1318 



INDUCTION PHENOMENA 



CHAP. 33 



2 minutes at 20° and 3 minutes at 14°. A somewhat longer induction 

 period was found by Emerson and Green (1934) in the red alga Gigartina 

 harveyana, approximately 15 minutes at low carbon dioxide concentrations, 

 and 20 minutes at higher ones. 



The length of the induction period may be different for different species; but ob- 

 servations of McAlister (section 3) make it more Ukely that induction periods in excess 

 of 5 minutes occur (in higher plants as well as in algae) only after extended periods of 



0.6 - 



0.4 



0.2 



I 0.0 



O 



"g -0.2 



E 



or 



o -0.4 

 o 



-0.6 



_L 



_L. 



282,000 



11,800 



1,740 



282,000 



282,000 



_L 



, mole/1 



2.90 X lO^'' 

 2.90 X 10' 

 2 90 X 10" 

 7 87 X 10" 

 2 05 X 10 



0.3 



■0.5 



0.2 



•0.2 



0.0 0.2 



0.4 0.6 0.8 

 LOG TIME, min. 



1.0 



1.2 



Fig. 33.1. Rate of photosynthesis as a function of time for different light intensities 

 and ICO2] for Cabomba (after Smith 1937). Scale is correct only for cui-ve A; the others 

 are displaced as indicated at right of figure. 



darkness, under conditions that favor the development of "long induction." The ex- 

 periments of Osterhout and Haas with Ulva (1918), of Li Tsi Tung (1929) with higher 

 aquatic plants and of Briggs (1933) with Mnium probably belong to this group. They 

 were carried out after dark periods of one or several hours, and the observed induction 

 periods were of the same order of magnitude. These experiments will be discussed in 

 section 4. 



The first investigation in which the induction phenomena in a higher 

 plant were studied under conditions similar to those used by Warburg and 

 van der Paauw with unicellular algae {i. e., after dark periods of a few 

 minutes) was that of Smith (1937). He used the aquatic plant Cabomba 

 caroliniana. The procedure was indirect, similar to that followed by War- 



