Micropropagation of potato: Evaluation of closed, diffusive and forced ventilation on growth and tuberization

Abstract

Different types of ventilation of the culture vessel headspace, each with and without the ethylene inhibitor AgNO3 (3.0 μM) or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) (2.0 μM) in the culture medium, were investigated in terms of their effects on the growth of potato cuttings (Solanum tuberosum L. 'cara'). Concentrations of CO2, O2 and ethylene in the culture vessel headspaces were monitored during the study. Growth was substantially enhanced and vitrification (stunting and epinasty of leaves and hooking of stem apices) was reduced by increasing the efficiency of ventilation, the effects being greatest with forced ventilation. In the conventional diffusive treatment (via a polypropylene membrane), leaf epinasty occurred but the leaves were not stunted unless ACC had been added. AgNO3 prevented vitrification in the latter case and reduced it in the sealed treatment. On the other hand, with all forced ventilation treatments, even with the addition of ACC, the plantlets grew well and some of the growth parameters exceeded those in the diffusive + AgNO3 treatment. Ethylene removal was clearly an important factor contributing to the better growth found with diffusive and especially with the forced ventilation treatment; with the latter, ethylene concentrations in the culture vessels were virtually zero. In addition, enhanced CO2 supply probably contributed to the better performance under forced ventilation compared to diffusive ventilation. Callus developed on the stem bases in all sealed (airtight) and diffusive treatments except where AgNO3 was used. No callus was observed in any treatment where forced ventilation was applied and in vitro tuberization (tuber size) was considerably improved by this treatment. © 2000 Annals of Botany Company.