نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction
Drought stress is one of the most important abiotic factors limiting agricultural production in arid and semi-arid regions of the world. Water deficit disrupts physiological and metabolic processes in plants, leading to reduced growth, impaired photosynthesis, and decreased grain yield. Drought stress also increases the production of reactive oxygen species (ROS), damages cellular membranes, decreases photosynthetic pigments, and ultimately reduces plant productivity. Mung bean is an important legume crop because of its high nutritional value, short growth period, and nitrogen-fixing ability. However, this crop is highly sensitive to drought stress, particularly during flowering and grain filling stages. Therefore, improving drought tolerance in mung bean is essential under water-limited conditions. The application of plant growth regulators such as paclobutrazol has been considered an effective strategy for alleviating drought-induced damage. Paclobutrazol improves drought tolerance by enhancing plant water status, maintaining membrane stability, increasing osmotic adjustment compounds, and strengthening antioxidant defense systems. Therefore, the present study was conducted to evaluate the effects of paclobutrazol on the physiological and biochemical responses of two mung bean cultivars under drought stress conditions. In addition, previous studies have shown that triazole compounds can modulate stress-responsive pathways and improve plant performance under water deficit conditions. However, the response may vary depending on cultivar and stress intensity. Hence, further investigation is required to clarify the physiological mechanisms involved.
Materials and Methods
This experiment was conducted during the 2024–2025 growing season at the Research Farm of the Faculty of Agriculture, University of Ilam, Iran.
The experiment was arranged as a split-plot factorial based on a randomized complete block design with three replications. Experimental treatments consisted of three drought stress levels (40, 80, and 120 mm evaporation from Class A evaporation pan) as the main factor and three levels of paclobutrazol foliar application (0, 30, and 80 mg L⁻¹) along with two mung bean cultivars (Partow and Gohar) as subplot treatments.
Drought stress treatments were imposed after complete seedling establishment based on cumulative evaporation from the Class A evaporation pan. Paclobutrazol was sprayed three times at 72-hour intervals. Physiological and biochemical traits including relative water content, ion leakage, chlorophyll a and b, carotenoids, proline, soluble sugars, catalase activity, and ascorbate peroxidase activity were measured at the flowering stage, while grain yield was determined at maturity. Statistical analyses were performed using SAS software (Ver. 9.1), and mean comparisons were conducted using the Least Significant Difference (LSD) test at the 5% probability level.
Results and Discussion
The results indicated that increasing drought stress significantly reduced relative water content, chlorophyll a, chlorophyll b, carotenoid content, and grain yield in both mung bean cultivars. In contrast, ion leakage, proline accumulation, soluble sugars, and antioxidant enzyme activities increased under drought stress conditions. Paclobutrazol application improved physiological and biochemical characteristics in both cultivars, and the greatest positive effects were observed at 80 mg L⁻¹. Foliar application of paclobutrazol increased relative water content, photosynthetic pigments, proline, soluble sugars, and the activities of catalase and ascorbate peroxidase enzymes, while reducing ion leakage under drought stress conditions. The interaction effects of drought stress, paclobutrazol, and cultivar demonstrated that cultivar Gohar showed superior performance under mild and moderate drought stress conditions in terms of most physiological traits and grain yield. In contrast, cultivar Partow exhibited greater tolerance under severe drought stress conditions through better maintenance of physiological characteristics and stronger antioxidant defense responses. Enhanced antioxidant enzyme activities and increased accumulation of osmotic adjustment compounds in paclobutrazol-treated plants played an important role in reducing drought-induced oxidative damage, maintaining membrane stability, and improving drought tolerance.
Conclusions
Overall, drought stress adversely affected physiological traits and grain yield of mung bean plants. However, paclobutrazol application considerably alleviated the negative effects of drought stress. Foliar application of paclobutrazol, particularly at 80 mg L⁻¹, improved plant water status, enhanced antioxidant defense systems, increased osmotic adjustment compounds, and maintained membrane stability, resulting in greater drought tolerance in mung bean plants. In general, cultivar Gohar showed better overall performance in terms of physiological traits and grain yield, whereas cultivar Partow exhibited greater tolerance under severe drought stress conditions.
Acknowledgement: The authors would like to express their sincere gratitude to the University of Ilam and the Agricultural and Natural Resources Research Station of Sarableh for providing the facilities required for conducting this research.
کلیدواژهها English
