VENTILATION IN PLANT-TISSUE CULTURES AND EFFECTS OF POOR AERATION ON ETHYLENE AND CARBON-DIOXIDE ACCUMULATION, OXYGEN DEPLETION AND EXPLANT DEVELOPMENT

A simple technique for comparing and quantifying the ventilation capacity of vessels used for plant tissue culture is described. Ethylene was injected into culture vessels and its rate of loss monitored by gas chromatography. From the resulting exponential decay curves, the time in hours for half the ethylene to be lost (t50) was calculated and used to compare different containers and sealing methods. Cultures of Ficus lyrata Warb. and Gerbera jamesonii Bolus grown for up to 28 d in plastic vessels sufficiently well-sealed to generate t50 values of approx. 16 h, accumulated ethylene and carbon dioxide in association with depleted oxygen. The relationship between carbon dioxide accumulation and oxygen depletion within culture vessels indicated little if any anaerobic respiration. Gerbera explants did not appear to be affected by these gaseous environments. However, in Ficus, leaf expansion was approximately halved, although fresh and dry mass of whole shoots was not decreased. The smaller leaf size is attributed to the action of accumulated ethylene, because when the gas was absorbed with 'Ethysorb' granules or its action inhibited by 2,5-norbornadiene, leaf growth was normal. The removal of carbon dioxide with potassium hydroxide did not enhance the ethylene effect, indicating little if any antagonism of ethylene action by carbon dioxide. Shoots of potato (Solanum tuberosum L. cv. Red Craig's Royal) were shortened in sealed culture vessels, in association with swelling, diageotropism and miniaturization of the leaves. When tuber production was induced by decreasing the photoperiod, increasing the sucrose concentration and including cytokinin in the medium, partial sealing promoted conspicuous hypertrophy of the lenticels. These responses of potato were prevented if the ethylene absorbant mercuric perchlorate was enclosed together with the cultures. © 1991 Annals of Botany Company.