ULTRAVIOLET-MICROBEAM IRRADIATION OF REGENERATING STENTOR

SYNOPSIS. Regeneration of missing feeding organelles in the ciliate Stentor coeruleus can be delayed by ultraviolet (UV) irradiation. In an attempt to identify the radiation‐sensitive cellular component(s), cells in various stages of regeneration were immobilized, flattened and irradiated with a microbeam of 265 nm UV light. Targets included regions of either the macronucleus or the cytoplasm at varying distances from the ramifying zone of the cortex, which is the region where the new oral organelles are formed. During the early stages of regeneration the macronucleus is more sensitive to UV‐induced regeneration delay than the cytoplasm, but it is not possible to distinguish between direct and indirect effects. Damage to cortical primordia in middle or late stages leading to structural abnormalities appears to result only from direct effects. Copyright © 1969, Wiley Blackwell. All rights reserved