156 
PACIFIC SCIENCE, Vol. I, July, 1947 
TABLE 1. TOMATO 
Data for the accumulation of arsenic (as ppm 
AS2O3) AND PHOSPHORUS (AS PER CENT OF DRY 
weight), as well as dry weights of plants 
GROWN IN SOLUTIONS CONTAINING VARIOUS IN¬ 
CREMENTS OF PENTAVALENT ARSENIC (AS SODIUM 
ARSENATE) AT DIFFERENT PHOSPHATE LEVELS. 
ARSENIC 
IN 
SOLUTION 
DRY 
WEIGHT 
ARSENIC 
IN 
PLANT 
PHOS¬ 
PHORUS 
IN PLANT 
ppm AS2O3 
gm. 
ppm AS2O3 
% dry wt. 
Low phosphorus level (P = 10 ppm) 
0.0 
27 
trace 
0.72 
1 
30 
5.0 
.67 
2.5 
34 
10.6 
.61 
5 
21 
22.5 
.75 
10 
18 
42.2 
.75 
15 
10 
76.5 
.72 
20 
10 
81.3 
.67 
25 
6 
93.0 
.50 
30 
3 
106.3 
.72 
40 
2 
162.5 
.60 
Medium phosphorus level (P = 60 
ppm) 
0.0 
28 
0 
.75 
6 
29 
6.7 
.72 
15 
19 
17.2 
.84 
30 
18 
49.7 
.84 
60 
9 
74.1 
.69 
90 
4 
120.1 
.63 
120 
2 
193.7 
.60 
High phosphorus level (P = 120 ppm) 
0.0 
28 
trace 
.72 
12 
23 
12.2 
.78 
30 
19 
26.6 
.69 
60 
11 
61.3 
.64 
120 
6 
103.9 
.60 
7 H 2 0), and in Tables 4, 5, and 6 the data 
for the same species treated with sodium 
arsenite (NaAs0 2 ). 
Since it will be shown later that the phos¬ 
phorus level has an important influence on 
arsenic toxicity, comparisons between arsen¬ 
ate and arsenite must be made within series 
of similar phosphorus concentration. Com¬ 
parisons of the arsenate and arsenite experi¬ 
ments at the medium phosphorus level 
(P = 60 ppm) indicate marked differences 
between the action of pentavalent and of 
trivalent forms. 
The tomato plants growing in 60 ppm of 
pentavalent arsenic accumulated 74.1 ppm 
of arsenic in their tops, yet were normal ex¬ 
cept in size. Tomato plants grown in solu¬ 
tions containing 90 ppm and 120 ppm of 
pentavalent arsenic lived to the end of the 
experiment despite accumulations of 120 
ppm and 194 ppm of arsenic in their tops. 
The lethal concentration was between 120 
ppm and 150 ppm in the culture solution. 
In the arsenite series, on the other hand, 
concentrations of 7 ppm and 11 ppm in the 
solution very nearly stopped growth, al¬ 
though the plants on analysis showed only 
12.5 ppm and 24.1 ppm of arsenic respec¬ 
tively in their tops. Even the low level of 
3 % ppm in the culture caused marked stunt¬ 
ing; the lethal concentration was 11 to 15 
ppm. Approximately 10 times as much 
pentavalent arsenic is required in the culture 
solution and in the plant tissue as trivalent 
arsenic to produce equivalent injuries to 
tomato plants. 
TABLE 2. SUDAN GRASS 
Data for the accumulation of arsenic (as ppm 
AS2O3) AND PHOSPHORUS (AS PER CENT OF DRY 
WEIGHT), AS WELL AS DRY WEIGHTS OF PLANTS 
GROWN IN SOLUTIONS CONTAINING VARIOUS IN¬ 
CREMENTS OF PENTAVALENT ARSENIC (AS SODIUM 
ARSENATE) AT DIFFERENT PHOSPHATE LEVELS. 
ARSENIC 
IN 
SOLUTION 
DRY 
WEIGHT 
ARSENIC 
IN 
PLANT 
PHOS¬ 
PHORUS 
IN PLANT 
ppm AS 2 O 3 
gm. 
ppm AS 2 O 3 
% dry wt. 
Low phosphorus level (P = 10 ppm) 
0.0 
40 
trace 
0.61 
1 
23 
13.5 
.53 
2.5 
21 
,19.1 
.56 
5 
11 
47.4 
.42 
10 
5 
67.2 
.44 
15 
2 
88.8 
.42 
20 
2 
103.1 
.53 
25 
2 
139.1 
.54 
Medium 
phosphorus level (P = 
60 ppm) 
0.0 
37 
trace 
.72 
6 
29 
29.4 
.75 
15 
18 
41.0 
.75 
30 
8 
74.1 
.39 
60 
4 
98.4 
.56 
90 
2 
513.1 
.66 
High phosphorus level (P = 120 ppm) 
0.0 
36 
trace 
.84 
12 
28 
12.8 
.91 
30 
20 
49.7 
.78 
60 
14 
84.4 
.59 
120 
6 
142.3 
.52 
