Morphological and physiological responses of two common bean cultivars to drought stress

Drought stress is the major problem in arid and semi-arid regions of the world. Investigating the response of different cultivars of crop plants to drought stress can help to select the tolerant ones for agriculture in arid lands. In this study, a greenhouse experiment was conducted as a factorial experiment based on completely randomized design with two common bean cultivars (Phaseolus vulgaris L.) including Derakhshan and Goli, and four moisture levels of 25, 50, 75 and 100% field capacity. When the true leaves were emerged (10 days after planting), the seedlings were exposed to the different levels of drought stress until the end of the flowering stage. Based on the morphological (stem length, leaf and root area, dry weight of shoot and root, and the root/shoot ratio), physiological (leaf relative water content, membrane stability index, photosystem II photochemical efficiency, stomatal resistance, chlorophyll index, and water use efficiency), and biochemical (proline content, soluble protein content, and the activity of antioxidant enzymes including superoxide dismutase, polyphenol oxidase, and peroxidase) characteristics, both cultivars showed a relatively good tolerance to the low and intermediate drought stress, while both were sensitive to the highest level of drought condition (25% field capacity). The main characteristics which indicated the tolerance of common bean cultivars to drought stress was an increase in the root/shoot ratio, stomatal resistance, water use efficiency, proline content, and antioxidant enzyme activity. Regarding these characteristics, the responses of Derakhshan cultivar was more associated with drought tolerance, compared with Goli cultivar.