Crescimento radicular em plântulas de tomate em resposta a inoculação da estirpe ENA 4593 de Serratia sp

Abstract

Growth-promoting rhizobacteria are soil bacteria that inhabit the surrounding root, and are directly or indirectly involved in promoting plant growth and development. The productivity efficiency of these groups of microorganisms can be applied to crop planting, constituting an interesting alternative to minimize the negative effects of water stress. Therefore, the present thesis had as objectives; to verify if the mechanism of growth promotion of the bacterium is similar to that promoted by PEG6000, indole acetic acid (IAA) and clay and to compare the possible effects of water stress on tomato with the effects of inoculation ENA 4593 strain of Serratia sp. The methodology was based on laboratory bioassays using tomato seed cv. Santa Clara (Solanum lycopersicum L.), previously disinfected and kept in a growth chamber with temperature and photoperiod of 25 ° C and 12 hours, respectively. The germinated seeds were submitted to different treatments: control; PEG 7%; Serratia sp., IAA and Clay. The treatments were arranged in a completely randomized design, and the obtained data were submitted to analysis of variance (ANOVA) with the aid of the statistical software Microsoft Excel and Sars, and the means compared by Tukey test at 5% probability. The results found revealed that the promotion of tomato root growth by Serratia sp. it is similar to that promoted by PEG 7%, differing significantly from the results found with different doses of IAA and clay. The promotion of root growth in tomatoes by Serratia sp. and PEG 7% indicate, in part, a physical effect, since the water restriction imposed by the PEG molecule decreases the water movement capacity by increasing the solute concentrations in the exogenous environment (colloidal stress), a fact also observed by bacteria, by colonizing plant tissues and cells - biofilm formation, and consequently reduced hydraulic conductivity of water through the root. Conclusions, ENA 4593 strain of Serratia sp. causes tomato root to grow, affecting root morphology and this can be partially explained by a physical effect of PEG and the stimulus to promote root growth in tomato produced by the bacterium cannot be reproduced by auxin, suggesting that the mechanism of promotion growth factor is not associated with this phytohormonium.