盐碱胁迫对草地早熟禾生长和生理代谢的影响

以两个耐盐碱性差异较大的草地早熟禾品种‘午夜'(Midnight,耐盐碱性强)和‘旅行者Ⅱ号'(Voyager Ⅱ,耐盐碱性弱)为试验材料,分析了在生长箱水培模拟中性盐和碱性盐两种条件下,盐碱胁迫对早熟禾生长、电导率、叶绿素、光合特性、脯氨酸和有机酸代谢的影响。结果表明,盐碱胁迫下早熟禾两个品种的生长率下降,叶片电导率升高,叶绿素含量和光合作用显著下降,尤其是在碱胁迫下,但在耐性强的品种中变化程度均小于耐性弱的品种;两个品种叶片脯氨酸含量主要在盐胁迫下升高,碱胁迫下无显著变化甚至下降;根系分泌的有机酸主要为草酸,且仅在碱胁迫下升高;盐碱胁迫下草酸在叶片和根系中的含量均呈下降趋势,尤其是根系在碱胁迫下;叶片和根系的苹果酸、柠檬酸和琥珀酸在盐胁迫下无显著变化,在碱胁迫下则显著升高,其中‘午夜'显著高于‘旅行者Ⅱ号'。由此可见,碱性盐比中性盐对草地早熟禾的伤害更大,中性盐胁迫下主要以积累脯氨酸等物质来调节渗透压,而在碱性盐胁迫下主要通过加强有机酸的代谢、积累和分泌来调节植株体内和根际环境的pH值;耐盐碱的品种在盐碱胁迫下能维持较高的光合作用和有机酸代谢,提高了植株内和根际环境pH的调节能力,因此具有较强的耐盐碱能力。

Effects of neutral and alkaline salt stresses on the growth and physiological metabolism of Kentucky bluegrass

In order to investigate the effects of neutral and alkaline salt stresses on growth,leaf electrolyte leakage,chlorophyll content,photosynthetic characteristics,proline content and organic acid metabolism,two Kentucky bluegrass (Poa pratensis) cultivars,' Midnight' (tolerant of saline-alkaline conditions) and ' Voyager Ⅱ ' (sensitive to saline-alkaline conditions) were subjected to neutral and alkaline salt treatments in hydroponic culture in growth chambers.The growth rate,chlorophyll content and photosynthesis decreased and leaf electrolyte leakage increased significantly under both types of salt stress,particularly under alkali stress.The tolerant cultivar showed less variation in response to the two salt stresses than the sensitive one.Leaf proline content only increased under neutral salt stress in both cultivars and no increase was observed under alkali stress.Oxalic acid was the only organic acid secreted by roots of either cultivar and increased significantly under alkali stress.The contents of leaf and root malic acid,citric acid and succinic acid in both cultivars hardly changed under neutral salt stress,but increased under alkali stress,with greater increase in 'Midnight' than in 'Voyager Ⅱ '.Alkaline salt stress caused more damage to Kentucky bluegrass than neutral salt stress.Under neutral salt stress,proline accumulation was the key metabolite associated with change in the osmotic potential.Under alkaline salt stress,organic acids were linked to regulation of pH values in the plant and the rhizosphere.Midnight,the cultivar tolerant of both types of salt stress,can maintain a higher photosynthesis rate and organic acid metabolism,and stronger ability to regulate pH in the plant and in the rhizosphere under neutral and alkaline salt stresses.In summary,Midnight possesses stronger tolerance to neutral and alkaline salt stresses in Kentucky bluegrass.