Plant biostimulants (PBs) attract interest in modern agriculture as a tool to enhance
crop performance, resilience to environmental stress, and nutrient use efficiency.
PBs encompass diverse organic and inorganic substances (humic acids and protein
hydrolysates) as well as prokaryotes (e.g., plant growth promoting bacteria) and
eukaryotes such as mycorrhiza and macroalgae (seaweed). Microalgae, which comprise
eukaryotic and prokaryotic cyanobacteria (blue-green algae), are attracting growing
interest from scientists, extension specialists, private industry and plant growers
because of their versatile nature: simple unicellular structure, high photosynthetic
efficiency, ability for heterotrophic growth, adaptability to domestic and industrial
wastewater, amenability to metabolic engineering, and possibility to yield valuable
co-products. On the other hand, large-scale biomass production and harvesting still
represent a bottleneck for some applications. Although it is long known that microalgae
produce several complex macromolecules that are active on higher plants, their targeted
applications in crop science is still in its infancy. This paper presents an overview of the
main extraction methods from microalgae, their bioactive compounds, and application
methods in agriculture. Mechanisms of biostimulation that influence plant performance,
physiology, resilience to abiotic stress as well as the plant microbiome are also outlined.
Considering current state-of-the-art, perspectives for future research on microalgaebased
biostimulants are discussed, ranging from the development of crop-tailored,
highly effective products to their application for increasing sustainability in agriculture.
Department of Agricultural Sciences, University of Naples Federico II, Portici, Italy
Copyright: published: 07 December 2018 doi: 10.3389/fpls.2018.01782. Copyright © 2018