How do free amino acids work against stress?

 

Energy savings of the nitrogen metabolic route

Plants synthesize their own amino acids out of inorganic nitrogen, thus producing glutamic acid. The plants synthesize all other amino acids out of that amino acid.  Since this process requires elevated amounts of energy, giving plants free amino acids in these moments of stress provides them with enough energy for other physiologic processes. Amino acids are molecules which are easily absorbed through leaves and roots and may be immediately used by the plants.

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Osmoregulation

The free amino acids that accumulate inside the cells when in a stressful situation are created out of the synthesis of their precursors or out of the catabolism of the proteins.  These have a high cellular osmotic regulation capability that increases resistance of cells against adverse factors. 

Regulation of stomatal aperture and photosynthetic capacity

The closure of the stomas caused by adverse situations decreases the photosynthetic activity, slowing down all metabolic processes. The application of free amino acids to plants under stress favors the opening of the aperture of the stomas. This allows increased water retention in their tissues, thus increasing photosynthesis and delaying wilting.

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Antioxidant action

Plants under stress situations react by accumulating oxidative compounds that cause cell damage. To counter these effects, plants use nitrogen compounds that act as natural anti oxidants: amino acids, amines, polyamines, etc. 

Amino acids that have noted antioxidant capacity are arginine, histidine, cisteine, tryptophan, lysine, methionine and threonine. Furthermore, it has been proved that the application of free amino acids causes an increase in the level of antioxidant compounds. 

 

Promotion of hormone regulation

It has been observed that amino acids play a role in the regulation of hormone levels in plants. Certain external factors cause hormone imbalance in plants, and amino acids have the ability to form hormones and balance hormone levels in plants.