The Involvement of Current Photosynthesis in Rooting of Hardwood Cuttings of ‘Delaware’ Vines

Abstract

Distribution of current photosynthates was studied in hardwood cuttings of ‘Delaware’ vines which were exposed to ¹⁴CO₂ at different stages of rooting to clarify the involvement of photosynthesis in rooting. The ¹⁴C activity in the ethanol soluble fraction of the new shoot, upper stem, lower stem and roots were measured 6, 24 and 72 hours after ¹⁴CO₂ feeding.
At the early stage of rooting, nearly all of the fixed ¹⁴C remained in the new shoots, while after root appearance the amount of ¹⁴C translocated from new shoots into roots increased with time after ¹⁴CO₂ feeding. This suggests that the developing roots may become a significant sink for current photosynthates. Separation of ethanolic extracts into sugar, organic acid and amino acid fractions revealed that over 90% of the ¹⁴C in each extract was found in sugars 6 hours after ¹⁴CO₂ feeding, and that the percentage of radioactivity in sugars declined with time in new shoots and roots, but changed little in the upper and lower half of stems. Organic acids in the roots showed a sharp increase in the level of ¹⁴C but there was little increase in amino acids. The increased incorporation of ¹⁴C into organic and amino acids in roots seemed to be involved in the active growth of roots.
The present result that a considerable amount of current photosynthates is supplied to the developing roots confirms our previous assumption that photosynthesis in hardwood cuttings of ‘Delaware’ vines plays an important role in root development during the latter half of the propagation period.