Plant biostimulants: physiological responses induced by protein hydrolyzed-based products and humic substances in plant metabolism

Abstract

In recent years, the use of biostimulants in sustainable agriculture has been growing. Biostimulants can be obtained from different organic materials and include humic substances (HS), complex organic materials, beneficial chemical elements, peptides and amino acids, inorganic salts, seaweed extracts, chitin and chitosan derivatives, antitranspirants, amino acids and other N-containing substances. The application of biostimulants to plants leads to higher content of nutrients in their tissue and positive metabolic changes. For these reasons, the development of new biostimulants has become a focus of scientific interest. Among their different functions, biostimulants influence plant growth and nitrogen metabolism, especially because of their content in hormones and other signalling molecules. A significant increase in root hair length and density is often observed in plants treated with biostimulants, suggesting that these substances induce a "nutrient acquisition response" that favors nutrient uptake in plants via an increase in the absorptive surface area. Furthermore, biostimulants positively influence the activity and gene expression of enzymes functioning in the primary and secondary plant metabolism. This article reviews the current literature on two main classes of biostimulants: humic substances and protein-based biostimulants. The characteristic of these biostimulants and their effects on plants are thoroughly described.

Induction of Cadmium Stress Tolerance in Triticum Aestivum L. By Alfalfa Leaf Extract

“…These plant-based biostimulants are thought to enhance plant growth, yield via improving the efficiency of plant metabolism, increasing tolerance to abiotic stresses, enhancing quality attributes of crops and facilitating uptake, translocation and assimilation of nutrients etc. (Ertani et al, 2014;Nardi et al, 2016). To examine the potential role of alfalfa leaf extract, it was hypothesized that foliar application of alfalfa leaf extract can reduce the adverse effects of cadmium stress on different growth and physiochemical attributes of different wheat varieties.…”

Commercial Humates in Agriculture: Real Substance or Smoke and Mirrors?

“…A vast amount of literature exists on the effects of HS on soil micro-organisms, plant physiology and plant growth, and important reviews include those of Canellas and Olivares [12] and Nardi et al [13], the latter focussing on the biostimulant role of HS and protein hydrolysed-based products. The authors noted that the biostimulatory activity of HS was usually due to hormone-like activity, which may be due to auxins, which were analysed in the HS.…”

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

“…Most published studies of HS show wide range of benefits including a growth of beneficial soil microbes, improvements in soil structure including water retention capacity as well as a soil porosity, aeration, compaction, and adhesion (Piccolo et al 1993;Nardi et al 2016;Ouni et al 2014;Ciarkowska et al 2017). Another experiment has shown numerous benefits of HS application to plants including root respiration, enzyme activity, and resistance to abiotic stress like salinity and extreme pH.…”

“…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.…”