Rizobactéria e fertiactyl GZ® aumentam a tolerância ao déficit hídrico e promovem a reidratação de mudas de açaizeiro.

Abstract

The açaí palm (Euterpe oleracea Mart.), originating from the Amazon estuary, is considered a palm tree of great economic importance in the Amazon region. The high sensitivity to water deficit limits the production of seedlings and hinders the expansion of commercial plantations. Biostimulants can be used as an efficient strategy to reduce seedling losses, as they increase tolerance to the negative effects of water deficit (WD) and help plants recover after rehydration. The objective of the study was to evaluate the effect of the biostimulants Bacillus subtilis (BS) and Fertiactyl GZ® (BC) on changes in gas exchange, oxidative stress and accumulation of osmoregulators caused by water deficit and to analyze the capacity of biostimulated seedlings in water recovery after a period of water deficit. The experiment took place in the greenhouse of the soil building of the Universidade Federal Rural da Amazônia-UFRA, in Belém, Pará. The study was divided into two chapters, the first one referring to the imposition of water deficit with four treatments and six repetitions. The treatments consisted of non-inoculated plants (control) and inoculated with BS, BC and BS+BC, which were evaluated under full irrigation conditions and after seven and 14 days of water suspension. At seven days of water deficit, seedlings biostimulated with BC increased, respectively, 76%, 100%, 39% and 75% to A, gs, E and A/Ci. At 14 days of water deficit, plants with BC and BS +BC increased by 71% and 35% to A; 100% and 63% on gs; 75% and 25% to A/Ci and with BC, 64% to E, in relation to the control. At 14 days of water suspension, Ψw was 24% and 35% higher in seedlings biostimulated with BS and BC, compared to non biostimulated ones. The proline content was higher in biostimulated seedlings, being more expressive in plants with BS, 75% higher than the control. At 14 days of WD, the MDA content of the control plants was higher than all the averages of the biostimulated plants. The highest enzymatic activity of SOD and CAT was found for BC and BS+BC and of the APX enzyme for the BS+BC treatment. The objective of the second chapter was to evaluate the physiological performance of açaí seedlings after rehydration and was composed of five treatments and six repetitions. The treatments were BS, BC, BS+BC and non-biostimulated plants (WD control and IRR control), which were evaluated in water recovery condition at zero, seven and 14 days of rehydration. At seven days of rehydration, compared to the WD control, all biostimulated plants had statistically higher means of A and A/Ci. Plants with BC increased 101% A and 100% A/Ci. When compared to the IRR control, all treatments showed lower means of A, gs, E and A/Ci. At 14 days of rehydration, plants inoculated with BC and BS+BC presented, respectively, 20.2% and 25.3% higher A; 29.4% and 35.3% higher A/Ci compared to control in WD. Compared to the IRR control, biostimulated plants showed the same average of A and A/Ci. Açaí seedlings biostimulated with BS, BC and BS+BC accumulated more proline than control plants WD and IRR, at zero and 14 days of rehydration. At 14 days of water deficit, the levels of MDA in control plants increased by 20.3% in relation to plants with BC. The BS+BC treatment showed higher activity for the SOD, CAT and APX enzymes in 49.6%, 160% and 75.5% higher than the WD control, respectively. The application of BC isolate or in combination with BS+BC can be an efficient alternative to reduce the losses of açaí seedlings in nurseries with inadequate irrigation or located in regions with a period of marked water restriction, in addition to contributing to increase the availability of seedlings for field with greater quality of vigor and tolerance to water deficit, given the growing threats of global climate change.