French bean (Phaseolus vulgaris L. cv. Shravani Ghevada) cuttings, made from stock plants 8–10 days after pretreatment of 10-day-old seedlings with a morphactin formulation, EMD 7301 (10 ppm effective cone, spray application), showed a significant inhibition of adventitious root formation. Rooting was, however, greatly promoted by the pre-planting application of the auxins indoleacetic acid, indolebutyric acid and naphthaleneacetic acid to the base of cuttings resulting in a synergistic effect on regeneration of adventitious roots. When cuttings were made soon after morphactin pretreatment of stock plants auxie-induced rooting of cuttings was inhibited; a time-gap of over a week between spraying and preparation of cuttings was necessary for the synergistic effect.
The beneficial effect of morphactin pretreatment on rooting of cuttings in the presence of auxins cannot be interpreted in terms of differential uptake and distribution of the labelled auxins, IAA-1-14C and IAA-2-14C or the activity of the IAA-oxidizing enzymes. Growth suppression because of morphactin pretreatment resulted in an accumulation of carbohydrates and nitrogenous reserves in shoots. This, coupled with increased synthesis of rooting factors in the pretreated plants, may account for the observed positive interaction between morphactin pretreatment and auxin application.
