effect of drought stress on some morphophysiological traits and chlorophyll fluorescence of red bean seedlings (phaseolus vulgaris l.)

drought is one of the most important factors limiting growth and yield in many parts of the world. in order to evaluate the effects of drought stress on some morphological and physiological traits of two cultivars of bean, two red beans (derakhshan and goli) in four drought treatments including 25%, 50%, 75%, control 100% field capacity were studied in a factorial experiment based on complete randomized design with three replications. results showed that morphological traits inducing plant height, leaf area, root area, total root length and shoot and root dry weight were significantly (p≤0.01) decreased under drought stress. so, results showed that physiological traits such as leaf relative water content (rwc), membrane stability index (msi), psιι photochemical efficiency (fv/fm), and quantum yield of photosynthesis (y) were significantly declined under drought stress (p≤0.01). but, stomatal resistance and chlorophyll index (spad) significantly increased in bean seedlings under drought stress (p≤0.01). the root to shoot ratio was increased further in derakhshan cultivar in severe stress than control. rwc, msi, and fv/fm showed a greater reduction in severe stress than control in goli cultivar. results showed that probably derakhshan cultivar was affected fewer by drought stress, by means of applying drought tolerance different mechanisms than that of goli cultivar. the derakhshan cultivar in most physiological traits, was not represent significant differences between 75% of field capacity and control.