盐、碱胁迫下小冰麦体内的pH及离子平衡

pH and ion balance in wheat-wheatgrass under salt-or alkali stress

通过混合两种中性盐(NaCl和Na2SO4)和两种碱性盐(NaHCO3和Na2CO3)分别模拟出不同强度的盐、碱胁迫条件,对小冰麦苗进行12d胁迫处理,测定茎叶组织液的pH值及Na+、K+、Ca2+、Cl-、SO42-、NO3-、H2PO4-和有机酸等溶质的浓度,以探讨盐、碱两种胁迫下小冰麦体内的pH及离子平衡特点.结果表明:盐、碱胁迫下小冰麦茎叶内的pH值均稳定不变;随胁迫强度的增加,盐胁迫下小冰麦茎叶内有机酸浓度没有明显变化,Cl-浓度大幅度增加,而碱胁迫下有机酸浓度大幅度增加,Cl-浓度没有明显变化.盐、碱胁迫下小冰麦茎叶中的阳离子均以Na+和K+为主,但阴离子的来源明显不同.盐胁迫下无机阴离子对负电荷的贡献起主导作用,其贡献率达61.3%～66.7%;而碱胁迫下,随胁迫强度的增大,有机酸对负离子的贡献率从38.35%上升到61.60%,逐渐成为主导成分.实验结果表明,有机酸积累是小冰麦在碱胁迫下保持体内离子平衡和pH稳定的关键生理响应.

Abstract： Different intensities of salt- or alkali stress were established by mixing different concentrations of NaCI and Na2SO4 or NaHCO3 and Na2CO3, respectively, and wheat-wheatgrass （Triticum aestivum L. -Agropyron intermedium） seedlings were grown under the stresses for 12 days. The pH value and the Na^＋ , K^＋ , free Ca^2＋ , Cl^-, SO4^2- , NO3^- , H2PO4^-, and organic acid concentrations in-the fresh shoots of stressed wheat-wheatgrass seedlings were determined, aimed to approach the characteristics of pH and ion balance in wheat-wheatgrass under salt- or alkali stress. The results showed that intracellular pH was relatively stable under both stresses. Cl^- concentration increased sharply and organic acid concentration changed less under increasing intensity of salt stress, while it was, in adverse under increasing intensity of alkali stress. Under both stresses, the cations in the fresh shoots were mainly Na^＋ and K^＋ , but the anions were different. Under salt stress, inorganic anions were the dominant components and contributed 61.3%-66. 7% to the total negative charge, while under alkali stress, the contribution of organic acid to total negative charge increased from 38. 35% to 61.6% with increasing stress intensity, and became the dominant component. It was concluded that organic acid accumulation might be a key physiological response of wheat-wheatgrass for its keeping pH and ion balance under alkali stress.