نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction
Plants respond to drought by synthesizing osmo-protectants like proline and antioxidants, which help mitigate stress effects. This study was performed to evaluate effects of seed priming on yield, some morpho-physiological traits of pinto bean (Phaseolus vulgaris L.) cultivar under water deficit stress. Drought is a major limiting factor in bean production worldwide. Given Iran’s location in an arid and semi-arid climate and the sensitivity of bean growth stages to moisture stress, the adoption of mitigation strategies is essential. Therefore, this study aimed to investigate the effect of seed priming on yield and some morphophysiological traits of pinto bean under water stress conditions. The experimental design included drought stress at three levels: control (50 mm evaporation), moderate stress (75 mm evaporation), and severe stress (100 mm evaporation) from a class A evaporation pan. Seed priming treatments included four levels: no priming (control), priming with distilled water, priming with 0.5 mM salicylic acid, and priming with 100 ppm gibberellic acid. Optimal priming conditions (temperature, duration, and drying time) were determined in a preliminary study. The results showed that treatments significantly affected physiological, agronomical traits and antioxidant enzyme activities. Under drought stress, severe stress caused the greatest reductions in relative water content (RWC), chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids by 19%, 27%, 29%, 28%, and 28%, respectively. It also resulted in the largest decreases in pods per plant, seeds per pod, pod yield, 100-seed weight, seed yield, and biological yield, with reductions of 42%, 32%, 19%, 10%, 45%, and 15%, respectively, compared with the control. Priming with distilled water (optimal priming time, temperature, time and drying time were all determined in a pre-test), priming with 0.5 mM salicylic acid and priming with 100 ppm gibberellic acid and a new pinto bean cultivar, Koosha. In the case of priming, the gibberellic acid treatment had the highest mean RWC (60%), chlorophyll a (1.03 mg.g-1 FW), total chlorophyll (1.63 mg.g-1 FW), while the salicylic acid treatment had the highest mean chlorophyll b (0.61 mg.g-1 FW). and carotenoids (2.59 mg.g-1 FW). Regarding the interaction effects of treatments, priming reduced the negative effects of drought stress on physiological traits at all stress levels (control, mild and severe stress), such that salicylic acid treatment had the highest mean RWC, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids. In the case of priming, salicylic acid treatment had the highest mean number of pods per plant (15.82), number of seeds per pod (3.81), pod yield (0.79 g.m-2), hundred seed weight (48.37 g), seed yield (30.1 g.m-2) and biological yield (79.4 g.m-2). Regarding drought stress, the most severe stress level showed the greatest reduction in the number of pods per plant, number of seeds per pod, pod yield, 100-seed weight, seed yield, and biological yield, which were 42, 32, 19, 10, 45, and 15 percent, respectively, compared to the control treatment.
Materials and Methods
The field experiment was performed in 2019 and 2020 in the field of Markazi Province Agricultural and Natural Resources Research Center, located in the northern belt of Arak (latitude 34° 5’ N, longitude of 49°42’ E), at an altitude of 1757 meters above sea level and with an average annual rainfall of 230 mm. A split-plot experiment was conducted in a randomized complete block design (RCBD) with three replications. The experimental factors included drought stress at four levels (control, 50 mm evaporation, 75 mm evaporation, and 100 mm evaporation from the evaporation pan), and seed priming at four levels (no priming [control], priming with distilled water, priming with 0.5 mM salicylic acid, and priming with 100 ppm gibberellic acid). The optimal priming duration, temperature, and drying time were determined in a pre-test, and the Koosha cultivar was used for the experiment. Field preparation, including plowing, disking, and land leveling, was carried out in early spring of both cropping years, following standard regional practices. Before planting, all the seeds were disinfected with benomyl fungicide at a ratio of two per thousand. Seeds were sown in six rows, each 4 meters long, with 50 cm spacing between rows (Kamankesh & Shafiei, 2017). The first irrigation was done immediately after planting and the subsequent irrigations were done according to the relevant treatments based on the plant's needs and environmental conditions.
Results and Discussion
The results showed that treatments significantly affected physiological traits. Regarding priming, Gibberellic acid treatment had the highest mean RWC (60%), chlorophyll a (1.03 mg.g-1 FW), total chlorophyll (1.63 mg.g-1 FW), and the salicylic acid treatment had the highest mean chlorophyll b (0.61 mg.g-1 FW), and carotenoid (2.59 mg.g-1 FW) values. Regarding treatment interaction, priming reduced the negative effects of drought stress on physiological traits, at all drought stress levels (control, mild and severe); salicylic acid treatment had the highest mean of RWC, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids. Gibberellic acid (GA) priming significantly influences the activity of photosynthetic pigments in plants under drought stress by enhancing physiological and biochemical responses. This priming mechanism involves the regulation of key photosynthetic genes and the activation of protective pathways that mitigate stress effects. GA3 priming increases the net photosynthetic rate (Pn) and chlorophyll content, which are crucial for effective photosynthesis under drought conditions (Xie et al., 2016; Fu et al., 2023). In maize, GA3 application improved photochemical efficiency and stomatal conductance, leading to better photosynthetic performance under drought stress (Fu et al., 2023). Regarding drought stress, the severe stress had the highest reduction of RWC, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids with 19, 27, 29, 28 and 28%, respectively compared to the control. Chlorophyll concentration has been known as an index to evaluate source activity, therefore a decrease in this can be considered a non-stomata limiting factor in the drought stress conditions (Hasnain et al., 2023). Chlorophyll concentration has been known as an index for evaluation of source, therefore decrease in this can be considered as a non-stomata limiting factor under drought stress conditions. There are reports of a decrease in chlorophyll under drought stress conditions. Also, it is reported that the chlorophyll content of resistant and sensitive cultivars to drought and thermal stress is reduced. However, resistant cultivars to drought and thermal stress had a high chlorophyll content (Kausar et al., 2023).
Conclusions
The results showed that treatments significantly affected agronomic traits. Regarding priming, Salicylic acid treatment had the highest mean pod per plant (15.82), seed per pod (3.81), pod yield (0.79 g.m-2), 100-seed weight (48.37 g.m-2), seed yield (30.1 g.m-2) and biological yield (79.4 g.m-2) values. Salicylic acid (SA) plays a crucial role in enhancing the yield of beans through various physiological and biochemical mechanisms. Its application has been shown to improve plant resilience against abiotic stresses such as waterlogging and salinity, leading to better growth and yield outcomes.
کلیدواژهها English
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