Copper tolerance, uptake and accumulation by Phragmites australis.

Copper (Cu) uptake and accumulation of five populations of Phragmites australis growing in two mine sites (Parys Mountain, Wales, UK and Plombières, Belgium) contaminated with Cu and three 'clean' sites (Felixstowe, UK; Wisbech, UK and Mai Po, Hong Kong) were studied under field and glasshouse conditions. Cu tolerances in these populations of seedlings raised from seeds collected from the above five sites were also studied under glasshouse conditions. Although concentrations of Cu in the plant tissues (leaves, stems, rhizomes and roots) of P. australis and the associated soils from the Cu-contaminated sites were significantly higher than those of the plant tissues and the soils collected in the clean sites, small differences were found between the two Cu-contaminated populations and the three clean populations when seedlings were grown in 0.1 and 0.5 microg ml(-1) Cu treatment solutions. In general, different populations of seedlings showed similar growth responses, metal uptake and indices of Cu tolerance when cultured in the same Cu treatment solution for 3 weeks. There was insufficient evidence to support the hypothesis that the Cu-contaminated populations have evolved to Cu-tolerant ecotypes.

Current approaches to the revegetation and reclamation of metalliferous mine wastes.

Abandoned metalliferous mine wastes can result in severe pollution and have aesthetic impacts on the local environment. Use of a vegetation cover gives a cost-effective and environmentally sustainable method of stabilising and reclaiming wastes such as mine-spoils and tailings. Many characteristics of metalliferous wastes are often inimical to successful vegetation establishment, most notably phytotoxic levels of residual heavy metals, low nutrient status and poor physical structure of the substratum. Current approaches to revegetation and reclamation involve both ameliorative and adaptive strategies to allow plant establishment and encourage subsequent vegetation development. Different techniques of revegetation are available for temperate and arid, subtropical regions depending on the characteristics of the waste. These include direct seeding with commercially available plants, use of cover and barrier systems and the enhancement of natural revegetation processes.

Localized prior knowledge and optimal interpolation in high-resolution tomography.

The problem of electromagnetic tomographic reconstruction is approached in terms of the derivation of a minimum norm interpolator, incorporating a priori knowledge gained from a previous reconstruction. An algorithm is suggested for the initial estimate and both images are compared to that of bilinear interpolation.

Biocontrol-risky but necessary?

There is currently much debate concerning the risks of biological control and the potential harmful effects of nonindigenous species introduced for controlling exotic pests. Biocontrol advocates generally appear reluctant to accept the possibility that there could be side-effects associated with biocontrol, often refuting evidence of harmful effects and suggesting that current practices are sufficient to minimize any risks. The biocontrol critics, on the other hand, although eager to provide evidence to the contrary, appear reluctant to propose any detailed, constructive criticisms or workable solutions. Here, we attempt to put these arguments into context, and suggest some directions for future research that might help to resolve some of the problems.

Zinc, lead and cadmium tolerance, uptake and accumulation by Typha latifolia.

Zinc, lead and cadmium tolerance in four populations of Typha latifolia raised from seed collected from metal-contaminated and uncontaminated sites were investigated. Metal concentrations in natural plant populations showed that Zn, Pb and Cd in the leaves were maintained at low levels (Zn: 22-122, Pb: 4.7-40 and Cd: 0.2-0.8 µg g-1 d. wt), although concentrations of these metals in the associated soil-sediments (total concentrations of Zn: 86-3009, Pb: 26-18894 and Cd: 1.4-26 µg-1 d. wt) and in the roots (Zn: 46-946, Pb: 25-3628 and Cd: 1.0-17 µg g-1 d. wt) varied widely. Some differences were found between metal-contaminated and uncontaminated populations in terms of metal uptake under controlled conditions. Seedlings from metal-contaminated populations accumulated considerably more metals (up to nearly twice as much Zn and Pb and three times as much Cd) in roots than the uncontaminated population in a pot trial. In general, however, different populations of T. latifolia showed similar growth responses (the longest leaf elongation, the longest root elongation, shoot and root d. wt), metal uptake and indices of metal tolerance when seedlings were grown in the same metal treatment solutions or in the same metal-contaminated media under laboratory conditions. The data do not support the hypothesis that populations from metal-contaminated sites have evolved tolerance to Zn, Pb and Cd, but rather that T. latifolia shows constitutional tolerance.

Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface.

The effects of iron plaque on the growth of Typha latifolia L. and accumulation of copper and nickel in T. latifolia were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without iron plaque on their roots were exposed to 0.05 µg ml-1 Cu and 0.10 µg ml-1 Ni solutions for 72 d. The results showed no differences in root and shoot d. wt and leaf elongation when Cu or Ni were added to the solution and in the presence or absence of plaque. However, root length was reduced by Cu and Ni, and the reduction in root length was greater in the presence of plaque. Some Cu and Ni was adsorbed on root surfaces; roots with plaque took up more Cu, but less Ni than those without. The presence of plaque did not alter Cu uptake and translocation but increased Ni uptake and translocation. Most of the Cu and Ni taken up was retained in the roots, suggesting that the root tissue rather than the root surface or plaque is the main barrier for Cu and Ni transport. The results differ from those reported for other species.

Revegetation of peat excavations in a derelict raised bog.

Thorne Waste, S. Yorkshire, is a large raised bog, subject to extensive commercial peat extraction, which retains some re-flooded, revegetated peat cuttings. The composition of the vegetation of some of these cuttings (96 sampled quadrats, each of 25 m2 ) has been related to a number of environmental variables. Revegetation sequences in the abandoned cuttings (all less than 60 years old and with less than 20 cm peat infill) were established by stratigraphical analyses. In some cuttings a basal layer of ericaceous peat apparently marks temporarily drier conditions preceding deeper inundation. Some former mire species (e.g. Sphagnum imbricatum have not survived the peat-cutting period even on uncut surfaces (baulks) but these have been much drained and burnt. The revegetated cuttings contained species typical of poor-ten (e.g. Carex curta) as well as of ombrotrophic mires (e.g. Andromeda polifolia); chemical analyses indicated weakly minerotrophic peat water. This may favour such species as Sphagnum recurvum. There was no indication of chemical enrichment from inflow from surrounding farmland, from underlying mineral ground or from the clay-lined canals excavated across the bog. Release of cations following drainage and re-flooding may provide some explanation. Only soluble reactive phosphorus (SRP) concentration in peat water samples showed consistent and significant seasonal variation, with the lowest values in summer. There were also only a few consistent differences in water chemistry amongst most of the vegetation units identified by TWINSPAN. Nodum 4 (Eriophorum-Sphagnum) stands (richest in ombrotrophic species) occupied the least minerotrophic conditions. One culling, dominated by Juncus, effuses, had no ombrotrophic species (nodum 6). Water concentrations of Ca2+ , Na+ , K+ NH4 + , SO4 2 and SRP were significantly larger here than in other cuttings and peat fertility (estimated phytometrically) and K, N and P concentrations in peat extracts were significantly greater than in a Sphagnum-dominated cutting. The J. effuses samples had strong negative loadings on axis 2 of a Principal Components Analysis (PCA) of the Adriatic data; concentrations of NH4 + , Na+ and SO4 2 in the water showed significant negative correlation with axis 2 ordination scores. Seasonal fluctuation of water level was similar in most cuttings (the J. effuses cutting was exceptional) but variation in depth relative to the peat surface (caused by excavation to different depths) was related to floristic variation. PCA axis 1 may reflect a water-table gradient with TWINSPAN noda 2 (Calluna Sphagnum recurvum) and particularly 1 (Pteridium Campylopus) occupying drier conditions than the others. The wetter cuttings (except the J. effusus site) supported most ombrotrophic and poor-fen species. They were not readily segregated into discrete vegetation types and the two TWINSPAN classes (noda 3 and 4) that accommodated them showed much overlap on the PCA ordination. Nodum 4 samples tended to have higher loadings on PCA axis 2 and to be more species-rich than nodum 3 samples. Species-richness was strongly positively correlated with PCA axis 2. This may reflect, in part, stand maturity, vegetation with most species having been disturbed least recently.

PLANTS AND PEAT CUTTINGS: HISTORICAL ECOLOGY OF A MUCH EXPLOITED PEATLAND - THORNE WASTE, YORKSHIRE, UK.

Although many lowland raised bogs have been much modified or completely destroyed by agricultural reclamation, peat cutting, unaccompanied by reclamation, is not necessarily so destructive, and abandoned workings may provide a range of habitats that can support some of the original wetland plant species. Thome Waste, a much exploited raised bog in Eastern England, has a varied and well-documented management history and comparatively good botanical records. It thus provides an exemplary site to assess the effect of peat exploitation upon its flora. The origin and development, and subsequent drainage, reclamation and peat extraction history of the site are described, and their impact upon the past and present flora is evaluated. Some ombrotrophic mire species have been lost from the site, but one section of peat cuttings (the Dutch canal system, abandoned about 1920) has revegetated and supports an important range of these plants. Fen species, which once occupied the marginal lagg, have been almost completely eliminated from their original sites (which have mostly been reclaimed) but many have become re-established in various new habitats created within the peat-cutting complex. This illustrates the potential of artificial modification of worked-over peatland sites to sustain a range of wetland plants.

Primary melanoma of the bladder: a case report and review.

A case of primary melanoma of the bladder is presented along with a review of the 3 previously reported cases. The criteria for classification of the bladder lesion as the primary site are discussed. Symptomatology and patient presentation are described.