A Porphyrin Pigment from Photosensitive Non-chlorophyllous Plant Tissues.

Abstract

An olive-green pigment has been found in low concentrations in several non-chlorophyllous plant organs that respond to red light. The extraction and purification of this pigment from bluegrass seed is described, and absorption and fluorescence spectra are given for the purified pigment. Major absorption maxima occur at 410 and 667.5 m[mu] and minor maxima at 505, 534 and 610 m[mu]. A fluorescence maximum of the pigment in vivo occurs at 665 m[mu]; in the purified pigment this maximum is shifted to 677 m[mu]. Chemical and physical tests performed on the pigment indicate that it is a metal-free porphyrin, similar to or identical with methyl pyropheophorbide a. Several lines of indirect evidence indicate that the pigment may be involved as photoreceptor in the various red-light sensitive processes: (a) Irradiation of lettuce seeds with red-light results in a decrease in extractable pigment with an absorption maximum at 667.5 m[mu]. (b) The light sensitivity of several varieties of lettuce seeds correlates with the quantity of pigment extractable from such seeds. (c) Action spectra for the promotion of germination of lettuce seeds by red light have been determined both by a monochromator device and by an interference filter device. A fairly sharp peak obtained in the region of 650 m[mu] could be attributed to photo-reception by the pigment here described.