Roots are the primary organ that the plants use to absorb
nutrients and water, therefore Al toxicity will be most significantly
reflected in root activities. As shown in Table 1, root activity of both
cultivars increased slightly in low Al conditions but dropped when
the Al concentration exceeded 30 mg L1 for Z.2 and 10 mg L1 for
Z.3. The data showed that with the increase of Al concentration, the
growth of root was inhabited, and that Z.3 was more sensitive to Al
toxicity than Z.2. The lowest root activity for both cultivars were
observed in the treatment of 90 mg L1 concentration. Compared to
the check, the relative reductions for Z.2 was 44.8% and for Z.3 was
74.6%, indicating that Z.2 is more tolerant to Al toxicity than Z.3. For
both cultivars, root hair zone activities followed a similar pattern in its response to Al toxicity as that of root activities, where low Al
toxicity also increased the activity of the root hair zone and high Al
toxicity decreased the activity (Table 1), but there was little
difference between the two cultivars.