Light Induced Absorption Changes in Photosynthetic Organisms. II. A Split-beam Difference Spectrophotometer.

Abstract

An apparatus is described, designed to register the small changes of absorption which are induced by light in photosynthetic organisms. A split-beam arrangement allows the simultaneous observation of fast reversible absorption changes, caused by flashing actinic illumination, and of slow shifts of background absorption. A few examples of its application are discussed. One of these concerns the observation of an antagonistic effect between red and far-red light on Anacystis. It concerns the build up and break down of a pigment, normally absorbing at 700 m[mu], present in low concentration, and tentatively identified as the end point of energy transfer in photosynthesis.