What are amino acids and how are they used in agriculture?
The use of amino acids in Brazilian agriculture and in other countries has been increasing significantly, due to the numerous benefits that these organic substances have been providing to plants (GAZOLA et al., 2016). Amino acids contribute to increasing the productivity of the most diverse crops and the quality of agricultural products (GAZOLA et al., 2016). Their importance in plants, as in all living beings, is indisputable, as they are involved in a large part of the primary and secondary metabolism, leading to the synthesis of several compounds that influence the production and quality of fruits (ALBUQUERQUE & DANTAS, 2010).
Amino acids are organic units that form proteins, which are made up of a nitrogenous group called amine (NH2), and a carbon group called carboxylic (COOH), and proteins are formed from 20 amino acids (PICOLLI et al., 2009). According to Floss and Floss, (2007), they are organic acids whose molecules end with one or more amine groups, their main function being to constitute proteins and as a precursor of several substances that regulate plant metabolism. Their application in various crops is not intended to meet the need for amino acids for protein synthesis, but rather to activate the physiological metabolism of plants.
Some of the benefits provided by amino acids for plants are cited by Brandão (2007), according to him, amino acids provide balance in plant metabolism, improve photosynthesis, reduce the phytotoxicity of some pesticides, provide greater tolerance to pests and diseases, promote better absorption and translocation of nutrients applied via foliar application, making the root system more developed and more vigorous, regulate the hormonal activities of plants, provide greater tolerance to water stress and frost, greater flowering of plants and increase the quality of harvested products.
Amino acids provide energy to plants, compensating for losses due to respiration and decomposition processes, as well as those caused by stress-reducing agents, thus contributing to the cellular capacity to absorb water and nutrients (BAQIR; ZEBOON; AL-BEHADILI, 2019). In addition, they promote growth, increase the synthesizing proteins that participate in metabolic functions, improve the quality of grains in some crops, are precursors of hormones, signal different physiological progressions, regulate nitrogen absorption, root system development, among others (BAQIR; ZEBOON; AL-BEHADILI, 2019). In this link: https://ilsabrasil.com.br/estresse-oxidativo-em-plantas-tudo-o-que-voce-precisa-saber/ You can understand a little more about how oxidative stress can be harmful to the plant.
The use of amino acids becomes an alternative in adverse stress conditions that may occur in the production process, becoming an ally in reducing losses, leading to the physiological balance of the plant more quickly and thus the plant's defense against stress.
How stress can affect plants
Many biotic and abiotic events generate stress for plants, such as stress generated by low temperatures. Naidu et al. (1991) studied the changes in the amino acid profile in wheat plants during cold stress, and observed that the content of glutamine, proline, alanine, aspartic acid, asparaginine, glycine, valine, threonine, and isoleucine increased while glutamic acid decreased. Proline is the metabolite considered an osmoregulator and osmoprotector within cells (CUSHMAN, 2001). This amino acid is accumulated in large quantities in response to environmental pressures, acting as a compatible solute and redox buffers, which are potential in cells (SANTOS et al., 2014). Studies indicate that proline levels are interconnected with various types of stress as an alternative way to minimize their effects. In addition, it acts as an osmoprotector of molecules and membranes, forming hydration walls on phospholipids, reducing the action of free radicals, producing chemically stable molecules, both in seeds and plants (DELAUNEY, 1993).
Another important factor is the application of agricultural pesticides, as they can cause phytotoxicity, for example: burning the leaves, causing stress in the plant and reducing the photosynthetic rate and consequently delaying its development. Even with the application of pesticides and taking all recommended precautions, it can occur phytotoxicity. An alternative for controlling phytotoxicity was extensively debated by Yamada and Castro (2007), suggesting the application of aromatic amino acids in sprays, which can help in the recovery of plants intoxicated by the herbicide glyphosate. The best responses of amino acids have been in situations of biotic stress, such as those related to the attack of pests and diseases, and abiotic stress, such as nutritional disorders, climate, water deficiencies or stress related to the application of pesticides, especially herbicides. giving amino acids the title of anti-stress agents (ZOBIOLE et al., 2010). The 24-hour interval between exposure to glyphosate and the application of amino acids was efficient in reversing the symptoms of phytotoxicity, expressed by the increase in the levels of photosynthetic pigments (DA ROCHA PINHO et al., 2021).
Plants subjected to water stress suffer a reduction in water availability for processes associated with transport, which can cause changes in the concentration of many metabolites, followed by disturbances in carbohydrates and amino acid metabolism (SANTOS et al., 2010). The accumulation of free amino acids and sugars can originate from the restriction of protein synthesis and hydrolysis of starch reserves, and may also originate from disturbances caused by water deficiency in phloem tissues, reducing its translocation to other organs of the plant (CARVALHO, 2005).
For Da Silva Galdino et al. (2018), the study of water stress in plants and their responses involves physiological and biochemical processes, which are of fundamental importance for plant development. Among these, variations promoted in the levels of amino acids that act as osmoregulators. According to Paixão et al. (2014), osmotic adjustment through the accumulation of this class of solutes in plants is one of the alternatives to ensure turgor and water content in cells. Stress causes changes in the composition of cells in higher plants, leading in many cases to the production and accumulation of osmotically active substances (SANTOS et al., 2010). This process, known as osmoregulation, is a very important component in drought tolerance in several species (SUBBARAO et al., 2000).
Among the stresses mentioned above and as a way of using amino acids, we can mention two compounds that stand out in the physiological metabolism of the plant, acting in the defense mechanism, which are proline and glycine betaine.
How can proline and glycine betaine help reduce stress?
The amino acid proline and the quaternary ammonium glycine betaine have very valuable functions, especially for plants that suffer abiotic stresses resulting from water deficiency, which is one of the main causes of dysfunctions and reductions in productivity (MONTEIRO et al., 2014). Proline activates the physiological protection mechanism in adverse situations, promoting osmotic adjustment, efficient in maintaining cell turgor, providing protection for short periods of stress and preserving the integrity of proteins, enzymes and cell membranes (MARIJUAN et al., 2013). Likewise, glycine betaine, a quaternary ammonium compound, has a physiological function related to the osmoregulation of the cytosol and cellular compartments, in the protection of proteins and in the stabilization of membranes (biomolecular mechanism) (BAQIR; ZEBOON; AL-BEHADILI, 2019). Therefore, these compounds are osmoprotectants that are involved in signaling and regulating plant responses to multiple stresses, playing adaptive roles in measuring osmotic adjustment and protecting subcellular structures in stressed plants. However, not all plants are able to accumulate these compounds in adequate amounts to prevent these effects caused by water stress (drought stress in plants), making it necessary to supply them via fertilization (MELO, 2022).
Silva et al. (2010), when evaluating the physiological response of a “Conilon” coffee clone sensitive to water deficit, grafted onto a tolerant rootstock, observed that the concentration of amino acids increased significantly in all plants subjected to water deficit. In plants under water deficit, there is an increase in amino acid levels, especially proline, which may be related to the increased activity of proteolytic enzymes, promoting greater availability of free amino acids, in order to protect plant tissues against this stress (DA SILVA GALDINO et al., 2018).
According to the literature (FAROOQ, 2009; CLAUSSEN, 2005), the presence of amino acids combats hydroxyl radicals, promotes the maintenance of cell turgor and protects enzymes and molecules from oxidation due to the presence of reactive oxygen species. In addition, the accumulation of proline in leaf tissues can also be used as a source of energy, N and carbon that promotes the recovery of physiological activities in the plant (HEMAPRABHA et al., 2013).
Glycine betaine is required to protect the plant by maintaining the water balance between the plant cell and the environment, stabilizing the macromolecules (Figure 1) (CHEN; MURATA, 2002;). Plants synthesize glycine betaine by two oxidation reactions of choline (Choline Betaine aldehyde glycine betaine) (RHODES; HANSON, 1993).
Figure 1 – Soybean plants 45 days after sowing, subjected to glycine application in different treatments. A – Control; B – Application via seed; C – application via foliar; D – application via seed and foliar. Source: adapted TEIXEIRA, Walquíria Fernanda. Evaluation of the use of amino acids in soybean crops. 2017. Thesis (Doctorate in Plant Science) – Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, 2017.
In addition to its role as an osmoprotectant, glycine betaine stabilizes photosynthetic reactions, the structure of extrinsic proteins of the Photosystem 2 (PSII) complex, and ATP synthase, as well as cell membranes and enzyme activation (IBGE; TAIZ & ZEIGER, 2009). Regarding environmental conditions, plants only grow when cells remain turgid, where water deficit will be reflected in their growth rate (FERRI, 1985). According to Mäkelä et al. (1998), exogenous applications of glycine betaine, via foliar application, in tomato plants subjected to salt stress or high temperatures resulted in an increase of 40% in fruit yield compared to untreated plants.
ILSA BRASIL fertilizers help in this stress process in plants
ILSA BRASIL fertilizers are obtained from two organic matrices with high nutritional value and which have amino acids in their composition that will directly interfere in the oxidative processes in plants. Both the matrix AZOGEL (solid fertilizers) as the matrix GELAMIN (liquid and water-soluble fertilizers) have high levels of amino acids in their composition (Figures 2 and 3). AZOGEL is obtained from the THERMAL HYDROLYSIS of collagen, where the protein chains are cut by the action of water vapor in autoclaves under high temperature and pressure conditions, without the addition of any type of chemical substance, which keeps the amino acids in their biologically active form. Likewise, in the process of obtaining GELAMIN amino acids remain biologically active, where in the reactors, in addition to collagen, a pool of selective enzymes are added that will cut the protein molecules into different fragments through the process of ENZYMATIC HYDROLYSIS.
Figure 2. AZOGEL matrix aminogram. Source: ILSA Brazil
Figure 3. GELAMIN matrix aminogram. Source: ILSA Brazil
In this text, we discuss the importance of two main compounds that interfere with and increase the plants' ability to overcome stress. The amino acid proline has an important osmoprotective function in plants subjected to stresses such as drought, high temperature and salinity. The accumulation of proline in plant cells subjected to water stress is suggested as an osmotic adjustment mechanism (Nepomuceno, AL, et al 2001). The quaternary ammonium glycine-betaine also has this osmoprotective function in plants during times of stress caused by lack of water in the production system. For this compound to be formed in the plant, the amino acid glycine must be synthesized or supplied exogenously in satisfactory quantities.
The two organic matrices of ILSA (www.ilsa.com.br) high levels of essential amino acids for plant metabolism, and among them, glycine and proline are present in greater quantities. Thus, ILSA fertilizers, in addition to efficiently providing nutrients to plants, also interfere in the main stress processes, which leads to an increase in the plant's metabolic activity, increasing its ability to overcome these stress conditions and, consequently, its productive potential.
Among the benefits of using matrices GELAMIN and AZOGEL we can mention: activation and stimulation of primary metabolism (photosynthesis, respiration, green leaves for longer, less senescence), greater resistance to abiotic stresses, greater resistance to attack by pests and diseases (secondary metabolism), among others.
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Authors
- Agr Eng. Dr. Angélica Schmitz Heinzen
- Agricultural Eng. Msc. Carolina Custodio Pinto
- Agricultural Eng. Msc. Thiago Stella de Freitas
