Tolerance of Miscanthus × giganteus to salinity depends on initial weight of rhizomes as well as high accumulation of potassium and proline in leaves

Abstract

Miscanthus×giganteus, a species useful for sustainable agriculture, can be cultivated on soils with lower bonitation and also with higher salinity. The study aimed to estimate NaCl concentrations which limit growth of Miscanthus×giganteus plants and to determine physiological parameters best reflecting the response of Miscanthus to salt stress. The experiment was conducted on plants grown at 0–200mM of NaCl. All analyses were done after 12 weeks of salt treatment. In rhizomes and leaves, fresh (FW) and dry weight (DW), relative water content (RWC), electrolyte leakage (EL), and ion content were determined; in leaves only, chlorophyll fluorescence, net photosynthesis rate (PN), transpiration (E), stomatal conductance (gs) and proline content. Shoots developed at all NaCl concentrations, but at 200mM many rhizomes produced none; thus analyses on leaves were done only on plants grown at 0–150mM of NaCl. Salinity decreased FW and DW of roots and shoots significantly, and retarded increases in rhizome weight. In leaves, salinity of 100 and 150mM NaCl did not damage membrane structures, while in rhizomes only 200mM increased EL considerably. Most parameters of chlorophyll fluorescence and gas exchange declined under salinity. High amounts of proline, K and Na were accumulated in leaves at 100 and 150mM NaCl. RWC remained unchanged in roots and leaves and decreased in rhizomes under rising salinity. The initial FW of the rhizomes studied correlated with the salt tolerance of Miscanthus plants. Changes in chlorophyll fluorescence, PN, FW and DW of roots and leaves as well as potassium and proline concentrations in leaves are the most reliable indicators of the response of Miscanthus to salinity. A high accumulation of K+ and proline in leaves reduces the sodium effect and determines the tolerance of Miscanthus to salinity.