Possible involvement of greening in cell growth of Suaeda japonica under salt stress

Abstract

Suaeda japonica, a member of the family Chenopodiaceae, is a halophyte that grows on the shores of the Ariake Sea in Japan. Using yellowish and selected green callus tissues of S. japonica, we examined the correlation between cell growth and glycinebetaine content, as well as the activity of betaine aldehyde dehydrogenase (BADH), under salt stress. Although the growth of yellowish callus tissues was markedly inhibited by 0.1 M NaCl, that of green callus tissues was not. However, in 0.3 M NaCl, the fresh weight of green callus tissues was decreased by 15%. Both the endogenous level of glycinebetaine and the activity of BADH in yellowish callus tissues were very low, but green callus tissues contained very high levels of glycinebetaine and high BADH activity. The activity in green callus increased significantly with increases in the concentration of NaCl. The increase in levels of Chl was also observed, but the increase occurred earlier than that in the level of glycine-betaine. Functional development of chloroplasts (an increase in the level of Chl) seems to be involved in the increase in the activity of BADH, and the resultant increase in levels of glycinebetaine seems to facilitate callus growth under salt stress.