the issue of whether the shade will reduce the negative impacts of drought.The results showed that:both light and water significantly affected morphological and physiological parameters,and their interactions?P<0.05?.The phenotypic plasticity of light?0.47?were higher than that to water?0.21?,indicating that light was the main factor caused the changes,moreover,the phenotypic plasticity of leaf physiological parameters were higher than that of morphological parameters.Under 80%and 50%irradiance,drought significantly decreased growth,total biomass,leaf and stem biomass allocation,whereas under 30%irradiance,there was no significant difference of leaf photosynthesis,stomatal conductance and transpiration rate between moisture and drought groups.So,shade did not alleviate the negative effects of drought stress under50%light environment,whereas it did reduced the negative effects of drought stress under 30%light intensity.In brief,the effect of drought on C.bungei plantlets depended on the irradiance conditions.Our results showed that the necessity of stand density regulation and light environment management in afforestation of C.bungei in arid area.?3?The morphophysiological responses of both sun and shade leaves in four-year old C.bungei 9-1 clone trees were analyzed,the results showed that:There were significant difference in leaf structure,nutrient content,non structure carbon content,gas exchange parameters,light response parameters and fluorescence?P<0.05?,whereas no significant difference in chlorophyll content between sun and shade leaves.The net photosynthesis of sun leaves was five fold than that of shade leaves.The order of different light response models in sun and shade leaves were:exponential model>rectangular hyperbola>non-rectangular hyperbola.The phenotypic plasticity of physiological parameters was higher than that of morphological parameters,and fluorescence and gas exchange parameters had higher phenotypic plasticity index.Our results provided the first hand information for forest management.?4?Six samples of both sun and shade leaves of four year old C.bungei 9-1 clone saplings were used as materials to finish transcriptome sequencing.A total of 48.78Gb Clean Data were obtained,and the Clean Data of all samples reached 6.91Gb,and Q30 percentage was above 96.36%.A total of 81,395 Unigene after assembly.There were 18,575 Unigene above 1KB.The total length of Unigene was 67,432,983,indicating that assembly integrity was high.Based on the Unigene library to make gene structure analysis,in which SSR analysis was performed to obtain a total of7829 SSR makers.Differential expression analysis showed that the number of differential expressed genes between sun and shade leaves was 1306,sun leaves VS shade leaves,the number of up-regulated genes was 826,the number of down-regulated genes was 480,the number of genes without significant differences in expression was 20,471.Making analysis of pattern clustering,function annotation,and enrichment analysis for differentially expressed genes.A comparison of Unigene with GO database can be divided into 3 categories:biological process,cellular component and molecular function,and 53 branches.A comparison of Unigene with COG database can be divided into 25 categories.Taking the KEGG database as reference,according to the metabolic pathway,the transcriptome data can be divided into 5 categories and 50 branches.In summary,firstly,we quantified the strength of the pruning and thinning,and ultimately the practice can be divided into several times instead of once.Secondly,based on the conclusion of less damage in shade leaves under drought stress,we further suggested much attention should be focused on the amount of reservation of shade leaves in arid afforestation.Finally,we analyzed ecopysiological and transcriptome response of sun and shade leaves,making some differential expression analysis of the phenotype and gene,further more,some of the differentially expressed genes were annotated.Our research can provide scientific evidence and data support for C.bungei seedlings cultivation,stand density regulation,stand light management,gene express,etc. |
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