Biostimulants and their Roles in Plant Physiology, Nutrient Absorption, and Tolerance to Abiotic Stresses

Improved product quality, sustainable cultivation systems, and reduced production costs are among the objectives of modern agriculture despite the global and local climate changes that have faced crops with a variety of stresses. Biostimulants seem to be capable of helping plants in their struggle against these stresses toward the goals of modern agriculture. These compounds include humic substances, seaweed extracts, amino acids, microbial inoculants, and minerals such as useful elements and inorganic salts including phosphates and antiperspirants. While application of biostimulants has witnessed a dramatic increase in the world and in Iran over the past few years, it must be noticed that they might have different effects on different species and even on different varieties of a given plant species. Their application for agricultural and horticultural purposes must, therefore, be duly modified in accordance with local and regional research findings. It is the objective of this paper to provide a better understanding of plant biostimulants based on scientific findings and practical experience in agriculture and horticulture. It will be shown that plant biostimulants are capable of improving crop production, enhancing plant resistance to abiotic stresses, and elevating crop quality. Future research in this area should aim at the determination of the mechanism(s) underlying the activities of such materials since a better understanding of their activities and effects will be necessary for achieving sustainable agricultural production systems.