Toxicity symptom was solely shown as shoot growth repression at 33.5 and
67M As exposures. Dry weight (DW) enhanced by 19.4% in shoot and 38.9% in root in the 6.7M As
level as compared to control but decreased by 48.1% and 72.1% DW in shoot and 24.1% and 61.1% DW in
root in the 33.5 and 67M As levels, respectively. This result indicated that As at lower concentration
might have slight stimulating effect on JM-spinach growth, but toxicity increased with increasing As.
Based on the regression lines between growth and As concentration in the plant tissues, the critical
toxicity level (CTL) of As in JM-spinach shoot was 7.85gg−1 DW considering 10% DW reduction. The
CTL for the root was almost 2110gAsg−1 DW, indicating that shoot of JM-spinach was more sensitive
to As-toxicity than that of root. Arsenic concentrations increased in plant parts with increasing As in the
medium. Arsenic concentrationswere also compared in DWand freshweight (FW) basis. The JM-spinach
concentrated unaccepted level of As in shoots for human consumption in the higher As levels without
showing visible toxicity symptom. In spite of decreasing iron (Fe) concentration in shoot in the highest
As level, chlorophyll index did not decrease accordingly. Phosphorus (P) concentration also decreased.
Phosphorus concentration decreased much more than Fe concentration. Low P might help to mobilize Fe
in shoots, resulting in higher chlorophyll index at 67M As level. Phosphorus might compete with Fe in
shoot tissues of As-stressed JM-spinach.