根茎是根状茎型克隆植物的特有结构，在养分储存、运输和分蘖茎的形成等方面起关键性作用。然而有关根茎生理学方面的研究却十分匮乏。为了探讨根茎在植物感应环境胁迫中的作用, 本文以羊草（Leymus chinensis）为实验材料，研究和比较了短期NaCl胁迫根、根茎、根和根茎3种处理方式下羊草对盐胁迫的响应。试验结果表明：200 mmol·L-1 NaCl处理羊草根、根茎、根和根茎24 h，显著（p<0.05）降低羊草叶片净光合速率和蒸腾速率，增加叶片渗透浓度与脯氨酸含量；其中同时处理根和根茎叶片，蒸腾速率和净光合速率的降低程度显著高于分别处理根和根茎。在分别处理根与根茎的情况下，叶片含水量、脯氨酸含量、净光合速率、蒸腾速率均无显著性差异。不论单独胁迫根、根茎还是同时胁迫根和根茎，羊草根、根茎和叶片内Na+含量都显著高于对照，而羊草根、根茎和叶片内K+含量都显著低于对照。这些结果显示：1）根茎在羊草响应盐胁迫的生理过程中与根系具有类似的功能；2）羊草根茎在盐胁迫条件下能够有效地吸收Na+；3）鉴于根茎的生物量和表面积都明显地低于根系，在盐胁迫下羊草根茎吸收Na+的效率高于根系。
Background and Aims Rhizomes in clonal plants play a key role in storage and transport of nutrients as well as production of tillers. However, physiological functions of rhizomes in response to abiotic stress are poorly known. We investigated physiological responses ofLeymus chinensis to salinity.
Methods We measured the following physiological parameters after 24 h exposure of roots and rhizomes separately and exposure of roots and rhizomes together to 200 mmol·L-1 NaCl: water and proline content in leaves, K+ and Na+ content in leaves, roots and rhizomes, and osmolality, net photosynthesis rate and transpiration rate in leaves.
Key Results Net photosynthesis rate and transpiration rate of leaves were significantly (p<0.05) reduced when roots and rhizomes individually and roots and rhizomes together were exposed to NaCl. The same treatments led to increases in osmolality and proline contents in leaves. There was a greater reduction in net photosynthesis rate and transpiration rate of leaves when roots and rhizomes were treated together with NaCl than treated separately. However, when roots and rhizomes were treated with NaCl separately, no significant differences in leaf water content, proline content, net photosynthesis rate and transpiration rate were observed, suggesting that the roots have a similar role to the rhizomes in response to salinity stress in L. chinensis. When roots and rhizomes were treated with NaCl either together or separately, the Na+ contents in roots, rhizomes and leaves were higher than those of controls, by contrast, the K+ contents were lower than those of controls.
Conclusions Rhizomes of L. chinensisare important in sensing and responding to salinity and have a similar function to that of roots in uptake and translocation of Na+ under salinity stress. Because rhizomes have smaller biomass and surface area than root systems, we speculate that rhizomes of L. chinensis may have greater capacity than roots for uptake and translocation of Na+ ions under salinity stress.