Glutathione supplementation prevents iron deficiency in Medicago scutellata grown in rock sand under different levels of bicarbonate

Abstract

The effects of root glutathione (GSH) supplementation on leaf chlorophyll, Fe concentrations and contents in leaves, stems and roots, and traits associated to Fe deficiency were studied in Medicago scutellata plants grown in rock sand under conditions of Fe deficiency, in the presence of different concentrations of bicarbonate. Plants were grown in acid-washed rock sand irrigated with a zero Fe solution (pH 7.8 with 0.5 g L−1 CaCO3) or a 45 μM Fe(III)-EDDHA solution (5 mM MES, pH 5.5), with 0, 5 or 15 mM NaHCO3, and 250 mL of 1 mM GSH was added daily to half of the pots. Iron deficiency caused characteristic symptoms in plants, with GSH supplementation relieving them. Glutathione supplementation led to increases in total Fe, chlorophyll and leaf total and extractable Fe, whereas root Fe concentrations decreased. Traits associated to Fe deficiency, including changes in biomass, root morphology, carboxylate contents and antioxidant parameters became less intense with GSH supplementation. Glutathione supplementation allowed plants to take up Fe from the rock sand via a reductive solubilization mechanism. Also, the distribution of Fe within the plant changed, with more Fe being allocated to the shoot tissues and less to the roots.