970 



THE LIGHT FACTOR. I. INTENSITY 



CHAP. 28 



400 



800 1200 600 



LIGHT INTENSITY, foot candles 



2000 



Fig. 28.1. Light curve.s of photosynthesis in whole young wheat plants at 

 19° C. (after Hoover, Johnston and Brackett, 1933). Parameters: Vol. % COi; 

 one foot candle equals about 10 lux. 



8 X 10^ 



INCIDENT INTENSITY, erg/cm'^ sec. 



' Fig. 28.2. Light curves of strawberry leaves (after Wassink 1946). 

 Leaf disks floating on water in equilibrium with air containing 9% COj, at 

 17"'and 25°. Broken line: same, in Warburg buffer No, 9, at 25 °. 



