Effect Of Exogenous CaCl₂ On The Cold Resistance Of Three Machilus Nees Seedings

The study aimed to explore the effect of exogenous CaCl₂ on the cold resistance of three Machilus Nees（Machilus ichangensis,Machilus versicolora and Machilus glaucifolia）seedings.In the artificial climate box,three kinds of Machilus Nees were sprayed by different concentration of exogenous CaCl₂（5mmol/l,15mmol/l and 25mmol/l）under chilling stress and the physiological indexes（malondialdehyde,soluble protein and soluble sugars）,antioxidant enzyme activities（POD and SOD）,chlorophyll index and hormone were measured.The results were as follow:1.In the present study,the chlorophyll indexs（chlorophylla,chlorophyllb,total chlorophyll and chlorophylla/ chlorophyllb）were measured after chilling stress,the different results may decide by species-specific.The content of chlorophylla,chlorophyllb,total chlorophyll and chlorophylla/ chlorophyllb of Machilus ichangensis have the some trend after spraying different concentrations of CaCl₂.At 5℃ and-5℃,the content of total chlorophyll was increased with increasing concentrations of CaCl₂ at 5mmol/l,and then decreaed with increasing concentrations of CaCl₂.At 0℃,the chlorophylla/ chlorophyllb was increased with increasing concentrations of CaCl₂.At 5℃,the content of total chlorophyll in Machilus glaucifoliawas increased with increasing concentrations of CaCl₂ at 5mmol/l,and the dcreased with increasing concentrations of CaCl₂.But,at 0℃,the contentof total chlorophyll was increased with increasing of CaCl₂.Furthermore,the content of chlorophylla/ chlorophyllb was not significant changes both at 5mmol/l and 15mmol/l CaCl₂,suggesting that the chlorophylla and chlorophyllb are not sensitive about chilling stress.The contents of total chlorophyll of treated groupin Machilus versicolorawere lower than that of control at 5℃.At 0℃,the content of total chlorophyll was increased with increasing concentrations of CaCl₂ at 5mmol/l,and then dcreased with increasing concentrations of CaCl₂.Forthermore,at-5℃,the content of total chlorophyll was higher than that of control at 5mmol/l.The content of chlorophylla/ chlorophyllb and total content of chlorophyll both decreaed with increasing concentrations of CaCl₂ at-5℃ and 5℃,but the opposite trend was found at 0℃.2.The content of MDA in the three three kinds of Machilus Nee was different after spraying different concentrations of CaCl₂.The content of MDA in Machilus ichangensi and Machilus glaucifolia was similar,whichwas decreased with increasing concentrations of CaCl₂ at 5℃,but the content of MDA in Machilus glaucifolia was increased with increasing concentration of CaCl₂ at 0 ℃.At-5℃,compared to Machilus glaucifolia,the content of MDA in both Machilus ichangensi and Machilus versicolora were the lowestat 5mmol/l CaCl₂.The different content of MDA in the three kinds of Machilus Nee after spraying may depend on species specific and dependent-concentration of CaCl₂.3.In the present study,the SOD activity of Machilus ichangensi was decreased with increasing concentrations of CaCl₂ at 5℃,the opposite trend was found both in Machilus versicolora and Machilus glaucifolia.At 0℃,the SOD activities of three Machilus Nee were increased with increasing concentrations of CaCl₂.But,at-5℃,the SOD activities of three Machilus Nee was highest at 15mmol/l.Furthermore,the POD activities of the Machilus Nee were higher than that of control（p <0.05）.At 0℃,the POD activities of Machilus ichangensi and Machilus glaucifolia after spraying 15mmol/l CaCl₂ and the POD activity of Machilus versicolora after spraying 25mmol/l CaCl₂ were lowest than other concentrations（p <0.05）.The POD activity of Machilus ichangensi was increasing with increased the concentration of CaCl₂,but the opposite trend was found in Machilus versicolora and Machilus glaucifolia at-5℃.The results suggested that the activities of SOD and POD were improved after spraying the CaCl₂ under chilling stress.4.In the present study,at 0℃,the soluble sugar content for Machilus ichangensi was higher than that of control,but the soluble sugar content of other treated groups were lower than that of control after spraying the concentration of 5mmol/l CaCl₂（p <0.05）.At-5℃,the content of solube sugar for Machilus ichangensiwas increased with increasing the concentration of CaCl₂,and the content of solube sugar was the highest at the 15 mmol/l CaCl₂.At-5℃,the content of solube sugar was higher thanthat of control for Machilus versicolora both at 5 and 15mmol/l CaCl₂.Forthermore,the soluble sugar content for Machilus versicolora was increased with increasing concentration of CaCl₂,which was lower than that of control.At 5℃,the soluble protein content for Machilus glaucifolia was higher than that of control at both 5 and 15 mmol/l CaCl₂.At 0℃,the soluble protein content for Machilus glaucifolia was decreased with increasing concentration of CaCl₂.The opposite result was found at-5℃,although the content of treated groups were lower than that of control.The soluble protein content for Machilus versicolora was higher than that of of control both at 0 and-5℃.Those results show that the expression of cold resistace genes was induced by chilling stress,and then related proteins were up-regulated.5.In the present study,at 0℃,the content of ABA for three Machilus plants was similary,showing decreased trend.At-5℃,the Machilus versicolora’s ABA after spraying CaCl₂ was increasing,not significiant for Machilus glaucifolia,but the ABA content for Machilus ichangens was decreased.ABA content followed the order: Machilus ichangens>Machilus versicolora> Machilus glaucifolia,which implied cold resistance was species-specific and has low response to temperature stress.And furthermore,at 5℃,the GA3 content for three Machilus plants were higher than that of control after spraying CaCl₂.The GA3 content for Machilusichangens was significiant decreased after spraying CaCl₂（p< 0.05）,but the content of Machilus glaucifolia and Machilus versicolora were higher than that of other’s（p< 0.05）.According the GA3 content in control,we speculate the cold resistance followed the order: Machilus versicolora> Machilus glaucifolia> Machilus ichangens.