Selective Scattering of Light by 

 Pigment-Containing Plant Cells* 



PAUL LATIMER and EUGENE L RABIXOWITCH, Photosynthesis Re- 

 search Project, Department of Botany, University of Illinois, Urbana, Illinois 



We have observed a strong spectral selectivity in the scattering of 

 light by pigmented algal cells. Sharp maxima in the scattering occur on 

 the long- wavelength side of absorption bands (c/. Figs. 2, 3, 4). 



The experimental apparatus is shown diagrammatically in Fig. L 

 The cell suspensions were illuminated with light from a Bausch and 

 Lomb grating monochromator (3.3-m/i band half-width). The in- 

 tensity of light scattered at approximately 90° (more precisely, 

 75° to 105°) to the incident beam, 7^, was measured with a photo- 

 multiplier tube and was compared with that of the incident light, 

 /o, by replacing the cell suspension with a white (MgO) surface. The 

 scattered light collected by the measuring device was of the order of 

 0.1% of the incident light. In the range of cell concentrations used 

 (corresponding to optical densities of ~0.01 to 0.05 per 1-cm. path in 

 the maxima of the absorption bands), the amount of scattering per 

 cell did not vary with cell concentration. 



A correction was made for attenuation of the incident and scat- 

 tered beams in the suspension by cells other than the primary scatter- 

 ing cell itself. This was accomplished by attenuating the incident 

 light in the measurement of /o by means of a cell suspension of prop- 

 erly adjusted optical density which was placed immediately before the 

 MgO surface. No correction was made, however, for absorption 

 within the scattering cell itself, since this would require a detailed 

 knowledge of the structure and optical properties of the cell. The 

 asymmetry of the scattering curves in relation to the absorption 

 curves clearly shows, however, that the presence of scattering maxima 



* This work was carried out under a grant fiom the Office of Naval Research 

 with some assistance from tlie National Science Foundation Grant 1398 (Dr. 

 Emerson). The paper is based on a dissertation submitted by Paul Latimer in 

 partial fulfillment of the requirements for the degree of Doctor of Philosophy in 

 the Graduate College of the University of Illinois, 1956. 



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