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- Differences in Al tolerance between Plantago algarbiensis and P. almogravensis reflect their ability to respond to oxidative stressPublication . Martins, Neusa; Osório, Maria Leonor; Gonçalves, Sandra; Osório, Júlio; Romano, AnabelaWe evaluated the impact of low pH and aluminum (Al) on the leaves and roots of Plantago almogravensis Franco and Plantago algarbiensis Samp., focusing on energy partitioning in photosystem II, H2O2 levels, lipid peroxidation, electrolyte leakage (EL), protein oxidation, total soluble protein content and antioxidant enzyme activities. In both species, Al triggered more changes in oxidative metabolism than low pH alone, particularly in the roots. We found that Al increased the levels of H2O2 in P. algarbiensis roots, but reduced the levels of H2O2 in P. almogravensis leaves and roots. Neither low pH nor Al affected the spatial heterogeneity of chlorophyll fluorescence, the maximum photochemical efficiency of PSII (F-v/F-m), the actual quantum efficiency of PSII (I center dot(PSII)) or the quantum yields of regulated (I center dot(NPQ)) and nonregulated (I center dot(NO)) energy dissipation, and there was no significant change in total soluble protein content and EL. In P. algarbiensis, Al increased the carbonyl content and the activities of superoxide dismutase (SOD) and catalase (CAT) in the roots, and also CAT, ascorbate peroxidase and guaiacol peroxidase activities in the leaves. In P. almogravensis, Al reduced the level of malondialdehyde in the roots as well as SOD activity in the leaves and roots. We found that P. almogravensis plantlets could manage the oxidative stress caused by low pH and Al, whereas the P. algarbiensis antioxidant system was unable to suppress Al toxicity completely, leading to the accumulation of H2O2 and consequential protein oxidation in the roots.
- Physiological responses of Plantago algarbiensis and P. almogravensis shoots and plantlets to low pH and aluminum stressPublication . Martins, Neusa; Osório, Maria Leonor; Gonçalves, Sandra; Osório, Júlio; Palma, Tânia; Romano, AnabelaWe investigated the impact of low pH and aluminum (Al) stress on the growth, nutrients concentration, chlorophyll a fluorescence, photosynthetic pigment contents, proline and carbohydrate accumulation in shoots and plantlets (leaves and roots) of Plantago almogravensis and P. algarbiensis. Both species accumulated considerable and similar amounts of Al in their tissues, mainly in the roots. The presence of Al caused a significant reduction on root elongation in P. algarbiensis. Low pH and Al induced significant changes on nutrient accumulation, but no significant alterations on the maximum efficiency of PSII (Fv/Fm), quantum yield of PSII photochemistry (FiPSII), quantum yield of regulated energy dissipation (FiNPQ) and quantum yield of non-regulated energy dissipation (FiNO) were detected in both species in response to these stresses. However, Al increased significantly the nonphotochemical quenching and the hlorophyll b content and decreased the PSII excitation pressure (1 - qp) in P. almogravensis leaves. Both stress treatments induced carbohydrate accumulation in the shoots and roots of this species, but not in leaves. In P. algarbiensis, low pH and Al decreased the photosynthetic pigment contents in the shoots, whereas Al stimulated the carbohydrate accumulation in the leaves. Although our data showed that both species are tolerant to Al3+ and H+, P. almogravensis appeared to be more adapted to maintain cellular physiology and growth under those conditions.