Tomato (Solanum lycopersicum L.) is one of the most important crops worldwide as per its production and the surface cultivated. The use of biostimulant products plays a fundamental role in mitigating the negative effects of climate change and reducing the use of conventional fertilizers. Many of these products are formulated with amino acids (AAs). This study was conducted to elucidate the effects of the foliar application of tyrosine (Tyr) (15 mM), lysine (Lys) (15 mM), methionine (Met) (15 mM), and a Tyr + Lys + Met (15 mM + 15 mM + 15 mM) mixture on the physiological and metabolic processes, vegetative growth, and nutritional state of Optima variety tomato plants. The results showed that application of the AAs, individually and combined, was beneficial for the growth of the aerial part, net assimilation of CO₂, and water use efficiency (WUE). Application of Tyr resulted in the best WUE. The metabolomics study revealed that AA treatments increased the concentration of proline, fructose, and glucose, whose role was to stimulate glycolysis and the Krebs cycle. Thus, the plants could have greater reduction power and energy, as well as more carbon molecules for their growth processes.

Biostimulants are agronomic products that have become highly important in agriculture, as they are formulated with substances capable of stimulating physiological and biochemical processes in plants that help them adapt to different detrimental environmental conditions such as drought, salinity, high temperatures, nutritional deficiencies, etc. in such a way that the crops, under these conditions, maintain a good agronomic yield and quality of harvest. Every two years, the International Congress on Biostimulants is held with the aim of publicizing the most innovative and recent advances in every relevant type of product: new active ingredients, modes of action, cultivation protocols, test platforms and phenotyping, use of analytical omics tools, etc. In December 2021, the 5th World Congress on Biostimulants was held in Miami (Florida, USA). This publication summarizes the most relevant results that were presented at this congress, in which biostimulants formulated with algae extracts and amino acids stood out in a number of presentations. The various studies presented were carried out on diverse crops such as apple, blackberry, carrot, celery, cherry, corn, grape (table and wine), olive, pear, pepper, potato, rapeseed, spinach, sunflower, soybean, tomato, and wheat. The future lines of the new generation of biostimulants were also marked.