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Additional file 1: Table S1. Primer sequence of the genes analysed by RT-qPCR. Table S2. Genes related to osmotic stress (drought/salinity) in the acclimation period in a significant differential expression (in respect to control) in maize root seedlings treated with humic acids. Figure S1. CP/MAS 13C NMR spectrum of humic-like acids (HA) isolated from vermicompost produced with sugarcane filter cake residue. Figure S2. NaCl stress-signalling pathways and interactions with humic acids. The stress signal is perceived by a salt sensor present at the plasma membrane. The signal is responsible for kinases activation, including ones that participated in SOS pathways. The kinases were correlated to induced pumps/channels and transcription factors expression (NAC and bZIP family). Activation of Na2+/H+ antiporter (SOS1, vacuolar Na+/H+ antiporter (NHX) was correlated to tolerance to salt stress. Na2+ exclusion (to apoplast) or compartmentalizing (vacuole) is powered by electrochemical gradient generated by H+-ATPase or H+-PPase. The proton electrochemical gradient generated by plasma membrane H+-ATPase results in antiporters ions coupling (antiport K+/Na+). Sodium (Na2+) can enter the cell through voltage independent nonselective cation channels like HKT, generating membrane depolarization. Both depolarization of membrane and changes in turgor pressure affect kinases pathways, and increased Ca2+ cytoplasmic concentration, resulting in vacuolar two pore channel 1 (TPC1) activation, which in turn also increases cytoplasmic Ca2+. High cytosolic Ca2+ activates, among others calcium-binding, calmodulin (CDKs), and was also related to HKT activation. Cytosolic Ca2+ signal is sensed by an SnRK3/calcineurin B-like (CBL) calcium-binding protein complex (SOS3/SOS2) which activates SOS1. Humic acids (HA) increased cytosolic Ca2+, proton pumps, and transcription factors related salt stress responses, such as bZIP and NAC. NAC transcription factor is associated to auxin pathway. SnRK1 regulates carbon metabolism by direct phosphorylation or redox activation or inactivation of metabolic enzymes like nitrate reductase (NR). The SnRK1 activated SnRK2 by Abscisic acid (ABA)-dependent signalling pathways which, in turn, activates AREBPs inducing gene expression. Abscisic acid can also induce SOS3. Enzymes or transcripts evaluated in this work are in cyan.

The objective of this work was to evaluate the effects of water-soluble humic extract (EHSA), Hortbio® biofertilizer (HORT) and both compounds combination (EHSA+HORT) on vegetative growth, nutrient absorption and chlorophyll levels in guanandi (Callophyllum brasiliense) seedlings. Isolated and combined additions of EHSA and HORT did not affect seedlings height, number of leaves, leaf and root dry matter and leaf area during early stages of seedling growth. However, HORT and EHSA+HORT treatments increased chlorophyll levels and total N content. Addition of HORT resulted in S, Zn, Mg, Mn and Cu increases in the seedlings leaves, while ESHA application increased K, Mg, S and B. P and Ca levels were not altered by the treatments, however, addition of EHSA and EHSA+HORT reduced significantly the absorption of Cu, Fe, Mn and Zn. O presente trabalho teve por objetivo avaliar os efeitos da aplicação de extrato húmico solúvel em água (EHSA), biofertilizante Hortbio® (HORT) e a combinação dos dois produtos sobre o crescimento vegetativo, indicador fisiológico (medida do teor de clorofila) e a capacidade de absorção de nutrientes em mudas de guanandi (Callophyllum brasiliense). A adição isolada ou em conjunto de EHSA e HORT não alterou a altura das mudas, o número de folhas, a matéria seca foliar e radicular e a área radicular e foliar durante a fase inicial de crescimento em viveiro. Entretanto, os teores de clorofila e N total aumentaram significativamente nas mudas que receberam os tratamentos HORT e EHSA+HORT. Além disso, a adição de HORT resultou em maiores teores de S, Zn, B, Mg, Mn e Cu nas plantas, enquanto a aplicação do ESHA aumentou os teores de K, Mg, S e B. Os teores de P e Ca não tiveram seus teores alterados pela aplicação dos tratamentos, mas a adição do EHSA e ESHA+HORT reduziram significativamente a absorção de Cu, Fe, Mn e Zn.

The mangrove sediments are rich in organic matter and humic substances, responsible for important functions such as reducing the toxicity of heavy metals, nutrient stabilization, serving as drain to atmospheric carbon and increasing the plant growth. In this study, we observed the effect of humic substances, humic acids and fulvic acids isolated from sediments of a mangrove forest, sampled from the Municipal Ecological Station Ilha do Lameirão (EEMIL, located in Vitória, Espírito Santo State, Brazil), on the growth and root acidification of Rizophora mangle and Laguncularia racemosa seedlings. For this, R. mangle and L. racemosa propagules were transferred to pots and then treated with different humic materials. The evaluation in root architecture change was performed by analyzing the main root axis length, lateral root length, density of lateral roots, fresh and dry mass weight of roots and estimated H+-ATPase activity by specific root acidification measurement. The results indicate that all humic materials extracted from mangrove organic matter were able to modify the root architecture systems of the studied plants. In addition to inducing an increase in the number of lateral roots and root branching, it also stimulated specific root acidification when compared to control groups. There is a good potential in developing technologies for the production of seedlings of mangrove plant species treated with biostimulants based in humic materials isolated from the mangrove ecosystem itself.Keywords: Humic substances, humic acids, fulvic acids, mangrove

Using herbaceous legumes in agricultural systems yields great quantities of plant residues, allowing changes in soil organic matter quality and content over the years. This study was conducted on an Ultisol, at Seropédica, RJ, Brazil, to evaluate the effects of different perennial herbaceous legumes on soil organic matter quality. A factorial scheme with three replications was used to evaluate the species: forage groundnut cv. BR-14951 (Arachis pintoi), tropical kudzu (Pueraria phaseoloides), and siratro (Macroptilium atropurpureum). After the first cut, each plot was divided into two subplots; plants were cut and left on the soil surface or cut and removed. Soil samples of a closed area covered by spontaneous vegetation (mainly C3 plants) or by Panicum maximum were also analysed. Samples were collected from two layers (0-5 and 5-10 cm), processed for the fractionation of organic matter and the evaluation of structural characteristics of humic acids (HA). Evaluated legumes did not change total organic carbon contents, but promoted HA accumulation in the superficial soil layer. Humic acids may be used as indicators of the management effects on soil organic fractions, because there was significant incorporation of carbon and nitrogen derived from the legume residues, even for the short experimentation time (28 months). Residue management did not modify quantitative aspects of the distribution of the humified organic matter, but promoted, however, a higher condensation degree of humic acids evaluated by the elementary composition, IR and fluorescence spectroscopy. O uso de leguminosas herbáceas em sistemas agrícolas permite o aporte de quantidades expressivas de fitomassa, possibilitando alterações no teor e na qualidade da matéria orgânica do solo ao longo dos anos. Este trabalho avalia a qualidade da matéria orgânica de um Argissolo Vermelho Amarelo localizado em Seropédica, RJ, e cultivado com diferentes espécies de leguminosas herbáceas perenes: amendoim forrageiro cv. BR-14951 (Arachis pintoi), cudzu tropical (Pueraria phaseoloides) e siratro (Macroptilium atropurpureum),num delineamento fatorial com três repetições, considerando a manutenção da parte aérea depois do corte na parcela ou a retirada da parte aérea da área experimental. Foram também analisadas amostras de uma área adjacente com vegetação espontânea (mata de capoeira) e capim colonião (Panicum maximum). As amostras de solo foram coletadas em duas profundidades (0-5 e 5-10 cm), realizando-se o fracionamento da matéria orgânica e a avaliação das características estruturais dos ácidos húmicos. As leguminosas avaliadas não alteraram o conteúdo de carbono orgânico total, mas promoveram acúmulo de ácidos húmicos (AH) na camada superficial. Os AH podem ser utilizados como compostos indicadores dos efeitos do manejo sobre a fração orgânica do solo, pois apesar do pouco tempo de implementação do experimento (28 meses) foi verificada incorporação significativa de carbono e nitrogênio provenientes dos resíduos orgânicos das leguminosas. O manejo dos resíduos vegetais não alterou aspectos quantitativos da distribuição de matéria orgânica humificada, mas conferiu maior grau de condensação aos ácidos húmicos avaliados pela análise da composição elementar, espectroscopia de IV e de fluorescência.