MORPHOGENESIS OF POTATO PLANTS IN-VITRO .2. ENDOGENOUS LEVELS, DISTRIBUTION, AND METABOLISM OF IAA AND CYTOKININS

The levels of endogenous IAA and cytokinins (zeatin, zeatin riboside, isopentenyladenine, and isopentenyladenosine) were determined in potat o plants cultured in vitro under red light (R) and blue light (B) on m edium with or without hormones. On medium without hormones in B, plant s contained much higher cytokinin levels, particularly in leaves and r oots, and also slightly elevated IAA levels. Kinetin in the medium in B changed the distribution of cytokinins and significantly increased I AA level in roots. In R, the presence of kinetin led to an increased c ytokinin level in the whole plant, while the IAA level was slightly lo wer. IAA in the medium in B decreased cytokinin level in all plant par ts, while the IAA level did not change significantly. In R, the presen ce of IAA in the medium led to a moderate increase of CK level and to a significant increase in IAA level, especially in roots. Uptake of 1- C-14-IAA and of H-3-zeatin was generally higher in B than in R. Higher percentage of IAA taken up in B was converted to conjugates in the ro ots. Metabolism of H-3-zeatin was similar in R and B with only slight differences in metabolite amounts. Thus, in all experimental situation s in which tuber formation was stimulated, IAA level in roots and stol ons rose significantly, stressing the importance of an IAA gradient fo r tuber formation.