Artículo original

Early interconnectivity between metabolic and defense events against oxidative stress induced by cadmium in roots of four citrus rootstocks

Resumen:

Cadmium effects on roots of four citrus rootstocks were studied to assess relationships between oxidative stress, carbohydrates, phenolics and antioxidant responses. Swingle Citrumelo (SC), Rangpur Lime (RL), Troyer Citrange (TC) and Volkamer Lemon (VL) genotypes were exposed to 0, 5 and 10 µM Cd during 7 days. Cd accumulation was markedly higher in roots compared with stems and leaves. Malondialdehyde (MDA) and lipoxygenase (LOX) activity increased in Cd-treated SC and RL roots, suggesting that a lipid peroxidation is the main responsible of the plasma membrane damage. Contrarily in TC and VL genotypes, LOX-mediated lipid peroxidation does not play a key role in Cd-induced lipid peroxidation, but H2O2 accumulation seems to be responsible of less plasma membrane damage. Catalase (CAT), superoxide dismutase (SOD), and guaiacol (G-POD) and syringaldazine (S-POD) peroxidases were differentially affected by Cd. Lipid profile and ATPase-dependant proton extrusion indicated higher disfunctionality of root plasma membrane in SC and RL genotypes compared with TC and VL ones. Differences in carbohydrates and phenolic compounds also occurred. Histochemical analysis of G-POD activity and lignin and suberin deposition revealed differences among genotypes. A model to explain relationships among carbohydrates, soluble phenolics, lipid peroxidation and H2O2 accumulation in Cd-exposed roots was proposed.