ACTION SPECTRA OF CHROMATIC TRANSIENTS AND THE EMERSON EFFECT IN MARINE ALGAE

Abstract

The action spectra for chromatic transients and the Emerson effect ("enhancement") in the photosynthesis of a variety of marine algae are presented. Chromatic transients are the changes in O2 evolution rate recorded on alternating the color of light incident on tissues, even though the intensities are adjusted to give equal steady rates of photosynthesis at both wavelengths. The Emerson effect signifies the more than additive effect of 2 superposed wavelengths so that the far red becomes more effective when shorter wavelengths are given simultaneously. When light of 700 m[mu] is altered or supplemented with other wavelengths, the greatest effects occur at the absorption maxima of the accessory pigments: chlorophyll b and carotenoids in green algae; chlorophyll c and fucoxanthin in brown algae; phycobilins in red and blue-green algae. In the blue end of the spectrum (435 m[mu].) both effects also occur equally well when the chlorophyll a is absorbing.