Different Ecophysiological Responses Between Females And Males Of Populus Yunnanensis In Enhanced UV-B Radiation,Pb And Cu Stress

With growing environmental damage by human activities,ecological problems have become increasingly prominent.The growth of plant is affected by environmental change.Dioecism is common in plants,their differences in growth,sex ratio,reproductive patterns,spatial distribution,as well as resource allocation between males andfemales because of different resource requirements during the long-term evolution process.Populus yunnanensis belongs to Populus is a dioecious plant.It is also a unique tree growing in southwest China.In this study,P.yunnanensis was used as the experiment materials to study the sex-related responses to enhanced UV-B radiation,lead,enhanced UV-B radiation and lead's combination;copper,copper and lead's combination in growth,physiology,biochemistry,and sub-cellular ultrastructure.The study aimed toinvestigate the physiology of different gender to adapt to environmental change mechanism,provide a theoretical basis for the change of distribution,and also provide theoretical basis for the distribution of P.yunnanensis population and the possible change of sex ratio after environmental destruction,as well as providing a practical reference for breeding P.yunnanensis against enhanced UV-B stress population for planting and cultivating Populusin heavy metal contaminated areas.The results are follows:(1)Sex-related adaptive responses to enhanced UV-B radiation,Pb stress and their combined stressUnder the control treatment,there were no significant differences in most of two sexes' ecophysiological characteristics.Enhanced UV-B radiation,Pb stress and their combination changed many ecophysiological characteristics,such as inhibited plant growth,reduced biomass and pigments contents,increased proline and membrane lipid peroxidation contents,changed the activities of antioxidant enzymes,and injured subcellular ultrastructure.In the activities of antioxidant enzymes,the POD content of male plants increased by 356%,264% and 303%,respectively,under the enhanced UV-B radiation,Pb stress and their interaction stress.Males had a better growth status comparing to females: higher biomass,lower pigments reduction,more capable of maintaining enzyme activities,and more NP-SH contents.That means males have better abilities of adaptation,self-defense ability and detoxification of heavy metalthan females.There was little difference between combined stress and individual stress;many ecophysiological indexes did not show further reduction under combined stress.Those results showed that: females are more sensitive and subjected to more severe stress than do males under enhanced UV-B radiation,Pb stress and their combination;sex-specific reactions affected by environment.(2)Sex-related adaptive responses to Cu stress,Pb stress and their combined stressComparing to the control condition,all of the ecophysiological characteristics had changed under Cu stress,Pb stress and their combination in plants.Compared with males,females suffered more in the soil polluted by heavy metals,such as more growth inhibition,higher membrane lipid peroxidation contents,lower antioxidant enzyme activities,lower levels of NP-SH and GSH contents.Lower ability of scavenging ROS and detoxification of Cu and Pbindicatethat females havelower tolerance capacity of heavy metals.The POD content of male plants increased by 311%,264% and 329%,respectively,under Cu stress,Pb stress and their interaction stress.P.yunnanensis under combined stress showed more damage than individual stress,lower biomass and membrane lipid peroxidation contents means more inhibition.The MDA content in females increased by 195% under the combined stress.Those results showed that: females are more sensitive and subjected to more severe stress than males under enhanced under enhanced Cu stress,Pb stress and their combination;there was a difference sex-specific reaction in P.yunnanensis between single metal stress and their combination.