VOL. 12 (1953) 



GROWTH OF Chlorella 



37 



It also follows from Eq. (15) that the light intensity at which i — A becomes a half of 



1— A^ is 



a value which is equal to the half-saturating light intensities for 



growth rate (Eq. 13). This deduction is also corroborated by our experiment. 



It should be remarked that all the ^-values used in the above theory are those referred to the 

 natural logarithms (see Eq. 5), whereas in our experiments they have been expressed in terms of 

 Brigg sian logarithms. However, the equations (6) to (16) may all be applied as such to our ex- 

 perimental values. 



By applying the experimental values of ky (0.40 at 7°, 0.86 at 15°, and 1.79 at 25°) 

 and a(o.45) to Eq. (8), the value of k-Q was estimated to be 0.12 at 7°, 1.32 at 15° and 5.38 

 at 25° C. Fig. 12 shows to what extent the value of k^ calculated by Eq. (8) with these 



/O 12 14 16 18 20 22 

 LIGHT INTENSITY IN KILOLUX 



24 26 



50 



Fig. 12. Comparison of the calculated and observed values of relative growth rate {kg) at different 



temperatures and under different light intensities. 



values of kp, kj^ and a coincides with the experimental data.* By applying the same 

 values of kp, kjy and a in Eqs. (10), (13) and (16), the values of Uq, fx^, jUg and A^ were 

 calculated and they are compared with observed values in Table III. 



As may be seen, the agreement between calculated and observed values is fairly good for kQ, 

 but not quite satisfactory for ^Up, /ig and A^. The discrepancy regarding the ^w-values is attributable to 

 the fact that both Eqs. (6) and (7) are simplified to fit only with cases of sufficiently high or sufficiently 

 low light intensities. As to the discrepancy concerning A^, it is probabty due to the situation we have 

 mentioned in the footnote on page 35. 



TABLE III 



CALCULATED AND OBSERVED VALUES OF AQ' /'p- ,"g -^^'^ Zlg 



Temperature (C) 



H (in lux) 



/ig (m lux) 



obs. 



cal. 



obs. 



cal. 



obs. 



cal. 



obs. 



cal. 



25° 

 15° 



7' 



1. 19 

 0.49 

 0.09 



1-34 

 0.52 

 0.09 



2400 



1200 



500 



3980 



1910 



890 



1600 

 600 

 no 



2980 



1 160 



200 



0.66 



0.55 

 0.38 



0.7.5 

 0.61 

 0.23 



* The phenomenon of growth retardation at very high light intensities, which was especially 

 notable at lower temperatures, was not taken into consideration in our theory. 



References p. 40. 



