From the middle of 2024, Brazil began to experience a phenomenon known as La Niña. In Brazil, when La Niña is active, rainfall tends to decrease in the South (causing drought in many cases) and increase in the North and Northeast regions. In the Southeast and Central-West, on the other hand, there is no such clear correlation, but the chances of cold and rainy periods increase (FABBRI, 2024).

Water deficit is one of the major causes of reduced agricultural productivity as it negatively affects plant growth and development (JOSHI et al., 2016; KOCH et al., 2019). The scarcity of water availability limits the maintenance of processes crucial to plant survival, promoting significant reductions in the yield of cultivated species by limiting maximum production potential (ANSARI et al., 2019; CONTI et al., 2019; CRUZ et al., 2023).

Among the technologies currently being disseminated in the market to optimize productivity is the use of foliar fertilizers containing amino acids in their composition. Thus, the objective of these products is to provide more complete nutrition for plants, increasing productivity. The presence of amino acids aims to enhance nutrition by providing molecules that are used to form proteins. With amino acids readily available for absorption, the plant saves energy by synthesizing these compounds, which is why they are used in conjunction with other nutrients (ROSA et al., 2023).

Furthermore, there are particular functions in which amino acids are present, such as in the formation of chlorophyll, growth and functioning of meristems, in fruiting, responsible for the fertility of the pollen grain, for the consistency of cell walls, in addition to providing the connection between the carbon and nitrogen cycle in plants, influencing the synthesis of sugars and proteins, among others (COLLA et al., 2015; NARDI et al., 2016).

On the other hand, they can act as physiological modulators, acting on the signaling pathway for development processes and in defense against biotic and abiotic stresses (LAMBAIS, 2011). In this aspect, the application of amino acids does not aim to supply the blocks for protein synthesis, but rather to activate the physiological metabolism of plants, having an important anti-stress action (TEIXEIRA et al., 2017; ALFOSEA-SIMÓN et al., 2020).

Amino acids are organic, soluble, energetic and easily degraded molecules, synthesized from the process of nitrogen assimilation and photosynthesis in the glycolysis, citric acid cycle and pentose phosphate pathways. In total, plants produce 20 essential amino acids and in the absence of one or more essential amino acids the plant does not complete the life cycle (Revista Cultivar, 2024).

The main function of amino acids in plants is the formation of proteins, which are formed from the union of amino acids. In general, there are more than 3,000 proteins in a single plant cell and to compose each protein, at least 70 amino acids are required. The main amino acids and their respective functions in plants are presented below, according to Revista Cultivar (2024).

• Serine – acts in the formation of the embryo in seeds;
• Cysteine- acts on tolerance to drought and high temperatures, acting as a precursor of antioxidant and glutathione metabolism;
• Glycine – increases sugars, carbohydrates, proteins, chlorophyll and acts in osmotic and cellular regulation. In addition, this amino acid plays an important role as an osmoprotector in drought resistance and biological nitrogen fixation in leguminous plants;
• Phenylalanine – synthesis of flavonoids, phenylpropanoids, lignin and anthocyanins;
• Tryptophan – auxin synthesis, cell differentiation and ABA inhibition;
• Valine – regulates plant growth and provides an additional supply of nitrogen;
• Leucine – increases the speed of the germination process and influences the synthesis of other amino acids;
• Alanine – acts to protect plants against stresses such as high temperatures, hypoxia and drought;
• Aspartate – precursor of methionine, biosynthesis of biomolecules necessary for plant growth and defense, formation of chlorophyll and pollen development;
• Asparagine – storage and transport of nitrogen in the plant;
• Methionine – biosynthesis of polyamines, zinc chelating, ethylene formation, aids in the incorporation of sulfur, favors nitrate assimilation and increases cuticle thickness;
• Lysine – natural zinc chelator;
• Tyrosine – precursors for the formation of specialized metabolites;
• Isoleucine – accumulation of anthocyanin;
• Proline – increases sugars, carbohydrates, proteins, chlorophyll and acts on osmotic and cellular regulation, in addition to influencing the biological fixation of nitrogen. Proline is an important osmoprotective amino acid in drought resistance;
• Glutamate – acts on seed germination, root architecture, pollen germination and pollen tube growth;
• Arginine – stimulates the growth of the root system and is directly related to the synthesis of cytokinin and chlorophyll;
• Glutamine – acts on the synthesis of flavonoids, chlorophyll and increases seed nodulation and germination, in addition to having high chelating power;
• Histidine – natural chelator of copper, zinc and nickel.

Amino acids are organic acids whose molecules are formed by one or more amine groups, and their main functions are to constitute proteins and to be precursors of several substances that regulate plant metabolism (FLOSS and FLOSS, 2008). They are involved in a large part of primary and secondary metabolism, leading to the synthesis of several compounds that influence production (ALBUQUERQUE and DANTAS, 2010) and also favor significant plant tolerance against environmental adversities by activating plant physiological metabolism.

In bean cultivation, studies concluded that, after the use of amino acids, plants resisted heat stress better, both at high and low temperatures, and also showed an increase in plant height, number of pods and grain mass (CASTRO et al., 2011).

An amino acid that is present in most products is L-glutamic acid, of great importance for cellular metabolism, as it has a range of biological functions, acting as a central molecule in the synthesis of other amino acids and in the metabolism of higher plants (FORDE AND LEA, 2007), acting as a precursor of chlorophyll synthesis (YARONSKAYA et al., 2006).

In a study carried out by Collaço Junior (2019), it was concluded that moderate and acute water stress causes a reduction in root development in bean crops, decreasing root volume and root dry matter mass. However, the application of amino acids significantly reduces these losses when applied before the period of water stress at flowering. In addition, the productivity component, number of pods per plant, suffers a great reduction under the effect of moderate and acute water stress. When the water deficit occurs acutely, the number of grains produced per plant is significantly reduced. These losses can be significantly minimized when the application of amino acids occurs at flowering preceding the period of stress.

ILSA has a range of products that can help in these periods of water stress, the GELAMIN matrix (Figure 1), which is the basis of liquid and water-soluble organic and organomineral fertilizers of different products and which contains organic nitrogen derived from enzymatic hydrolysis, therefore it mainly presents the amino acids glycine, proline, hydroxyproline, glutamic acid, and alanine.

Figure 1- Amino acid composition in the GELAMIN matrix.

Glycine is the amino acid present in the largest quantity in the GELAMIN matrix. This amino acid is involved in the formation of glycine betaine. This compound accumulates in plants that are under water or salt stress or due to climatic factors such as temperature.

Glycine betaine is the best-known quaternary ammonium compound in cultivated plants, synthesized endogenously in chloroplasts in response to abiotic stresses, such as water deficit (JÚNIOR et al., 2021). In several crops, its concentration is correlated with the capacity for stress tolerance (ASHARAF and FOOLAD 2007, DAWOOD 2016).

The use of glycine betaine can increase the synthesis of compatible solutes in stressed plants (FAROOQ et al. 2008), thus improving growth and adaptation under water deficit conditions (ANJUM et al. 2012).

Júnior (2021) concluded that foliar application of glycine betaine improved the relative growth rate of sugarcane plants under water stress, especially after rehydration, which reduced the negative effects of stress on dry mass production.

References:

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Authors

Agr Eng. Dr. Angélica Schmitz Heinzen

Agricultural Eng. Msc. Thiago Stella de Freitas

Agricultural Engineer Tuíra Barcellos