Lipid peroxidation

Lipid peroxidation was measured in A. thaliana leaves taken at 7 dpt from Zn‐deficient, Zn‐sufficient or Zn‐excess plants, with or without 0.1 mg l^‐1 SA, using the malondialdehyde (MDA) assay (Heath & Packer 1968). Leaf samples (200 mg FW) were homogenized with 1.5 ml 0.1% trichloroacetic acid (TCA), centrifuged at 10 000 g for 20 min and 1.0 ml 0.5% thiobarbituric acid (TBA) in 20% TCA added to a 0.5 ml aliquot of the supernatant. After incubation at 95 °C for 30 min, the mixture was immediately cooled on ice, centrifuged at 10 000 g for 10 min then absorbance recorded at 532 and 600 nm with the above UV‐Visible spectrophotometer. MDA content was calculated using an extinction coefficient of 155 mM⁻¹ cm⁻¹ by subtracting non‐specific absorption at 600 nm from absorption at 532 nm. Each experiment was independently repeated three times, with three plants per treatment and two leaves per plant.