150 



PHOTOSYNTHESIS 



of normal and yellow varieties of various plants vi^as compared (Plester). 

 These demonstrated that there was no direct proportionality between 

 chlorophyll-content and rate of photosynthesis. Willstatter and Stoll made 

 similar experiments using 5 per cent carbon dioxide and high light inten- 

 sity. The yellow varieties of the plants used by them contained 3 to 15 

 per cent, and even less, of the chlorophyll of the normal varieties. It was 

 found that on the basis of chlorophyll-content the yellow varieties show 

 a much greater photosynthetic activity than the normal ones. The Pc of 

 the former was in some cases almost 20 times that of the latter ranging 

 from 6 to 12 for the normal varieties against 50 to 120 for the yellow 

 varieties. 



TABLE 27 



Photosynthesis of the Green and Yellow Varieties of Elm, 5 Per Cent CO2, 

 About 24,000 Lux. (Willstatter and Stoll.) 



A most striking case of the disproportionality between chlorophyll- 

 content and photosynthetic rate was found by Willstatter and Stoll in the 

 elm. These results are reproduced in Table 27. 



In the case of the elm (Table 27) though there is a great difiference in 

 the chlorophyll-content of the two varieties, the rate of photosynthesis 

 shows but slight differences, and at 15° the one poor in chlorophyll has 

 a higher rate of photosynthesis on the basis of equal surface. 



Experiments of this nature may be of considerable value in analyzing 

 the photosynthetic mechanism. Temperature variations do not afifect the 

 rate of photosynthesis of the yellow varieties as much as of the normal 

 ones. Dififerences in light intensity have apparently a profound effect on 

 the yellow varieties. Undoubtedly it will be essential to gain more knowl- 

 edge of the nature of the internal protoplasmic factor before a clear under- 

 standing can be had of the whole photosynthetic process. The time factor 

 seems to become apparent in the yellow varieties more slowly than in the 

 normal ones. 



Willstatter and Stoll point out that the relatively high photosynthetic 

 rates of yellow varieties cannot be attributed to the carotinoids. The 

 content of the latter pigment in the yellow varieties is in many cases con- 

 siderably less than in the normal varieties. What is the function of the 



