燕麦幼苗对两种碱性盐(NaHCO₃和Na₂CO₃)胁迫的适应性形态和生理响应

Adaptive Morphological and Physiological Responses of Oat Seedlings to Stress on Two Basic Salts (NaHCO₃ and Na₂CO₃)

摘要: 本研究以燕麦(A. sative L.)幼苗为研究对象，通过不同浓度梯度的NaHCO₃与Na₂CO₃两种碱性盐胁迫处理，每个组又设置了5个盐浓度梯度，盐浓度共覆盖了总盐浓度为48~144 mmol∙L⁻¹，pH值分别为8.03、8.12、8.18、8.22、8.26、9.91、10.22、10.82、11.11、11.27的碱度(pH值)各不相同的10种碱条件。对燕麦幼苗进行胁迫处理9天后，测定燕麦幼苗生长指标和生理学指标的变化。结果表明：随着盐碱强度的增大，分蘖数、株高、生物量、叶绿素含量、含水量下降且差异显著(P < 0.05)；脯氨酸含量、膜透性随盐碱强度的增大而增大且差异显著(P < 0.05)；Na⁺、Ca²⁺含量增大，K⁺下降，Na⁺/K⁺比值增大，有机酸增大，地上部分组织液中的pH值相对平衡。地下部分组织液的pH值增大，导致根代谢紊乱而致死。从存活率看，燕麦对Na₂CO₃处理液的耐受极限为96 mmol∙L⁻¹；对NaHCO₃的耐受极限144 mmol∙L⁻¹，燕麦对碱性盐的耐受极限随pH值的增大而减小。此外，虽然这两种压力都降低了根干重，但它们并没有显著影响根系扩展的生长。这表明，燕麦采用了一种机会主义的游击策略，它避免了资源贫乏的土壤(如高碱)，而通过维持根延伸，优先利用更有利的栖息地。

Abstract: In this study, we took oats (A. sative L.) seedlings as plant material. NaHCO₃ and Na₂CO₃ were treated with different concentration gradients under alkaline salt stress. Five salt concentration gradients were set for each group, and the total salt concentration was covered by salt concentration 48 - 144 mmol∙L⁻¹, 10 base conditions with varying alkalinity (pH) of 8.03, 8.12, 8.18, 8.22, 8.26, 9.91, 10.22, 10.82, 11.11, and 11.27, respectively. Oat seedlings were stressed for 9 days; we measured the growth and physiological index of oat seedlings. The results showed that the number of tillers, plant height, biomass, chlorophyll content and water content decreased with the increase of saline-alkali strength, and the difference was significant (P < 0.05). Proline content and membrane permeability with saline-alkali strength increase with significant difference (P < 0.05); Na⁺ and Ca²⁺ content increased and K⁺ decreased. As the ratio of Na⁺/K⁺ increased, so did the organic acid. The pH value in the shoot tissue fluid was relatively balanced due to the increase of acid. The pH value of the tissue fluid in the root increased, leading to root metabolism disorder and death. In terms of survival rate, the tolerance limit of oat to Na₂CO₃ solution was 96 mmol∙L⁻¹; the NaHCO₃ tolerance limit was 144 mmol∙L⁻¹, and the tolerance limit of oat to alkaline salt decreased with the increase of pH value. Additionally, while both stresses reduced root dry weight, they did not significantly affect root extension growth. This indicates that oat adopts an opportunistic guerrilla strategy by which it avoids resource-poor patches of soil (e.g. high alkali) while preferentially exploiting more favorable habitats by maintaining root extension.