The role of rhizome system in the distribution of cadmium load among ramets of Phragmites australis

The common reed, Phragmites australis (Cav.) Trin. ex Steud. , is a clonal plant which is sensitive to environmental disturbances. A clone is composed of large number of ramets which are physically interconnected. In this work the translocation of cadmium from a selected ramet towards the rhizome network of 15 to 30 ramets was investigated in model experiments with known rhizome systems. At the site of treatment, Cd 2+ uptake was much higher both in the roots and rhizome than in the shoot, however, at the distal ramets, shoots accumulated higher concentration of Cd 2+ than roots and rhizomes, and the ramets at the farthest site contained the highest levels of Cd2+. The control of transport through the rhizome network by the distal ramet so far has not been described. The mechanism by which the farthest ramet attracts the heavy metal remains to be investigated. Acta Biol Szeged 46(3-4):81-82 (2002) The common reed, Phragmites australis (Cav.) Trin. ex Steud., is a clonal plant which is often used for cleaning wastewaters and polluted environment. At the same time this species is sensitive to certain environmental disturbances and its closed stands undergo fragmentation and die-back as seen also along the shores of Lake Balaton (Erdei et al. 2001). The capability of reed to accumulate the heavy metal cadmium, one of the most frequent environmental pollutants, was recently investigated and compared to that of in cattail (Typha latifolia L.) (Fediuc and Erdei 2002). It was found that the defense strategy in reed, unlike cattail, relies on increased antioxidant enzyme activities rather than on thiol induction characteristics. Under natural conditions, in a closed stand, a clone is composed of large number of ramets which are physically interconnected. This network may help the clone in giving an adequate response to the effects of the spatial hetero- geneity of the habitat. The unfavourable or favourable conditions alter the growth pattern or growth rule of the clone ("division of labour", foraging response, etc.) (Oborny and Cain 1997). We hypothesized that a point-like source, in this case cadmium, taken up by one selected ramet would be translocated via the rhizome system to a certain distance and may exert its effect on any ramet of the network. For this reason, model experiments were carried out on known rhizome networks of 15 to 30 ramets.