Aplicação exógena de 24-epibrassinolídeo como mitigador dos efeitos do déficit hídrico em feijão-caupi (vigna unguiculata l. Walp.)

Abstract

Cowpea (Vigna unguiculata L. Walp.) is one of the most important legumes for the food security of different populations, especially in tropical and subtropical areas due to its tolerance to drought and elevated temperatures. Those characteristics make the cowpea an interesting agricultural crop for global food security, as climate change is projected to increase the frequency of droughts, which will be more intense and last longer. Drought is one of the most detrimental environmental factors that can negatively affect global food production, affecting millions of hectares and severely impacting the food security of a growing world population. The water deficit created by droughts led to cellular dehydration and loss of turgor pressure, activating several signaling mechanisms, triggering the synthesis of several drought-related proteins and metabolites. Phytohormones are an integral part of the stress signaling mechanisms, and the exogenous application of them can mitigate some of the detrimental effects of abiotic stresses. Thus, the present work aimed to evaluate the efficiency of the exogenous application of the phytohormone 24-epibrassinolide (24-EBL) in the mitigation of the effects of the water deficit in cowpea. The experiment used a completely randomized experimental design in a 3 × 3 factorial scheme, with five replicates and a total of 45 plants. The first factor consisted of three levels of water deficit (100%, 70% and 50% of the field capacity), while the second factor consisted of three 24-EBL concentrations (0 nM, 150 nM and 300 nM). Several physiological parameters were measured, such as growth and biomass accumulation, compatible solute dynamics, leaf relative water content and gas exchange. The application of both 24-EBL concentrations (150 nM e 300 nM) showed efficacy in mitigating the effects of water deficit, promoting an increase in the leaf relative water content, CO2 uptake and carbohydrate synthesis, leading to an overall positive effect in the growth and biomass accumulation in plants under water deficit. Not only, the application of this phytohormone also generated positive effects in almost all variables in plants without water deficit, and can be considered not only as a mitigator of abiotic stress, but as a promoter of plant growth at the dosages of 150 nM and 300 nM.