Study On Sex Ratio Pattern And Sexual Differences Of Gorddejevii In Hunshandake Sandy Land

Salix gordejevii is a common dioecious plant in Hunshandake sandy land and one of the important sand-fixing pioneer plants in the region.In the long-term evolution process,male and female plants are likely to have significant sexual differences in quantity,spatial distribution,age structure,functional traits and adaptability to the external environment because of different reproductive costs.In this study,male and female S.gordejevii plants in Hunshandake sandy land were used as experimental materials to study sex ratio,spatial distribution pattern and age structure characteristics,compare sexual differences in scaling relationship between functional twig traits and adaptability to drought and aeolian environments,and reveal the extent and main reason of sex ratio bias.The results are asfollows:(1)The sex ratio(female/male)was female-biased(P<0.01)in natural population of S,gordejevii.Among them,the number of young-and middle-aged females was significantly higher than that of young-and middle-aged males.The number of males and females approached the balance gradually as age increased.Male and female populations were mainly distributed in a clumped pattern on 0?25 m scales,and were occasionally randomly distributed on a small scale.The sexual spatial segregation phenomenon only occured in relatively resource-limited area.The age structure and dynamic change between male and female populations were significantly different.Among them,the age structure of female population was stable type,and that of male population was declining type.The survival curves and survival function curves showed that female population entered the recession earlier than male population.Time series analysis showed that the number of old individuals increased with time,and lack of young individuals was an important reason for the decline of male and female population.(2)There were sexual differences in biomass accumulation,allocation and scaling relationship among traits in male and female functional twigs,and females had more lamina area and mass per unit supporting organ mass than males.Males had significantly higher supporting organ(stem and petiole)mass and the percentage of them in twig mass than females,and lower the percentage of lamina mass than females.At the twig level,females were more inclined to increase longitudinal growth rate than males.With the increase of stem mass or twig mass,females had significantly higher total leaf mass than males,and the growth rate of total lamina area of females was faster than that of males.At the leaf level,females had higher lamina mass and lamina area under the same petiole mass than males.Meanwhile,the growth rate of lamina area was greater than that of lamina mass in females,while the growth rate of the two traits were similar in males,which indicated that female lamina trend with larger.(3)Drought significantly reduced growth and photosynthesis,seriously disrupted biomass allocation,osmotic regulation function and antioxidant enzymes system of male and female S.gordejevii cuttings,and led to significant sexual differences between male and female cuttings in these traits.Under the well-watered treatment,no significant differences were detected in plant height,basal diameter,total leaf number,individual leaf area,stem dry weight,root dry weight,root weight ratio,root shoot ratio,chlorophyll b content,total chlorophyll content,carotenoid content,gas exchange,chlorophyll fluorescence,relative water content,malondialdehyde content,proline content and soluble sugar content between the sexes.However,under drought stress,females exhibited significantly higher plant height,total leaf number,leaf area,stem dry weight,root dry weight,total chlorophyll content,net photosynthetic rate,maximum efficiency of PSII(photosystem ?),effective quantum yield of PSII and relative water content,and lower non-photochemical quenching coefficient,malondialdehyde content,proline content and soluble sugar content than males.Meanwhile,leaf dry weight,total dry weight,leaf weight ratio,chlorophyll a content,superoxide dismutase activity and peroxidase activity of females were always significantly higher than that of males.The results indicated that drought inhibited growth and physiological characteristics more in males than in females,and females possess greater drought resistance than do males.(4)Sand burial could significantly increase the growth and photosynthesis of male and female S.gordejevii cuttings,promote the growth of basal diameter,leaf biomass and stem biomass more in females,and promote the growth of plant height and crown width more in males.Affected by sand burial,root dry weight,total dry weight,chlorophyll a content,total chlorophyll content,net photosynthetic rate and stomatal conductance in both sexes were significantly increased,with females having significantly higher total chlorophyll content,net photosynthetic rate and chlorophyll fluorescence than males.Meanwhile,sand burial had little effect on physiological and biochemical substance content in both sexes,and no sexual differences were found.However,wind erosion significantly decreased the growth and photosynthesis of S.gordejevii,affected osmotic regulation function and antioxidant enzyme system,and inhibited more in males than females.Affected by wind erosion,plant height,basal diameter,crown width and biomass were decreased more in males than in females.And females had significantly higher root weight ratio and root shoot ratio than males.The net photosynthetic rate,intercellular CO2 concentration,transpiration,relative water content and soluble protein content were significantly decreased,while the content of malondialdehyde,proline,soluble sugar,tannin and antioxidant enzyme activity were significantly increased,with males possessing significantly lower net photosynthetic rate,chlorophyll fluorescence,relative water content and antioxidant enzyme activity,and significantly higher the content of malondialdehyde,proline and soluble sugar than females,which indicated that wind erosion caused more serious physiological damage to males than to females.In conclusion,the sex ratio(female/male)was female-biased of 5.gordejevii population in Hunshandake sandy land.The sexual spatial segregation phenomenon existed in relatively resource-limited area.There were sexual differences in age structure,developmental trends,functional traits and environmental adaptability between male and female populations.Females possess greater adaptability than males by maintaining higher photosynthesis to ensure the normal growth of plants,which is an important reason why the number of females is more advantageous in the long-term.