Responses Of Male And Female Plants Of Populus Tomentosa To Drought, Saline-alkali Stress And Mycorrhizal Fungal Infection

Drought and soil salinization are the environmental factors that plants often suffered from natural growth conditions.At the same time,mycorrhiza is one of the most widely distributed mutualistic symbiosis.Plants inoculated with mycorrhizal fungi can promote the growth and increase their resistance in a certain extent.On the other hand,dioecious plants are excellent materials for the study of species adaptability.Due to the different distribution of energy in growth and development for both sexes,there are sex differences in adversity response.In this experiment,annual male and female Populus tomentosa Carrière cuttings were selected as experimental materials,to study the different responses of two sex cuttings in terms of morphological characteristics,physiological and biochemical indicators,and cellular ultrastructure under drought,saline alkaline stress and AM fungal colonization.It is used to reveal the different response mechanism of dioecious plants to environmental changes,and also provides theoretical reference for phytoremediation in drought and saline-alkali areas.The key research findings are following:1.Different responses to arbuscular mycorrhizal fungi,salt stress and their interactions in dioecious plant Populus tomentosa.Female and male cuttings of Populus tomentosa were treated with two AM fungal regimes,with or without Glomus constrictum inoculation,and three salt regimes,no salt,low-salinity level（100mM NaCl）and high-salinity level（200mM NaCl）.The results showed that salt stress alone had significant effects on growth,dry matter accumulation,photosynthetic capacity,and active oxygen accumulation of male and female plants,but had less negative impact on male plants.On the other hand,Under the low-salinity level（100mM NaCl）condition AM fungal colonization alleviated the salt-induced reduction in growth,gas exchange,photosynthetic pigment content and nitrogen（N）and phosphorus（P）concentrations in the leaves,stems and roots for both sexes.However,the AM fungal colonization had no significant impact on the majority of the examined parameters under the high-salt level（200mM NaCl）.The reason may be that male and female plants can increase the activity of superoxide dismutase（SOD）and guaiacol peroxidase（GPx）and the inhibition of malondialdehyde（MDA）due to AM fungi colonization under low-salt treatment.Furthermore,sodium（Na⁺）and chlorine（Cl^-）concentrations in three organs were lower in the AM vs.non-AM plants under the 100mM NaCl condition for both sexes.AM fungal treatment may protect salt-stressed plants by inhibiting the salt-induced oxidative stress,thereby improving the nutrient absorbance and inhibiting Na⁺transport from the roots to the shoots.In addition,a little differences induced by AM fungal colonization in plant growth between the two sexes were observed,but significant differences were obtained in some parameters such as SOD,GPx and N,P concentrations differed between the two sexes.2.Different responses to drought,alkaline stress and their interactions in dioecious plant Populus tomentosa.Two different drought degrees were used to treat female and male cutting of Populus tomentosa,well water and drought;three alkali degrees,control,low alkali（75mM Na₂CO₃）stress and high alkali（150m M Na₂CO₃）stress.The results showed that female and male Populus tomentosa exhibited different plasticity to both stresses:males adopt“conservative”strategies,whereas females exhibit relatively“acquisitive”strategies.A shown by the fact that both gender exhibited significant inhibition on the growth and physiological indicators,such as leaves,stems,total biomass（TB）,total leaf area（TA）,photosynthetic capacity(A_net,g_s,E and PNUE),mineral element content,N use efficiency（NUE）,N uptake efficiency（NU_pE）,WUE_i,in response to drought and alkaline conditions.On the other hand,drought and alkali stress have less inhibitory effects on male,as shown by the higher biomass accumulation,photosynthetic capacity,water and nutrient use efficiency.Females showed a higher plasticity of root/shoot ratio（RS ratio）,fine root/coarse root ratio（F/C ratio）,C isotopic content compared with males,which suggested that the high tolerance of male Populus tomentosa trees is realized by the phenotypic canalization except for these three parameters,which are related to the maximization of water and nutrient gain under drought and alkaline stresses.