Effects of lead (Pb, 150 and 300 µM) alone or in combination with methyl jasmonate (MJ, 0.5 and 1 μM) on the expression of PCS1 (A, B), PCS2 (C, D), ABCC1 (E,F) genes in rice roots and leaves. Values (means ± SD, n = 5) followed by the same letter are not significantly different (P < 0.05; LSD test)