Photosynthetic apparatus protection and drought effect mitigation in açaí palm seedlings by rhizobacteria

Water deficit sensitivity decreases the açaí palm seedling production in nurseries. The goal of this study was to evaluate gas exchange, chlorophyll a fluorescence, lipid peroxidation and antioxidant enzymes in açaí palm seedlings inoculated with rhizobacteria. Four rhizobacteria isolates (UFRA-58, UFRA-92, BRM-32111 and BRM-32113) and one control (without inoculation) were inoculated on açaí palm seedlings at field capacity (FC) 100%, 75%, 50% and 25%. Water deficit reduced photosynthetic performance in all açaí palm seedlings, but to a lesser extent in seedlings inoculated with rhizobacteria. At 75% FC, all inoculated seedlings maintained greater water potential, gas exchange and chlorophyll a fluorescence and, at 50% FC, only the seedlings inoculated with BRM-32111 and BRM-32113 were able to maintain these advantages in relation to the control. In 25% FC, no effect was observed for rhizobacteria inoculation. At 50% FC, the increase in catalase (CAT) enzymatic activity was induced by UFRA-58. The ascorbate peroxidase (APX) enzymatic activity was greater for UFRA-92, whereas superoxide dismutase (SOD) enzymatic activity was higher only for BRM-32113. The malonic aldehyde (MDA) content was greater only for control. Rhizobacterial inoculation in açaí palm seedlings attenuates the water deficit effects by photosynthetic performance maintenance and antioxidant enzymes activation, contributing to decrease the seedling mortality rate in nurseries.