Physiological Responses of Cowpea (Vigna unguiculata) Under Irrigation With Saline Water and Biostimulant Treatment

Abstract

Cowpea (Vigna unguiculata) is one of the world’s main crops, and it is a fundamental source of protein for semiarid regions population. In these regions, the use of high salts concentration water in irrigation systems is one of the major factors that contributes to reduced cowpea yield. One way to alleviate the negative effects of salinity is through the biostimulants application, which is a product that has beneficial substances to the plants metabolism. The aim of this study was to evaluate the application of biostimulant in cowpea cultivars under irrigation with saline water. The study was carried out in the Agrarian Sciences Center, of the Department of Agronomic and Forest Sciences of the Federal Rural University of the Semi-Arid, in the city of Mossoró, RN. The experimental design was completely randomized, with four replications. The treatments were arranged in 5 × 2 × 2 factorial scheme, with five doses of biostimulant (0, 15, 30, 45 and 60 mL L-1), two electrical conductivities of the irrigation water (0.5 and 5.0 dS m-1), and two cowpea cultivars (IPA-206 and BRS Guariba). The evaluated characteristics were: chlorophyll content index, stomatal conductance, net photosynthesis, internal CO2 concentration, transpiration rate, shoot height, stem diameter and shoot dry mass. The biostimulant application was not efficient in attenuating the salinity stress effect on the development of cowpea cultivars. The higher biostimulant concentrations along with the use of saline water increased the negative effects of salinity on the cowpea plants physiology. There was no difference between the cultivars regarding the tolerance to saline stress and the application of biostimulant.

Photosynthetic Responses, Growth, Production, and Tolerance of Traditional Varieties of Cowpea under Salt Stress

“…We recommend the Ceará, Costa de Vaca, Pingo de Ouro, Ovo de Peru, and Semper Verde varieties for grain production under saline stress conditions. Those results differed from studies with conventional cowpea bean varieties under salt stress, e.g., [28] (EPACE 10); [29] (MNC04-762F-9, MNC04-762F-3, MNC04-762F-21, MNC04-769F-62, and MNC04-765F-153); [30] (IPA-206 and BRS Guariba); [27] (BRS Pajeu); [24] (BRS Imponente, MNC04-795F-168, and MNC04-795F-161); [31] (CE 790 and CE 104); [32] (BRS Pajeú); and [33] (BRS Itaim), who reported that these conventional varieties were susceptible to high irrigation-water salinity (5.0, 4.8, 5.0, 4.5, 6.4, 5.0, 6.0, 4.5, and 6.0 dS m −1 , respectively). These findings support the hypothesis that traditional varieties are more tolerant of salt stress than conventional varieties; however, further field studies are necessary.…”