盐胁迫对小型西瓜幼苗体内离子分布的影响

采用营养液水培法，研究了不同NaCl浓度对耐盐性不同的两个小型西瓜品种（秀雅和秀丽）幼苗体内离子分布的影响。结果表明，NaCl胁迫抑制了西瓜幼苗的生长，秀雅生长受抑制程度明显小于秀丽； 随NaCl浓度的提高，植株体内Na+和Cl－含量增加，K+、 Ca2+和Mg2+含量降低。5种离子在器官间呈区域化分布，Cl－主要积累在茎中而Na+主要积累于茎和根中； K+含量在茎中降低幅度较大，叶中降低幅度较小； Ca2+和Mg2+主要存在于茎和叶中，且在叶中降低幅度较小。NaCl胁迫下，西瓜根向茎选择性运输K+和Ca2+的能力降低，而茎向叶选择性运输的能力提高，有利于减轻NaCl胁迫对叶片的伤害。与秀丽相比，秀雅叶中K+、 Ca2+含量降低幅度较小，Cl－和Na+积累量较少，K+/Na+和Ca2+/Na+比值均较高，茎向叶运输的SK，Na和SCa，Na值也较高。以上结果说明，向叶片运输Na+的选择性较低，是秀雅耐盐性较强的主要原因之一，离子在器官水平上的区域化分布是西瓜植株适应盐胁迫的重要生理机制之一。

Effect of salinity on distribution of ions in mini-watermelon seedlings

A hydroponic cultivation experiment was carried out with two mini watermelon cultivars differing in salt tolerance to study the effect of different NaCl concentrations on ions distribution in watermelon seedlings. The results show that NaCl stress inhibits the growth of watermelon seedlings, and the extent of inhibition for Xiuya is less than that of Xiuli. Increasing NaCl concentration, the Na+ and Cl- contents of the seedlings are increased, while the K+, Ca2+ and Mg2+ contents decreased. The five ions present a compartmentalized distribution. Cl- mainly accumulates in the stems and Na+ mainly concentrates in roots and stems. The decreased range of the K+ contents is larger in stems and smaller in leaves, Ca2+ and Mg2+ mainly exist in stems and leaves and the declined extent in leaves is less. The abilities of selective transportation of K+ and Ca2+ from roots to stems are decreased, while the abilities from stems to leaves are increased under the NaCl stress, which contributes to alleviate the damage of NaCl stress to leaves. Compared to cv. Xiuli, the K+ and Ca2+ contents in leaves of cv. Xiuya reduced less, Cl- and Na+ accumulations are less. As a consequence, K+/Na+ and Ca2+/Na+ radios are higher, and SK，Na and SCa，Na ratios of selective transportations from stems to leaves are also higher. This research reveals that lower selective transportation of Na+ to leaves is one of main reasons for cv. Xiuya with more salt tolerance, and the compartmentalized distribution of ions on the organs is one of physiological adaptation mechanisms of watermelon plants to salinity.