The length of the primary stem(Fig. 2b) and the average surface area
per leaf (Fig. 2c)were also affected by nZnO significantly; bothwere decreased
with increase in nZnO concentration. At nZnO concentration of
750 mg/L, the primary stemlength and the average surface area per leaf
were ca. 67% (p b 0.001) and 25% (p b 0.001), respectively,with respect
to controls; the EC50 was 305 mg/L and 420 mg/L in terms of stem
length and average surface area per leaf, individually (see the downward
arrows). The stem length was more susceptible to nZnO than
the average surface area per leaf