Effects of hydroperiod and iron on Typha latifolia grown in a phosphorus-enhanced medium

This study was designed to mimic a phosphorus-(P)-enhanced environment and focused on the effects of hydroperiod and dissolved iron (Fe) concentrations on Typha latifolia. The physiological responses and nutrient uptake capabilities of plants were quantified. The research was conducted in a greenhouse utilizing a factorial design with three soil-moisture treatments (permanently flooded, periodically flooded, drained) and three Fe levels (0 mg Fe L(-1), control; 1 mg Fe L(-1); 10 mg Fe L(-1)). All treatments also received P at 0.2 mg l(-1). Plant gas exchange, growth, biomass, and tissue Fe and P concentrations were measured. Permanent flooding enhanced height growth, shoot weight, and root weight, and led to high Fe concentrations in the roots. Plants receiving the 10 mg Fe L(-1) treatment had taller shoot heights compared with those receiving the control and 1 mg Fe L(-1) treatments. It appeared that a concentration of 10 mg Fe L(-1) did not significantly affect T. latifolia under moderately reduced soil conditions. However, low soil-redox potential levels below +70 mV and iron levels of 10 mg L(-1) may eventually lead to a photosynthetic decline in T. latifolia. Results highlighted two important findings: (1) Fe treatment and moisture regimes, as tested, did not affect tissue P concentrations and thus the ability to uptake and sequester P, and (2) a treatment of 10 mg Fe L(-1) may have led to some initial beneficial effects in T. latifolia, such as producing the greatest shoot growth, but a photosynthetic decline was noted in the last week as redox potential levels fell below +100 mV. This effect potentially hinders the use of Fe to aid P retention in wetlands, due to the possibility of inducing physiological dysfunction in some species, such as noted in T. latifolia.