Chemical Regulation of Sexual Processes in Fungi 



JOHN R. RAPER 



IN 1880 Sachs (61) advanced the hypothesis that the differentiation, 

 development, and the proper function of vegetative and sexual organs 

 of plants depend upon the activity of specific chemical substances. 

 Shortly thereafter chemical correlative mechanisms were postulated to 

 explain a number of well-known sexual phenomena in fungi: conjugation 

 between smut spores (13), antheridial production in Saprolegriia (10), 

 hyphal fusions (70), and so on. None of these, however, claimed a more 

 definitive basis than deductive speculation. 



In the seventy years which have elapsed since the publication of 

 Sachs's work numerous authors have contributed to the greater under- 

 standing of the role of chemicals in the regulation of sexual processes 

 in fungi. These contributions fall naturally into two categories dealing 

 respectively with i) the chance effects of various chemical substances 

 upon the sexual process as measured by the quantitative and/or quali- 

 tative effect upon the final product of sexual reproduction, and 2) the 

 effects of specific chemical substances secreted by a plant and playing 

 indispensable roles in the regulation of its own sexual process or of those 

 of another and compatible individual of the same species. The first type 

 of regulation may be considered as a biological accident, whereas the 

 second type of regulation constitutes an integral and necessary part of 

 the mechanism of the plant's vital reproductive process, and the chemical 

 regulators, originating and exerting their physiological role within the 

 plant, may be considered as true hormones. 



The first category will be reviewed briefly here while the second will 

 be given more thorough attention with considerable detail of those all 

 too few cases where the broad outlines of the chemical correlative 

 mechanisms have been elucidated. 



