Influência de biorreguladores sobre a fisiologia e crescimento inicial de cana-de-açúcar submetida ao déficit hídrico

Abstract

Several environmental factors can alter the physiological processes of sugarcane plants, however, water deficit is the main factor limiting the productivity of this crop. The use of plant growth regulators can mitigate the effects of the drought, because these substances improve the regulation of physiological processes in the plant. In this context, the aim of this study was to evaluate the effects of a plant growth regulators solution (auxin, cytokinin and gibberellin) on the initial development and photosynthesis of sugarcane under water deficit. It was adopted a completely randomized 2 x 3 factorial design, two water regimes - control (100% of field capacity) and water deficit (20% of field capacity), and three doses of the bioregulators solution (0, 0.5 and 1.0 L h-1). The experimental plot consisted of plastic pots containing 12.0 kg of soil with one plant per pot of RB867515 and SP81-3250 cultivars, with ten replicates. The treatments with bioregulators solution was carried out with the commercial solution of plant growth regulators Stimulate® on stalks at planting and at 64 days after planting (DAP) by foliar application. Water deficit was initiated at 55 DAP and during this period were held biometric and physiological evaluations in plants. At 110 DAP biomass evaluation was performed. The drought reduced the relative water content of the plants, and all physiological parameters, maximum CO2 assimilation (Amax), stomatal conductance (Gs), maximum speed of Rubisco carboxylation and PEPCase enzymes (Vcmax and Vpmax) and, reduced plant growth and biomass production. However, plants that were treated with Stimulate® showed lower reduction in all physiological parameters, biometric and a smaller reduction in biomass when compared to plants not receiving treatment with the bioregulator solution. The bioregulators mainly stimulated the growth of the root system, which promoted greater absorption of water by plants and, consequently, better physiological performance under drought. The Stimulate® attenuated the effects of drought on physiological processes, promoting smaller reduction in Amax, Vcmax and Vpmax and also lower photochemical damage. This condition was responsible for the largest growth (height and leaf area) increasing the total biomass of plants (root, leaf and stem).