ABSTRACT In order to explore the main limiting factors affecting the growth and physiological function of alfalfa under salt and alkali stress, the effect of the salt and alkali stress on the growth and physiological function of alfalfa was studied. The results showed that effects of the excessive salt concentration (100 and 200 mM) on the growth and physiological characteristics were significantly greater than that of pH (7.0 and 9.0). Under 100 mM salt stress, there was no significant difference in the growth and photosynthetic function between pH 9.0 and pH 7.0. Under the 200 mM salt concentration the absorption of Na+ by alfalfa treated at the pH 9.0 did not increase significantly compared with absorption at the pH 7.0. However, the higher pH directly reduced the root activity, leaf’s water content, and N-P-K content also decreased significantly. The PSII and PSI activities decreased with increasing the salt concentration, especially the damage degree of PSI. Although the photoinhibition of PSII was not significant, PSII donor and electron transfer from the Q A to Q B of the PSII receptor sides was inhibited. In a word, alfalfa showed relatively strong salt tolerance capacity, at the 100 mM salt concentration, even when the pH reached 9.0. Thus, the effect on the growth and photosynthetic function was not significant. However, at 200 mM salt concentration, pH 9.0 treatment caused damage to root system and the photosynthetic function in leaves of alfalfa was seriously injured.

中文翻译：

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盐浓度、pH 值及其相互作用对苜蓿 (Medicago sativa) 叶子的植物生长、养分吸收和光化学的影响

摘要 为探讨盐碱胁迫下影响苜蓿生长和生理功能的主要限制因素，研究了盐碱胁迫对苜蓿生长和生理功能的影响。结果表明，盐浓度过高（100和200 mM）对生长和生理特性的影响显着大于pH（7.0和9.0）。在100 mM盐胁迫下，pH 9.0和pH 7.0之间的生长和光合功能没有显着差异。在 200 mM 盐浓度下，与 pH 7.0 下的吸收相比，在 pH 9.0 下处理的苜蓿对 Na+ 的吸收没有显着增加。然而，较高的 pH 值直接降低了根系活动、叶片的含水量、NPK 含量也显着下降。PSII和PSI活性随着盐浓度的增加而降低，尤其是PSI的破坏程度。尽管 PSII 的光抑制作用不显着，但 PSII 供体和 PSII 受体侧从 QA 到 QB 的电子转移受到抑制。总之，苜蓿在100 mM盐浓度下，即使pH值达到9.0，也表现出较强的耐盐能力。因此，对生长和光合功能的影响不显着。然而，在 200 mM 盐浓度下，pH 9.0 处理对根系造成损害，紫花苜蓿叶片的光合功能受到严重损害。尽管 PSII 的光抑制作用不显着，但 PSII 供体和从 PSII 受体侧的 QA 到 QB 的电子转移受到抑制。总之，苜蓿在100 mM盐浓度下，即使pH值达到9.0，也表现出较强的耐盐能力。因此，对生长和光合功能的影响不显着。然而，在 200 mM 盐浓度下，pH 9.0 处理对根系造成损害，紫花苜蓿叶片的光合功能受到严重损害。尽管 PSII 的光抑制作用不显着，但 PSII 供体和从 PSII 受体侧的 QA 到 QB 的电子转移受到抑制。总之，苜蓿在100 mM盐浓度下，即使pH值达到9.0，也表现出较强的耐盐能力。因此，对生长和光合功能的影响不显着。然而，在 200 mM 盐浓度下，pH 9.0 处理对根系造成损害，紫花苜蓿叶片的光合功能受到严重损害。