Abstract
Silicon (Si) is a macroelement in plants. The biological effects and mitigation mechanisms of silicon under environmental stress have become hot topics. The main objectives of this study were to elucidate the roles of Si in alleviating the effects on the phenotype, micromorphology and anatomy of the leaves of rice seedlings under acid rain stress. The results indicated that the combined or single effects of Si and simulated acid rain (SAR) stress on rice roots depended on the concentration of Si and the intensity of the SAR stress. The combined or single effects of the moderate concentration of Si (2.0 mM) and light SAR (pH 4.0) enhanced the growth of the rice leaves and the development of the mesophyll cells, and the combined effects were stronger than those of the single treatments. The high concentration of Si (4.0 mM) and severe SAR (pH 3.0 or 2.0) exerted deleterious effects. The incorporation of Si (2.0 or 4.0 mM) into SAR at pH values of 3.0 or 2.0 promoted rice leaf growth, decreased necrosis spots, maintained the structure and function of the mesophyll cells, increased the epicuticular wax content and wart-like protuberance (WP) density, and improved the stomatal characteristics of the leaves of rice seedlings more than the SAR only treatments. The alleviatory effects observed with a moderate concentration of Si (2.0 mM) were better than the effects obtained with the high concentration of Si (4.0 mM). The alleviatory effects were due to the enhancement of the mechanical barriers in the leaf epidermis.
Highlights
Silicon (Si) is a beneficial macroelement in plants [1,2,3,4]
The present study investigated the effects of Si on the leaf phenotype, mesophyll cell structure, Si content, stoma characteristics, epicuticular wax and wart-like protuberance (WP) characteristics of rice seedlings under simulated acid rain (SAR) stress
3.0 exhibited changes and had more small necrosis spots compared with the control (Fig 1G), and the leaves treated with SAR at pH 2.0 were more severely yellowed, and necrosis was observed on the whole leaves (Fig 1J)
Summary
Silicon (Si) is a beneficial macroelement in plants [1,2,3,4]. Many studies have shown that the application of silicon can enhance the resistance of plants exposed to abiotic and biotic stresses, such as acid rain [5], UV-B [6], drought [7,8], metal toxicity [9], salt [8], diseases [10,11] and others [12]. Si is taken up by the roots as silicic acid, and the silicic acid is transported to the shoot through the xylem and undergoes polymerization to hydrated. Effects of silicon and acid rain on Oryza sativa L. seedlings
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