L.N.M. Duysens 



rlydi"o^»n or fle^trori 

 transport, in phptosynthetis 



^M ""I* 



Pig. 1. Scheme for photosynthesis. The direction of hy- 

 drogen or electron transport of oxygen evolving photo syn- 

 thetic organisms is indicated by the direction of the ar- 

 rows. The redox substances surrounded by a rectangle may 

 be partly bypassed. The two light reactions are represen- 

 ted by the large open arrows. Action spectra of the two 

 pigment systems driving these reactions are shown for two 

 algal species. A more detailed description is given in 

 the text. 



fective in excitixxg system 2. In Chlorella , chlorophyll b is more 

 active in system 2. Both systems contain about equal amounts of 

 chlorophyll a, but a form of chlorophyll a with absorption at 

 lunger wavelengths is preponderant in system 1. Wavelengths 

 shorter than 680 m^x^ are more effective for system 2 than for 

 system 1 in Chlorella . The relative amounts and activities of 

 the various pigments being present in the two systems is not 

 only different for different species, but also for different 

 cultures of the same species. 



