Title : Application of bioregulators Acetylcholine and GABA enhancements yield in soybean plants under water deficiency
Water deficiency is an important factor in limiting crop productivity and production potential. Alternatively, the plants can be “prepared” to successfully tolerate abiotic stress conditions, such as water deficiency. The use of priming presents more effective opportunities for the studies of stress physiology. The use of bioregulators as primers is an emerging approach that can modify plant physiology and may play a crucial role in regulating plant growth, leading to a possible yield increase in food crops. Consequently, they are often used to increase both plant growth and yield, and could promote a potential stress reduction. Bioregulators, such as γ-aminobutyric acid (GABA) and Acetylcholine (Ach), act as a defense of plants in response to stress, playing an osmoprotective role and promoting the growth of the root system, respectively. The objective of this study was to analyze the exogenous application of these two bioregulators, Gaba and Ach, in different stages of development, and to study its effect on the regulation of soybean response processes to the water deficit. To achieve this, we combined the application of Gaba and Ach, at the dose of 2.0 mM in soybean plants cv. Intact under different water regimes. The factors studied were: 1) application of Gaba and Ach (i) in S-seeds; (ii) L-leaf; (iii) in the seed and leaf - SL; (iv) control without application - C; and (2) water regimes: (i) 100% field capacity (FC) and (ii) irrigation suspension (IS). Leaf gas exchange and biomass analyses were performed for the physiological characterization of the plants. In observation of water deficit treatments, a 93% decrease in photosynthetic capacity was noted on the sixth day after the suspension of irrigation, as well as biomass decrease. The treatments of GABA and Ach, regardless of the mode of application under water deficit, were characterized by a lower fall in photosynthesis, an increase in stomatal conductance, and growth parameters (such as root dry mass and leaf area). Additional characteristics also included; the parameters of production, number of pods, number of seeds and mass of seeds per plant. Based on the results obtained in the present study, we suggested that the combined exogenous application of GABA and Ach bioregulators acted synergistically, promoting an increase in the performance of cv. Intact, by means of a greater tolerance to the damages caused by water deficit conditions, as well as promoting a greater growth in general, independent of the environmental conditions tested. This indicates that there is a potential use of these bioregulators for agricultural success.