Arsenic Toxicity Studies— Clements and Munson 
167 
determined in part by the nature of the root 
structure and in part by the intimacy as well 
as nature of the contact between the root 
surface and the soil surface bearing the 
arsenic. Tissue tolerance, on the other hand, 
may be related in part to protoplasmic struc¬ 
ture and in part to the form in which the 
arsenic is held within the protoplasm after 
it is absorbed. 
Bean: Red Soil .—The bean plant (see 
Table 11 and Figure 5), which in culture 
solution was the most susceptible of the three 
plants to arsenic injury, showed a tolerance 
to soil arsenic only slightly below that of the 
tomato, but considerably above that of Sudan 
grass. 
For.the bean, as for the tomato and Sudan 
grass, although the level of soil arsenic at 
which growth was sharply curtailed was the 
same for the first crop as for later crops, the 
actual amount of arsenic absorbed was 
greater in the first crop than in later crops. 
Also, the differences in the amounts of 
arsenic absorbed by the various crops are not 
all related to the differences in growth made. 
GENERAL DISCUSSION 
It is apparent that production of crops in 
heavy Hawaiian soils which have been con¬ 
taminated with the herbicide sodium arsen- 
ite will be affected variously depending on 
the particular crop. Furthermore, crops which 
may be looked upon as tolerant to arsenic 
when grown in culture solution may become 
relatively susceptible to fixed arsenic in the 
soil. In culture solutions, the bean plant was 
by far the most susceptible of the three plants 
used, whether the arsenic was trivalent or 
pentavalent. The tomato was the most re¬ 
sistant toward pentavalent arsenic, but was 
about equal to Sudan grass in resistance to 
trivalent arsenic. In soil cultures, however, 
Sudan grass was considerably less resistant 
to sodium arsenite than either of the other 
TABLE 11 . BEAN-RED SOIL 
Yield Data and Arsenic Content of Tissues. 
CAN 
NUMBER 
AS2O3 
CONTENT 
OF SOIL 
SERIES I 
AVERAGE OF 2 LATER SERIES 
Green weight 
of plants 
AS 2 O 3 content 
of tissues 
Green weight 
of plants 
As 2 Os content 
of tissues 
* 
ppm 
gm. per can 
ppm 
gm. per can 
ppm 
1 
15 
18.7 
0.5 
24.3 
1.5 
2 
25 
18.0 
1.1 
23.7 
1.5 
3 
34 
19.0 
1.8 
25.9 
1.8 
4 
45 
17.3 
2.4 
22.8 
2.2 
5 
54 
20.7 
2.9 
23.5 
5.0 
6 
65 
24.0 
7.9 
27.5 
1.8 
7 
74 
24.7 
9.0 
28.0 
2.0 
8 
85 
26.7 
6.9 
25.2 
3.2 
9 
95 
22.7 
4.8 
25.9 
2.1 
10 
104 
22.3 * 
3.4 
23.0 
1.7 
11 
115 
22.3 
3.7 
22.8 
2.1 
12 
214 
22.0 
5.5 
26.7 
2.5 
13 
314 
14.0 
6.3 
22.7 
3.7 
14 
414 
18.0 
10.3 
21.2 
6.9 
15 
514 
11.0 
14.0 
14.2 
6.6 
16 
614 
7.7 
26.4 
9.5 
6.9 
17 
714 
6.3 
11.1 
10.8 
18 
814 
9.0 
24.6 
6.8 
12.8 
19 
915 
6.0 
. 35.4 
6.1 
12.9 
20 
1014 
2.5 
4.2 
12.8 
21 
1514 
2.3 
3.2 
15.7 
22 
2014 
1.1 
2.0 
25.1 
23 
2515 
0.7 
1.6 
32.7 
24 
3014 
0.2 
1.5 
46.5 
