Subcellular distribution and physiological responses of native and exotic grasses from the Pampa biome subjected to excess manganese

Fungicides containing manganese (Mn) applied to control plant diseases increase the concentration of Mn in soils, which may potentiate Mn toxicity in acid soils. Some species of wild grasses, such as those from the Pampa biome located in South America, or even those introduced into this biome, may possess different mechanisms of tolerance to excess Mn. The present study aimed to evaluate the subcellular distribution and physiological and biochemical responses of exotic and native grasses from the Pampa biome, cultivated in Mn excess. The experiment was conducted in nutrient solution in a greenhouse, in an entirely randomized design, bifactorial 4 x 4, consisting of four Mn concentrations (2 [control], 300, 600 and 900 mu M) and four species (two exotic: Avena strigosa and Lolium multiflorum; and two native: Paspalum notatum and Paspalum plicatulum). At 27 days of exposure to the treatments, biomass and growth rates, leaf gas exchange with the environment, photosynthetic pigment concentrations of malondialdehyde and H2O2, antioxidant enzyme activities (SOD and POD), and subcellular distribution of Mn were evaluated. Most of the grasses showed high concentration of Mn in tissues, mainly, in the shoot. In the presence of 900 mu M Mn, more than 80% of the absorbed Mn was compartmentalized in the cell walls and vacuoles of the cells. Compartmentalization of Mn excess into metabolically less active organelles is the main tolerance factor in grasses. Physiological and biochemical responses were stimulated in the presence of 300 mu M Mn, while 900 mu M Mn negatively affected biochemical-physiological responses of grasses. The species L. multiflorum was most sensitive to excess Mn, while P. notatum was the most tolerant.

Automated summary

This study evaluated the subcellular distribution and physiological and biochemical responses of exotic and native grasses from the Pampa biome under excessive manganese (Mn) conditions. The results showed that grasses accumulated high concentrations of Mn in their tissues and compartmentalized the excess Mn into cell walls and vacuoles to minimize its impact on cell activity. Physiological and biochemical responses of the grasses were stimulated in the presence of 300 µM Mn, while 900 µM Mn negatively affected their physiological and biochemical responses.