467 



S. S. Brody and M. Brody 



OCHROMONAS DANICA 

 10 DAYS 



N, TEMP. 



ROOM TEMP. 



550 600 650 



WAVELENGTH, m/, 



<50 500 550 600 650 700 750 



WAVELENGTH, m/i 



Fig. 10 Fluorescence spectra excited Fig. 11 Fluorescence spectra 

 at 436 m|ji. excited at 436 m|j.. 



monomer and aggregate bands characteristic of chlorophyll a^ Chlorella 

 exhibits a third band (or rather a shoulder) at 700 mfji. This may correspond 

 to the aggregate band of chlorophyll b^ or to the new band, described below 

 in Section III - E. As the cells age, and the monomer and aggregate bands of 

 chlorophyll a increase in size, this shoulder is obliterated. 



It may be recalled that these " Chlorella - type" cells, when excited with 

 various wavelengths of light at room temperature, yield essentially 

 unchanged fluorescence spectra. Remembering also that the shapes of the 

 emission spectra in Euglena do depend upon the wavelength of excitation, one 

 might suspect that in " Euglena - type" organisms much more of the aggregate 

 form is present. To investigate this possibility the following procedure 

 was utilized. Etiolated cells were cultured in the dark on organic media for 

 3 days and then placed in light for specified periods of time. 



This was done in order to obtain large quantities of pale-green cells. 

 (Incidently, Euglena may be considered an extreme "sun" plant because of its 

 low proportion of chlorophyll b to a. ) In Figs. 13, 14 and 15 may be seen 

 fluorescence spectra of 1, 2 and 3 day old Euglena, respectively. 



The total fluorescence from chlorophyll at room temperature is quite low 

 in young cells, however, it can be seen that with ageing fluorescence 

 intensity does increase. (In these experiment^ emiission from chlorophyll 

 at room temperature was too small to measure in 24 hour cells.) Measure- 

 ments made at room temperature also indicate a shift in monomer and aggre- 

 gate maxima from 685 to 690 m|jL, and 715 to 720 mfi, respectively. Although 



