Na_2CO_3胁迫下星星草(Puccinellia tenuiflora)幼苗叶表皮和叶肉细胞中K、Na的相对含量

The content of K and Na in epidermis and mesophyll cells of Puccinellia tenuiflora seedling leaves under Na_2CO_3 stress

对不同强度Na2CO3胁迫处理下星星草幼苗叶片表皮和叶肉细胞中K、Na的透射电镜X-射线电子探针显微分析和叶片表面扫描电镜X-射线电子探针显微分析,结果表明:在相同胁迫强度下,无论是表皮细胞还是叶肉细胞的细胞壁和液泡中的Na相对含量均明显高于细胞质中的Na相对含量,并且K的相对含量均明显比相应部位Na的相对含量高,细胞壁与液泡中的Na相对含量变化范围非常接近。在Na2CO3胁迫浓度低于0.1molL-1时,在相同胁迫强度下,K的相对含量高于Na的相对含量,使细胞质保持相对高的K/Na比。而尽管向细胞壁和液泡分流了大量的Na,但是细胞质中的Na相对含量仍然随着Na2CO3胁迫强度的增加而增加,一方面证明星星草在Na2CO3胁迫下维持相对高的K/Na比的能力是有一定限度的,另一方面暗示星星草作为盐生植物在盐碱环境中一定程度上Na可以部分地代替K而行使部分K的生理功能。

Puccinellia tenuiflora, a perennial gramineal plant, which can grow in alkalized soil after artificial planting, and it has been emploied in the biological harness of alkalized soil. The salt entered PuccineUia tenuiflora can be eliminated via stoma or along with wax secretion to leaf surface. There is high content of Na and K and other elements on leaf surface when it grows normally, and content of Na and K on leaf surface shows regular changes under the Na2 CO3 stress of different concentrations. However, how the Na and K content alternate and the function of maintaining the ion balance and osmotic adjustment in mesophyll cells under Na2 CO3 stress are not completely understood？ The K and Na level in epidermis and mesophyll cells of Puccinellia tenuiflora seedling leaves under the Na2CO3 stress of different concentrations was investigated by using transmission electron microscopy, environmental scanning electron microscopy, and X-ray electron probe microanalysis. Under the same stress intensity, the relative content of Na in either cell wall or vacuole of epidermis and mesophyll cells was higher than that in cytoplasm, and the K level was significantly higher than Na in the same location. The changes of Na content in cell wall and vacuole had the same range. When Na2 CO3 concentration was lower than 0.1 mol L^-1, the relative content of K was higher than that of Na under the same stress intensity, so the K / Na ratio in cytoplasm was relatively high. Although plenty of Na was dispersed into cell wall and vacuole, the relative content of Na in cytoplasm was still elevated along with Na2 CO3 stress. These data confirmed that the ability of Puccinellia tenuiflora to maintain the higher K / Na ratio in cytoplasm is finite, and implied that Puccinellia tenuiflora, as salt tolerant plant growing in salt and alkali environment, its cytoplasmic Na may partially substitutes for K and takes the function of K to some extent.