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

' Received Sept. 27, 1962. ing 125 mm being miiade up with either argon or ethylene. The followiing gas mixtures were used: air, 10 % 02 + 90% A, 7.5% O., + 92.5 % A, 5% 02 + 95% A. In other experimlenits the partial pressure of ethylene in the jars was varied from 0 to 253 nim Hg, while the O. level was maintained at 5 % and total pressure adjusted to 760 mim with argon. For comparative purposes. the effects of gibberellin A, (GA;<) on abscission in air and in 5 % O2 was investigate(l. Following the technique described by Carns et al. (5), GA) in agar was applied distally to the petiole (cut surface) at 20 ig/petiole. Abscission was miieasured bv examinationi of the total numbers both of explanits and petioles whiclh had undergone abscission. Sample size was five explants (10 petioles) and the numiiber of replicates varied from two to six. The results are expressed