Betaine is a quaternary ammonium alkaloid, widely existing in animals and plants.It is a secondary product of metabolism,and its unique molecular properties makes it have polar and non-polar. It can combine to hydrophilic and hydrophobic regions of biological macromolecules, such as enzymes or protein complexes, and is an important non-toxic osmotic regulatory substance in higher plants。

Betaine application in plant is to maintain the cell osmotic presure:When subjected to saline-alkali or water stress, a large number of organic osmotic regulators such as betaine accumulate in the cytoplasm, and the inorganic osmotic regulators in the cytoplasm mainly help to extrude to the vacuole, so as to maintain the osmotic balance between the cytoplasm and the external environment of the intracellular vacuole.Betaine accumulation in plants under salt stress is a kind of important physiological phenomenon is beneficial to plants grown in stress, positive correlation between plant salt resistance and its content of alcohol protection: the solubility of betaine is very high, with no net charge, the high concentration has no effect on many enzymes and other biological macromolecules, even have a protective effect. 

Betaine can protect beetroot cell membranes from heat damage and improve the temperature required for enzymatic denaturation. It can protect spinach against freezing stress and remove the toxic effect of high concentration salt on enzyme activity.It has a good protective effect on aerobic respiratory metabolic process.Betaine is rapidly synthesized and accumulates in high concentrations in the body。Betaine is the best osmotic regulator.