Alleviation of water stress in beans by exogenous glycine betaine

The effect of exogenously applied glycine betaine on the ability of bean (Phaseolus vulgaris) plants to; withstand water stress was investigated. Water stress induced endogenous accumulation of glycine betaine in the leaves, resulting in an increase of similar to 26% over the level in well-watered plants. Plants treated with exogenous glycine betaine (10 mM) maintained better water status during water stress treatment than the untreated plants. During water stress treatment, glycine betaine-treated plants showed a slower decrease in leaf water potential, thus developing wilting symptoms much later than the untreated plants. In addition, glycine betaine-treated plants showed better ability to recover from wilting than the untreated plants. Water stress adversely affected the photosynthetic activity of plants as indicated by a reduction in the leaf CO, absorption rate, the ratio of variable to minimal chlorophyll fluorescence (F-v/F-a,), and the overall growth. Glycine betaine treatment fully overcame the adverse effects on CO, absorption and chlorophyll fluorescence during water stress. However, little or no effect of glycine betaine on shoot biomass and pod yield was observed in water stressed plants. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.