Influence of Auxins on in vitro Incorporation of Glycine-C14 in Pea Shoot Proteins

Radioactive amino acids have been utilized in the study of protein synthesis in both detached plant tissues and plant mitochondria. When a plant tissue is incubated in the presence of a radioactive amino acid, the radioactivity is rapidly accumulated in the cells (1, 7,,8, 11, 12, 13, 14)'. The accumulation process is dependent on respiration and varies somewhat according to the amino acid and experimental conditions. Stephenson et al. (10) demonstrated that labeled amino acids were incorporated into protein of tobacco leaves. Christiansen and Thimann (2) have found that auxin-induced growth in pea stem sections is accompanied by an increase in protein synthesis. They concluded that synthesis of new protein may be of the utmost importance in auxin-induced growth. However, auxin-induced increases in expansion are not always paralleled by increases in protein (3, 7). Cleland (7) cited a decrease in protein nitrogen in maize mesocotyl section during expansion and this decrease is not affected by auxin. Boroughs and Bonner (1) reported that there was no increase in incorporation of radioactive glycine into protein of Avena coleoptile sections in the presence of 17 ,umoles IAA per liter. This communication reports the observation made during a study of the incorporation of glycine-1-C'4 or -2-C'4 in the protein of pea shoots with or without the influence of 2,4-dichlorophenoxyacetic acid (2,4-D) or indole-3-acetic acid (IAA).