The Influence of Low Substrate Sodium Levels upon the Free Amino Acid Content of Cotton Leaves

The sodium nutrition of cotton (Gossypium hirsutum L.) was investigated. Plants were grown in purified nutrient solutions within a chamber designed to minimize sodium contamination. Three nutrient solutions were employed that contained in microequivalents/liter: (a) 0.17 Na, (b) 43.5 Na and (c) 0.75 Cs, 14.41 Li, and 1.17 Rb. All solutions had adequate potassium. Total free amino acids were increased by sodium. Leaves from plants grown in the high sodium solution contained significantly more free asparagine, arginine, and methionine than leaves from plants of the other treatments. The other alkali metals had little or no effect on concentrations of the free amino acids. An unknown was tentatively identified as argininosuccinic acid.