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Physiological response of Cinnamomum camphora seedlings to NaCl stress

Wang Jinping;Wang Shutian;Yue Jianmin;Zhang Jinchi;Zhang Liang;You Yanhuang;Zhao Wenrui;Key Laboratory of Soil and Water Conservation and Ecological Restoration in Jiangsu Province,Collaborative Innovation Center of Sustainable Forestry in Southern China,Nanjing Forestry University;  
[Background]Cinnamomum camphora is a precious economic tree species,it has important application value in the southern coastal areas of soil and water conservation. There are varied degrees of salinity in the southern coastal regions,the research on C. camphora's salt tolerance had been little reported,nor systematically. The purpose of this work is to study the salt tolerance of C. camphora,and to provide the reference for the cultivation in saline alkali soil in southern coastal regions. [Methods]We chose C. camphora seedlings as test materials and used potted method,the seedlings were treated with NaCl treatment at 2‰,4‰,6‰ and 8‰,and fresh water as the control( CK). With different NaCl salt treatment,the C. camphora growth indexes,moisture physiological indexes,photosynthetic pigmentcontent,antioxidant enzymes activity,osmotic regulation substances and membrane stability of leaves were measured; the photosynthesis parameters and chlorophyll fluorescence parameters were measured by CIRAS-2 and CFI,respectively. [Results]1) With the increasing of salt concentration,C. camphora seedling height and relative growth rate of base diameter decreased,and more than 4‰ of the salt treatment had significant inhibitory effect on the growth( P 0. 05). 2) With the increasing of salt treatment concentration,the water saturation deficit( WSD) and malondiadehyde( MDA) content of seedling leaf rose gradually,while the membrane stability index( MSI) and photosynthetic capacity decreased gradually. 3) The leaf relative water content( RWC),the photosynthetic pigment content,Fv/Fm,NPQ,antioxidant enzyme activity,proline( Pro) content,and soluble protein( SP) content of seedling leaves at the salt concentration of 2‰ were higher than CK,while the MSI,Yield,and ETR reduced in a little magnitude. 4) The photosynthetic pigment content, net photosynthetic rate,photochemical efficiency,WUE,and MSI reduced significantly when the salt concentration was 4‰( P 0. 05), while MDA content, and Pro content increased significantly( P 0. 05), moisture conditions became worse; at the same time,the antioxidant enzyme activity,soluble sugar( SS) content,and SP content decreased. [Conclusions] The salt tolerance of camphor seedlings is 2‰ to 4‰,and when the salt concentration over 4‰,the growth of seedlings could be inhibited significantly. C.camphora seedlings could endure low salt stress( 2‰) via increasing RWC,photosynthetic pigment content,the dissipation of NPQ,the activity of antioxidant enzymes,the content of Pro and SP,and shutting down part of the stomas. But when the salt concentration reached 4‰,with the increase of salt concentration,the antioxidant enzyme activity of seedling leaves gradually declined,the damage of enzyme system was more and more serious; the regulating effect of SS and SP became smaller; Pro was producing massively,and the regulating effect of osmotic regulation increased gradually,but far enough to resist the salt stress. Thus,the water in leaves lost severely,membrane lipid peroxided,membrane stability deteriorated,photosynthetic agencies seriously damaged,which resulted in their lives in danger.
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