1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 451 



Feb. 5; very faint biuret test for copper, distinct ferrocyanide test. 



Corn, forty-eight days old in 50 p.p.rn. Cu sol., two days, gave faint 

 biuret and ferrocyanide tests. 



Corn, forty-eight days old in 500 p.p.m. Cu sol., two days, gave faint 

 tests for copper. 



From these observations it is evident that the nearly negative 

 results shown are due either to nutrient salts present or to the 

 older and therefore more quiescent material employed. To settle 

 this question, the following experiments were made: 



(1) Young (ten days) wheat and corn plants were placed in 

 copper solution in distilled water and in nutrient solutions and 

 observed after twenty and forty hours, as follows : 



2.5 p.p.m. Cu, distilled water — 20 hours 

 10 days old: Young Avheat; flaccid f; strong biuret test; strong KiFeCys test 

 60 days old: Old Avheat; not flaccid; no strong biuret test; distinct K^FeCye 



test 

 10 days old: Young corn; flaccid; strong biuret test; strong K^FeCye test 

 60 days old : Old corn ; flaccid ; no biuret test ; old tips, faint KjFeCye test 

 young tips, strong K4FeCy6 test 



10 p.p.m. Cu, distilled water — 20 hours 

 10 days old: Young wheat; flaccid?; strong biuret test; strong K^FeCy,; test 

 60 days old : Old wlieat ; not flaccid ; faint biuret test ; distinct K4FeCy6 test 

 10 days old: Young corn; flaccid; strong biuret test; strong KiFeCys test 

 60 days old: Old corn; flaccid?; distinct biuret test; strong K4FeCy,; test 



40 p.p.m. Cu, distilled water — 20 hours 

 10 days old: Young wheat; flaccid; strong biuret test; strong K^FeCyB test 

 60 days old: Old wlieat; flaccid?; faint biuret test; distinct K^FeCy,, test 

 10 days old : Young corn ; flaccid ; strong biuret test ; very strong KiFeCys 



test 

 60 days old : Old corn ; flaccid ; strong biuret test ; strong KiFeCy,, test 



The above results indicate that old roots of corn and wheat 

 are more resistant to the penetration of copper than are the 

 young roots. This is shown by less flaceidity in the weaker solu- 

 tions and by the fainter tests observed. A second series with 

 greater strengths (5, 20, and 100 p.p.m.) and longer exposure 

 (forty-five hours) showed distinctly less differentiation than in 

 the case of the series above given in detail. This is to be expected, 

 inasmuch as stronger solutions must overcome resistance of roots 

 exposed to them more quickly, and the longer time employed 

 would likewise tend to overcome differences existing in the first 

 few hours of the experiment. 



