489 



M. B. Allen and J. C. Murchio 



be more readily interpreted, the growth and decay of the signal 

 (in the presence of f errocyanide ) were examined. 



The rate of increase of signal in P-672 on illumination is much 

 lower than that in the intact cell. In whole cells of C. 

 pyrenoidosa ca. 50 millisec. is required for growth of the signal, 

 whereas in P^T2 the rise time is ca. 5 sec. with white light in 

 membranous material and greater than this in dispersed particles. 

 The rate of rise depends on wavelen^h, but is in all cases 

 faster than the rate of reaction of the radical with f errocyanide . 

 The curve for rate of increase of signal as a function of wave- 

 len^h for equal numbers of incident quanta is shown in Figure 6. 

 The peak at 695 m(i clearly indicates that the long wavelength 

 pigment system is responsible for the signal in these particles. 

 The slow rise in the blue is particularly striking. Althou^ 

 the steady state signal level is large in this region of the 

 spectrum, its rate of production is very low. The peak of 

 activity in the green remains a puzzle, since none of the known 

 photosynthetic pigments in green cells absorbs in this region. 

 The reasons for the lack of activity of the short wave length 

 pigment system in a particle that appears from spectroscopic data 

 to be enriched in this system are being explored. 



These investigations have been aided by Contract AT(o4-3)-232 

 with the U. S. Atomic Energy Commission, NTH grant 09558-02, 

 and contract AF 19(6oif )-6636, with the Department of the Air Raroe, 



REFERENCES 



(1) Allen, M.B., Murchio, J.C., Jeffrey, S.W., and Bendix, S.A., 

 Microalgae and Photosynthetic Bacteria (special issue of 

 Plant and Cell Physiol.) 4o7-^12 (I963). 



(2) Allen, M.B. and Murchio, J.C, Biochem. Biophys. Res. Comm. 

 11, 115-119 (1963). 



(3) Murchio, J.C. and Allen, M.B., Photochem. and Photobiol. 1, 

 259-266 (1962). 



{k) Williams, R.C. and Backus, R.C., J. Am. Chem. Soc. 71, i+052 

 (19^9). 



(5) Allen, M.B., Piette, L.R., and Murchio, J.C, Biochem^ Bio- 

 phys. Res. Comm. 4, 271-27^4- (I96I). 



