Molecular characterization and evaluation of plant litter-associated fungi from the spring ‘grazing corridor’ of a sheep herd vulnerable to alveld disease

This study sample and identify species of fungi on withered vegetation in the spring 'grazing corridor' from infields to Narthecium bogs for a sheep herd almost chronically vulnerable to phototoxic disease. Hepatogen photosensitizing disorders like alveld attack grazing sheep, especially lambs, in various parts of the world. It has been hypothesized that saponin metabolites in the monocotyledonous plant Narthecium ossifragum causes the disorder in Norway, however, this has not been verified. Thus, the search for other causal agents or saponin cofactors (the cofactor hypothesis) has been intensified, and endophytic poisonous fungi associated with dead N. ossifragum leaves and grasses are among the prime suspects. The fungal diversity was targeted by obtaining axenic cultures from surface-sterilized plant material, with subsequent DNA isolation, PCR, and sequencing of the ITS nrDNA region. The taxonomic affinities of the obtained sequences were thereafter explored by similarity searches against the public access sequence database EMBL/GenBank/DDBJ. Among the spectrum of identified taxa were representatives of Cladosporium, Fusarium, Penicillium, and Trichoderma, all of which are well known as potential producers of toxins. A possible involvement of these toxic species in the etiology of alveld is evaluated and discussed.     

Two mire species respond differently to enhanced ultraviolet-B radiation: effects on biomass allocation and root exudation

Increased ultraviolet-B (UV-B) radiation arising from stratospheric ozone depletion may influence soil microbial communities via effects on plant carbon allocation and root exudation. Eriophorum angustifolium and Narthecium ossifragum plants, grown in peatland mesocosms consisting of Sphagnum peat, peat pore water and natural microbial communities, were exposed outdoors to enhanced UV-B radiation simulating 15% ozone depletion in southern Scandinavia for 8 wk. Enhanced UV-B increased rhizome biomass and tended to decrease the biomass of the largest root fraction of N. ossifragum and furthermore decreased dissolved organic carbon (DOC) and monocarboxylic acid concentration, which serves as an estimate of net root exudation, in the pore water of the N. ossifragum mesocosms. Monocarboxylic acid concentration was negatively related to the total carbon concentration of N. ossifragum leaves, which was increased by enhanced UV-B. By contrast, enhanced UV-B tended to increase monocarboxylic acid concentration in the rhizosphere of E. angustifolium and its root : shoot ratio. Microbial biomass carbon was increased by enhanced UV-B in the surface water of the E. angustifolium mesocosms. Increased UV-B radiation appears to alter below-ground biomass of the mire plants in species-specific patterns, which in turn leads to a change in the net efflux of root exudates.     

Floral evolution in the monocot family Nartheciaceae (Dioscoreales): evidence from anatomy and development in Metanarthecium luteo‐viride Maxim.

The placement of Nartheciaceae within Dioscoreales is an unexpected result of molecular phylogenetics. Nartheciaceae generally differs from the rest of Dioscoreales in having less specialized flowers. Studies of this family are important to elucidate the evolutionary history of the order. Using scanning electron microscopy and light microscopy, we describe the details of the flower structure, initiation, and development in Metanarthecium, which is unique amongst Nartheciaceae in possessing both an almost superior ovary and septal nectaries. This is the first member of Dioscoreales for which all stages of organogenesis have been studied. Within Nartheciaceae, the presence/absence of septal nectaries and the position of the ovary are labile. The presence of post‐genital fusion in the gynoecium correlates with the presence of septal nectaries. Septal nectary morphology is complicated in Metanarthecium, which raises the question of whether its floral structure (including superior ovary) is plesiomorphic within Dioscoreales. The septal nectaries of Metanarthecium show homoplastic similarity with those of Allium (Asparagales). The presence/absence of a compitum is probably variable at the infraspecific level in Metanarthecium as a result of alternative possibilities of post‐genital fusion between ventral carpel margins. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 1–18.     

Comparative morphology of the carpel in the Liliaceae: Tofieldieae

The Tofieldieae consist of Narlhecium, Nietneria, Pleea , and Tofieldia. Although the three carpels of the pistil are generally coherent, their bases are separate for a short distance in some species of Tofieldia and in Pleea , where a septal nectary seems to be differentiated. These two genera are also alike in the extension of the chalaza as a filiform hook. The sutures are open at flowering only in some species of Tofieldia. Nietneria is distinguished by its inferior ovary and the alternate structure of the pistil. No raphide idioblasts were found in the carpels of any species.