流苏树对NaCl的生理响应及耐盐阈值分析

Physiological response and salinity tolerance threshold analysis of Chionanthus retusus to NaCl stress

研究NaCl胁迫下珍稀乡土树种流苏树(Chionanthus retusus)的生长及生理生化指标的变化机制,计算流苏树耐盐阈值,揭示耐盐机理,为流苏树耐盐材料的筛选与推广应用提供参考。以三年生流苏树扦插苗为材料,通过盆栽试验,设置不同土壤NaCl含量(分别为0、2.34、4.68和7.02 g·kg^(-1)),测定了流苏树生长及气体交换参数、抗氧化酶活性、脯氨酸及丙二醛(MDA)含量的差异。结果表明:(1)随着土壤NaCl含量增加,流苏树的外部形态逐渐发生变化,表现为叶片逐渐白化脱落,出现渗盐甚至死亡。(2)胞间CO_(2)浓度(Ci)随土壤NaCl含量增加先下降后上升,而净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(Tr)显著下降。在7.02 g·kg^(-1) NaCl处理下,流苏树叶片P_(n)较对照显著下降91.61%,G_(s)与对照相比下降77.21%,Tr显著下降至0Ci在此浓度下比对照增加22%。(3)流苏树叶片的光系统II(PSII)最大光能转化效率(Fv/Fm)在2.34、4.68、7.02g·kg^(-1) NaCl胁迫时,分别下降了12.15%、22.13%和35.11%,与光合指标相对应,说明2.34 g·kg^(-1) NaCl胁迫没有对流苏树的光合机构造成破环,4.68和7.02 g·kg^(-1) NaCl胁迫已经伤害了流苏树的光合机构,故其不能耐受类似于7.02 g·kg^(-1) NaCl含量的高盐渍化土地环境。(4)超氧化物歧化酶(SOD)、过氧化物酶(POD)活性先升后降,MDA含量先降后升,与脯氨酸(Pro)含量变化趋势相反。流苏树主要通过活性氧清除和渗透调节机制适应轻度的盐分胁迫。(5)以P_(n)为指标,流苏树耐盐阈值为2.81 g·kg^(-1),对此阈值内的盐土有一定适应性。

The growth and physiological responses of the rare native tree species Chionanthus retusus under NaCl stress were studied,the salinity tolerance threshold was calculated,and the salt tolerance mechanism was revealed.The cutting seedlings of three-year-old C.retusus were treated with different NaCl contents in soil(0,2.34,4.68 and 7.02 g·kg^(-1))through pot experiment,and the differences of growth,photosynthetic characteristics,protective enzyme system,osmotic adjustment substances and cell membrane injury were analyzed.The results show that:(1)with the increase of NaCl concentration,the external morphology of C.retusus changed gradually,when the leaves became albino,were gradually dropped off,permeated salt and even died.(2)Net photosynthetic rate(P_(n)),stomatal conductance(G_(s))and transpiration rate(T_(r))decreased significantly,but intercellular CO_(2) concentration(C_(i))decreased first and then increased with the increase of soil salinity.Under 7.02 g·L^(-1) NaCl treatment,the P_(n) of leaves decreased significantly by 91.61%,G_(s) by 77.21%and T_(r) had dropped significantly to 0,and C_(i) increased by 22%.(3)The maximum light conversion efficiency of photosystem II(PSII),F_(v)/F_(m),decreased by 12.15%,22.13%and35.11%under 2.34,4.68 and 7.02 g·kg^(-1) NaCl stress,respectively.Corresponding to the photosynthetic index,2.34 g·L^(-1) NaCl stress did not damage the photosynthetic apparatus of C.retusus,while 4.68 and 7.02g·kg^(-1) NaCl stress had damaged the photosynthetic apparatus of C.retusus.Therefore,it could not withstand the highly salinized soil environment with NaCl content of 7.02 g·kg^(-1).(4)The activities of SOD and POD increased,and then decreased,and the content of MDA decreased firstly,and then increased,contrary to the change of Pro content.C.retusus can adapt slightly salt stress through removal of reactive oxygen species and osmotic adjustment.The reason why it has a certain salinity tolerance is related to the protection mechanism and that can spontaneously produce to cope with external stress environment.(5)Considering P_(n) as a tolerance index,the salinity tolerance threshold was 2.81 g·L^(-1).