Bacillus spp. alivia o efeito do déficit hídrico sobre o metabolismo fotossintético e de proteção da soja

Abstract

The use of bacteria such as those of the genus Bacillus spp. has demonstrated efficiency in acting on the homeostasis of leaf metabolism under adverse conditions. However, little is known about the dosage of these substances and their role in soy. We aimed to evaluate the effect of doses of Mix of B. aryabhattai, B. haynesii and B. circulans on the photosynthetic and protective metabolism of soybeans during and after water deficit. The plants were grown under the following conditions: I) control: daily irrigation, II) water deficit (DH): suspension of irrigation (SI), and DH with III) 100 mL ha-1 and IV) 200 mL ha-1 of Bacillus spp. The evaluations were carried out at time zero, 3 and 6 days of SI in the stress phase and at 5 and 10 days of resumption of irrigation (DRI) (post-stress). In each period, the characteristics of electron transport, photochemical aspects and gas exchange were evaluated, and at the end of each phase, that is, at 6 DSI and 10 DRI, we evaluated the relative water content, growth, total proteins and enzymatic activities. We observed a reduction in water content and electron transport rate in DH plants, negatively reflecting on photochemical activities in photosystem II reaction centers, especially at 6 DSI, but rhizobacteria favored higher values in the stress phase and post -stress. The application of 200 mL ha-1 of Bacillus spp. contributed to the regulation of photosynthesis, mesophyll efficiency and carboxylation at 3 and 6 DSI, contributing to greater leaf area in the stress phase. However, post-stress, all plants resumed photosynthetic metabolism, especially those with 100 mL ha 1 of Bacillus spp. The application of rhizobacteria was decisive and contributed to mitigating the negative effects of water deficit during and after exposure to the stressor. Therefore, it is a promising strategy for maintaining productivity when subjected to stress conditions due to water deficit.