General Discussion' 



211 



TABLE XXX 



Summary of Copper Content of Aerial Vegetation 



Mill. Max. Ave. 



No. of . — -' ^ 



samples Parts per million copper 



1. Field vegetation from upper Gila...'. 10 trace 7.60 3.41 

 Field vegetation from other sources 



in Arizona 9 none 6.30 1.52 



2. Corn plants grown in pots .01-.05 



per cent Cu 3 6.5 21.00 13.30 



Tops of corn, beans and squash 



grown in Cu water culture 6 11.7 32.00 22.90 



Tops of corn, beans, etc., irrigated 



with copper solutions 14.00 



Beans in soils containing Cu 9 13.0 44.00 26.00 



Squash ditto 5 14.0 61.00 39.00 



Corn ditto 20 4.4 239.00 42.00 



3. Field samples collected by Leh- 



naanni« i3 560.00 86.00 



Field samples collected by Ved- 

 rodii" 



1894 26 40.0 1350.00 257.00 



189.5 26 10.0 680.00 151.00 



patches that may possibly have been due to presence of copper, 

 inasmuch as appearances of this character are sometimes noted 

 as an effect of the application of Bordeaux mixture. Bain 

 states, for instance, that extremely minute amounts of copper 

 stimulate formation of chlorophyll in a cell and therefore in- 

 crease the formation of starch.i^ Ewart. also, shows that solu- 

 tions of copper as dilute as 1 to 30,000,000 prevent the action 

 of diastase upon starch.^^ It is possible, therefore, that the juices 

 of plant tissues containing traces to 239 parts (observed) of 

 copper in 1,000,000 of dry matter may carry sufficient of this 

 amount in solution in the cell sap to hinder the action of enzymes 

 upon starch, and thus prevent its normal translocation. 



16 Dcr Kupfergelialt von Pfianzcn und Thieren in Kupferreichen Gegen- 

 den, Lehmann Arcliiv fiir Hygiene, vol. 27, pp. 1-17, 1896. 



17 Quoted in Brenchley, Inorganic Plant Poisons, p. 17, 1914. 



18 Bain, Tenn. Agr. Exp. Sta., vol. 15, Bull. 2, p. 93, 1902. 

 i9Ewert, Zeitschr. fiir Pflanzenkrankli., vol. 14:3, p. 135, 1904. 



