Physiological responses to humic substances as plant growth promoter

Abstract

Humic substances (HS) have been widely recognized as a plant growth promoter mainly by changes on root architecture and growth dynamics, which result in increased root size, branching and/or greater density of root hair with larger surface area. Stimulation of the H + -ATPase activity in cell membrane suggests that modifications brought about by HS are not only restricted to root structure, but are also extended to the major biochemical pathways since the driving force for most nutrient uptake is the electrochemical gradient across the plasma membrane. Changes on root exudation profile, as well as primary and secondary metabolism were also observed, though strongly dependent on environment conditions, type of plant and its ontogeny. Proteomics and genomic approaches with diverse plant species subjected to HS treatment had often shown controversial patterns of protein and gene expression. This is a clear indication that HS effects of plants are complex and involve non-linear, cross-interrelated and dynamic processes that need be treated with an interdisciplinary view. Being the humic associations recalcitrant to microbiological attack, their use as vehicle to introduce beneficial selected microorganisms to crops has been proposed. This represents a perspective for a sort of new biofertilizer designed for a sustainable agriculture, whereby plants treated with HS become more susceptible to interact with bioinoculants, while HS may concomitantly modify the structure/activity of the microbial community in the rhizosphere compartment. An enhanced knowledge of the effects on plants physiology and biochemistry and interaction with rhizosphere and endophytic microbes should lead to achieve increased crop productivity through a better use of HS inputs in Agriculture.

Liquid organomineral fertilizer containing humic substances on soybean grown under water stress

“…Various authors (Benites et al, 2006;Andrade et al, 2007;García et al, 2012;Canellas & Olivares, 2014;Zandonadi et al, 2014) mention that HSs improve the agronomic performance of many crops under conditions of nutritional or climatic stress; however, in the present study, the organomineral fertilizer enriched with HSs was not efficient at effectively mitigating the adverse effects of environmental stress, probably due to the severity of the stress to which soybean plants were subjected.…”

“…Besides the positive effects on soil attributes, they have direct effect on plant physiology and growth, especially for stimulating root growth (Rima et al, 2011;Canellas & Olivares, 2014). Many studies show that HSs increase the absorption of nutrients due to the increment in the permeability of the cell membrane; chelation and the carrying of nutrients have an auxin-like hormone effect and reduce the effects of the damages caused by the abiotic stress (García et al, 2012).…”

“…The increase in the contents of soil organic matter (SOM) improved physical, chemical and biological attributes and stimulated plant growth and development (Zandonadi & Busato, 2012;Baldoto et al, 2012;Canellas & Olivares, 2014;Zandonadi et al, 2014).…”

Agronomic performance and soil chemical attributes in a banana tree orchard fertigated with humic substances1

“…The significant effect of humic substances on transplanting to bunch harvest may likely be explained by the stimulating effects, albeit not significant, of humic substances on plant metabolism (Baldotto & Baldotto 2014, Canellas & Olivares 2014, Caron et al 2015 Table 6. Average growth and yield properties, as a function of cycle and total dose applied is no consensus regarding the mechanisms of action of these organic acids, given the varied responses of plants with concentration, molecular weight, organic acid structure and sources of humic substances, in addition to variations by plant species (Lodhi et al 2013, Muscolo et al 2013, Zandonadi et al 2013, Caron et al 2015.…”

Evaluation of the possibilities of using humic acids obtained from lignite in the production of commercial fertilizers

“…These substances can immobilize and neutralize heavy metals, contributing to the process of soil detoxification; however, their main use is to enhance nutrient and micronutrient uptake including their bioavailability and, as a consequence, increase growth, yield, and product quality (Piccolo 1996;Tipping Responsible editor: Elżbieta Jamroz Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11368-017-1907-x) contains supplementary material, which is available to authorized users. 2002;Canellas et al 2002Canellas et al , 2014Canellas et al , 2015Nardi et al 2016). For these reasons, it seems that the use of humic acids as agents which improve soil properties and affect the amount and quality of crops, it may be a perspective direction in the development of modern agriculture.…”