The Combined Stress Of Elevated Temperature And Drought And Rewatering On The Physiological And Hydraulic Architecture Characteristics Of Robinia Pseudoacacia L. Seedlings

Drought and elevated temperature are two main manifestations of global climate changescenario, which significantly affect plants growth and spread. Through4weeks’ differenttemperature and water gradients control and2weeks’ rewatering, physiological and hydraulicarchitecture characteristics of Robinia pseudoacacia L. seedlings were studied. The results weredescribed as follows:(1)Under the different treatments of combined stress of elevated temperature and drought,Pn、Tr were generally dropping; Gs showed a similar trend with Pn; Ci fluctuated significantlyafer10am, was well above CK. Ci、Pn and Gs were synchronous under the combined stress, Pnchanged with Ci and Gs, Ci was negatively correlated with Pn, but positively correlated withGs.(2)Within certain elevated temperature and a reasonable amount of time, F0, Fmrised withthe increasing drought, while Ft, Fv/Fmdeclined; Within certain drought and a reasonableamount of time, F0、Fm、Ft、Fv/Fmwere inhibited by temperature, generally dropping.(3) Elevated temperature and drought promoted seedlings’ SOD、POD、CAT、H2O2、O2-, which were significantly above CK; with the increasing drought, MDA had a decline afteran up, while had no regularity with elevated temperature. The combined stress aggravated thedecline of Pn、Tr、Gs、F0、Fm、Ft、Fv/Fm、CAT; rise of Ci、CAT、POD、H2O2、O2-; retardedthe rise of MDA.(4) Khof seedlings fell sharply with the increasing drought, while there was no significantvariation trend under elevated temperature, generally under CK. Under the combined stress,Kh、Kswere significantly under CK and the combined stress aggravated their decline.(5) Pn、Tr、Gs、Ci、F0、Fm、Ft、SOD、POD、CAT and H2O2were significantly affectedby water, Tr、Ci、F0、Ft、SOD、H2O2、O2-、MDAwere significantly affected by temperature,Pn、Tr、Fm、Fv/Fm、SOD were significantly affected by temperature×water.(6)After rewatering, Pn、Tr、Gsrised rapidly, but generally hadn’t reached the CK level; Cideclined, also hadn’t reached the CK level, was still relatively high. F0rised under mild drought,while declined under severe drought; Fmkept declining; Ftwas generally rising above CK,which had a significant recovery; Fv/Fmgenerally kept declining.(7) After rewatering, SOD’s change differed from treatments but all above CK; POD,H2O2,O2-kept rising, while CAT declined; MDA had a significant recovery, declined to CK. Khshowed a similar trend with Ks, rised to CK under25℃, kept declining under33℃and40℃.In conclusion, photosynthetic performance, fluorescence parameters and hydraulicarchitecture characteristics of Robinia pseudoacacia L. seedlings were generally droppingunder the combined stress of elevated temperature and drought, while antioxidative enzymeactivities, reactive oxygen content were rising. Except for the hydraulic architecture characteristics, most indicators had a certain amount of recovery. Time of stress and rewateringconsidered, Robinia pseudoacacia L. seedling has a strong high-temperature and droughtresistance capability.