In contrast to earlier reported results of similar experiments in peas, in which almost no increase in protease activity occurred in incubated detached cotyledons, we report here an increase in protease activity in both attached and detached bean cotyledons. Detached bean cotyledons showed continually increasing protease activity up to the 12th day, while that in attached cotyledons declined after 6 days. The Rapid liberation of low molecular weight nitrogenous compounds at the expense of stored proteins at the early stage of bean germination was reported by Pusztai and Duncan (7). They also reported in that paper a time course of protease activity which reached maximum on the 8th day of germination. Seeschaaf and Pirson (8) reported that in half cotyledons of blue lupine, protein breakdown proceeded, and the amounts of protease and several other enzymes, including 6-phosphogluconic acid dehydrogenase, increased during incubation of detached cotyledons more than those in attached cotyledons did during germination. They found that the increase occurred only in the absence of the buds; removal of roots or hypocotyl had no effect. Addition of IAA to incubated cotyledons inhibited the increase of 6-phosphogluconic acid dehydrogenase activity. They concluded that auxin from the bud controls enzyme levels in the cotyledons. However, there are no data to show whether auxin has a similar effect on digestive enzymes. a-Amylase activity was also reported to increase dur1Brooklyn Botanic Garden Contribution No. 203. This work was supported by Grant GB 32196 from the National Science Foundation.ing both germination and incubation of axis-free half cotyledons of beans by Dale (1) and by Gepstain and Ilan (2). Dale suggested that gibbereilin is involved in a-amylase formation, while Gepstain and Ilan observed an enhancing effect of kinetin. Yomo has reported that formation of a-amylase in detached bean cotyledons was inhibited by ABA during incubation (10). Yomo and Varner (11) found that in detached cotyledons (a) a-amylase activity was also inhibited by ABA, and (b) protein breakdown and protease formation were very slight compared with attached cotyledons. We report here on the protein breakdown and the formation of protease in comparison with that of a-amylase, during incubation of excised bean cotyledons, in relation to effects of cycloheximide and ABA. MATERIALS AND METHODSGeneral Procedure. Bean (Phaseolus vulgaris L. cv. Kentucky Wonder) seeds were sterilized in 1 % aqueous NaOCl (Allied Chemical) solution for 10 min and imbibed at 22 C for 16 hr. Imbibed seeds were germinated on moist vermiculite in the dark. Cotyledons from germinated seedlings are referred to as attached cotyledons. For incubation experiments, the imbibed seeds were cut transversely in half and the axisfree half cotyledons (detached cotyledons) were sterilized for 1 min in 0.2% NaOCl solution which had been neutralized with 2 N HCI just before use. They were then put in a 125-ml Erlenmeyer flask containing 10 ml of 2% agar solution whic...