Amino-Acid Composition of Rhizosphere as Affected by Soil Temperature, Fertility and Growth Stage

Analyses were made of the amino acid composition of rhizosphere soil of plants, grown in the greenhouse at two fertility levels and two soil temperatures of 30 and 10 C. An increase in soil fertility led to a large increase in the amounts of amino acids found in the rhizosphere soil. An increase in soil temperature produced irregular results. The quantity of amino acids in the rhizosphere was greatly influenced by the stage of growth. Concentrations of amino acids were highest at third-leaf and heading stage and lowest at the fifth-leaf stage. A parallel between an increase in amino acid from the fifth-leaf to the heading stage and certain plant characteristics during the same growth interval suggests that plant growth, physiology or metabolism may play a prominent role in the amino acid concentration of the rhizosphere.