Wetland plants

A balanced landscape needs waterbodies. These should be designed to have shallow margins to provide the appropriate conditions for wetland planting which, in turn, provide the balanced habitats for a rich wetland ecosystem. 

Metal removal in SSFCWs has been recently focused on metal elimination from synthetic water and different wastewaters,66-86 on the evaluation of the effects of season, temperature, plant species, and chemical oxygen demand (COD) loading on metals removal,87 and on the accumulation of metals in wetland plant species and sediments.88-89 Recent reviews on heavy metal phytoremediation wetlands are also available.48... 

Rai, P.K., Heavy metal pollution in aquatic ecosystems and its phytoremediation using wetland plants An ecosustainable approach, International Journal of Phytoremediation, 10, 133-160, 2008a. 

Weis, J.S. and Weis, P., Metal uptake, transport and release by wetlands plants implication for phytoremediation and restoration, Environment International, 30 (5), 739-753, 2004. 

Figure 1 represents the layout of the treatment plant, which had a start up in 2006. It includes two wetlands, planted with typha, and an initial inorganic stage with a reception basin (of which the bottom is filled with limestone), a cascade aeration facility and a limestone channel. 

Radionuelides can be also used to study the accumulation and degradation of organic pollutants. In our experiments we have followed the uptake and degradation of labelled TNT by wetland plants (Nepovim et al., 2005), and showed that about 63% of the localized in the roots of Ph. australis was bound (Fig. 6) and the remainder was acetone-extractable. An HPLC analysis of the acetone extract failed to detect any TNT, showing that all TNT had been chemically transformed. Thus TNT was not adsorbed on the root surface. In similar experiments performed in wheat (Triticum aestivum). Sens et al. (1999) found that 57% of the taken up was bound... 

Because of rice s origins as a wetland plant, it is more sensitive to water deficiency than most other crops. But provided sufficient water is supplied to periodically inundate the land and the soil is able to retain the water, rice will thrive on almost any type of soil. The productivity of rice land therefore often depends more on position in the landscape and soil physical properties than on the finer attributes of the soil. Nonetheless, subtle differences in properties distinguish productive and problem soils and affect the behaviour of the soil in the environment. 

Transport of gases through the aerenchyma may occur by diffusion and, where pressure gradients develop, by convection. Pressurized flow is important in wetland plants with root systems permitting a throughflow of gases, but is insignificant in other plants (Beckett et al., 1988 Skelton and Alloway,... 

NUTRIENT ABSORPTION PROPERTIES OF WETLAND PLANT ROOTS... 

Nutrient Absorption Properties of Wetland Plant Roots... 

Of wetland plants, rice has been studied the most extensively, and nitrogen has been the most extensively studied element. In this section the rates at which rice roots can absorb nitrogen are discussed and whether this is affected by the morphological and physiological adaptations to anoxic soil conditions. 

This chapter has shown the complexity of the chemical and biological processes around wetland plant roots and the effects of the extreme electrochemical gradient between the root surface and surrounding soil. Models of nutrient uptake by plants in aerobic soil, which treat the root as a simple sink to which nutrients are delivered by mass flow and diffusion but the root not otherwise influencing the surrounding soil, work reasonably well for the more soluble nutrient ions. However, the complexity of the wetland root environment is such that such models are inadequate and more elaborate treatments are necessary. Many of the mechanisms involved are still poorly defined and speculative, but their potential significance is clear. 

Armstrong W, Cousins D, Armstrong J, Turner DW, Beckett PM. 2000. Oxygen distribution in wetland plant roots and permeability barriers to gas-exchange with the rhizosphere a microelectrode and modelling study with Phragmites australis. Annals of Botany 86 687-703. 

Bedford BL, Bouldin DR, Beliveau BD. 1991. Net oxygen and carbon dioxide balances in solutions bathing roots of wetland plants. Journal of Ecology 79 943-959. 

Sorrell BK, Armstrong W. 1991. On the difficulties of measuring oxygen release by root systems of wetland plants. Journal of Ecology 82 177-183. 

Constructed wetlands may not be applicable to all sites. The site must have the proper conditions to produce and support a wetland. The performance of a constructed wetland may be limited by its design criteria. Freezing conditions can limit the effectiveness of a constructed wetland. The long-term effectiveness of constructed wetlands in unknown. Wetland wildlife may be adversely affected by the accumulation of heavy metals in wetland plants. 

Xu S, Leri AC, Myneni SCB, Jeffe PR (2004) Uptake of Bromide by Two Wetland Plants (Typha latifolia L. and Phragmites australis (Cav.) Trin. ex Steud). Environ Sci Technol 38 5642... 

Neori, A., Clark, M., Beck, J., Huang, F., Kane, M.A. and Bitton, G. (1993) Heavy metal binding by natural waters and soluble exudates from micropropagated axenic wetland plants, measured with MetPLATE, a bioassay for rapid assessment of heavy metal toxicity, Amer. Soc. Limnol. Oceanog. (ASLO)-Soc. Wetland Scientists Ann. Joint Meeting, Univ. Alberta, Edmonton, May 31-June 3, 1993. 

Nava-Rodriguez, V. Hemandez-Bautista, B.E., Cruz-Ortega, R., Anaya, A.L. Allelopathic potential of beans (.Phaseolus spp.), other crops, and weeds from Mexico. Allelopathy J Neori, A., Reddy, K.R., Ciskova-Koncalova, H., Agami, M. Bioactive chemicals and biological-biochemical activities and their functions in rhizospheres of wetland plants. Bot Rev 2000 66 350-378. 

This paper summarizes the results of emission measurements made from several wetlands in Florida. The two environments mentioned above were sampled, in addition to sites with predominant plant communities of Cladium jamaicense. Juncus roemerianus. Disticlis spicata. Avicennia germinans. Batis maritima. and coastal seawater surfaces. Complete descriptions of the sites are given in refs. (8-111. These sites were chosen to represent the major wetland plant communities of Florida, and their geographic locations are shown in Figure 1. 

The uptake of sulfides by rooted wetland plants living in anoxic sediments presents the problem of coping with toxicity since H2S is highly toxic to many organisms (Howarth and Teal, 1979). Dissolved sulfides have also been shown to inhibit coupled... 

---