Avaliação do crescimento inicial da cana-de-açúcar, variedade RB867515, sob o efeito de bactérias endofíticas

Abstract

This present research aimed to evaluate the effects of different endophytic bacteria species regarding the tolerance of sugarcane water stress in the initial growth phase. With that purpose, an experiment was installed, in the greenhouse at the Centro de Ciências Agrárias of Universidade Federal de Alagoas, located in the city of Rio Largo, in the state of Alagoas (9° 28 S, 35° 49 W, altitude 127 m), completely ramdomized on a factorial arrengement 4x2 (endophytic bacteria and levels of water stress in this order), with 8 replications. The levels of the first factor were composed of: non-inoculated plants; inoculated plants with complete inoculant (mix of Gluconacetobacter diazotrophicus, Burkholderia tropica, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans e Azospirillum amazonense); inoculated plants with G. diazotrophicus; inoculated plants with B. tropica. The levels of the second factor were: plants kept on the soil with moisture next to field capacity (without stress); plants under water deficit due to irrigation suspension. The morphological and physiological variables analyzed were plant height, stalk diameter, number of green leaves, leaf area, dry mass analyze, leaf water potential (ψwf), potential and effective quantic efficiency and chlorophyll content. The bacteria application didn t interfer in stalk diameter, plants height and estimated leaf area. When the plants average growth was evaluated, it was verified that plants treated without bacteria (control) and with inoculum B. tropica presented showed greater aerial part mass, whereas the bacteria application G. diazotrophicus and the control treatment presented greater root mass. The water stress has significantly affected the potential quantic efficiency (Fv/Fm) on the irrigated plants (control) which the Fv/Fm values were above 0,79 statistically differing of water stress (draught) and rehydratation, wherein the values were below 0,79. Apparently, the damages presented on the photosystem II at midday were recovered during nighttime, showing higher Fv/Fm values at predawn. The presence of bacteria hasn t significantly affected the biometric characteristics of sugarcane plants grown in vases at 114 days after planting (DAP). The leaf area ratio (LAR) utilized the measured leaf area, being greater on control and complete inoculant treatments. On these, the plant developed more leaves and was less efficient on carbon fixation, which refleced on dry mass increase.