Resposta de plantas de arroz a aplicação de ácido húmico e bactérias promotoras de crescimento

Abstract

The difference in nutrient absorption capacity between different plant species is related to the variation in the magnitude of the root system and / or the kinetics of nutrient absorption. The more efficient use of nutrients by plants shows less loss of these by percolation, volatilization (N) or water drainage, by absorbing them effectively faster and in greater quantity. The spatial distribution of the root system determines the ability of the plant to efficiently exploit these resources, which in many environments are found in low availability. The objective of this work was to evaluate the morphological alterations of the root system and its influence on the increment of phytomass of rice plants by inoculation with plant growth-promoting bacteria (PGPB) and also by the application of humic acid (HA) nutritious solution. The thesis was divided into two chapters: in the first chapter the study evaluated morphological and phytomass changes of rice plants by inoculation with PGPB in Hoagland nutrient solution, Escherichia coli, Azospirillum brasilense sp 245, Gluconacetobacter diazotrophicus PAL 5, Gluconacetobacter diazotrophicus lao-; in the second chapter the morphophysiological response of rice plants in the presence and absence of humic acids in nutrient solution during eleven evaluations was evaluated in order to characterize the physiological components, differences in the accumulation and the distribution of dry mass of the rice in response to the application of humic acid by quantitative analysis of plant growth. In Chapter I, fresh weight and dry mass of shoot and mean diameter showed significant differences between treatments. Inoculation of the G. diazotrophicus PAL 5 strain resulted in higher growth of rice plants, and E. coli promoted root thickening. In Chapter II, the physiological components: rates of absolute growth and relative growth and net assimilation rate were higher in humic acid treated plants, due to differences in accumulation and distribution of dry mass of plants. In both experiments the treatments influenced the morphology of the root system which had repercussions on changes in the phytomass increment in the plant. The plant growth promoting bacteria stimulate the morphological parameters of the root system and increase the phytomass of the rice plants. The bioactive properties of vermicompost humic acid promotes the formation of a larger root system, which possibly improves the uptake of water and nutrients by the plants of the nutrient solution, providing a faster and more vigorous growth of the rice seedlings.