Effects of Indoleacetic Acid and Kinetin on Scopoletin-Scopolin Levels in Relation to Growth of Tobacco Tissues in Vitro

Abstract

Changes in growth (weight increase) and in the levels of scopoletin and its glucoside, scopolin, have been determined in pith and callus tissues of tobacco (Nicotiana tabacum, var. Wisconsin no, 38) grown in vitro over periods up to 24 days and supplied with various concentrations of indoleacetic acid (IAA) and kinetin. The amounts of scopoletin released to the medium under these conditions have been determined also and the effect of temperature on these levels have been observed. It is concluded that the formation of scopolin by the tissues is dependent on a supply of kinetin and that a steady state equilibrium exists between this glucoside and its aglycone which is regulated by the relative auxin-kinetin supplies. In healthy tissue the scopolin: scopoletin ratio is high. Values of ca. 13:1 were observed. Under favorable growth conditions scopolin is converted to a nonfluorescent material presumed to be utilized in the growth process. High IAA levels or injury bring about its degradation to scopoletin. Kinetin favors the retention of high glucoside levels even in the presence of high, nontoxic supplies of IAA. Death or abnormal cell function result in release of scopoletin to the medium. The data are discussed in relation to earlier findings.