Influência da substância húmica em plantas de arroz (Oryza sativa L.) inoculadas por fungos micorrízicos arbusculares sob estresse salino

Abstract

This dissertation aimed to evaluate the effect of humic substances (HS) extracted from vermicompost (Vc) and characterized by spectroscopic techniques in combination with arbuscular mycorrhizal fungi in rice plants under to salt stress conditions. The chapter I evaluated the influence of different NaCl dose on the roots morphological parameters and physiological systems of the aerial part in plant growth under stress conditions. It was found that the highest salt concentration triggered deleterius effects in some stages of photosynthesis, resulting in a production decrease of biomass in plants. Salt treatments in rice plants exerced negative influence on the development of the root system showing a physiological stress condition. The higher NaCl concentration caused a reduction in all the quantified morphological characteristics, mainly affecting the length and number of roots, exerting harmful effects on the growth and development of plant. This harmful effect results in a decline of water and nutrient absorption capacity. However, it was evident that the doses of salt stress tolerated by rice plant were those that contained 150 mM and 200 mM NaCl. Chapter II aimed to characterize by spectroscopic technics the HS isolated from vermicompost and, subsequently, to evaluate at different times, the effect of different HS concentrations on root morphological indicators and photosynthetic quantum yield. The 13C NMR spectra show a predominance of aliphatic structures and the predominance of CAlkyl (H, R), CAlkyl-O groups and the aliphatic C content was greater than the aromatic C content. Then, when assessing the influence of this substance on rice plants growht, it was found an increase in photosynthetic performance in plant treated with concentrations of 40 and 60 mg (AH) L-1, 144 hours after application, once there was an initial decline. There were different changes in the root system due to the application of the humic substance, correlated with the development aspects of the plant cell wall. The Chapter III evaluated the influence of the application of HS and the mycorrhizal fungi Acaulospora mellea, Glomus formosanum, Rhyzoglomus clarum and Glomus sp. in rice plant under saline stress. The application of HS in plants inoculated with AMF, both in normal conditions and under salt stress, significantly increased the biomass production of the aerial part and the morphological parameters of root system, with greater expressiveness of interactions with the fungus Rhyzoglomus clarum and Glomus sp in saline stress, standing out for having presented symbiosis and reproductive structures in relation to the efficiency of mycorrhizal colonization according to the methodology used