The eelgrass (Zostera marina L.) was treated with artificial seawater (ASW) of different salinities (100%, 150% and 200% seawater) for 5 d. The activities of two enzymes extracted from the plant leaves were determined under a salinity grade in vitro. So were the photosynthesis rates of the plants from the three treatments in the media with different salinities (100%, 150%, 200%, 300% ASW) and some physiological data. The data showed that under increased salinities （concentrated seawater）, Na+, Cl-, MDA (malon dialdehyde) and glucosecontents and the osmotic potentials (absolute value) in the leaves increased with the salinity elevation in the medium (ASW), but both K+ and free amino acid (mainly proline) contents decreased. Malate dehydrogenase (MDH) from the plant leaves under a salinity grade showed its activities (A) as follows: A 100% ASW>A 150% ASW>A 200% AS. Phosphoenolpyruvate carboxylase (PEPC) extracted from the 100% ASW and 200% ASW treated plants showed similar activities (both insensitive to salinities) under the salinity grade in vitro, but the activities of PEPC from plants treated with 150% ASW were dependent on salinity. Whether the plant is stressed at 150% ASW and can stand higher salinity than seawater needs to be studied further. Meantime, the data do not agree with the opinion that the adaptation of the eelgrass to seawater salinity is partly fulfilled by its insensitiveness to salinities in some metabolic enzymes. It can be inferred that the lack of transpiration may be an important aspect of the plant‘s tolerance to seawater salinity.
盐分胁迫对大叶藻某些胞内酶耐盐性及其生理功能的影响
叶春江 赵可夫*
（山东师范大学逆境植物研究所，济南250014）
摘要： 分别以3个盐度(100%、150% 和200%人工海水)处理大叶藻(Zostera marina L.)植株5 d,然后在体外测定了大叶藻叶片中两个胞内酶(PEP羧化酶和苹果酸脱氢酶)的耐盐性和在不同盐度介质中(100%、150%、200%、300%人工海水)经不同盐度(100%、150% 和200%人工海水)海水预处理的大叶藻叶片光合速率以及一些生理指标的改变.结果表明在高于海水的盐度下,大叶藻叶片中丙二醛(MDA)、还原性糖和Na+, Cl-含量及渗透势(绝对值)均随海水盐度的提高而增加,但K+和游离氨基酸的含量均降低.从处理5 d的植株中提取的苹果酸脱氢酶在体外每一盐度下,其活性(A)大小依次为: A100% ASW>A150% ASW>A200% ASW(artificial seawater),并且其活性对盐度敏感(低盐度激活高盐度抑制);但从100%及200%人工海水(ASW)处理的植株中提取的PEP羧化酶的活性在体外对盐度不敏感,而从150%人工海水处理的植株中提取的PEP羧化酶的活性对盐度具有很高的抗性.实验结果显示由150%人工海水处理的植株,在每一特定的盐度下其光合速率均高于另外两组处理(100% ASW和200% ASW),并且3个处理的光合速率均与其PEPC在不同盐度下的活性表现相一致.但是,经150% ASW 处理的大叶藻植株是否受到盐害还有待于进一步探讨.实验表明"大叶藻耐盐性在一定程度上是由于其代谢酶对盐度的耐性造成的"这一说法是不合适的;不存在蒸腾作用可能是大叶藻耐盐机理的重要组成部分.
关键词： 大叶藻；盐度适应；酶的耐盐性；PEP羧化酶；苹果酸脱氢酶；丙二醛
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