COMPENSATION POINT 



983 



Table 28. Ill (continued) 



" Values remarkably high for shade plants. '' The high values of h are caused by the 

 respiration of the (photosynthetically inactive) fungus. 



while light absorption, in an optically dense system, increases more slowly 

 than proportionally with the concentration (Beer's law). Therefore, if we 

 compare a dense suspension with a thin suspension of identical cells, we can 

 expect to find the compensation point of the second one at a lower light 

 intensity. AVhen, on the other hand, a decrease in optical density is 

 brought about by a decline in the concentration of chlorophyll within the 

 cells (without a change in the number of the cells per unit volume), the 

 compensation point will be shifted in the opposite direction (i. e., toward 

 higher intensities), because in this case the decline in the total yield of 

 photosynthesis will not be compensated by an even stronger decline in total 

 respiration. 



The respiration of chlorophyll-deficient cells is either the same as that of normal 

 green cells (cf. Noddack and Kopp) or even stronger (chlorotic Chlorella cells grown by 

 Emerson and Lewis; most sun-adapted, light-green leaves). Three examples of the 

 latter behavior will be found in Tables 28.111 and 28.IV (p. 989). 



