Secondary metabolites as biostimulant and bioprotectant agents: A review

Increasing crop productivity to feed a growing population, while conserving the natural resources, is one of the humanity's major challenges that needs to be overcome. To achieve these goals while decreasing and/or rational-izing the application of chemical fertilizers and pesticides, scientists are nowadays more interested in plant-and microbial-based solutions to develop a new up-coming green revolution being much defined by cost-effective and eco-friendly approaches to sustain the agricultural sector. Biostimulants and bioprotectants are natural prep-arations, that have gained a big interest in the last years because of their role in improving plant growth and yields and reducing the impact of abiotic and biotic stresses. Seaweed extracts, humic substances, protein hydro-lysates, amino acids, plant extracts, and beneficial microorganisms have gained importance as biostimulants and bioprotectants because of their valuable effect on plant growth and their ability to alleviate the detrimental ef-fects of different abiotic and biotic stresses. Likewise, microbial-based biostimulants and bioprotectants are shown to impact positively cropping systems through different mechanisms (e.g., increase nutrients uptake and use efficiencies, boost root system development, suppress phytopathogens infection, and alleviate heavy metals (HMs) toxicity among many others), eventually leading to better crop growth and yields. Among the dif-ferent classes of molecules extracted from plants, seaweeds and microorganisms, secondary metabolites, repre-sent a major group of bioactive compounds that could be responsible for the biostimulant effect. In addition to their effect as biostimulants, these molecules, are endowed with a wide range of bioprotectant activities and could, therefore, play an important role as protectors for plants against multiple attacks from insects and phyto-pathogens. Given all this knowledge, the exploitation of these bio-based and cost-effective compounds is worth further investigations to develop propitious approaches that should sustain agricultural productivity in an envi-ronmentally friendly manner. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Increasing crop productivity while reducing the use of chemical fertilizers and pesticides is a major challenge that scientists are addressing by focusing on plant and microbial-based solutions to sustain the agricultural sector in a cost-effective and eco-friendly manner. Biostimulants and bioprotectants have gained interest for their ability to improve plant growth and yield, as well as reduce the impact of abiotic and biotic stresses. Microbial-based biostimulants and bioprotectants have been shown to positively impact cropping systems through various mechanisms, ultimately leading to better crop growth and yields.