420 



PLANT GROWTH SUBSTANCES 



(20) that such phenohc groupings arise by the dehydration of fructose. 

 For example, the 2,3-enol of fructose (I) would yield pyrogallol (II): 



'ho^ 



HO' 



Yl H j 



ri--'ri -" 

 HOjC-H 



C-OH 



3 HjO 



I 

 OH 



The close chemical relationship which may exist between tannins and 

 anthocyanins is well illustrated by the formulas for the tannin, gambir 

 catechin (I), and for cyanidin (II), the aglycone of cherry fruits, cran- 

 berries, and so on. 



OH 



n 



As regards the precursors of anthocyanins, many workers have sub- 

 stantiated the fact that there are more sugars and glycosides in leaves 

 high in anthocyanins, and that high anthocyanin content is found 

 especially in leaves where the transport of carbohydrate has been im- 

 peded by damaged conducting systems. 



In galls such as that caused by the grape phylloxera (to be discussed 

 later), the numbers of chloroplasts are greatly reduced so that local 

 carbohydrate production must be small. Yet such galls are rich in 

 starch grains in certain areas, and are high in polyphenolic compounds 

 which presumably arise at the expense of carbohydrate. Possibly the 

 developing galls are regions into which sugars move from the photo- 

 syntheiically more active normal leaf tissue. Pertinent to this point of 

 view is Molliard's (12) analysis of elm leaf galls produced by two species 

 of plant lice. The galls were higher in reducing sugars than the normal 

 leaf tissues, and were four times as rich in tannin. 



Another parallel between anthocyanins and tannins lies in the correla- 

 tion of high anthocyanin or tannin content with high oxidase activity. 

 In general, the distribution of oxidase activity in flowers coincides 

 exactly with that of the anthocyanin pigments. According to Armstrong 



