Peptidase Activity in the Avena Coleoptile Phytohormone Test Object

Avena seedlings were grown in darkness at 25⚬ C. on moist filter paper in preparation dishes. When the coleoptiles were 1.5, 4, 10, 17, and 36 mm. in length, they were uniformly sectioned at 125 or 250 μ on a rotary microtome. Peptidase determinations were made on these segments, and their reduced weights were obtained by use of the gradient tube. Cell counts were made for successive 125-μ segments of coleoptiles 4 and 10 mm. in length. On a per segment basis, peptidase activity, reduced weight, and cell number were found to decrease in progressively older coleoptiles. 2. For any given coleoptile 4 mm. or more in length, enzyme activity per unit weight of tissue, or per cell, was consistently greater at the tip. Correlations between morphological structure and auxin and peptidase gradients in the coleoptile are pointed out.