Effects of the humic acid extracted from vermicompost on the germination and initial growth of Brachiaria brizantha cv. MG5

The biological effects of humic substances on vegetables depend on the source of extraction and the concentration used, on the vegetable species and on the age of the plant. This study aimed to evaluate the effect of different humic acid (HA) doses extracted from vermicompost on the germination and initial growth of Brachiaria brizantha cv. MG5. To that end, germination tests were conducted in germination agents, as well as emergence test in greenhouse and seedlings growth test for those agents. For all these tests, five doses of HA [0.0; 1.0; 2.0; 4.0 e 8.0 mM C.L-1] were used, with and without reapplying HA. The following characteristics were analyzed: percentage of germination, percentage of normal seedlings in the first counting of the germination test, percentage of abnormal seedlings, percentage of non-germinated seedlings, percentage of emergence, emergence speed rates, fresh and dry matter of the upper and roots part, length of the upper and roots part and number of lateral roots. Positive effect of HA reapplication in the percentage of abnormal seedlings was observed. With increasing doses of HA, there was a reduction in the percentage of germination and normal seedlings in the first count. The application of HA promoted increase in shoot length and number of lateral root. There was no significant difference in the length of the root. Humus acid affects positively the initial growth of B. brizantha cv. MG5, with the best stimulation being observed when the 2.0 mM C.L-1 dose was applied.Keywords: Forage, Urochloa sp., vigor.Abbreviation: HA, Humic acid

The mechanisms of humic substances self-assembly with biological molecules: The case study of the prion protein

Humic substances (HS) are the largest constituent of soil organic matter and are considered as a key component of the terrestrial ecosystem. HS may facilitate the transport of organic and inorganic molecules, as well as the sorption interactions with environmentally relevant proteins such as prions. Prions enter the environment through shedding from live hosts, facilitating a sustained incidence of animal prion diseases such as Chronic Wasting Disease and scrapie in cervid and ovine populations, respectively. Changes in prion structure upon environmental exposure may be significant as they can affect prion infectivity and disease pathology. Despite its relevance, the mechanisms of prion interaction with HS are still not completely understood. The goal of this work is to advance a structural-level picture of the encapsulation of recombinant, non-infectious, prion protein (PrP) into different natural HS. We observed that PrP precipitation upon addition of HS is mainly driven by a mechanism of “salting-out” whereby PrP molecules are rapidly removed from the solution and aggregate in insoluble adducts with humic molecules. Importantly, this process does not alter the protein folding since insoluble PrP retains its α-helical content when in complex with HS. The observed ability of HS to promote PrP insolubilization without altering its secondary structure may have potential relevance in the context of “prion ecology”. These results suggest that soil organic matter interacts with prions possibly without altering the protein structures. This may facilitate prions preservation from biotic and abiotic degradation leading to their accumulation in the environment

Structural Characterization and Bioactivity of Humic and Fulvic Acids Extracted from Preserved and Degraded Brazilian Cerrado Biomes Soils

Humic substances are an important soil quality indicator, influencing its physical-chemical and biological characteristics while directly affecting plant growth, through their biostimulant activity. To elucidate the role of humic substances in seedlings acclimation it's important to establish a relationship among the origin, the structural composition and their biological activity. The aim of the present paper is to characterize the soluble humic fractions extracted from soils of the Brazilian Cerrado biome with different levels of preservation, and to verify their biological activity on seedlings of the pioneer Cerrado native species Enterolobium contortisiliquum (Vell.) Morong. Humic and fulvic acids were isolated from preserved and degraded Cerrado areas. Humic compounds were characterized assessing total acidity, UV-VIS and IR spectra. Humic substances bioactivity was evaluated on E. contortisiliquum seedlings grown in Leonard pots, supplied with nutrient solution added with the optimal concentrations of humic and fulvic acids and their mix. Seedlings root structure, antioxidant enzymes activity and photosynthetic pigments contents were evaluated. The humic substances showed different chemical characteristics and bioactivity depending on sampling area. Mixed humic and fulvic acids showed higher efficacy, especially those coming from the preserved area. It is noteworthy that A) the type of management influences humic fraction chemical structure, well reflected in their biological activity B) E. contortisiliquum, shows a better response to humic substances coming from a well-established and stable canopy