Professor Gembloux Agro-Bio Tech, University of Liège Gembloux, Namur, Belgium
Body of Abstract: Plant biostimulants are products applied to plants for the purpose of improving their nutrition, tolerance to abiotic stress, yield or quality. The main categories on the market include seaweed extracts, protein hydrolysates, humic/fulvic acids and polysaccharides like chitosan, but microbial inoculants are also covered by the regulatory definitions adopted by different countries. Market growth has been important over the last 20 years and is driven by regulatory advances and by the raising awareness among farmers and other professionals. Biostimulants are a functional category of agricultural inputs defined by claims, which need to be supported by evidence, communicated to the farmer in a sound way and validated by certifying authorities. Yet, efficacy in the field is often inconsistent and it proves difficult for the farmer to quantify the actual benefits of biostimulants. This is due to the limited understanding of the mode of action of biostimulants and their interaction with fertilizers, soil properties and plant varieties. As many biostimulants aim at improving abiotic stress tolerance, monitoring of the stress experienced by the crop is also important for driving the use of biostimulants. Precision agriculture might provide the tools for informing the use of biostimulants, indicating the right times and places for the treatments over the crop-growing season. Plant biostimulants raise interesting questions of plant biology, like how application of low doses of bioactive substances can have prolonged effects in the life cycle of the plant and how plants can be ‘primed’ for enhanced stress response. The putative epigenetic mechanisms involved still need to be described. The plant biology community, the industry and the farmers should all reap the benefits of a better understanding of plant biostimulation.