FUNCTION OF CAROTENOIDS IN PHANEROGAMS 



to this problem is the recent finding of Bandurski and Galston * •* * that 

 an albino mutant of Zea mais, which contains no carotene but normal 

 amounts of riboflavin, responds phototropically almost as well as the 

 normal strain. For a full and stimulating discussion of this problem 

 the reader is referred to a recent article by Galston. ^ <* ^ 



12 



120 



100 



400 



420 



440 460 



Wavelength (mfj.) 



4-30 



500 



Fig. 16. — Showing the similarity between the absorption spectrum of the caro- 

 tenoids extracted from Avena seedlings and the action spectrum for the 

 phototropic bending of these seedlings {after Johnston, £. S. (1934) 

 Smithsonian Inst. Pub. Misc. Coll. 92, No. II., and Wald, G. (1943) 

 Vitamins & Hormones, i, 208). 



Tauc 2 « has shown that illumination of the epicotyl of Vicia faba 

 produces a potential difference between the illuminated and non- 

 illuminated side. The action spectrum for the photo-electric effect is 

 very similar to the absorption spectrum of ^-carotene and this, together 

 with the fact that the effect is most marked in the regions of carotenoid 

 accumulation inclines Tauc to the view that carotenoids mediate in this 

 response. 



CAROTENOIDS AND REPRODUCTION 



It will be noted in later chapters that there is considerable cir- 

 cumstantial evidence that carotenoids have a part to play in the repro- 

 duction of cryptogams and of various animal species ; this possibility 

 must now be considered in the phanerogams. The whole problem of 

 carotenoids and reproduction has recently been diacussed. ^ » ^ 



