40 CHAP. V. PHOTOSYNTHESIS AND INTENSITY OF LIGHT 



V, Activity at 500 lux = 41-0 

 750 ,, = 74*o 

 tz 74 — 4 1 

 7-5-5 

 The data given above show the accuracy with which the 

 coefficient may be determined from experimental results. 

 Another remarkable feature is that the values of the co- 

 efficient obtained from different specimens in the same 

 season are nearly the same. 



The ratio of activities in spring and winter. — The co- 

 efficient for spring-specimens is about 24 • 9 ; that for winter 

 in the majority of specimens is 13-2. Occasionally it may 

 be as low as 10 -8. The ratio of activities in spring and 

 winter may therefore be taken as 24-9 to 13-2, or as 1 -8 : 1. 



Summary 



Photosynthesis is slight under feeble intensity of light. 

 The activity then increases at a uniform rate under increas- 

 ing intensity, the curve being straight with a uniform slope. 

 The turning-point occurs at about 1200 lux, after which the 

 curve tends to become horizontal. 



Photosynthetic activity is found to vary with the seasons. 

 The minimal intensity effective in spring may be as low as 

 100 lux, whereas in winter it is about 500 lux or more. The 

 photosynthetic curve in spring is relatively the more erect. 



The approximate formula for determination of enhanced 

 activity under stronger light is 



A L = A l X J 



A — A; 



The coefficient for light, K = 



and A L = A; -f K (L - T) 



The mean coefficient for spring-specimens is 24-9. In 

 winter-specimens it varies from about 11 to 13. 



The ratio of activities in spring and in winter may be 

 taken as about 1 -8 : 1. 



