1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 449 



Peas 



Drv matter, Cu found, Cu p. p.m. in 



No. Sample grams grams dry matter 



6327 250 tops 7.0850 .00012 16.90 



6325 Coarse roots 1.2827 .00180 1400.00 



6326 Fine roots .8393 .00141 1680.00 

 6324 5500 root tips .4462 .00153 3428.00 



Amount of copper per root tip required to show slight toxic effects, 



.001.53 H- 5500= .000000278 gm. 



Total roots examined for nitrogen 4.41730 gms. 



Albuminoids in roots (Alb. N. X 6i) 83929 



Copper required to saturate albuminoids (factor 11.7%) .09819 



Total Cu found 00784 



•00784 „„^^ 

 Saturation ^^^^ = 7.99% 



Wheat 



Dr- matter, Cu fmmd, Cii p.p.m. in 



No. Sample grams grams drv matter 



6332 530 tops 12.7 .00165 129.90 



6331 Roots .6902 .00020 297.00 



6330 16000 root tips .3664 .00103 2811.00 



Amount of copper per root tip associated with slight toxic effects, 

 .00103 -^ 16000 = .000000064 gm. 



Total roots examined for nitrogen 2.9223 gms. 



Albuminoids in roots (Alb. N. X 6^) 30794 



Copper required to saturate albuminoids (factor 11.7%) .03603 



Total Cu found 001789 



.001789 , ^^^ 

 Saturatton .03-603" ^ ^'^'^^ 



These figures show, as usual, relatively small amounts of 

 copper ill tops of plants, with large amounts in roots, increasing 

 from coarser to finer portions, until in the root tips corn con- 

 tains 545, peas 3428. and wheat 2811 parts per million of copper 

 in dry matter. For peas and wheat these are the largest propor- 

 tions of copper thus far observed in any plant samples. 



When the total amount of copper found in each sample is 

 divided by the number of root tips employed, an extraordinarily 

 small amount of copper is found necessary to bring about toxic 

 effects. For instance 



One corn root tip (terminal 3 cm.) required 000000382 gms. Cu 



One jiea root tip (terminal 1 cm.) required 000000278 gms. Cu 



One wheat root tip (terminal 1 cm.) required .000000064 gms. Cu 



