【作者】 王家源；

【导师】 喻方圆；

【作者基本信息】 南京林业大学 ， 森林培育， 2013， 博士

【摘要】 本文以两个种源苦楝种子和一年生实生苗为材料，采用不同浓度盐胁迫处理(CK，25，50，100，150，200mmolL^-1)，研究了不同浓度盐胁迫对苦楝种子萌发和一年生苗木生长的形态及生理状况的影响，探讨苦楝在萌发阶段和幼苗生长阶段的耐盐机理。盐胁迫下，苦楝种子发芽率和发芽指数先上升后下降，在100mmol L^-1浓度下对种子发芽率和发芽指数有促进作用。活力指数、苗高、根长和干重均呈现下降趋势，盐胁迫抑制了幼苗苗高、根长生长和干重增加，使幼苗质量下降。在盐胁迫下，苦楝种子可溶性糖、可溶性蛋白、游离氨基、酸脯氨酸和甜菜碱含量总体变化不是很大，到了胁迫后期，游离氨基、酸脯氨酸含量还略有下降，Ca²⁺、Mg²⁺、K⁺含量也变化不大，Na⁺含量有显著增加。苦楝种子O₂^-·、MDA含量未显著增加，SOD、POD、CAT等抗氧化酶活性有一定程度的增加，GSH、ASA等非酶促抗氧化剂含量也有所增加。苦楝种子在盐胁迫下，既受到了渗透胁迫，也受到一定程度的离子毒害，以渗透胁迫为主。苦楝是比较耐盐树种，滨海种源苦楝比滁州种源苦楝耐盐性更强，在150mmolL^-1盐浓度下，滨海种源苦楝的苗木成活率为79%，100mmolL^-1盐浓度下，滁州种源苦楝的苗木成活率保持在77%以上。随着盐浓度的增加，两个种源苦楝幼苗的苗高、地径和干重均逐渐降低，浓度越高，抑制作用越强。盐胁迫对苦楝苗木不同器官的的抑制作用的大小不同，不同器官对盐胁迫的敏感程度表现为叶＞茎＞根。盐胁迫下，苦楝叶片叶绿素含量逐渐下降。盐胁迫对苦楝苗木光合作用具有显著影响。在胁迫前期，随NaCl处理浓度增大，两个种源苦楝幼苗光合因子发生显著变化， Pn、Gs、Ci、Tr下降，而Ls上升，Pn降低主要受气孔因素控制。在胁迫后期，滨海种源，Pn、Gs、Tr下降，Ci先下降后上升，而Ls先上升后下降，低盐浓度下Pn降低主要受气孔因素控制，而高盐浓度下Pn降低主要受非气孔因素控制；滁州种源，Pn、Gs、Tr下降，Ci逐渐上升，而Ls下降，Pn降低主要受非气孔因素控制。对于有机渗透调节物质（可溶性糖、可溶性蛋白、游离氨基酸、脯氨酸、甜菜碱）来说，盐胁迫对苦楝具有一致的影响趋势，即均总体表现增加。只有可溶性蛋白，胁迫前期增加，而到了胁迫后期，可溶性蛋白含量下降。从总量上看，可溶性糖含量最多，而从增加幅度看，在盐胁迫下脯氨酸增加幅度最大，因此，可溶性糖和脯氨酸是苦楝两种比较有效的有机渗透调物质。苦楝叶片中Na⁺含量最高，是非常重要的无机渗透调物质。盐胁迫下，Ca²⁺、Mg²⁺、K⁺含量下降，但并不显著，而且依然保持较高的水平，因此，苦楝幼苗控制营养平衡能力较强，幼苗产生的盐害可能主要是由单盐离子毒害引起的而非营养失调。在盐胁迫下，苦楝叶片内O₂^-.含量、H₂O₂大量积累，MDA含量升高，膜系统受到了损伤。苦楝主要通过高活性的POD和较高效率的AsA-GSH循环系统清除ROS，减轻了ROS对膜的氧化损伤程度，CAT也有一定的贡献，但是SOD活性受到抑制。更多还原

【Abstract】 The seeds and one-year-old seedlings in Melia azedarach L. from two provenances wereused as the tested materials. The seed germination and seedling growth were studied under saltstress with six concentrations. The physiological responsing mechanism of Melia azedarach L.was explored by investigating the effects of salt stress on physiological and biochemicalcharacteristics in seed germination and seedling growth.With the increasing salinity stress, germination rate and germination index fistly increased,and then decreased. When salt concentration was100mmolL^-1, the germination rate andgermination index were higher than that of the control, indicating that salt could promote seedgermination; but when salt concentration was higher than100mmolL^-1, it had an inhibiting rolein germination rate and germination index. The vitality index, seedling high, root length and dryweight gradually reduced with the increasing salinity stress. So the seedling quality wasrestrained by salt stress.The content of soluble sugar, soluble protein, free amino acid, proline, betaine in seed didnot change much under salt stress. In the late stage, the content of free amino acid and prolinealso declined slightly. The content of Ca²⁺, Mg²⁺and K⁺changed little, but the content of Na⁺increased significantly. The content of O₂^-· and MDA in seed did not increase significantly,antioxidant enzyme activities including SOD, POD and CAT increased, non-enzyme antioxidantcontent including GSH and ASA also increased. So the seeds of Melia azedarach L. were notonly subject to osmotic stress, but also ion toxicity under salt stress. However, osmotic stress wasmajor.Melia azedarach L. was a salt tolerant species, the salt tolerance of Binhai provenance wasstronger than that of Chuzhou provenance. At150mmol/L salt concentration, seedling survivalrate in Binhai provenance was79%. At100mmol/L salt concentration, seedling survival rate inChuzhou provenance maintained above77%. With the increasing of salt concentration, the height,ground diameter and dry weight of Melia azedarach L. seedlings gradually reduced, the higherthe concentration, the stronger the inhibition effect. With the inereasing of salt concentration, theincrements of the seedling height, ground diameter and dry weight expressed a decreasing trend.Salinity significantly inhibited the growth and development of Melia azedarach L. seedlings, andthe sensitivity to salt of different organs performed leaf>stem>root.Photosynthesis of Melia azedarach L. seedlings were significantly affected by salt stress.Under salt stress, the chlorophyll content of leaves decreased gradually. In the first period, withthe increasing of NaCl concentration, photosynthetic parameters of Melia azedarach L. seedlingsfrom two provenances changed significantly. The net photosynthetic rate（Pn）, stomatalconductance（Gs）, intercellular CO2concentrations（Ci） and transpiration rate（Tr） dropd, butstomatal limiting value （Ls） rised, which denoted that the the main factor inhibiting Pn was stomatal control. In the later stress period, Pn, Gs and Tr in the Melia azedarach L. seedlingsfrom Binhai provenance decreased, Ci firstly decreased and then increased, while Ls increasedfirstly and then decreased. So drop of Pn was mainly controlled by stomatal factor at low saltconcentration and drop of Pn was mainly controlled by non-stomatal factor at high saltconcentration. In the later stress period, Pn, Gs and Tr in the Melia azedarach L. seedlings fromChuzhou provenance decreased, Ci increased gradually, and Ls decreased, so drop of Pn wasmainly controlled by non-stomatal factors.The organic osmotic adjustment substances such as soluble sugar, soluble protein, freeamino acid, proline, betaine in Melia azedarach L. seedlings, had an identical changing trendunder salt stress, that is, all above substances increased. The content of soluble sugar was themost highest among all the organic osmotic adjustment substances, and the increment of theproline was the highest among all the organic osmotic adjustment substances under salt stress.Therefore, soluble sugar and proline were two effective organic osmotic adjustment substances.The content of Na⁺in leaves was the highest positive ion, Na⁺is a very important inorganicosmotica. The content of Ca²⁺, Mg²⁺and K⁺decreased, but this decline was not significant, andthe content of Ca²⁺, Mg²⁺and K⁺still maintained a high level. Therefore, seedlings of Meliaazedarach L. had strong nutrition balance control ability; salt injury might be caused mainly bythe single salt ion toxicity rather than malnutrition.Under salt stress, the content of O₂^-., H₂O₂and MDA in leaves increased, so the membranesystem was damaged. ROS in Melia azedarach L. seedlings were cleaned mainly throughAsA-GSH circulatory system and the high POD activity, which reduced the oxidative damagedegree of ROS to the membrane, CAT also had a certain contribution to clean ROS, but SODactivity was inhibited.更多还原