Effects Of Spermidine On Physiological And Biochemical Characteristics Of Ilex Verticillata Under Salt Stress

The effect of 0.5 mmol·L^-1 spermidine?Spd?treatment on growth,physiological and biochemical characteristics of four-year Ilex verticillata under 4 g·L^-1 and 8 g·L^-1 NaCl stress was studied.This research can provide theoretical reference for the cultivation management and resistance screening.Main results and conclusions are as follows:?1?Under NaCl stress,the specific leaf weight,chlorophyll content,Pn,Amax,AQE,Gs,Ci and Tr of Ilex verticillata decreased,while LCP increased with the increase of salt stress.However,0.5 mmol·L^-1 Spd can promote specific leaf weight and chlorophyll content increased,maintain assimilation capacity of mesophyll cell.?2?Y???,Fv/Fm,qP and ETR of the leaves of Ilex verticillata increased first and then decreased under salt stress,but qN and Fo of the leaves of Ilex verticillata under salt stress were significantly higher than those under the control.0.5 mmol·L^-1 Spd treatment could maintain the stability of chloroplast in the early and middle stage of salt stress.The ultrastructures of the chloroplasts in the leaves of Ilex verticillata were damaged under NaCl stress,while 0.5 mmol·L^-1 Spd can protect the chloroplast structure.?3?The SOD and POD in the leaves of Ilex verticillata increased first and then decreased,while the CAT decreased with the increase of salt stress.There was no significant differences between the three indexes after exogenous Spd treatment and those under control,which indicated that Spd treatment could enhance the activity of enzymatic system significantly under NaCl stress.?4?ABA,IAA and Spd in the leaves of ilex verticillata increased under NaCl stress,which was significantly higher than that under control.But GA3 showed a decreasing trend.Under exogenous Spd treatment,the contents of ABA,IAA and GA3 increased.It indicated that 0.5 mmol·L^-1 Spd could participate in the regulation of endogenous hormones under NaCl stress,and inhibit the damage caused by NaCl stress.The K⁺,Na⁺ contents and the ratio of Na⁺/K⁺ in the leaf of Ilex verticillata increased under salt stress.But exogenous Spd treatment could inhibit the increase of K⁺ and Na⁺ contents and the ratio of Na⁺/K⁺ of Ilex verticillata.