不同水陆生境下入侵种喜旱莲子草与土著种莲子草表型变异和细胞渗透势调节能力的比较研究

Comparisons of Morphological Variation and Cellular Osmotic Potential Adjustment between Invasive Species Alternanthera philoxeroides and its Native Congener A. sessilis under Different Water Treatments

喜旱莲子草(Alternanthera philoxeroides(Mart.)Griseb.)能成功入侵不同水陆生境,而其同属近缘种莲子草(A.sessilis(Linn.)DC.)适于生长在潮湿的陆地环境中。为揭示两物种生态幅差异的机理及与其入侵潜力的关系,我们在模拟不同水陆生境的同质园环境下,比较了喜旱莲子草和莲子草的形态特征、细胞渗透势变异状况和细胞内溶质物质合成相关基因(蛋氨酸合成酶基因)的表达水平。结果表明:喜旱莲子草对环境变异更敏感,表型变异幅度更大,具有更有效的渗透势调节能力;蛋氨酸合成酶基因在喜旱莲子草进入水生环境的早期阶段表现出短暂上调的特殊表达趋势。这说明有效的细胞渗透势调节机制与喜旱莲子草对不同水陆生境的广泛适应性和较强的表型可塑性能力可能有关,从而帮助其在不同生境中成功入侵。

To understand the mechanisms underpinning the invasion of Alternanthera philoxeroides （Mart.） Griseb. in diverse water regimes, we compared its morphological traits, osmotic potential and methionine synthase （MS） gene expression with its native congener A. sessilis （Linn.） DC., which mainly occurs in moist terrestrial habitats in China. Results showed that A. philoxeroides exhibited greater phenotypic plasticity and possessed a more effective mechanism for osmotic adjustment than that of A. sessilis. The MS gene exhibited an ＇ up- down＇ expression pattern in A. philoxeroides, its mRNA levels increased during the first 3 hours of flooding treatments and then fell rapidly thereafter. Thus, higher flexibility in the internal environment and gene expression adjustment may play an important role in the rapid responses of A. philoxeroides to water regime changes, which are associated with its invasiveness.