Effects of methyl jasmonate and excess copper on root and leaf growth

A short time effects of 25 and 150 mu M Cu2+ or 50 mu M methyl jasmonate (MJ) on growth of roots and leaves of Phaseolus coccineus, Allium cepa and Zea mays were investigated. Both Cu2+ and MJ inhibited root growth. Jasmonate synthesis inhibitors (ibuprofen, IB, salicylhydroxamic acid, SHAM, and propylgallate, PG) partially reversed the inhibitory effect of Cu2+ in P. coccineus, but in A. cepa this effect was not clear. Pretreatment with NADPH oxidase inhibitor (20 mM imidazole, IM), and especially ethylene inhibitor (silver thiosulphate, STS) mostly weakened Cu2+ effect on root growth in P. coccineus and A. cepa. The growth of P. coccineus leaves also slowed down by Cu2+ and this effect was partially ameliorated by IB, PG and IM, and completely by SHAM and STS. In Z. mays the effect of STS was considerably lower than that of PG and SHAM which reversed the effect of Cu2+. These results indicate that jasmonate, ethylene and NADPH oxidase activity may be involved in Cu2+ inhibitory action on the roots of dicotyledon plants, but in A. cepa only ethylene and NADPH oxidase are involved. However, leaf growth inhibition induced by excess Cu2+ is connected in Z. mays especially with jasmonate, and in P. coccineus with ethylene, NADPH oxidase and, to a minor degree, with jasmonate.