ABSORPTION SPECTRA OF SINGLE CHLOROPLASTS IN LIVING CELLS IN THE REGION FROM 664 mμ TO 704 mμ

The absorption of light in living plant material, either in the form of living leaves or suspensions of algae, is a complicated optical process. The problems involved have been treated in detail by MESTRE (3). It is well known that the position of the red absorptioni band of the living material is displaced toward the red end of the spectrum about 20 mp from that of the red absorption band of pure chlorophyll a. WLODEK (5) has suggested that the displacement may be due to an optical property of the living leaf or that it may be due to unstable compounds formed by the pigments in the photosynthetic process. An attempt has been made by BAAS-BECKING and Ross (2) to eliminate the complicated scattering processes, usually encountered, by photographing the absorption spectrum of a single Euglena, using a microspectrograph. Since they show only a densitometer curve of the spectrogram, and since the resolving power of their experimental arrangement was very low, their results do not give a complete answer to the problem. Furthermore, the Euglena cell does not represent a single chloroplast. This investigation was undertaken for the purpose of determining the absorption spectra of individual chloroplasts, in the region of the red absorption band, with a high resolving power spectrograph, using calibrated plates so that the actual absorption curve in that region could be determined.