Protects cells and enzymes from oxidative damage, by catalyzing the reduction of hydrogen peroxide, lipid peroxides and organic hydroperoxide, by glutathione. a hydroperoxy polyunsaturated fatty acid + 2 glutathione = a hydroxy polyunsaturated fatty acid + glutathione disulfide + H2O Expressed in leaves, stems, flowers, green siliques and seeds. By salt stress, osmotic stress, metals and heat treatment. Up-regulated by abscisic acid (ABA) and auxin. Belongs to the glutathione peroxidase family.