Abstract

In order to evaluate the influence of application of brassinosteroid phytohormone in mitigating the effects of salt stress at the height, root growth, leaf area, dry mass of leaf and root, stomatal conductance and transpiration, plants of cowpea bean [Vigna unguiculata (L.)Walp, cultivars BR3 Guariba and BRS Tracuateua, they were sown in a greenhouse in the absence and presence of brassinosteroid (24-epibrassinolid) in concentrations (0.2 and 0.4 µM), under diferent concentrations of NaCl (50 mM and 100 mM). The highest concentration of NaCl was 100 mM, affects plant growth. This treatment reduced by 46% the length of the BRS Tracuateua root, and 82 and 50% stomatal conductance and transpiration of BR3 Guariba respectively. However, the effects of salinity have been attenuated by supplementation as phytohormone. Under effect of treatment interaction Br of 0.4 µM and NaCl of 100 mM, root length and dry mass of leaves was increased by 87 and 37% in Guariba and Tracuateua cultivars concomitantly compared to those under stress by NaCl to 100 mM. For the same concentration of NaCl and Br 0.2 µM, there increases of 88% in stomatal conductance BR3 Guariba. It is suggested a possible regulation of 24-epibrassinolid on photosynthetic mechanisms of cowpea plants, in order to change made promoted stomatal conductance, which may have induced the greatest uptake and sequestration of CO2 thereby allowing the growth processes in plants.

Key words: Brassinosteroids, expansion and development, Vigna unguiculata (L.) Walp.