The effect of Application of Cycocel on Morphophysiological and Biochemical Characteristics of Mung Bean (Vigna radiata L.) Genotypes under Water Deficit Conditions

IntroductionDrought is one of the most important abiotic stresses that has an undesirable effect on crop production and their quality and leads to osmotic, ionic, and nutritional limitations as well as growth delay, metabolic disorders and oxidative stress in plants. Iran has a dry and semi-arid climate. Due to this problem, there is a possibility of drought stress during the growth period of plants. Presently, the production of legumes in the country is mostly under rainfed conditions and drought stress is one of the main factors reducing the yield of legumes. Mung bean is a small grain of valuable legume. Evaluation of the performance of different cultivars is considered a starting point in identifying drought-resistant cultivars. Cycocel is one of the most important growth retarders for tampering with growth and performance. Therefore, the present study was conducted to investigate the effect of foliar application of cycocel on morphophysiological and biochemical characteristics of mung bean (Vigna radiata L.) genotypes under water deficit conditions. Materials and MethodsThis study was conducted in order to investigate the effect of foliar application of cycocel on the morpho-physiological and biochemical characteristics of mung bean (Vigna radiata L.) genotypes under water deficit conditions, split-split plots based on a randomized complete block design with three replications, in the research farm of Ferdowsi University of Mashhad. Experimental factors included 3 levels of drought (non-stress, mild stress, and severe stress), 3 levels of cycocel foliar spraying (0, 400, and 800 mg.l-1), and 2 levels of mung bean cultivars (Hendi landrace and Zarbakhsh). Statistical analysis was performed using SAS 9.4 and comparing the means was based on the LSD method at a 5% probability level. Results and DiscussionThe experimental results showed that the effect of drought stress, cycocel, genotype, and the interaction of drought stress and cycocel as well as drought stress and genotype on height, stem diameter, relative water content, stomatal conductance, leakage of electrolytes, greenness and chlorophyll content were significant. Severe stress, compared to non-stress conditions, caused a decrease in height (53%), stem diameter (30%), relative water leaf content (29%), stomatal conductance (68%), greenness (37%), chlorophyll a content (25%) and chlorophyll b content (30%) and leakage of electrolytes increased (60%). The results showed that both drought stress and cycocel caused a decrease in the height of the plant. At all levels of drought stress, the Hendi genotype had a higher plant height. Drought stress caused a decrease in the diameter of the stem, while the application of cycocel reduced the decrease in the diameter of the stem due to drought stress. Drought stress caused a decrease in the relative content of leaf water, while the application of cycocel reduced this decrease. Also, Drought stress reduced the stomatal conductance, while the application of cycocel slightly compensated this reduction. At all levels of drought stress, Zarbakhsh genotype had higher stomatal conductance, but the difference between the two genotypes in the treatment of non-stress was not significant. Drought stress increased the leakage of membrane electrolytes, and the use of cycocel reduced the increase in electrolyte leakage due to drought stress, and it was also found that the increase in electrolyte leakage due to drought stress was more intense in the Hendi genotype. Drought stress reduced the greenness of the leaf, while the application of cycocel slightly compensated this reduction. Also, at all levels of drought stress, the Zarbakhsh genotype had higher leaf greenness, but the difference between the two genotypes in the treatment of 100% crop water requirement was not significant. The chlorophyll a content of leaves decreased due to drought stress, while the application of cycocel reduced the severity of this decrease. Also, at all levels of drought stress, the Hendi genotype had lower leaf chlorophyll a content. ConclusionsThe results of this study showed that under drought stress, there was a decrease in plant height, stem diameter, relative water content, stomatal conductance, greenness, chlorophyll a and b content, along with an increase in electrolyte leakage. Among mung bean cultivars, the Zarbakhsh cultivar showed superiority in tolerance to water shortage conditions compared to another one. The use of cycocel reduced the negative effects of drought stress on the plant. It appeared that the use of cycocel under drought stress conditions is effective for improving plant performance.