CYANOGENETIC SUBSTANCES 1 87 



HCN occurred. Ermakov (1960) likewise noted that linamarin content 

 of flax was higher under controlled conditions of lower soil moisture, 

 low temperature, after mechanical injury, and in young growing 

 organs, so apparently in this species cyanogen content is quite sensi- 

 tive to environmental factors. 



It is evident from these data that both genetic and ecological 

 factors affect the production of the cyanogenetic compound. It would 

 be interesting to know whether the enzyme concentration was affected 

 similarly. The marked influence of ecological factors upon the occur- 

 rence of a biochemical component, while it may be exceptional in this 

 instance, needs to be taken into account in the studies of physiological 

 races either in population studies or classical genetic studies. In con- 

 trast to the situation in Lotus corniculatus, separate reports by 

 Williams (1939) and Atwood and Sullivan (1943) indicate that Tri- 

 folium repens produces similar quantities of cyanogen under differing 

 conditions. These authors, studying the inheritance of cyanogen 

 production, observed plants over a period of several years and re- 

 ported that individual plants always tested about the same for 

 cyanogen. 



With rare exceptions, cyanogenetic glucosides are accom- 

 panied by enzymes which catalyze their hydrolysis with liberation of 

 HCN and sugar. A complex of enzymes is involved in the breakdown 

 of amygdalin, but the system of enzymes is called emulsin. 

 According to Robinson (1930) the emulsin system will liberate HCN 

 from sambunigrin, dhurrin, vicianin, prunasin, and prulaurasin but 

 not linamarin. Since, in all but the last-named, the linkage is quite 

 similar, this fact is not surprising. However, reports that linase will 

 liberate HCN from amygdalin are surprising and perhaps should be 

 treated with some conservatism. Certain plants which do not them- 

 selves form cyanogenetic substances contain enzymes which break 

 down amygdalin (Robinson, 1930). 



Gibbs (1954) and Hegnauer (1958, 1959b) have reviewed the 

 distribution of cyanogenetic compounds from a taxonomic viewpoint. 

 Hegnauer investigated over 400 species and reported a number as 

 cyanogenetic. Included were first records of the conifers Taxus 

 cuspidata and T. media. It is unnecessary to reproduce their data in 

 detail, for no clear-cut systematic implications are evident. The most 

 interesting data are those in which subfamilies rich in cyanogenetic 

 species are compared. For example: 



Rosaceae: Cyanogenesis is pronounced in the Pomoideae 



and Prunoideae, less frequent in the Rosoideae 

 and Spiraeoideae. 



