Suplementação de piruvato em genótipos de cana-de-açúcar sob déficit hídrico no segundo ciclo de cultivo.

Abstract

Sugarcane is one of the world's largest agricultural commodities, in terms of foreign exchange and jobs generated. Production in the Brazilian Northeast is generally low, due to various factors, including the irregular distribution of rainfall, which highlights the importance of studies aimed at minimizing the effects of water deficit on its cultivation. Pyruvate, for example, is one of the products that can be used because, in plant metabolism, it participates in the processes of respiration and the production of energy molecules that are vital for plant development. The aim of this study was to evaluate the effects of pyruvate supplementation on the ecophysiology of five sugarcane genotypes under water deficit in the second crop cycle. The experiment was carried out in a greenhouse at the Agricultural Engineering Academic Unit at the Federal University of Campina Grande, where five commercial sugarcane genotypes were tested (G1- RB863129, G2- RB92579, G3- RB962962, G4- RB021754 and RB041443) subjected to three management strategies (E1 - full irrigation throughout the crop cycle, E2 - water deficit and application of pyruvate and E3 - water deficit). The water deficit was interspersed during the tillering and stem elongation phases, corresponding to 30% of the volume of water applied to the plants under full irrigation. A concentration of 30 mM pyruvate was applied through foliar application. The design was in randomized blocks, in a 5 × 3 factorial scheme, resulting in 15 treatments, with three replications, making up 45 experimental units. Growth variables, physiological and biochemical parameters, production components and technological attributes were evaluated. Water deficit reduced stomatal conductance (36.0%), transpiration (50.9%), maximum quantum efficiency of PSII (24.3%), chlorophyll a (59.9%), chlorophyll b (61.6%), carotenoids (55.7%), leaf area (29.7%), internode length (34.1%), purity (3.7%) and total recoverable sugars (4.9%). The pyruvate supplementation improved gas exchange, antioxidant enzyme activity, photosynthetic pigments and chlorophyll a fluorescence, with no interaction with the genotypes, as well as plant height (RB021754), number of stalks (RB863129), stalk mass (RB041443), stalk length and water productivity (RB863129, RB92579, RB962962 and RB041443). In addition, the technological attributes also benefited from pyruvate application, with greater expression in the pol of corrected cane (RB863129) and apparent sucrose content of the juice (RB863129 and RB021754). Due to the beneficial effects of pyruvate, validation tests are recommended for the adoption of this technology in field conditions.