Fisiologia da produção da soja em resposta à aplicação de reguladores vegetais

Abstract

Soybean is one of most important crop in the world. The oil and protein present in the seeds, associated to low cost of production, make this crop a protagonist when it’s come to the raw material to human and animal alimentation. In this way, the global demand for soybeans, breaking records with each new harvest and the crop already requires the highest technical levels to achieve the best productivities. In situations where production is not conditioned by nutritional, water and / or pest restrictions, the use of hormone-action agrochemicals in this crop is promising for increased production and consequently reduced agricultural costs. The objetive of this study was to evaluate effect of the foliar application of plant growth regulators, in different stages of development on physiological, morphological parameters and soybean grain yield. The experimental design adopted was randomized block, with three repeats. The treatments contemplated foliar applications of plant growth regulators kinetin (citocinin), indole-3-butyric (auxin) and gibberellic acid (gibberellins) and controls (Stimulate® and water). The foliar applications were on phenological stages V4, R1 e R4, in an indeterminate type cultivar (95Y72) and other semi-determinate cultivar (TMG 7262RR). Were evaluated physiological traits (chlorophyll a, chlorophyll b, total chlorophyll, CO2 assimilation rate, stomatal conductance, water use efficiency, transpiration rate and intercellular CO2 concentration), morphological (fresh and dry mass accumulated in roots, number of pods per plant, number of grains per plant, number of grains per pod, mass of one thousand grains and productivity. The treatments of this study not influenced on characters such height plant, first pod insertion height, number of pod per plant, number of grains per pod, and mass of one thousand grains of tested cultivars. KIN application on stages R1 and R4, GA3 applied at the R4 stage, result in a decrease in the number of pods per plant of cultivar TMG 7262RR. The application of plant grow regulators does not result in a variability in Pearson's linear correlation coefficient among the characters related to grain yield. The application of the different plant growth regulators decreases the correlation between grain yield and number pods per plant. Thus, in view of the constant search for the evolution in crop productivity, the need for new work, for a more precise conclusion as to the efficiency or not of the plant growth regulators on the physiology of soybean production.