Different Eco-physiological Responses Between Females And Males Of Populus Deltoides To Different Waterlogging Conditions And Leaf Blight Pathogen Infection

The vegetation in the reservoir water level fluctuation zones(WLFZ)and riparian zones must experience long time flooding,or even adverse seasonal winter flooding due to the influence of artificial water level regulation of reservoir.The tree species suitable for construction of the protect forests in these regions must have a certain flooding tolerance.The plants survived in submerged environmental conditions from the WLFZ may not adapt to the ecological environment of estuarine and coastal beach areas with high salt content and frequent flooding.Poplar has some the characteristics such easy reproduction,rapid growth,strong adaptability and resistance to environmental stresses.It is often used as a pioneer tree species for vegetation ecological restoration.Therefore,poplar has important ecological and economic values.High temperature and high humidity environments in summer often occur in the reservoir WLFZ,riparian zone,estuarine area,and coastal beach coating areas,and poplar is susceptible to leaf blight under these environmental conditions,especially for poplar belonging to Secti.Aigeiros Duby.In addition,poplar belongs to dioecious plant,and the different sexual dependent responses of males and females of Populus to biotic and abiotic stresses are often found.The females and males of P.deltoides were used as materials to investigate the different sexual responses in growth and development,photosynthesis,chlorophyll fluorescence,soluble contents,reactive oxygen species(ROS)accumulation,antioxidant enzyme activities,and ultra-structural variations under the simulated combined adverse season water flooding with spring waterlogging and post waterlogging recovery,and100 mmol/L salt stress,10 mmol/L calcium stress,salt-calcium compound stress under waterlogging conditions,and leaf blight pathogen infected condition,respectively.This study attempts to clarify the sexual specific physiological and ecological mechanisms of P.deltoidesin response to different waterlogging environments(abiotic stresses)and leaf blight pathogen infection(biotic stress),and to provide scientific basis for the application of P.deltoides in reservoir WLFZ,riparian zones,estuary and coastal beach areas.The results from the studies on sexual different morphological,eco-physiological,and ultrastructural response between females and males of P.deltoides to combined adverse season winter flooding with spring waterlogging,and post waterlogging recovery showed that:(1)the females and males of P.deltoides had strong tolerance to winter flooding,and were not sensitive to winter flooding duration.(2)P.deltoides males were more tolerant to winter flooding than females in terms of photosynthesis and chlorophyll fluorescence.(3)P.deltoides females showed more oxidative damages than males,whereas males had more effective antioxidant enzymatic system to control the ROS accumulation under severe waterlogging conditions.(4)Both females and males of P.deltoides had strong recovery ability in plant growth,photosynthesis,physiology and biochemistry,and ultrastructure during post waterlogging period,and males had better recovery ability in comparison to females,particular in pigment content and photosynthesis.These results enhanced the cognition of the adaptation to anti-season winter flooding stress in woody plants,and also clarify the gender differential response of males and females of P.deltoides to waterlogging stress during dormancy period and post waterlogging recovery period,which would helpful to guide the construction of poplar shelterbelt in reservoir WLFZ and riparian zones.The results from the studies on gender-specific responses between females and males of P.deltoides to salt-calcium compound stress under waterlogging condition showed that:(1)the females and males of P.deltoides were sensitive to salt and calcium whether under normal water condition or under waterlogging condition.(2)Under the normal water conditions,salt stress could significant increase the leaf Na content of P.deltoides females,while salt and calcium stress could increase the leaf potassium and calcium contents of males.(3)Under the sufficient sodium ion conditions,waterlogging could significantly promote the absorption of sodium in the leaves of P.deltoides,especially in females,whereas the stimulated effects of waterlogging on calcium absorption in leaves of males and females were not obvious under the sufficient calcium conditions.(4)The effects of salt-calcium compound stress on physiological and biochemical parameters exceeded that of single salt stress or calcium stress in P.deltoides,but insignificant difference was observed between males and females,which indicatd that males and females had the similar responses.(5)The higher sodium contents and ratio of sodium to calcium in females,and the higher content of potassium and calcium in males indicated that P.deltoides males possessed better abilities to maintain ion balance than females did.(6)Some gender specific differences in net photosynthetic rate(A),intercellular CO₂ concentration,effective quantum yield of PSII,non-photochemical quenching coefficient q N,photosynthetic electron transport rate ETR,contents of superoxide anion radical(O₂^·-),hydroxyl radical(·OH),hydrogen peroxide(H₂O₂),and soluble protein,and superoxide dismutase activity were found between females and males of P.deltoides under certain stressed conditions.Although P.deltoides had strong waterlogging tolerance,it was not suitable for the construction of protected forests in estuaries and coastal beach areas with flooding,high salt,and high calcium environmental conditions.The results from the studies on sexual specific responses to leaf blight pathogen(Alternaria alternata)infection in P.deltoides showed that:(1)P.deltoides females was more susceptible to leaf blight than males,and the incidence rate was faster.(2)The A and instant water use efficiency(WUEi)in females and males of P.deltoides decreased significantly after leaf blight pathogen infection,the A and WUEi of females decreased more significantly;the changes of chlorophyll fluorescence parameters were not obvious in females and males,but the photochemical quenching coefficient(q P)of females increased significantly.(3)The relative water content and soluble protein content decreased significantly,while glutathione content increased significantly in both of females and males leaves.The free proline content increased significantly in males,but not in females.(4)The contents of H₂O₂and·OH plants increased significantly in both males and females,O₂^·-content increased significantly in females,but not in males.In general,the increments of H₂O₂ and O₂^·-contents in females was larger than that in males,and the significant increases of malondialdehyde content in males and females were not found.(5)The insignificant increases in peroxidase(POD)activity were found in both males and females.The superoxide dismutase(SOD)activity of males increased significantly,but the SOD activity of females did not change significantly.The insignificant decreases in ascorbic acid peroxidase(APX)activity were found in females,whereas significant increases in APX activity were found in males.Therefore,the activities of SOD and APX in males increased more than that of females after leaf blight pathogen infection.(6)The different variations in ultrastructure were found in both infected males and females,and leaf blight significant decreased the ratio of chloroplast and starch granules in both infected males and females,especially inducing more blank vacuoles in females.The different responses of males and females to leaf blight pathogenic infection would be helpful to guide the construction of poplar protected forests in reservoir WLFZ and riparian zones.In conclusion,males and females of P.deltoides have strong adverse season winter flooding tolerance,and are not sensitive to winter flooding durations.Both of them are suitable tree species for the protect forest construction of in reservoirs WLFZ and riparian zones.Compared with females,P.deltoides males had better adaptive mechanism to waterlogging stress in terms of growth,photosynthesis,physiology and biochemistry,and ultrastructure,and had stronger recovery ability during post waterlogging recovery period.The females and males were sensitive to salt and calcium whether under normal water condition or waterlogging conditions,and the tolerance was very poor.Therefore,they were not suitable tree species for the protect forest construction in the estuaries and coastal beach areas with waterlogging,high salt,and high calcium environmental conditions.Under the sufficient sodium ion conditions,waterlogging could significantly promote the absorption of sodium in the leaves of P.deltoides,especially in females,whereas the stimulated effects of waterlogging on calcium absorption in leaves of males and females were not obvious under the sufficient calcium conditions.Under high temperature and high humidity environmental conditions,the P.deltoides females were more easily infected by leaf blight pathogen than the males,and the infected speed was faster that that of males.The P.deltoides males had more effective mechanism of scavenging ROS to maintain the redox balance in cells than fesmales did.Therefore,the prevention and treatment of leaf blight in poplar,and the reasonable collocation of male and female of Populus should be paid attention to in the construction of protect forests in the reservoir WLFZ and riparian zones.