Responses of Suaeda maritima to flooding and salinity
PublisherUniversity of Sussex
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Suaeda maritima is an annual halophyte commonly found in salt-marshes. Its salt tolerance has been well studied, though there is little published on the effect of simultaneous waterlogging. The effects of saline waterlogging on growth, antioxidants (glutathione and total polyphenolic compounds, antioxidant activity) and oxidative damage were investigated with simulated tides in a controlled glasshouse and on plants collected from the field. Flooded shoots possessed higher levels of antioxidants than those from plants growing in well-drained situations, in the glasshouse and the field. The effects of hypoxia, (simulated in nutrient solution by flushing with nitrogen in a solution containing a low concentration of agar, which limits convection within the solution and so the transport of oxygen from the air) were determined on growth and trace metal concentrations, in plants grown in different concentrations of artificial seawater (100 and 350 mM Na+ at low pH, > pH 5.5), in sand/mud irrigated with halfstrength fresh seawater (at high pH, ca 7-8) and in different concentrations of manganese and iron in solution culture. High salt concentration reduced accumulation of trace metals in plants. Optimal growth occurred in 14 μM Fe and 1 mM Mn. Accumulation of trace metals was reduced at high pH, with more accumulating in the roots than the shoots. Hypoxia increased soluble sugars in shoots and roots, and this was affected by the salt concentration. Hypoxia also caused adventitious root development in hydroponic experiments, while in sand, adventitious root development was greater in drained than flooded conditions. Hypoxia significantly reduced shoot sodium concentration, sodium flux and bypass flow, at low and high salt concentrations. In high salt conditions, S. maritima reduced its transpiration rate and improved its water use efficiency. It was also shown that the roots contained high lactate concentrations under aerated and hypoxic conditions. S. maritima demonstrated many adaptations for tolerating extreme hypoxia.