NaCl和Na_2CO_3对星星草生长及营养液中主要矿质元素存在状态的影响

Effects of Sodium Chloride and Carbonate on Growth of Puccinellia and on Present State of Mineral Elements in Nutrient Solution

星星草生长在０～６００ｍｍｏｌ／ＬＮａＣｌ和０～２００ｍｍｏｌ／ＬＮａ２ＣＯ３的盐胁迫下，测定了其生长状况及营养液中主要矿质离子的游离度、活度等。结果表明：相同Ｎａ＋活度下，Ｎａ２ＣＯ３对星星草的生长尤其是根生长的抑制作用明显大于ＮａＣｌ。两种盐胁迫下，星星草根生长与营养液中Ｃａ２＋活度／（Ｎａ＋活度）２比值间密切相关。Ｎａ２ＣＯ３使营养液中Ｃａ２＋、Ｍｇ２＋、ＨＰＯ２－４和Ｈ２ＰＯ－４的游离度及活度下降，其程度远大于ＮａＣｌ；也使Ｋ＋游离度及活度较ＮａＣｌ有更明显的下降。Ｎａ２ＣＯ３使根系环境ｐＨ升高，Ｃａ、Ｍｇ、Ｐ的可利用性及Ｃａ２＋活度／（Ｎａ活度）２比值极度下降，可被认为是Ｎａ２ＣＯ３胁迫甚于ＮａＣｌ胁迫的重要原因。

Puccinellia tenuiflora was grown under the stress conditions of sodium chloride (0～600 mmol/l) and sodium carbonate (0～200 mmol/l) solutions, and thereby the effects of the salts on plant growth and on the state of major ions in the nutrient solutions were studied. It was shown that the stress effect of sodium carbonate on plant growth, root growth in particular, was significantly greater than that caused by sodium chloride. Under the stress of either salt the growth of roots was highly correlated with the ratio of Ca 2+ activity/(Na + activity) 2 in the nutrient solution. The number and activity of free ions of potassium, calcium, magnesium, HPO 2- 4 and H 2PO - 4 decreased more dramatically in sodium carbonate solution than in sodium chloride. The higher stress effect of sodium carbonate on plant growth could be attributed to the higher pH value around the root system, the less availability of calcium, magnesium and phosphorus to the plant and the much smaller ratio of Ca 2+ activity/(Na + activity) 2 caused by sodium carbonate than in cases of sodium chloride.