REGENERATION OF ROOTS FROM APPLE STEM SEGMENTS IN VITRO: EFFECT OF ORIENTATION ON THE MEDIUM

One-mm stem segments excised from apple microcuttings regenerated adventitious roots when they were cultured on medium with auxin.
With the apical cut surface down on the medium, the segments produced more roots than with the basal side down.
When the orientation of the segments was reversed at the time when the meristemoids had been formed (the segments were turned after five days from an apical to a basal orientation or the other way around), rooting was reduced in both cases.
This indicates a general inhibition by the basal orientation.
Experiments in which the uptake of labelled indoleacetic acid and rooting performance at a range of auxin concentrations were determined, showed that the differences in rooting performance were not caused by differential auxin accumulation.
Since the roots are formed from cells close to the basal cut surface, another possible explanation for the poor rooting of basally orientated segments is that the tissue that produced the roots was under partial anaerobiosis.
Evidence is presented that anaerobiosis indeed played a major role and that it was alleviated by gas exchange via the epidermis of the stem when long segments were used (3 mm long) that emerged from the medium for a few mm.

XXV International Horticultural Congress, Part 10: Application of Biotechnology and Molecular Biology and Breeding – In Vitro Culture.

H. Guan, G. Klerk

Adventitious root formation, Anaerobiosis, Auxin uptake, Cuttings, Malus, Micropropagation, Regeneration, Tissue culture

https://doi.org/10.17660/ActaHortic.2000.520.18