1242 THE TEMPERATURE FACTOR CHAP. 31 



experiments at 5° C. (c/. Emerson and Arnold 1932') showed that at this 

 temperature dark intervals required for "flash saturation" are longer — of 

 the order of 0.08 second. This difference corresponds to a Qio of about 2, 

 or an activation energy of about 12 kcal, in agreement with the steady light 

 results of Noddack and Kopp and many others, listed in Table 31. IV. 

 This supports the view that in Chlorella, at least, the same "finishing" 

 dark reaction that limits the maximum yield per flash also limits the rate 

 in strong continuous light. 



3. Temperature Curves in the Carbon Dioxide-Limited State 



No systematic measurements of the temperature dependence of photo- 

 synthesis in the "carbon dioxide-limited" state {i. e., in strong light and 

 with a reduced concentration of carbon dioxide) are available in the litera- 

 ture. The case nearest to this limiting one, which was much studied, was 

 that of free atmosphere (0.03% CO2). In this case, the carbon dioxide con- 

 centration, although not strictly "limiting," exercises a strong influence on 

 the rate, and the effect of heating may be largely due to the accelerated 

 supply of carbon dioxide. It was mentioned on page 1232 that Prjanishni- 

 kov (1876), Kreusler (1887, 1888, 1890) and Lubimenko (1906) found, for 

 photosynthesis in the open air, Qw values between 1 and 1.5. Similar or 

 smafler values were found by Stalfelt for mosses and Uchens (Table 31.V). 



Table 31.V 



Qio Values for the Photosynthesis of Mosses and Lichens 

 (after Stalfelt 1937, 1939) (0.03% CO2) 



Species 0-10" 10-20° 20-30° C. 



MOSSES 



Hylocomium proliferuni 1.56 1.13 0.74 



Hylocomium triquetrum 1 . 43 1 . 00 . 60 



Hylocomium squarrosum — 1.13 . 65 



Hylocomium parietinum 1 .52 1 . 13 0.60 



Ptilium crista castrensis 1 . 43 1.15 . 69 



Sphagnum Girgensohrii 2 . 67 (5-15 ° ) 1 . 35 . 66 



LICHENS 



Usnea dasypoga 2.65 0.97 . 43 



Cladonia silveslris 2.42 1 .04 0.63 



Ramalina fraxinea 1 . 55 1.15 . 62 



Ramalina farinacea 1 . 95 1 . 03 . 68 



Umbilicaria pustulata 1 . 40 . 86 . 48 



Evernia prunastri 2 . 07 1.14 . 75 



Cetraria islandica 1 .08 0.81 0.46 



Peltigera aphtosa 1.06 1.14 0.73 



Cetraria glauca 1.0 0. 84 0. 62 



