Effect of Indolebutyric Acid on Distribution of 14C-Photosynthate in Softwood Cuttings of ‘Marianna 2624’ Plum1

Abstract

Abstract Treating the bases of ‘Marianna 2624’ plum cuttings with indolebutyric acid (IBA) enhanced rooting and affected the distribution of labeled assimilate. IBA, however, did not significantly affect the uptake of 14CO2 by a single leaf or the proportion of fixed radioactivity that was translocated in 20 hours. Approximately 60% of the translocated 14C remained in the stem portion immediately below the treated leaf, whereas less than 5% reached the basal end. The rest of the activity was recovered in the upper stem. This distribution pattern was present in both control and IBA-treated cuttings, and remained essentially unchanged until callus appeared at the base of the latter group. The base of treated cuttings then began to accumulate an increasingly larger share of translocated 14C. This value eventually reached 6 times that found in unrooted controls. Throughout the study, 87-95% of the radioactivity in the base of either type of cutting was in an ethanol-soluble neutral fraction which contained sucrose, glucose, fructose, and sorbitol. Treatment with IBA increased starch loss in the base of the cutting, while the sugar content rose similarly in both types of cuttings. The time of increased mobilization of photosynthate to the base may be influenced more by the extent of local carbohydrates reserves than by a particular stage of rooting.