Effect of Oxygen Tension on the Course of Ethylene- & Gibberellin-Induced Foliar Abscission

As early as 1886, Molisch (6) reported an increase of abscission rate with increasing oxygen tension. This correlation has been confirmed in recent years by Carns et al. (4) for bean explants kept in atmospheres of oxygen content ranging from 0 to 55 %. In a study of the toxicity of elevated oxygen tension on plants, Siegel and Gerschman demonstrated oxygen-induced abscission in Begonia and Euphorbia (8). Furthermore, the effects of N2, CO,, ethylene, and gas mixtures have been examined in relation to constitutional changes, respiration, and hormone levels associated with abscission without yielding a satisfactory exposition of its mechanism (2, 3, 4, 7, 11). The present investigation stems from work on the comparative physiological behavior of plants at subatmiiospheric 09 levels, which suggested that the responses to abscission agents other than oxygen might be altered bv a change in the level of O02 itself.