Volume 1 Number 1 2007

CONTENTS AND ABSTRACTS

Wolf-Ekkehard Lönnig, Kurt Stüber, Heinz Saedler, Jeong Hee Kim (Germany) Biodiversity and Dollo’s Law: To What Extent can the Phenotypic Differences between Misopates orontium and Antirrhinum majus be Bridged by Mutagenesis? (pp 1-30)

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Special Feature: According to Dollo’s law, evolution is irreversible. Yet, of the eight derived features essentially distinguishing Misopates orontium from its closely related Antirrhinum majus, five differences have phenotypically been clearly diminished or fully overcome by mutant genes, so that Misopates orontium outwardly approaches, meets or even overlaps the features of Antirrhinum majus or vice versa (aspects of the life cycle, leaf form, flower size, flower colour and mode of fertilization). However, to date the morphological key distinguishing feature between the two genera, the strongly elongated sepals in Misopates (itself a feature being at odds with Dollo’s law), could not be reduced to that of the length of Antirrhinum nor could the development of the short Antirrhinum sepals be extended to that of the length of Misopates, in spite of extensive mutagenesis programmes with both species (agreeing with Dollo’s law as to the stasis of this difference). Also, the long sepal character strongly dominated almost all homeotic Misopates mutants. After a general discussion of Dollo’s law, its relevance for our mutants (and vice versa) is examined according to different evolutionary viewpoints. Furthermore, two concerns are raised: (1) To what extent can the hypothesis be substantiated such that the long and short sepals could really constitute genuinely persistent (“immutable”) characters? (2) To what magnitude can the unexpected constancy of a feature distinguishing genera like the sepal difference be generalized for systematics and paleontology? Moreover, four basic genetic explanations (losses of gene functions, redun-dancy, the origin of new genes and chromosome rearrangements) are examined in this connection, and their relevance for some pivotal questions on the origin of species is investigated. As far as the authors are aware, this is the first thorough paper on Dollo’s law in botany.

Pedro Martínez-Gómez (Spain), Khalid Majourhat (Spain/Morocco), Mehrshad Zeinalabedini (Spain/Iran), Deniz Erogul (Turkey), Mojtaba Khayam-Nekoui, Vazgin Grigorian (Iran), Abdellatif Hafidi (Morocco), Abel Piqueras (Spain), Thomas M. Gradziel (USA) Use of Biotechnology for Preserving Rare Fruit Germplasm (pp 31-40)

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Invited Mini-Review: The application of recent biotechnological tools for conservation of rare fruit species from developing countries, including in vitro and hydroponic culture protocols, improved propagation techniques and molecular marker application, is described. Promising propagation methods include forcing germination of seeds, in-vitro protocols well adapted to these rare fruit species that allow the introduction, micropropagation and rooting of plant material, and developing hydroponic culture protocols that allow the early propagation of high-risk genotypes. In addition, the growth of seedlings in controlled environmental conditions in greenhouse and cold chamber provides a useful strategy for obtaining vigorously growing plants from seeds year round. A standard karyotyping protocol has been described working in several species as preliminary tool to start molecular (DNA) studies. In addition, different protocols for DNA isolation and quantification have been assayed in these rare fruit species. Molecular markers based on PCR amplification of the DNA have also become an essential tool for the characterization and conservation of these species. Regarding this PCR amplification of the DNA, two main strategies, RAPD (if the DNA sequence is unknown) and SSR markers (if the DNA sequence is known), have been assayed. These markers have been applied in the genetic characterization of this germplasm, the establishment of genetic relationships between cultivars and species, and the future construction of genetic maps of these rare fruit species. Additional advantages encouraging the utilization of these new technologies in breeding programs include the high levels of synteny between genomes of related species, and a well-established international network of cooperation among researchers.

Sarah E. Sundberg-Jones, Sayed M. Hassan (USA) Sediment-Associated Elements in a Constructed Wetland Treatment System: Distribution, Characterization, and Toxicity (pp 41-55)

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Original Research Paper: In a pilot-scale constructed wetland treatment system, Hg, Se, and As were removed from flue gas desulfurization wastewater through a combination of physical, chemical, and biological processes that resulted in their accumulation in the sediment. The first objective of this research was to characterize sediment-associated Hg, Se, and As into operationally-defined fractions using sequential extraction procedures. All measurements were taken after 17 months of wastewater treatment. Mercury concentrations in the sediment varied from 0.025 to 0.035 mg kg^-1 in the treatment system, while concentrations of Se and As in the sediment increased from 3.57 to 8.79 mg kg^-1 and 11.91 to 14.08 mg kg^-1, respectively. Results suggest that Hg and As are stable, immobile, and non-bioavailable in the sediment, as long as current sediment conditions such as pH and redox potential remain stable. Approximately half of the total selenium in the sediment is mobile and bioavailable, while the other half is stable and not bioavailable to plants and organisms. Identification of the main phase associations of Hg, Se, and As in sediments helps to understand the biogeochemical processes involved and to evaluate the risk and remobilization potential of these elements in the constructed wetland. A toxicity assessment of this sediment was then performed to obtain the information needed to support environmental management decisions related to mitigating risks associated with FGD wastewater. The second objective of this research was to evaluate the toxicity of these sediments to Hyalella azteca. Despite the use of this constructed wetland treatment system to treat simulated FGD wastewater for over a year, the sediment was not toxic to H. azteca. It was apparent from this research that measuring sediment toxicity and total concentrations of Hg, Se, and As in sediment cannot provide the required information about mobility, bioavailability, and the potential impact on the aquatic system.

Martin Mkandawire, E. Gert Dudel (Germany) Are Lemna spp. Effective Phytoremediation Agents? (pp 56-71)

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Invited Review: Lemna spp. of the family Lemnaceae have been widely studied for their potential application in phytoremediation. A few Lemna species are already being adopted to enhance natural attenuation for both organic and inorganic pollution in polishing ponds of wastewater treatment facilities, and constructed wetland designed for decontamination of metal pollution. In view of this growing interest, we review in this article the potency and limitation of Lemna species as effective phytoremediation agents. We find that Lemna species have many unique properties ideal for phytoremediation plants species: they are have fast growth and primary production; high bioaccumulation capacity; ability to transform or degrade contaminants; ability to regulate chemical speciation and bioavailability of some contaminant in their milieu; resilient to extreme contaminant concentration; and can be applied on multiple pollutants simultaneously. In addition, they have properties significant for public health likewise livestock production and aquaculture, and ecological function. However, we also find a few important limitations of Lemna as an ideal phytoremediation agent. The plants are small in size and floating in nature. Hence, they are easily blown off the water surface resulting in transferring contamination to uncontaminated sites because Lemna biomass degrades easily thereby readily releasing the contaminant back into the water pathway. This also results in both low sedimentation and contribution to humic material in the benthic. Further, Lemna has very high wet-dry biomass ratios which may be deceiving to believe that they have high bioaccumulation on one hand, while on the other, the energy required to dewater the biomass may be equivalent to conventional treatment plants. Nevertheless, Lemna species remain one of excellent plants for studying process in phytoremediation, and a good phytoextraction agent for application in shallow and small polishing ponds.

Wei Shi, Daniel Bowman, Thomas Rufty (USA) Soil Microbial Community Composition and Function in Turfgrass Ecosystems (pp 72-77)

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Invited Mini-Review: Turfgrasses are an integral component of the urban landscape. Their ecology is strongly influenced by the primary management practices of frequent mowing, fertilization, and irrigation. While much is known about turfgrass plant function, relatively little research has addressed the attending soil microbial community, especially when compared to counterparts in forests, grasslands, and arable soils. This paper reviews available information on soil microbial community composition and function, focusing on organic matter decomposition, nutrient cycling, and response to global environmental change. Consideration also is given to unfavorable conditions that commonly influence the soil microbial community in turfgrass systems (soil compaction, salinity, and use of pesticides). Areas for future research emphasis in turfgrass microbial ecology are discussed.

A. Baeza, J. Guillén (Spain) Role of Fungi in the Determination of the Radiological Status of Terrestrial Ecosystems (pp 78-87)

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Invited Review: In an attempt to assess the importance of the role of fungi as bioindicators in terrestrial ecosystems, we compiled the results reported by more than 100 authors worldwide. These mostly were centred on the ¹³⁷Cs and ⁴⁰K contents. The genera Paxillus, Xerocomus, Cantharellus, and Hebeloma were among those with the highest radiocaesium contents. Studies in countries not highly contaminated in the Chernobyl accident, which included other anthropogenic and natural radionuclides in the assays find the order of relative accumulation to be: ⁴⁰K ≥ ¹³⁷Cs > ^228,230,232Th ≈ ^234,238U ≈ ²²⁶Ra ≈ ⁹⁰Sr >> ^239+240Pu > ²⁴¹Am. Laboratory studies showed that the relative position of anthropogenic radionuclides (mainly radiocaesium and radiostrontium) depends on the moment at which fallout occurred. In particular, if the radionuclide deposition occurred long before the formation of the fruiting bodies, the accumulation of radiocaesium was higher than that of radiostrontium. Other factors, such as the concentration of stable elements and the bioavailability of the different radionuclides in the soil, also affect the radioactive content of the fruiting bodies and hence the dose due to their consumption. While the dose from ingestion of mushrooms in areas clearly affected by the Chernobyl Nuclear Power Plant accident is currently estimated at 1.8 mSv/year due to ¹³⁷Cs, the maximum dose in unaffected areas estimated on the basis of the present findings is 4.60×10^-3 mSv/year for the main natural and anthropogenic radionuclides present in the environment.