TEMPERATURE EFFECT IN STRONG LIGHT 



1241 



Willstatter and Stoll's hypothesis improbable. It seems as if in their experiments the 

 rate was not free of carbon dioxide supply limitations, despite the high external value of 

 ICO2]. 



The marked difference between the temperature coefficients of green 

 and chlorophyll-deficient leaves, found by Willstatter and Stoll, also offers a 

 problem for interpretation. Perhaps the yellow leaves were incompletely 

 light-saturated under the conditions of the experiment. Emerson (1929), 

 working with chlorotic ChloreUa cells, found that the temperature curves 

 in the region 4-6° C. had the same slope for chlorophyll concentrations 



C vulgaris 



6 harveyana 



0.0034 



0.0035 



O0036 



\/T CK.) 

 Fig. 31.14. Comparison of log P — /(l/T) for Gigartina 

 harveyana, ChloreUa vulgaris, ChloreUa pyrenoidosa and Horvii- 

 dium (after Emerson and Green 1934). 



varying in the ratio of 1 to 6 (c/. fig. 31.13); in the case, apparently, hght 

 intensity was sufficiently high to produce light saturation at all tempera- 

 tures and chlorophyll concentrations. It should be recalled (c/. page 968) 

 that Emerson found no dependence of the saturating light intensity on 

 chlorophyll concentration in ChloreUa, whereas such a difference was noted 

 by Willstatter and Stoll in green and aurea leaves (c/. fig. 32.2). 



Warburg (1919) and Yabusoe (1924) suggested that the rate of photosynthesis is a 

 linear, rather than exponential, function of temperature, and considered this an essen- 

 tial characteristic of this process. (For the respiration of the same algae, they found the 

 normal exponential curve.) As pointed out by Emerson (1929), the number of points 

 determined (only three in Yabusoe's paper) was insufficient to warrant the unusual 

 conclusion. 



Emeison and Arnold (1932*) found that, in flashing light, intervals of 

 about 0.02 second between flashes are necessary at room temperature 

 (25° C.) to obtain the maximum oxj^gen yield per flash — i. e., to let the rate- 

 limiting dark reaction run to completion before the next flash. Similar 



