The action mechanisms of L-alanyl-L-cystine in plant stress resistance are mainly reflected in the following aspects:
I. Regulating Osmotic Equilibrium
Enhancing Osmotic Regulation Ability: Under adverse conditions such as drought and high salinity, plant cells will accumulate some small molecular substances to lower the water potential inside the cells, thereby maintaining the turgor pressure and normal physiological functions of the cells. L-alanyl-L-cystine can accumulate in plant cells as an osmotic regulating substance, helping plants retain the water inside the cells and preventing the cells from being damaged due to water loss. It can regulate the osmotic pressure of the cells, enabling plants to maintain a better water balance under adverse conditions such as water stress, and enhancing the drought and salt resistance of plants.
Stabilizing the Structure of Biological Membranes: An appropriate osmotic pressure is crucial for maintaining the stability of biological membranes. By regulating the osmotic equilibrium, L-alanyl-L-cystine helps to maintain the integrity and fluidity of biological membranes, making the biological membranes less likely to be damaged under adverse conditions, thus ensuring the normal operation of various physiological and biochemical processes inside the cells. For example, under low-temperature stress, maintaining the fluidity of biological membranes can prevent the phase transition of membrane lipids and avoid the damage of the membrane structure, thereby improving the cold resistance of plants.
II. Removing Reactive Oxygen Species
Participating in the Antioxidant Defense System: When plants are subjected to stress, reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide, will be produced inside the cells. Excessive ROS will cause oxidative damage to the cells and affect the growth and development of plants. L-alanyl-L-cystine can participate in the antioxidant defense system of plants. It can directly or indirectly remove ROS. For example, it can serve as a precursor for the synthesis of glutathione (GSH), an important antioxidant in plants. GSH can remove the ROS inside the cells through a series of reactions, reducing the damage to plants caused by oxidative stress.
Activating the Activity of Antioxidant Enzymes: L-alanyl-L-cystine can also enhance the antioxidant capacity of plants by regulating the activity of antioxidant enzymes in plants. It can induce the expression of genes of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and increase the activity of these enzymes, so as to more effectively remove the ROS inside the cells, keep the oxidation level of plants low under adverse conditions, and enhance the stress resistance of plants.
III. Regulating the Balance of Plant Hormones
Influencing Hormone Synthesis and Signal Transduction: L-alanyl-L-cystine may participate in the synthesis, metabolism, and signal transduction processes of plant hormones, thereby regulating the growth and development of plants and their responses to stress. For example, it may affect the synthesis of abscisic acid (ABA). ABA plays an important role in plants' responses to adverse stresses such as drought and low temperature. It can promote stomatal closure, reduce water loss, and induce the expression of stress-related genes. L-alanyl-L-cystine enables plants to better adapt to adverse environments by regulating the levels and signal transduction of hormones such as ABA.
Synergistic Effects with Other Hormones: In addition to ABA, L-alanyl-L-cystine may also interact with other plant hormones such as auxin, cytokinin, and ethylene, coordinately regulating the stress resistance of plants. It can change the growth state and physiological responses of plants by influencing the balance among these hormones, enabling plants to allocate resources reasonably under adverse conditions, giving priority to ensuring the progress of important physiological processes, and improving the survival ability of plants.
IV. Participating in Nitrogen Metabolism and Energy Regulation
Nitrogen Source Supply and Metabolic Regulation: Under adverse conditions, the nitrogen metabolism of plants will change to adapt to environmental changes. As a nitrogen-containing compound, L-alanyl-L-cystine can provide a nitrogen source for plants, meeting the plants' demand for nitrogen under adverse conditions. Moreover, it can also regulate the nitrogen metabolic pathways in plants, promoting the absorption, transportation, and assimilation of nitrogen, enabling plants to utilize nitrogen more effectively and maintain normal growth and metabolism.
Energy Regulation and Metabolic Equilibrium: The metabolism of L-alanyl-L-cystine is closely related to the energy metabolism of plants. Under adverse conditions, the energy supply and demand of plants will change. It can provide energy for plants by participating in metabolic pathways such as the tricarboxylic acid cycle, maintaining the energy balance of cells. In addition, it can also regulate other metabolic pathways, such as carbohydrate metabolism and fat metabolism, enabling plants to allocate energy and substances reasonably under adverse conditions and ensuring the basic physiological functions of plants and the progress of stress resistance reactions.
