Effect of drought stress on morphological and physiological traits of sesame (Sesamum indicum L.)

Drought stress is the most important factor in decreasing crop yield in most parts of the world. In order to investigate the effect of drought stress on some morphological and physiological traits of sesame plant, an experiment was conducted in a randomized complete block design with three replications. In this experiment, the effects of different levels of drought stress (5%, 10%, 15%, and 25% field capacity) were investigated on the activity of antioxidant enzymes (catalase, polyphenol oxidase, ascorbate peroxidase, and peroxidase, some photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, carotenoid), some osmotic regulators including proline, and some morphological parameters (number of leaves, root length, stem height, plant height, leaf length, leaf width, dry weight of root, fresh weight of root, fresh weight of shoots, dry weight of shoots, fresh weight of plant, and dry weight of plant). After planting in pots, drought stress (5%, 10%, 15% and 25% of field capacity) was applied at seedling (four-leaf) stage and then the desired traits were measured. Statistical analyses showed that drought stress had a significant effect on all physiological and morphological features at 1% level. Morphological traits and photosynthetic pigments decreased with increasing drought stress (irrigation up to 5% of field capacity). Increasing drought stress levels increased root length in sesame. The highest root length (3.375 cm) was related to 5% of field capacity irrigation and the lowest root length (2.5 cm) was related to control (25% of field capacity irrigation). The highest levels of antioxidant enzymes and proline were also observed at the highest levels of drought stress (5% of field capacity irrigation). Based on the findings, the plant's growth measurements are recommended to be carried out at various developmental stages to find the effects of stress at each stage  so as to get an appropriate understanding of the effects of stress on the plant.