In order to study the change of contents of chlorophyll, malonaldehyde and ions under the condition of the different proportional replacement of potassium by sodium in the coconut leaves, a test was attempted in which the replacement of potassium by sodium in the coconut leaves was carried out under the sand culture. The result showed that in a condition of which the total concentration of potassium and sodium was 4 mmol/L, compared to 100% treatment, the contents of chlorophyll a, chlorophyll b, total chlorophyll increased in the treatment of 25% replacement of potassium by sodium; decreased obviously in 50% and 75%, but reduced slightly in 100%. The tendency of changes of the ratios of chlorophyll a/b in all treamts was not only nearly alike and gradually steady, but also the difference between them was not significant (F>0.01). As time went, the contents of malonaldehyde was equal to the control and steady in the treatments of 25%, 50% replacement of potassium by sodium, but rose in 75% and 100%. After 80 days, Na contents in all treatments increased gradually with the increasing proportional replacement of potassium by sodium, compared to the control, which were extremely significant (P<0.01); however, K contents in the treatments of 25%, 50%, 75% replacement of potassium by sodium were slightly lower than the control, as well as non-significant(P>0.01), moreover, there were not significant (P<0.01) between them. K contents in 100% decreased apparently and were extremely significant (P<0.01), compared with other treatments. The results of the study expounded that the partial replacement of potassium by sodium had no or positive effect on contents of chlorophyll and K+ in the coconut leaves, displaying the ability of salt tolerance to a certain degree.%为探讨不同钠替代钾条件下椰子叶片叶绿素、丙二醛及Na+、K+含量的变化,在沙培环境中对椰子苗进行钠替代钾试验.结果显示:在Na+、K+总浓度为4 mmol/L的情况下,与100%钾的对照相比,25%的钠替代钾处理中叶绿素a、叶绿素b、总叶绿素含量上升;50%、75%处理明显下降,100%处理略有下降;各处理Chla/Chlb比值变化趋势基本一致,总体趋于平稳且各处理间差异不显著(P>0.01).随时间的推移,25%、50%处理丙二醛(MDA)含量与对照相当,趋于平稳,而75%、100%处理丙二醛(MDA)含量呈上升变化.80 d后,各处理的Na+含量随着钠替代钾比例的上升而逐渐增加,较之对照均达到了极显著水平(P<0.01);而25%、50%、75%的K+含量略低于对照但差异不显著(P>0.01),且各处理间差异也不显著(P>0.01),100%处理K+含量明显低于其他各处理且均达到了极显著水平(P<0.01).结果表明:部分钠替代钾处理对椰子苗的叶片光合色素及K+含量没有影响甚至有促进作用,表现出一定的耐盐能力.
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