Amino acids play an important role in the process of roots morphogenesis. On the one hand , they regulate roots morphogenesis , on the other hand ,they are a necessary material basis for root morphogenesis. In addition, it also play a role of improving soil condition, provide a good growth environment ,which is conducive to root growth
1. Amino Acids as Hormone Preconditions Regulate Root Morphogenesis
The precursors of auxin and ethylene synthesis are amino acids. Their synthesis and transportation lead to their different concentration distribution in plants, thus specifically regulating the morphogenesis of roots, mainly including the following three aspects：
1) To promote root elongation
serine and indole first synthesize tryptophan. Tryptophan is the synthesis precursor of plant auxin (IAA), which can promote the synthesis of plant auxin. After auxin combines with hormone receptors on the root cytoplasm membrane, it activates H+- ATPase to pump H+into the cell wall, so that cellulose molecules increase and loosen, cells absorb water, thus promoting root cell elongation
2）Induce the lateral root formation
The main plant hormone which participate in regulating the lateral root generation is plant auxin,which can promote the formation and elongation of lateral root primordium and lateral root meristem, thus inducing the formation of lateral root.
3) Induce root hair formation
The formation of root hair comes from specific epidermal cells in the mature zone of root tip. Ethylene synthesized by methionine has dual functions in the development of root hair. On the one hand, it can induce non hairy cells to grow root hair, and on the other hand, it can promote the elongation and growth of root hair.
2.Amino acids as nutrients participate in root morphogenesis
Enzymes involved in root morphogenesis are all composed of proteins,and amino acid is the smallest building block of protein. The formation of cell wall, cell membrane, cytoplasm and various organelles of roots all need protein . Therefore, amino acids play an irreplaceable role in the process of root morphogenesis.
3.Amino acids can also improve soil structure and provide a good growth environment for roots
Threonine is an acid-base amphoteric substance. When the soil is too acidic, the amino group of the basic functional group of threonine can neutralize with hydrogen ions to reduce the acidity. When the soil is too alkaline, the carboxyl group of the acidic functional group of threonine will react with hydroxide to reduce the soil alkalinity, alleviate the impact of environmental changes on the soil, and provide a good environment for root growth. In addition, amino acids can also promote the formation of soil aggregates, which is helpful to improve soil water and fertilizer conservation capacity. So as to provide good conditions for the growth and development of plant roots.