Physiological Response Of Four Species Of Camellia To Simulated Drought Stress

This study tested the influence of drought stress to Camellia oleifera,Camellia drupifera,Camellia semiserrata and Camellia azalea and evaluated their drought resistance by applying comprehensive evaluation methods.It aims to provide theoretical and experimental basis for selecting drought-resistant plants in seedling production and urban greening,further to lay the foundation for the cultivation and introduction and garden promotion of these four Camelia species.The seedlings of these four Camelia species were used as material for experiments.They were first tested by drought stress simulated with PEG-6000(10%,20% and 30%)and then gone through rehydration treatment.Physiological indicators were measured and the result shows that:(1)During the drought stress period,the water content of the leaves of the four plants decreased gradually,and after the rehydration treatment,the water content of the four plants gradually recovered to the control level.In contrast,the relative electrical conductivity and the content of malondialdehyde(MDA)of the four species showed a continuous increasing trend,which decreased after rehydration.The soluble sugar content of C.oleifera and C.azalea did not change significantly under different treatment conditions,it only increased slightly as the time of drought stress increase.While for C.drupifera and C.semiserrata,the content of soluble sugar were stable in early stage of drought stress,but significantly increased later and recovered after rehydration.(2)During the drought stress period,the soluble protein content of the four plant seedlings increased.The increase of soluble protein of C.oleifera is slight through out the whole process.While for C.azalea,no significant change of soluble protein in early stage,but after 36 th hours of drought it rose and reached maximum,failed to return to the control level even after rehydrated.The activity of superoxide dismutase and peroxidase increased as the drought leveled up and after the drought stress was relieved,the activity curves of superoxide dismutase of the four plants were similar-a decrease followed by a upward trend as drought stress time increase-regardless of the time span of drought stress treatment.(3)During the drought stress,chlorophyll content,chlorophyll a and b contents of four kinds of plants first increased then decreased.Only carotenoid content showed a continuous upward trend and decreased after rehydration.But the change is not significant compared to the control level.The SPAD values are basically declining with the degree of drought.(4)Through principal component analysis,the physiological indices to evaluate the extent of drought resistance were selected,including POD activity,chlorophyll content,SPAD value,relative conductivity,soluble sugar content and SOD activity.The results indicated that the drought resistance ranking of four species of Camellia is C.drupifera> C.Azalea> C.oleifera> C.semiserrata.