Adaptability of Typha domingensis to high pH and salinity.

The aim of this work was to compare the adaptability of two different populations of Typha domingensis exposed to high pH and salinity. The plants were sampled from an uncontaminated natural wetland (NW) and a constructed wetland (CW) for the treatment of an industrial effluent with high pH and salinity. The plants from each population were exposed to the following combined treatments of salinity (mg l(-1)) and pH: 8,000/10 (values found in the CW); 8,000/7; 200/10 and 200/7 (typical values found in the NW). Chlorophyll concentration, relative growth rates (RGR) and root structure parameters (cross-sectional areas of root, stele and metaxylem vessels) were measured. Images of roots and leaves by scanning electronic microscopy (SEM) were obtained, and X-ray microanalysis in different tissues was carried out. In all treatments, the RGR and chlorophyll increase were significantly lower in the plants from the NW than in the plants from the CW. However, stress was observed when the plants from the CW were exposed to treatment 200/7. In treatment 8,000/10 the tissues of the plants from the NW showed severe damages. The root structure of plants from the CW was modified by salinity, while pH did not produce changes. In plants from the CW there were no differences between Na concentration in leaves of the treatments 8,000/10 and 200/7, indicating that Na was not transported to leaves. The CW population already possesses physiological and morphological adaptations due to the extreme conditions of pH and salinity. Because of its adaptive capacity, T. domingensis is an efficient species to treat wastewater of high pH and salinity.