Protein synthesis and wall extensibility in the Avena coleoptile

The inhibitors cycloheximide and puromycin have been used to examine the relationship between protein synthesis and wall extensibility, as measured with an Instron, in Avena coleoptile segments. Cycloheximide at 4 μg/ml almost totally inhibits both auxin-induced cell elongation and protein synthesis with only a slight lag. Wall extensibility is unaffected by the inhibitor if auxin is absent. If added prior to auxin, cycloheximide prevents auxin-induced wall loosening while if added after auxin it causes a substantial decline in the wall extensibility. With puromycin there is a 2-4 hr lag before growth and wall loosening are inhibited. These results support the conclusions that the proteins needed for wall loosening are unstable, and that continued protein synthesis is necessary to maintain the wall loosening process.