Alleviation of water stress in beans by exogenous glycine betaine

Abstract

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 ∼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 2 absorption rate, the ratio of variable to minimal chlorophyll fluorescence ( F v/ F o), and the overall growth. Glycine betaine treatment fully overcame the adverse effects on CO 2 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.