416 BIOLUMINESCENCE IN GONYAULAX POLYEDRA 



maximum rate of growth was obtained at 500-800 foot-candles. The 

 generation time was 56 hours (0.43 division in 24 hours), and the 

 maximum cell densities were 30,000-50,000 cells per milliliter. 



Photosynthesis of Gonyaulax cell suspensions was measured in arti- 

 ficial sea water (formula of Emerson and Green, 1934, modified to 

 contain one-fourth the normal amount of Ca and Mg) by the direct 

 manometric method. In saturating hght (800 ft-c) at 20° C and non- 

 limiting COo concentration, as provided by 0.0234 M bicarbonate 

 - 0.0016 M carbonate buffer, the rate of photosynthetic oxygen 

 production was as follows (corrected for respiration): 350 mm^ 

 Oa/hr/lO^ cells; 14,800 mm^ Oo/hr/g sohds; 5000 mm^ Os/hr/mg 

 chlorophyll a plus c, estimated by the equations of Richards (1952). 

 Under these conditions, the rate of oxygen production was about 5 

 times that of respiratory oxygen consumption. The temperature opti- 

 mum for photosynthesis in Gonyaulax is about 30° C. 



Gonyaulax has retained the ability to luminesce in culture for 1^4 

 years. Light is emitted on mechanical stimulation as a bright bluish- 

 green flash of short duration. Stimuli repeated at intervals of one 

 minute elicit progressively weaker responses. Since preliminary ob- 

 servation with dark-adapted eyes indicated that luminescence of cell 

 suspensions exposed to light was considerably weaker than those 

 darkened for a few hours, a study was undertaken of the effect of 

 Hght on the luminescence of this organism. The apparatus employed 

 for measuring and recording light emission included a photomultiplier 

 tube (931A) and appropriate ampHfying circuit, with variable 

 sensitivity, coupled to a Speedomax recorder. Insertion of a con- 

 denser in the circuit served to slow down the instrumental response 

 and to provide smooth curves for convenience in planimetric calcula- 

 tions of total light emission.* Aliquot cell suspensions of 3 ml were 

 taken from mature cultures (20,000-40,000 cells per milliliter) grown 

 at 20° C in constant light of 700 ft-c. The aliquots were held in the 

 lighted incubator for 4 hours and then placed in darkness. Measure- 

 ments of light emission by different aliquots were made at intervals 

 during the dark adaptation period. Luminescence, stimulated by pass- 

 ing a stream of air through the cell suspension at a constant rate of 



" This apparatus was designed by Mr. James Snodgrass, Division of 

 Special Developments, Scripps Institution of Oceanography. 



