燕麦对松嫩草地三种主要盐分胁迫的生理适应策略

Physiologically adaptive strategies of oat seedlings to the three main salts in the soils of the Songnen Plains grasslands

为明确燕麦幼苗对松嫩盐碱草地3种主要盐分Na Cl、Na HCO_3和Na_2CO_3的适应机制,设定不同浓度梯度(48—144 mmol/L)的胁迫处理液,测定燕麦幼苗的生长与生理指标变化。结果表明,尽管试验设定的Na Cl浓度并不影响幼苗的存活率,但在各组胁迫处理下,随着浓度的增加,燕麦幼苗的分蘖数、植株高度、茎叶与根系的生物量均呈下降趋势,下降幅度为Na_2CO_3>Na HCO_3>Na Cl。另外,与Na Cl胁迫相比,Na_2CO_3与Na HCO_3胁迫下茎叶与根中积累了更多的有毒Na^+,同时K^+下降幅度也更大,并且根系中含有更高的Na^+与更低的K^+以及更高的Na^+/K^+。在Na Cl胁迫下,燕麦幼苗积累大量的无机Cl^-和脯氨酸来维持细胞内的渗透与离子平衡,而Na HCO_3与Na_2CO_3胁迫造成了燕麦幼苗体内阴离子的亏缺,此时幼苗主要通过积累大量的有机酸和更多的脯氨酸来维持渗透与离子平衡。上述结果表明,碱性盐Na_2CO_3与Na HCO_3对植物的胁迫伤害程度大于中性盐Na Cl,并且Na_2CO_3的毒害效应最强,而燕麦幼苗对不同的盐分胁迫伤害也有会产生不同的生理适应策略。

To identify the coping mechanisms and the adaptive strategies of oat seedlings exposed to NaCl, NaHCO3, and Na2C03, the main salts in the soils of the salt-alkali grasslands of the Songnen Plains of China, growth rates and physiological indices of oat seedlings were measured in plants grown in soils with different concentrations （48--144 mmol/ L） of the three salts. The result demonstrated that although oat seedling survival rates were unaffected by NaCl stress, the tiller number, plant height, and shoot and root dry weights decreased with increasing salt concentration, in the order of Na2CO3 〉 NaHCO3〉 NaCl. In addition, higher concentrations of Na^＋ accumulated in the shoots and roots of oat seedlings under Na2CO3 stress and NaHCO3 stress than in seedlings under NaCl stress. Reductions in concentrations of K^＋ were also greater under both Na2CO3 stress and NaHCO3 stress than under NaCl stress, especially in the roots. Large amounts of Cl^- and proline were found to accumulate in oat seedlings, most likely as a strategy for maintaining osmotic and ionic homeostasis under NaCI stress, whereas substantially higher accumulations of proline and organic acid were observed to balance cation deficiency under Na2CO3 and NaHCO3 stresses. These results indicated that the stress effects on oat seedlings of Na2 CO3 and NaHCO3 exposure were greater than that of NaCl exposure, with Na2 CO3 stress having the strongest detrimental effect. In addition, oat seedlings responded to different levels of salt stress through the adoption of various physiological mechanisms.