Anatomical Studies on Initiation and Development of Roots in Wild Peach Stem Cuttings

Abstract

Anatomical studies were made on root initiation process of the cuttings of a wild peach which is native of Shimoina district, Nagano Prefecture and known to be resistant to root-knot nematode, for the purpose of obtaining fundamental informations on mass production of peach rootstocks. Histochemical observation onthe activity of succinic dehydrogenase was also conducted.
No root primordia were present in stem tissues at the time cutting was made. Rooting was stimulated by the treatment with 25ppm indole butyric acid (IBA) in both of softwood cutting under mist and hardwood cutting with bottom hert (aver. temp.;20.4°C). When IBA-treated, root initials arose in secondary phloem parenchyma cells external to the cambium 5 days after planting on both of softwood and hardwood cuttings, and each of them developed into an organized group of cells, namely a root primordium 10-14 days and 7-11 days after planting on the former and the latter, respectively.
Root primordia before protrusion showed a highest succinic dehydrogenase activity in apical meristem and procambial strands. Subsequently, vascular connections developed between young roots and stem vascular systems. Young rootselongated at a right angle to the main axis of stem on softwood cuttings, while perpendicularly on hardwood ones. No root primordia were recognized in IBA-untreated cuttings.
The first protrusion of root was observed 17 days after planting on softwood cuttings and 13 days after on hardwood ones. Protrusion of root on softwood cuttings was recognized not only at the cut surface of the basal stem end but also at the part just above it. Hardwood cuttings formed callus vigorously at the basal stem end and rooted exclusively at the cut surface. Differences in the continuity of sclerenchyma between softwood and hardwood cuttings proved not to be related to their different rooting potentials.