VOL. 12 (1953) 



GROWTH OF Chlorella 



33 



At each temperature, the zl-value decreased with increase of light intensity, and except in the 

 culture at 7°, it tapered off gradually to a certain constant value at higher light intensities. At 7° the 

 zl -value decreased up to 800-2000 lux and then increased in a peculiar manner with further increase 

 of light intensity, which is obviously due to the injurious eiiect of stronger light at that temperature. 

 The minimum value of J attained at higher light intensities was larger at higher temperatures than 

 at lower ones, and, what is worth noticing, the light intensity at which zl attained its minimum value 

 approximately coincided with the light intensity at which the growth rates reached their light- 

 saturated values. To illustrate visually the relative abundance of dark and light cells in the culture 

 under different conditions, the frequency polygons of cell diameter found in some representative 

 cases are presented in Fig. 10. 



The main quantitative data brought out by the experiments described above arc 

 summarized in Table II. 



1.0 



0.8 



o 



I- 



-J 

 -J 



LU 



o 



S 0.4 



0.2 



!2 IS 20 



LIGHT INTENSITY IN KILOUJX 



24 



28 50 



Fig. 9. Dark cell ratio of cultures 

 at different temperatures and un- 

 der different light intensities. The 

 values given are the means of 

 several readings obtained during 

 the culture. The curve for 7°-cul- 

 ture bent in a peculiar manner at 

 higher light intensities, which is 

 obviously due to the injurious effect 

 of strong light at that temperature. 

 If there were no such effect, the 

 curve might have followed the 

 course as represented by the dashed 

 line. 



Fig. 10. Size distribution of cells 

 grown under limiting and saturating 

 lights at different temperatures. The 

 polygons represent the mean values 

 of several distribution data ob- 

 tained during the steady states of 



growth. 



References p. 40. 



WEAK LIGHT 



SATURATING LIGHT 



15° 



400 Lux 

 A = 0.90 



m^ 



400 Lux 

 A=0.15 



l"i' 



140LUX 

 A=0.67 



n_ 



25.000 Lux _ 

 /\=0.63 



I- I- -y-m^ 



25.000 Lux 

 A ^0.54 



' r"> 



i=L. 



C,000 Lux 

 a =0.39 



6 18 12 3 

 CELL DIAMETER IN ^. 



% 

 60 



40 



20 



% 



30 



30 

 20 



10 



