Effect of Infra-red Rays on Chromosome Breakage in Tradescantia

Abstract

1. A three hour infra-red treatment before or (to a lesser extent) after X-raying increases the observable chromosome breaks and reunions in pollen grains of Tradescantia bracteata (Figs. 1 and 2).
2. Interpolating a heat shock between the X-rays and infra-red treat-ments does not remove, but on the contrary further enhances, the action of the infra-red rays. Thus the combined effect of heat shock and infra-red is additive.
3. The data show that one of the actions of infra-red rays and of heat shock is to favour reunion, no doubt at the expense of restitution, thus increasing apparent breakage.
4. Spectrometrically it was shown that only one per cent of the infrared rays reach the anthers through the surrounding tissues. Moreover the inside body temperature of the bud does not show any appreciable increase over its surroundings. Thus an infra-red action must be due not to a rise of temperature but to a more direct physico-chemical action.