Bioaccumulation of Copper by Zea mays: Impact on Root, Shoot and Leaf Growth

Abstract

In the present study, the growth and the Cu2+accumulation by roots, shoots and leaves of Zea mays were examined using copper sulphate in the range of 10−4 to 10−2 M. Plants of Z. mays did not show inhibition of growth in the presence of 10−4 to 10−2 M Cu2+; however, it was observed growth effects on root when different Cu2+ solution concentrations were used. Only the seedlings exposed to 10−2 M exhibited substantial root growth reduction, yielding only 56% of length with respect to the control. Seedlings exposed to 10−4 M Cu2+ exhibited 16% and 42% growth increase in shoots and leaves, respectively, when compared with the controls. The seedlings treated with 10−3 and 10−2 M Cu2+ were inhibited in shoot and leaf growth. The fresh weights in roots, shoots and leaves significantly decreased at 10−2 M Cu2+. The tolerance index, based on root length, was not significantly different for the three different treatments with copper. However, the total accumulation rate was very low at 10−4 and 10−3 M compared to 10−2 Cu treatments. The capacity of copper accumulation by roots, shoots and leaves of Z. mays plants increased concomitant to the copper concentration, arriving to 382 times more in roots, 157 in shoots and only 16 in leaves, all compared to the controls. Cu could be accumulated by roots, shoots and leaves when the initial concentrations were 10−3 and 10−4 M. However, when it was 10−2 M, the metal could not be accumulated by leaf and shoot levels; the roots could increase their copper accumulation capacity three times compared to the control. Z. mays has potential ability to accumulate Cu without being overly sensitive to Cu toxicity.