Growth-Modifying & Antimetabolite Effects of Amino Acids on Chrysanthemum.

The question of the significance of free amino acids in soil or other cultural media has received attention in recent years in the fields of plant physiology (1, 3, 7, 13, 14, 15, 16, 17), soil microbiology (4, 5, 11, 16) and soil chemistry (9, 10,12). Although it originally appeared that free amino acids were not to be found in soils, later reports (2, 10) indicated they could be extracted with aqueous and alcoholic solutions and determinations made with chromatographic methods. The quantities of amino acids found were quite variable. Amino acids added to soil were quite rapidly transformed, and usually undetectable in extracts made after 72 to 96 hours of incubation (11, 16). D-Amino acids and L-alloisoleucine appeared more resistant to change than other amino acids studied (16). Reports indicate that amino acids are absorbed by plants (3, 13, 14) and translocated with great speed in both phloem and xylem (8). Inhibitors of respiratory processes as well as low temperatures applied to fibrovascular tissue considerably retard translocation. The potential applications of research with the so-called unnatural (D-) isomers was pointed out (6, 17) in connection with the natural occurrences of Damino acids in antibiotics and parts of microorganisms. More recently, Ikawa, et al. (6) reported the finding of D-phenylalanine, D-allothreonine and D-alloisoleucine3 in peptido-lipids of bacterial origin. The demonstrated effectiveness of amino acids applied to root zones of plants in producing changes in morphology and growth rate (1, 13, 17) suggests a need for further research along these lines. Steinberg (13) found that frenching of tobacco could be simulated by furnishing leucine, isoleucine, or alloisoleucine to tobacco plants growing in sterile cultures. He reported that relatively large amounts of these amino acids were required under non-sterile conditions to produce frenching symptoms. Woltz and Jackson (15, 16, 17) found that symptoms of