Effect of irrigation cut off and antitranspirants on yield and some physiological characteristics of pinto beans

Beans are one of the most important legumes in many developing countries as one of the sources of human protein. Drought stress is also one of the factors limiting the growth and production of plants in arid and semi-arid regions, which has reduced the yield of plants, especially legumes. The use of antitranspirants is an effective tool in regulating transpiration with the aim of preserving water in the plant. The aim of the present study was to compare the effects of antitranspirants in the condition of irrigation cut off on seed yield and some physiological characteristics of Kosha cultivar pinto beans. The study was carried out in the form of split plots based on a randomized complete block design with three replications in the two crop years of 2019 and 2020 in agricultural lands located in Khoi city. Experimental treatments include irrigation at two levels; Normal irrigation (irrigation according to local custom) and irrigation cut off at the stage of filling the seeds in the main plots and spraying antitranspirants on eight levels in the sub plots included: salicylic acid (0.5%), phenyl mercuric acetate (100 μM), gibberellic acid (150 μM), cytovit (2%), chitosan (0.5%), castor oil (6%), gum arabic (0.5%) and distilled water (control). The traits measured in the experiment included plant height, number of pods per plant, number of seeds per pod, hundred seed weight, seed yield, biological yield, seed protein percentage, relative water content and proline content. The results showed that the cut off Irrigation had a significant effect on the number of pods per plant, hundred seed weight, seed yield, biological yield, protein percentage, relative water content and proline content of bean leaves. antitranspirants also had a significant effect on all traits except for the number of seeds in pods. The interaction effect of irrigation withholding and antitranspirants was significant in the number of seeds in the pod and the percentage of seed protein. The triple interaction of year, irrigation cut off and antitranspirants on the number of pods per plant and hundred seed weight was significant. In the condition of irrigation cut off, antitranspirants increased the seed yield and the highest seed yield was obtained in the salicylic acid treatment, which increased by 41.1% compared to the control treatment. It seems that by applying a stage of irrigation restriction and consumption of antitranspirants in the areas that faced with the problem of water deficit at the end of the growing season, by improving some morpho-physiological characteristics such as reducing the amount of proline and increasing the relative moisture content of leaves and biological function, it is possible to effectively the slope decreased the yield of pinto beans under drought stress conditions. Therefore, in areas with water deficit, especially due to the simultaneous limitation of water resources, peak consumption in other agricultural products, which causes psychological pressure on to deal with the problem of water deficit, using antitranspirants as an efficient tool and removing a irrigation phase at the end of the growing season can partially compensated for the the reduction of damage caused by water deficit.