Study of the defensive mechanism against drought in French bean (Phaseolus vulgaris L.) varieties

The response to drought of six green- and yellow-podded varieties of green bean was investigated in a phytotron. These varieties were also grown without irrigation in field experiments and analysis of leaf samples was carried out three times; before and under flowering and pod ripening, respectively. At first, the carotene and raffinose contents of leaves increase during mild drought (30/15A degrees C). High temperature (35/25A degrees C) combined with water deficiency resulted in a considerable decrease in leaf weight, chlorophyll b, maltose content, as well as the level of water-soluble antioxidants of the leaves, while the content of lipid-soluble antioxidants and raffinose content increased when compared with the control. The yellow-podded varieties of green beans responded to drought much more sensitively than the green-podded ones. The results suggested that a selection method based on the activity of antioxidants in the leaves can be used for testing the adaptability of numerous bean genotypes to drought.