The Population Structure Characteristics And Responses To Drought Stress Of Different Gender Of Populus Euphratica

Drought is the key problem of plant survival in the lower reaches of Tarim river.Due to the lower reaches of Tarim river was setting off for a long-term which cause Populus euphratica-the main water sources is grounderwater-suffer severe drought stress.With the prolonged drought stress,Populus euphratica was faced with population decline,male-biased and serious insufficient supply of seedlings,reducing the use value of Populus euphratica as a dominant edificator of desert riparian forest.At present,the studies on the response of Populus euphratica to drought stress mainly focus on the age structure and distribution,root development and degeneration,but less on the gender differences.Based on this,the present study takes female and male Populus euphratica as the research object,analysis the Populus euphratica response to drought stress environment gender differences,designed to enrich the research content of gender differences in drought stress environment,and provide theoretical support for conservation recovery and effect of eco water transfer of Populus euphratica populations.In the context of many years of eco water transfer and recovery at the lower reaches of the Tarim River,this study selected the female and male Populus euphratica at the lower reaches of the Tarim River as the research object,and at the riverside of the Yingsu,Arakan and Yikanbujima sections and away from the river.The sample plots were used to analyze the differences in population structure,leaf configuration,and physiological and ecological responses of different populations of Populus euphratica through detailed plot surveys,field monitoring,and indoor laboratory analysis.The main results are as follows:(1)The age structures of Populus euphratica populations at the lower reaches of the Tarim River were all"inverted pyramid".The proportion of the number of seedings in the population decreased significantly with the distance from the river,and the over-aged plants were mostly in the declining trend.Populus euphratica populations at the lower reaches of the Tarim River had sex-specific spatial variability and showed male-biased.As the degree of deviation deviated from the river course,the depth of groundwater table tended to increase.(2)The results of leaf configuration showed that the leaf temperature,specific leaf area and leaf anatomical parameters of male plants were greater than female plants in most cases,and were significantly different from those of distant river(P<0.05)The thickness(134.3±10.1)and the female plant(113.3±10.5)of the palisade tissue on Yikanbujima,but the thickness of sponge tissue of male plants were lower than female plants in the Aragan,Yikanbujima at 50 m by the river;The male plants has a higher stomatal density than the female plants and the stomatal size is more stable than the female plants at 500 m by the river.The difference of leaf configuration showed that the male plants in the lower reaches of Tarim River had relatively stronger drought resistance.(3)The results of the differences in physiological and ecological responses indicated that there were significant differences(P<0.05)in the other indexes except the relative water content(%),the maximum photochemical efficiency(F_v/F_m);The lowest values of water potential of male and female plants appeared at noon on the riverside and away from the river,and the male plants were larger than the female plants(except at noon);The daily stem flow rate of male plants is greater than female plants at night,lower than female plants during the day and small fluctuations;Photosynthetic characteristics showed that the ETR of male plants was significantly greater with photosynthetically active radiation(PAR)than female plants,especially after the photosynthetically active radiation(PAR)reached 1000(?mol/m~2·S),and the farther from the river,the greater the difference.The physiological and ecological responses showed that when faced by drought condition the male plants are more conducive to survival.(4)According to the results,this study preliminarily shows that under severe drought stress in the lower reaches of Tarim River,the corresponding strategies were adopted for survival of male and female Populus euphratica,that is,different leaf configurations and physiological responses.This gender difference in the external and internal adaptation strategy cause the change of the sex ratio.And the deviation of sex ratio aggravates the degradation of Populus euphratica in the lower reaches of Tarim River.