STUDIES ON THE REGULATION OF CELLULASE ACTIVITY AND GROWTH IN EXCISED PEA EPICOTYL SECTIONS

Abstract

Applied indoleacetic acid (10⁻⁴ – 10⁻⁶ M) increased elongation and the amount and specific activity of cellulase in sections detached from the epicotyl of Pisum sativum L. var. Alaska. Actinomycin D (20 μg/ml) inhibited growth and the capacity of sections for synthesizing protein from absorbed ¹⁴C-leucine. At the same time it caused cellulase levels to decrease at a rate which indicated a half-life for the enzyme of less than 24 h. Pea cellulase was most stable in vitro between pH 6 and 7; at or below pH 5 its rate of denaturation was comparable to its turnover rate in vivo. Fractionation of sections yielded wall preparations which contained cellulase at a higher specific activity than particles or supernatant. It is concluded that cellulase is synthesized in excised sections by an auxin-regulated mechanism. It is proposed that the enzyme is transported to the wall where it may promote elongation and eventually become denatured.