Eco-physiological Responses Of Males And Females In Hybrid Poplor(Populus Deltoides×Populus Nigra)Under Salinity And Drought Stresses

The development of social economy leads to the ecological problems increase which affect the growth of plants,such as salinity,drought,and so on.The eco-physiological responses of hybrid poplor?Populus deltoides×Populus nigra?to salinity and drought stresses were explored by pouring the Na Cl solution and controlling the water,and the main results are follows:?1?Under salinity stress,the net assimilation rate?P_n?,stomatal conductance?g_s?,transmission rate?T_r?,isoprene emission rate,rate constant of Isps reaction?Isps?,relative height growth?RHG?,stem dry weight?SW?,leaf dry weight?LW?,total dry weight?TW?of Hybrid poplor?Populus deltoides×Populus nigra?decreased significantly,while the root-shoot ratio?R_s?of males increased obviously.Although the stomatal conductance decreased under the salinity stress,the concentration of CO₂ in the cells was not affected,so it was considered that the non-stomatal factors restricted the net assimilation rate.Correlation analysis showed that isoprene emission rate and net assimilation rate is linearly related to the inference,on the one hand,the isoprene emission rate affected by photosynthesis,on the other hand,the isoprene may protect the photosynthetic mechanism for the photosynthetic damage caused by salinity stress.Salinity stress reduced the isoprene emission rate,but its immediate precursor dimethylallyldiphosphate?DMADP?pool size was not affected,however,the rate constant of Isps reaction decreased significantly under salinity stress,therefore,the isoprene emission was mainly regulated by isoprene synthase.?2?During the drought stress,the high temperature lasted for more than 10 days from the 12 th day of treatment,so the results of the study were the effects of the drought coordinated high temperature.First of all,the net assimilation rate,stomatal conductance,transmission rate and intercellular CO₂concentration?C_i?were decreased,and it indicated that stomatal factors significantly limited P_n.Fluorescence parameters showed that the drought reduced coefficient of photochemical quenching?qL?,the actual quantum efficiency of photosystem II?PSII?and the relative electron transfer rate?rETR?,at the same time,the coefficient of non-photochemical quenching?NPQ?,quantum yield Y?NPQ?and primary electron acceptor?Qa?of PSII increased,it reflected that the photosynthetic mechanism of plants was damaged,that was to say,the reduction of P_n also included non-stomatal factors.Protective enzymes response to drought is complex,superoxide dismutase?SOD?decreased significantly under severe drought,but the catalase?CAT?increased,and the change of peroxidase?POD?was not significantly,in the end,the severe drought caused the accumulation of malondialdehyde?MDA?,it indicated that the antioxidant enzyme system had a low scavenging capacity for reactive oxygen species,finally,the leaves were damaged,which showed that P_n and rETR was hindered and the leaf of it lost more.Drought did not affect the isoprene emission rate,DMADP pool size and the rate constant of Isps reaction significantly.Therefore,the males and females have similar survival ability under normal conditions,However,males are more resistant to salinity and drought stress;the isoprene emission level and antioxidant enzymes may not be the only factor in the difference of salinity and drought tolerance between males and females.The growth of hybrid poplor?Populus deltoides×Populus nigra?can be attenuated by drought and salinity stress,but the mechanism of drought is different from the salinity.