Changes in auxin activity in tumourous and normal tobacco calluses treated with morphactin IT 3233
The addition of morphactin IT 3233 in 1-40 mg/dm<sup>3</sup> concentrations to the medium inhibited the growth <i>in vitro</i> of normal and tumourous tobacco calluses. The auxin activity (estimated by the <i>Avena</i> coleoptile straight growth test) of the acid ether extracts from these tissues increased. The activity of zone I (R<sub>f</sub> 0.2-0.4, 0.5, solvent system: butanol:water:ammonia 10:10:1) in normal tissues increased more intensively than that of zone II (Rf 0.6-0.8, 0.9). In tumourous tissues, however, these changes were smaller and they concerned merely zone I of auxin activity (R<sub>f</sub> 0.0-0.5). It seems that the mechanism of morphactin activity in both kinds of tissue is different. It may be supposed that the excessive accumulation of auxins induces growth inhibition of tissues. A previously found increase in the activity of IAA-oxidase influenced by morphactin might be considered as an adaptation to a higher level of IAA.