Effect of exogenous silicon (Si) on H~+-ATPase activity, phospholipids and fluidity of plasma membrane in leaves of salt-stressed barley (Hordeum vulgare L.)

摘要

Silicon (Si) is generally considered a beneficial element for the growth of higher plants, especially for those grown under stressed environments. Recently, the mitigating role of Si under salt stress has received worldwide attention. However, the mechanism of stress mitigation remain poorly understood. We studied the effects of Si on plasma-membrane fluidity, phospholipids, and H~+-ATPase activity in two contrasting barley cultivars differing in their salt resistance. The results showed that plasma-membrane H~+-ATPase activity decreased in leaves of plants treated with 120 mM NaCl, and this decrease was more pronounced in the salt-sensitive cultivar (Kepin No.7) than in the salt-resistant cultivar (Jian 4). Under NaCl stress, plasma-membrane fluidity decreased, and the ratio of phospholipids to proteins in plasma-membrane vesicles increased. Addition of 1.0 mM Si increased plasma-membrane H~+-ATPase activity in both cultivars as compared with that in plants treated with 120 mM NaCl only. The addition of Si was also found to recover membrane fluidity to control levels (neither NaCl nor Si added) level, and to decrease the ratio of phospholipids to protein. It is suggested that Si maintains an optimal membrane fluidity which contributes to reducing oxidative damage to enzymes induced by active oxygen species, and enhances plasma-membrane EF-ATPase activity under NaCl stress.