Promoção de crescimento e mitigação da deficiência hídrica em palma de óleo bioestimulada: uma abordagem fisiológica e bioquímica.

Abstract

The oil palm (Elaeis guineenses Jacq.) among oilseed crops, is the most productive in the world, standing out in the production of oil of high economic value. The production of seedlings requires a long period in the nursery and the water supply is essential at this stage, as it is one of the main limiting factors in the quality of the seedlings. However, there are studies that report the use of microbial technology (fungi and bacteria) as a possible effective strategy to promote growth and mitigate the effects of water deficiency. The study was composed of two chapters. The objective of the first chapter was to evaluate the growth promotion and gas exchange in oil palm seedling leaves inoculated with microorganisms. The experiment was carried out in a greenhouse in a completely randomized design with five treatments, consisting of the inoculation of four microorganisms (UFRABA01, UFRABA124, FT12, fungal MIX) and control (without inoculation) with five replications per treatment. The inoculation of microorganisms promoted the growth of oil palm seedlings. The height, stem diameter, number of leaves, leaf area, root length and total chlorophylls increased by an average of 37%, 49%, 16%, 223%, 63% and 15%, respectively, in the inoculated seedlings in relation to the control seedlings. Dry mass of leaves, shoots, roots and totals increased by an average of 214%, 228%, 213%, 71%, respectively, in inoculated seedlings compared to control seedlings. Net photosynthesis, stomatal conductance and transpiration increased by an average of 62%, 25% and 22%, respectively, in the inoculated seedlings in relation to the control seedlings. For chapter II, the objective was to evaluate biometry, gas exchange, water potential, lipid peroxidation and activation of antioxidant enzymes in oil palm seedlings inoculated with microorganisms and submitted to water deficit. The experiment was carried out in a greenhouse with a completely randomized design. The treatments consisted of the inoculation of the bacterium UFRAB01, collected from commercial plantations of oil palm, MIX of fungi and a control (non-inoculated), with five replications, in oil palm seedlings submitted to full irrigation and submitted to water deficit ( -2.5 MPa). Inoculation of these microorganisms increased plant height and stem diameter regardless of water condition. Water potential decreased in all seedlings submitted to water deficit, with the greatest reduction of 75% in control seedlings. Net photosynthesis was drastically reduced by the water deficit, but the treatments UFRAB01 and MIX managed to alleviate this reduction and maintained the highest averages, about 63% higher than the control. Stomatal conductance and transpiration were reduced by water deficit, however the inoculation of UFRAB01 and MIX managed to regulate these processes to increase water use efficiency by 23% and increase carboxylation by 51% compared to the control. Lipid peroxidation (MDA) was not affected by inoculation of microorganisms. However, there was an increase of 42% and 46% for the activity of the enzyme Ascorbate peroxidase in seedlings biostimulated with UFRAB01 and fungal MIX, respectively. Probably, some physiological mechanisms involving the regulation of stomatal opening and greater rubisco carboxylation activity may be being activated by microorganisms to sustain the greater demand for photoassimilates necessary for greater growth and to alleviate alterations by other non enzymatic defense systems.