The physiological basis of seed dormancy in Avena fatua VI. Respiration and the stimulation of germination by ethanol

Ethanol induced germination in several partly after-ripened dormant lines of Avena fatua L. The dose-response curves for the stimulation of germination and for oxygen uptake were similar, indicating that ethanol may stimulate germination by promoting oxygen uptake. A time-sequence study showed that ethanol stimulated oxygen uptake by as much as 70% prior to the first visible signs of germination. A similar methanol treatment failed to induce germination or significantly elevate oxygen uptake, indicating that the promotive effects of ethanol are not common to all alcohols. The stimulation of both germination and oxygen uptake by ethanol was not inhibited significantly by salicylhydroxamic acid, an inhibitor of alternative respiration. Thus, stimulation of germination and oxygen uptake by ethanol does not require the operation of the alternative pathway of respiration. Similarly, the stimulation of germination and oxygen uptake by ethanol were not inhibited by sodium azide, an inhibitor of cytochrome-mediated respiration. However, both germination and oxygen uptake were prevented when salicylhydroxamic acid and sodium azide were administered together. Thus, stimulation of these events by ethanol requires only the operation of one or other of these pathways of respiration; a specific requirement for the operation of the alternative pathway of respiration does not exist. The function of ethanol as a promoter of respiration is discussed with reference to dormancy and involvement of the Krebs cycle.