Effect of Leaves on Carbohydrate Content and Movement of 14C-Assimilate in Plum Cuttings1

Abstract

The top leaf of fresh softwood cuttings of ‘Marianna 2624’ plum ( Prunus cerasifera × Prunus munsoniana ) was exposed to 14 CO 2 and the effect of leaf area and indolebutyric acid (IBA) on rooting and distribution of 14 c was assessed. IBA enhanced the rooting of cuttings with 1/2 or 3 leaves, whereas leafless cuttings failed to root regardless of treatment. Most of the 14 C remained in the upper portion of the stem adjacent to the treated leaf; the mid-stem segment acquired about 40% of the activity. Little radioactivity reached the base of fresh cuttings, but upon rooting it accumulated 4 times the percentage of 14 c found in comparable non-rooting bases. In all cuttings the incorporation of 14 C into starch was much greater in the mid-stem than in the base. As much as 75% of the radioactivity in rooted bases was recovered in a residue remaining after ethanol soluble substances and starch were removed. The level of starch declined continually in the base but decreased in the mid-stem only at the end of the study. The concentration of sugars in both segments was relatively constant while that of sorbitol declined markedly and was hardly detectable in rooted bases. The largest loss of carbohydrates occurred in the bases treated with IBA. The similarity in levels and trends of carbohydrate utlization in the bases of cuttings with or without leaves indicated that in this cultivar the stimulatory effect of leaves on rooting is not associated with their being a source of carbohydrates.