Dear Colleagues,

Current agriculture prioritizes ecological forms that promote plant growth and crop productivity. A third of the investment in a crop goes to the use of fertilizers, fungicides, and pesticides. A fertilizer is an "organic or inorganic formulation containing nutrients in forms directly absorbed by plants, improving the quality of the substrate and stimulating the vegetative growth of plants." However, the deleterious effects of those products, used with little restraint during the last few decades, have led to the search for new strategies to identify compounds that improve plant production and stress tolerance in a sustainable way.

Within a situation of global warming and uncontrolled emission of greenhouse gases, new lines of research have been developed, aimed at the search for natural “environmentally friendly” products, as well as natural products revalorized from industrial processes, with beneficial effects on plant vegetative vigor and stress tolerance. Many of those products are biostimulants; legislation on the use of biostimulants is currently being developed in many countries around the world.

A biostimulant is a “formulation of biological origin that improves plant productivity due to the properties of its constituents and whose effects are not the only consequence of the presence in its composition of plant nutrients, growth regulators or protective compounds of plant". Biostimulants contribute to increasing the yield of plants and their absorption of nutrients, reducing dependence on chemical fertilizers. Biostimulants are environmentally friendly, contributing to reducing climate change effects and improving plant stress tolerance.

The main types of biostimulants fit into three main groups: One group is the well-known plant hormones, such as methyl jasmonate, ethylene, salicylic acid, abyssic acid, and brassinosteroids. The second most frequently used type of biostimulants are products derived from microorganisms, including bacterial, fungal, yeast and algae extracts, and consortia and mixtures of them. The last group is composed of pure natural-origin products, including peptides and proteins, polysaccharides, oligosaccharides, and wall-derived fragments, such as chitin, chitosan and its derivatives, and small peptides and cyclodextrins, as well as natural activating compounds, such as the well-known coronatin.

Our aim is to contribute to the dissemination of research articles related to the search and implementation of new technologies in the field of plant biostimulants. In particular, plant response to products of natural origin is still underexplored, including newly discovered biostimulants with unknown properties that have not been exploited until now, as well as their contribution to a sustainable agro-forestry environment. The valorization of new bio-compounds will contribute to increasing plant tolerance to both abiotic as well as biotic stress and soil health, reducing the impact of industrial activity and the production of industrial waste. The study of the physiological and molecular plant response to new biostimulants will increase our basic knowledge to improve the plant vegetative vigor associated with the increase of plant tolerance to stress. The use of new bio-compounds and the study of plant responses to them inside the natural environment will open the way to finding new strategies to reduce the use of contaminant fertilizers and pesticides, also reducing the emission of gases associated with global warming.

Research articles should cover aspects related to the study of new effects (including “-omics” studies) and the molecular mechanisms of plant biostimulants, as well as the use of new strategies using plant biostimulants, such as hormones including methyl jasmonate, ethylene, salicylic acid, abscisic acid, or brassinosteroids, and chemicals of natural origin. We welcome submissions related to the study of biostimulants derived from microorganisms, including bacterial, fungal, yeast and algae extracts, and consortia and mixtures, in addition to pure natural-origin products composed of small peptides and proteins, polysaccharides, oligosaccharides, and wall-derived fragments, such as cellobiose, cellulose, chitin, and chitosan and its derivatives, as well as natural activating compounds, such as cyclodextrins or phytoanticipins.

This Special Issue focus on new approaches for a greener, more sustainable future with respect to the field of plant biostimulants.

Dr. Marta Berrocal-Lobo
Guest Editor

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• plant biostimulant
• fungi
• bacteria
• plant hormones
• plant defense
• elicitors
• fertilizer
• phytopathogen
• climate change
• environmentally friendly
• vegetative vigor
• global warming
• stress response
• -omics (genomics, transcriptomics, proteomics, metabolomics, etc.)