Stratiotes

Abstract: The aquatic plant Pistia stratiotes L. (water lettuce) was studied due to its capability of absorption of contaminants in water and its subsequent use in wetlands constructed for wastewater treatment. The effects of Cd on root growth, accumulation of Cd, antioxidant enzymes, and malondialdehyde (MDA) content in P. stratiotes were investigated. The results indicated that P. stratiotes has considerable ability to accumulate Cd. Cadmium induced higher superoxide dismutase (SOD) and peroxidase (POD) activities than catalase activity, suggesting that SOD and POD provided a better defense mechanism against Cd-induced oxidative damage. The accumulation of Cd promoted MDA production.

Abstract: The bioaccumulation and rhizofiltration potential of P. stratiotes for heavy metals were investigated to mitigate water pollution in the Egyptian wetlands. Plant and water samples were collected mo...

Abstract: A survey of different Dutch Stratiotes stands showed that the density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between the rosettes of S. aloides. Analyses of water samples revealed that nutrient limitation was unlikely to have caused the lower phytoplankton biomass in the vicinity of S. aloides. 2. An in situ incubation experiment in the Danube Delta, Romania, indicated allelopathic activity against phytoplankton in S. aloides stands. The growth rate of natural phytoplankton populations exposed to water from S. aloides stands was significantly lower than that of populations that had not been in contact with S. aloides exudates. 3. A laboratory microcosm experiment showed a significantly lower phytoplankton biomass in treatments with S. aloides exudates. Nutrient concentrations and the light intensity were high enough that the lower phytoplankton biomass could not be explained by nutrient or light limitation. [KEYWORDS: allelopathy ; exudates ; field experiment ; infochemical ; natural phytoplankton]

Abstract: Stratiotes aloides L. is an aquatic macrophyte that occurs in waters on reduced peaty sediments which have a relatively narrow range of free-iron content in the sediment. Comparison of different aquatic macrophytes reveals that species from reducing sediments have much lower oxidizing ability than do species from oxidizing sediments. Compared with those other species from reducing sediments, the oxidizing ability of Stratiotes aloides is very low and probably makes the species very vulnerable to sulphide toxicity and internal precipitation of iron hydroxide. Apoplastic iron contents were determined for Stratiotes roots growing in sediments with different free-iron concentrations. Roots collected from sediment with a low free-iron content appeared to have a relatively low apoplastic-iron content whereas roots from sediments with a relatively high free-iron concentration had a relatively high apoplastic-iron content. In sediments with low free-iron levels, sulphide levels are generally high. Using light microscopy, iron hydroxide precipitates were observed around the endodermis and cortical air spaces of the roots of Stratiotes aloides growing in iron-rich sediments. Internal iron oxidation outside the endodermis can prevent iron toxicity inside the stele and thus enable root apices to survive. The root hairs, however, die because of iron hydroxide precipitation at their base; the dead roots have the highest visible iron hydroxide content. Excessive internal iron hydroxide precipitation and the consequential early death of the roots probably explains the absence of Stratiotes aloides in locations with high free-iron levels in sediment pore water.