736 A. M. Mayer and A. Poljakoff-Mayber 



4 nor 6 hydroxycoumarin. Mason (37) reviews a number of cases in 

 which unsubstituted benzene or naphthalene rings are hydroxylated 

 in animal tissues and Fernley and Evans (14) suggested a mechanism 

 by which bacteria metabolize such compounds. Thus, it seems very pos- 

 sible that in plant tissues also, coumarin can be broken down either 

 by ring opening and subsequent hydroxylation or it can be detoxi- 

 cated by hydroxylation of the coumarin ring. The latter could be due 

 to the action of some hydroxylating enzyme or to some mixed func- 

 tion oxidase [Mason (37)]. Phenolase itself has been shown to hydroxy- 

 late only monophenols but not unsubstituted benzene rings. 



The only evidence available for coumarin breakdown in plants 

 is that provided by Mayer (38) who showed that extracts of lettuce 

 seeds (variety 'Progress') can destroy coumarin but that extracts of 

 seeds pretreated with coumarin were unable to do so. 



During the last eight or nine years numerous references to the 

 physiological action of coumarin have appeared in the literature. 



In animals coumarin has been shown to have a rather general hyp- 

 notic and narcotic effect (13,80), while coumarins and especially 

 furanocoumarins are toxic to fish (74). Little work on specific effects 

 of coumarin on animal metabolism appears to have been reported. 



At the cellular level it has been shown (2) that coumarin causes 

 chromosome breakage in resting and in dividing nuclei of AlUum. 

 Quercioli (64, 65) and Steinegger and Leupi (75) have also shown that 

 coumarin derivatives affect chromosomal behavior during mitosis. 

 This effect results mainly in disorganized spindle formation (c-mitosis). 

 Cornman (11) showed that very high coumarin concentrations inhibit 

 mitosis. Winter (81), on the other hand, claims that low coumarin con- 

 centrations stimulated cambial division in seedlings of Beta vulgaris. 



As regards plant material, most of the references are concerned 

 with the inhibitory action of coumarin in growth and germination. 

 Inhibition of germination by coumarin has been shown by many 

 authors [Nutile (54), Sigmund (73), McLane and Murneek (35), Rous- 

 seau (70)] as well as in our laboratory. The latter work will be dealt 

 with in detail later on. Inhibition of potato sprouting has been re- 

 ported by Moewus and Schader (49). Growth inliibition has also been 

 frequently reported; Audus and Quastel (5) commented on the phyto- 

 static action of coumarin, and Audus (4) showed this inhibition to be 

 reversible on the removal of coumarin. Root growth inhibition has 

 also been often described, for example, by Goodwin and Taves (16), 

 Pollock, Goodwin, and Greene (63), and Moewus (50). Burstrom (9), 

 while studying the inhibitory action of coumarin on the gro^vth of 

 epidermis cells of roots, suggested that it affects cell Avail tensibility. 

 Other inliibitory effects whidi linvc been sliown are abolition of 



