Abstract
The distributions of Na and chlorophyll in the leaves of rice (Oryza sativa L.) seedlings grown under a saline condition were examined in relation to the anatomical changes caused by salinity. In salt-treated plants, the Na content was higher in older leaves and basal part of the leaf. In the 4th leaf of salt-treated plants, Na content was the highest in the middle part of the leaf sheath and decreased toward the tip of the leaf blade. The chlorophyll content in the 4th leaf was decreased by salt treatment at the tip and middle parts of the leaf blade, whereas it was unaffected in the leaf sheath and at the base of the leaf blade. Electron microscopic studies revealed that salt-treatment caused plasmolysis, vesiculation of cellular membranes and degradation of cytoplasm at the tip of the leaf blade, but scarcely caused such alterations at the base of the leaf blade. The present study suggests that the damage by salinity correlates more strongly with the age of the tissue than the Na content of the tissue.
Highlights
The effects of salt stress have been studied from physiological, biochemical and ultrastructural viewpoints
The higher Na content in the old leaves of nonhalophytes may result from a large cumulative duration of transpiration (Greenway and Munns, 1980) or from less exclusion of N a from the old leaves (Yeo and Flowers, 1982)
In salt-treated rice plants, the N a content was higher in the leaf sheath than in leaf blade (Fig. 1) and higher in the basal part than in the apical part of the leaf blade
Summary
The effects of salt stress have been studied from physiological, biochemical and ultrastructural viewpoints. Salt stress decreases photosynthetic activity (Sakamoto et al, 1998; Wang and Nii, 2000), inhibits foliar growth (Hu and Schmidhalter, 1998) and changes the ultrastructure (Pareek et al, 1997; 1--1itsuya et al, 2000; Rahman et al, 2000). The studies about the relationship between the distribution of salt in the various parts of shoots and the damages caused by salt are limited. We examined the distribution of N a and chlorophyll content in various parts of the leaf in relation to the ultrastructural changes caused by salinity in rice. The relationship between the distribution of N a and the damages induced by salt is discussed
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