Abstract: Disclosed are stable recombinant multi-gene nucleic acid constructs, such as plant binary vectors, comprising (i) a gene encoding &ggr;-glutamylcysteine synthetase and (ii) a gene encoding glutathione synthetase, plus preferably at least one, preferably two, genes which encode enzymes involved in the redox cycling of glutathione between its reduced and its oxidised forms e.g. glutathione reductase and/or glutathione peroxidase. Preferably the promoters linked to the genes are different and of different strengths, and may optionally be inducible. Also provided are related materials and corresponding methods and uses e.g. in plants to improve oxidative stress tolerance enhance root development, or to increase the post-harvest shelf life of the plant or part thereof.