Heavy-metal-induced ethylene production in Arabidopsis thaliana

Different plant parts varied in copper sulfate (CuSO₄) and cadmium sulfate (CdSO₄)-induced ethylene production, inflorescences showed the greatest induction, while all other plant parts tested produced significantly less. Leaf age had a dramatic effect on CuSO₄ and CdSO₄-induced ethylene production with the youngest leaves showing the greatest stimulation and as the age of the leaf increased there was a reduction in their ability to produce ethylene. However, there was no significant difference in CuSO₄, CdSO₄ and wound-induced ethylene production when whole rosettes were taken from plants that were 7, 14 or 21-day-old. The highest amount of CuSO₄ and CdSO₄-induced ethylene production was produced in the root tip with regions below this producing less. CuSO₄ and CdSO₄-induced ethylene production was also greatest from the tip of the inflorescence to 2 cm below the tip and from this point down there was a reduction in ethylene production. When inflorescence stalks or leaves were treated with CuSO₄ or CdSO₄ over a range of concentrations from 0 to 800 μM, there was an increase in ethylene production starting at 50 μM with increasingly greater responses up to 400 μM. There was no further increase at the 800 μM CuSO₄ concentration; however, there was a slight decline with 800 μM CdSO₄. Inflorescence stalks or leaves treated with either 400 μM CuSO₄ or CdSO₄ exhibited a dramatic increase in ethylene production 2 h following treatment initiation and remained high over a 24-h period with a decline in ethylene production after this time in inflorescence stalks but not the leaves. It was found that light caused a dramatic decrease in CuSO₄, CdSO₄ and wound-induced ethylene production in both inflorescence stalks and leaves. When inflorescence stalks or leaves were treated at 43 °C, there was a dramatic effect on CuSO₄, CdSO₄ and wound-induced ethylene production in each.