Influence of exogenous application of proline and glycinebetaine on growth of salt-stressed tomato plants

The ability of exogenous compatible solutes, such as proline and glycinebetaine, to counteract salt inhibitory effects in tomato (Lycopersicon esculentum L. cv. 'F144') was investigated. Both compounds were added 5 weeks after germination when final salt concentrations were achieved and plant response was followed for 3 more weeks. The most outstanding effect of exogenous application of proline and glycinebetaine on tomato plants was a decreased accumulation of Na+ and Cl-. Growth was seriously inhibited by the addition of proline or glycinebetaine to the growing media. This deleterious effect can be explained by the fact that plants adjusted only partially to the external osmotic potential, because of a decreased accumulation of either ions or proline. Besides, it can be attributed to a toxic effect of both, proline and glycinebetaine. (C) 2003 Elsevier Ireland Ltd. All rights reserved.