EFFECTS OF OSMOPROTECTANTS UPON NACL STRESS IN RICE

Plants accumulate a number of osmoprotective substances in response to NaCl stress, one of them being proline (Pro). While characterizing so me of the changes in solute accumulation in NaCl-stressed rice (Oryza sativa L.), we identified several other potential osmoprotectants. One such substance, trehalose, begins to accumulate in small amounts in r oots after 3 d. We performed a series of experiments to compare the ef fects of Pro and trehalose on ion accumulation to determine whether th e two chemicals protect the same physiological processes. We found tha t Pro either has no effect or, in some cases, exasperates the effect o f NaCl on growth inhibition, chlorophyll loss, and induction of a high ly sensitive marker for plant stress, the osmotically regulated salT g ene. By contrast, low to moderate concentrations of trehalose reduce N a+ accumulation, salT expression, and growth inhibition. Somewhat high er concentrations (10 mM) prevent NaCl-induced loss of chlorophyll in blades, preserve root integrity, and enhance growth. The results of th is study indicate that during osmotic stress trehalose or carbohydrate s might be more important for rice than Pro.