Study On Functional Traits Of Heteromorphic Leaves Of Populus Euphratica In The Lower Reaches Of The Heihe River Based On Comparative Transcriptomic

Populus euphratica is a unique dominant tree species of desert riparian forest in China.It is an ancient relic plant in the Tertiary period.It has strong adaptability to desert environment and great ecological research value.Exploring the adaptation mechanism of Populus euphratica and desert environment has important practical significance for protecting Populus euphratica forest.In this study,Populus euphratica in the Ejina oasis in the lower reaches of the Heihe River was used as the research object.The representative leaf shapes of typical plants at different growth and development stages of Populus euphratica were selected to study the functional traits of Populus euphratica leaves,and comparative transcriptomics was used to analyze the molecular regulation mechanism of Populus euphratica heteromorphic leaves to adapt to the environment.It provides a new perspective for revealing the physiological ecology and molecular mechanism of Populus euphratica to adapt to the environment,and provides a scientific basis for the population protection and local ecological restoration of Populus euphratica forest in the lower reaches of the Heihe River.The main results are as follows:(1)In this study,the morphology and photosynthesis mechanism of Populus euphratica leaves at different ages and different developmental stages were studied.The results showed that the leaf morphology and photosynthetic mechanism of P.euphratica varied with tree age,leaf age and leaf spatial distribution.With the growth and development of P.euphratica and the vertical spatial direction of leaves from the tree base to the canopy,the leaf area of P.euphratica increased,the leaf shape index decreased,and the light energy capture area increased.Young P.euphratica has higher light sensitivity,the highest utilization of weak light,and higher photosynthetic efficiency and organic matter accumulation.The old P.euphratica has a weak ability to regulate light.After being inhibited by light,it takes longer time to restore the photosynthetic rate,and its photosynthetic efficiency is low.The metabolic ability of middle-aged P.euphratica is strong.(2)The research on the physiological and ecological characteristics of P.euphratica to the environment shows that the transpiration rate of P.euphratica canopy leaves is higher than that of grass-roots leaves at the time of the strongest noon light and heat conditions.Under drought stress,P.euphratica improves drought resistance by improving water use efficiency.In addition,high temperature and drought inhibited the stomatal opening of P.euphratica leaves.Canopy leaves receive more direct sunlight than base leaves,and their stomatal opening is smaller.The stomatal regulation mechanism of young and old P.euphratica seems to be more perfect,and its photosynthetic rate is regulated by non-stomatal limitation for a longer time.Compared with stomatal regulation,the stomatal regulation mechanism of young and old P.euphratica is more self-regulated and less affected by the environment.(3)Comparative transcriptome analysis of typical leaves of four typical developmental stages of P.euphratica.Three comparison groups of P.euphratica seedlings and saplings,seedlings and adult trees,middle trees and adult leaves were set up,and 48,1764 and 196 significant differential genes were screened out respectively.Functional analysis of differential genes showed that P.euphratica seedlings mainly increased photosynthetic efficiency,promoted cell metabolism,and maintained the stability of internal cells to promote growth.During the growth and development from seedling stage to sapling stage,the transition from vegetative growth to reproductive growth was completed,more synthetic substances were synthesized,and metabolism was enhanced,mainly in pollen tube development,root development,and plant hormones.There were differences in genetic information processing and environmental response,and the adaptability to adversity was enhanced.GO item interaction network analysis found 22 key GO items regulating the growth and development of P.euphratica,and 7 candidate genes closely related to the growth and development of P.euphratica were screened.Among them,LOC105123506,LOC105136548 and PsSAMT may be three important candidate genes regulating the growth,reproduction and stress response of P.euphratica,and participate in the whole process of P.euphratica growth.LOC105098210 and LOC105095593 play a role in the early development of P.euphratica,which is related to the regulation of cell division and growth.LOC105139071 may regulate the growth and stress response of P.euphratica by regulating gibberellin content.LOC105131320 is an important candidate gene for regulating root development,pollen tube growth,plant photosynthesis and various stress responses of P.euphratica.