Effectiveness of Humic Substances and Phenolic Compounds in Regulating Plant-Biological Functionality

Adele Muscolo,Santiago Sanchez Cortes,Serenella Nardi,Ornella Francioso,Diego Pizzeghello

doi:10.3390/agronomy10101553

Abstract

Significant benefit of soil organic matter (SOM) to crop productivity is scientifically well documented. The main constituents and active fractions of SOM are humic substances (HS) and phenolic compounds. Since both these two components strongly impact plant–soil relationship, it is importantly from an ecological point of view to discriminate their biological effects and relating them to their composition. In this study we compared the biological effects of HS, and the soil water soluble phenols (SWSP) on growth, antioxidant activities, carbohydrates, proteins, phenols, and vitamins of Pinus laricio callus. Each extract was assessed for the content of low molecular weight organic acids, soluble carbohydrates, fatty acids, and phenolic acids. Moreover, Fourier transform infrared (FT-IR) and surface-enhanced Raman scattering (SERS) spectroscopies were applied to study their molecular structure. The results showed that HS produced better callus growth compared to the control and SWSP. Carbohydrates decreased in presence of HS while proteins, vitamin C and E increased. In contrast, in callus treated with SWSP the amount of glucose and fructose increased as well as all the antioxidant activities. The data evidenced that HS rich in tartaric and fatty acids had beneficial effects on callus growth contrary to soil water-soluble phenols rich in aldehydes, and syringic, ferulic, and benzoic acids.

Highlights

Soil organic matter (SOM) is a highly miscellaneous blend with well recognized effects on crop productivity
It is emerged that the effects of soil organic matter change on the basis of the fractions that prevail in its composition
Many compounds found in Humic substances (HS) have been proposed as plant growth promoters and their beneficial effects on plant growth have been attributed on the basis of their mode of action

Summary

Introduction

Soil organic matter (SOM) is a highly miscellaneous blend with well recognized effects on crop productivity. These benefits have been object of controversy for centuries and some are still debated today because of SOM is a mixture of organic material and meso–micro soil fauna and microflora with high complexity and heterogeneity. The majority of soil organic matter (~90%) is usually constituted by humus, a strongly decomposed organic material dark-colored, partly aromatic, acidic, hydrophilic, molecularly flexible polyelectrolytic matter [1]. The active pools are constituted by a stable pool (humic substances, HS) and a labile pool of phenolic compounds. Humic substances (HS) are a durable material, specific to each type of soil that have not markedly change over decades of land use [2]

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