Roots and associated fungi drive long-term carbon sequestration in boreal forest.

Boreal forest soils function as a terrestrial net sink in the global carbon cycle. The prevailing dogma has focused on aboveground plant litter as a principal source of soil organic matter. Using (14)C bomb-carbon modeling, we show that 50 to 70% of stored carbon in a chronosequence of boreal forested islands derives from roots and root-associated microorganisms. Fungal biomarkers indicate impaired degradation and preservation of fungal residues in late successional forests. Furthermore, 454 pyrosequencing of molecular barcodes, in conjunction with stable isotope analyses, highlights root-associated fungi as important regulators of ecosystem carbon dynamics. Our results suggest an alternative mechanism for the accumulation of organic matter in boreal forests during succession in the long-term absence of disturbance.

Vertical distribution of ectomycorrhizal fungal taxa in a podzol soil profile.

• Studies of ectomycorrhizal fungal communities in forest soils are usually restricted to the uppermost organic horizons. Boreal forest podzols are highly stratified and little is known about the vertical distribution of ectomycorrhizal communities in the underlying mineral horizons. • Ectomycorrhizal root tips were sampled from seven horizons in three continuous columns of a 52-cm deep podzol profile. Root tips were sorted into morphological groups and the colonising fungi identified by sequencing of the rDNA ITS region. The vertical distribution of mycorrhizal taxa was examined. • A relationship between ectomycorrhizal species composition and soil horizon was found. Tomentellopsis submollis, three Piloderma species and Dermocybe spp. were found predominantly in the upper horizons while Suillus luteus, Lactarius utilis and three undescribed Piloderma species were associated with the mineral horizons. • Two thirds of the root tips were found in the mineral soil and half of the taxa were restricted to the mineral horizons. The results highlight the need to include the mineral soil in order to gain a more accurate representation of the ectomycorrhizal community.

Linking plants to rocks: ectomycorrhizal fungi mobilize nutrients from minerals.

Plant nutrients, with the exception of nitrogen, are ultimately derived from weathering of primary minerals. Traditional theories about the role of ectomycorrhizal fungi in plant nutrition have emphasized quantitative effects on uptake and transport of dissolved nutrients. Qualitative effects of the symbiosis on the ability of plants to access organic nitrogen and phosphorus sources have also become increasingly apparent. Recent research suggests that ectomycorrhizal fungi mobilize other essential plant nutrients directly from minerals through excretion of organic acids. This enables ectomycorrhizal plants to utilize essential nutrients from insoluble mineral sources and affects nutrient cycling in forest systems.

Solubilisation and colonisation of wood ash by ectomycorrhizal fungi isolated from a wood ash fertilised spruce forest.

In Sweden application of granulated wood ash has been suggested as a method to supplement nutrient loss resulting from harvesting of forest residues for bioenergy production. Mycelia of two ectomycorrhizal fungi Piloderma sp. 1 and Ha-96-3, were commonly found to colonise ash granules in a wood ash fertilised spruce forest. Thirty-eight fungal isolates were selected from 10 taxa to investigate the possible role of different ectomycorrhizal fungi in nutrient mobilisation from ash. The taxa were Cenococcum geophilum Fr., Piloderma croceum Erikss. and Hjortst., Piloderma sp. 1, Thelephora terrestris (Ehrenb.) Fr., Tylospora fibrillosa Donk, and five unidentified species, all originating from a wood ash fertilised spruce forest. The isolates were tested for their ability to solubilise tricalcium phosphate (TCP) or hardened wood ash (HWA) in vitro. Ha-96-3, P. croceum and Piloderma sp. 1 were the only taxa which solubilised TCP. Abundant calcium oxalate crystals were formed in TCP and HWA plates with Piloderma sp. 1. Ha-96-3 and two isolates of P. croceum produced intermediate amounts of crystals. Ha-96-1 and T. fibrillosa produced low amounts of crystal but no crystal formation was observed by any of the other isolates. Piloderma sp. 1 from HWA plates had significantly higher concentrations of P, compared to P. croceum or Ha-96-3. Piloderma sp. 1 and P. croceum were further tested for their ability to colonise wood ash in microcosms containing intact mycorrhizal associations. After 7 months Piloderma sp. 1 colonised ash amended patches with a dense, mat like mycelium, whereas P. croceum mycelia avoided the ash patches. Possible differences between these fungi in patterns of carbon allocation were investigated by labelling seedlings with 14CO(2). Piloderma sp. 1 mycelia allocated significantly more 14C to ash patches than P. croceum. P. croceum allocated relatively more 14C to control patches than to the ash patches. The possible role of ectomycorrhizal fungi in mobilisation of nutrients from wood ash is discussed.

Sub-Tenon's local anaesthesia: the effect of hyaluronidase.

AIMS: A prospective, randomised, double blind study was used to investigate the effect of hyaluronidase on the quality of block achieved with sub-Tenon's local anaesthesia. METHODS: 150 patients scheduled for elective cataract surgery were randomly allocated to either sub-Tenon's block with 3 ml lignocaine 2%/adrenaline 1:200 000 alone or with the addition of 30 IU/ml of hyaluronidase. The blocks were assessed for degree of akinesia and reduction of eyelid movement, and also post-injection and postoperative pain scores. RESULTS: Akinesia and reduction of eyelid movement measured 10 minutes after injection were significantly better in the group with hyaluronidase added to the anaesthetic solution. Postoperative pain scores were not significantly different between the two groups but the post-injection pain score was greater (marginally significant) in the group with hyaluronidase added. CONCLUSION: The addition of hyaluronidase significantly improves the quality of the motor blockade achieved with sub-Tenon's local anaesthesia, but has no effect on the sensory blockade.

Respiration of [14C]alanine by the ectomycorrhizal fungus Paxillus involutus.

The ectomycorrhizal fungus Paxillus involutus efficiently took up exogenously supplied [14C]alanine and rapidly converted it to pyruvate, citrate, succinate, fumarate and to CO2, thus providing direct evidence for the utilisation of alanine as a respiratory substrate. [14C]alanine was further actively metabolised to glutamate, glutamine and aspartate. Exposure to aminooxyacetate completely suppressed 14CO2 evolution and greatly reduced the flow of carbon from [14C]alanine to tricarboxylic acid cycle intermediates and amino acids, suggesting that alanine aminotransferase plays a pivotal role in alanine metabolism in Paxillus involutus.

The structure and function of the vegetative mycelium of ectomycorrhizal plants III. Ultrastructural and autoradiographic analysis of inter-plant carbon distribution through intact mycelial systems.

Plants of Pinus sylvestris L. were grown in mycorrhizal association with Suillus bovinus (Fr.) O. Kuntze in observation chambers until an interconnecting mycelial network had developed between the seedlings. The shoot of an individual seedling was then scaled in a perspex cuvette and exposed to 14 CO2 . After incubation for 48 h, the'donor'shoot was removed and components of the mycelial network and mycorrhizal roots of connected and unconnected'receiver'seedlings were harvested, fixed, embedded and sectioned prior to being autoradiographed and examined by transmission electron microscopy. The patterns of distribution of 14 C-labelled material within the mycelial strands, the sheath and root tissues was examined. The results are discussed in relation to carbon metabolism of the fungus and of the interconnected host plant.

VESICULAR-ARBUSCULAR MYCORRHIZA IN NATURAL VEGETATION SYSTEMS: IV. TRANSFER OF NUTRIENTS IN INTER- AND INTRA-SPECIFIC COMBINATIONS OF HOST PLANTS.

The role of inter-plant hyphal bridges formed by vesicular-arbuscular (VA) mycorrhizal mycelia was investigated using double pots in which donor plants were grown in the mycorrhizal (M) or non-mycorrhizal (NM) condition with root systems split so that they could be supplied with nutrients in the donor pot. Plantago lanceolata L. and Festuca ovina L. were grown in intra-and inter-specific combination as donors and receivers. The normally non-mycorrhizal species Arabis hirsuta L. was included as an additional potential receiver. Nutrient solution or distilled water was applied to the donor pot and the patterns of growth responses, and of nitrogen and phosphorus accumulation were compared in receiver plants with and without mycelial interconnections. Yields of M receivers were significantly higher than those of NM plants in all combinations of plants at the second or third harvest, except in the case of the intra-specific combination of Plantago. A. hirsuta showed no response to nutrient application. Mycorrhizal infection of receivers in the distilled water treatment produced a relatively small response indicating that improved exploitation of sand in the receiver pots was not the cause of growth stimulation in M receivers. Yield increases were associated with higher total N contents of the mycorrhizal receiver plants in three of the species combinations and of P content in all combinations, by the third harvest the gain in P concentration being relatively greater than that of N. The results confirm that VA infection can provide channels for direct inter-plant nutrient transfer and that transfer is sufficient to sustain significant enhancement of both growth and nutrient composition of receivers, in some cases within six weeks of commencement of the treatment. The probable physiological and ecological significance of these observations is discussed.

Primary spheroidal degeneration of the cornea in Labrador and northern Newfoundland.

The reported prevalence and severity of primary spheroidal degeneration in Labrador and nothern Newfoundland is based on a survey of 929 patients. The degeneration is associated with man in outdoor occupations and with pinguecula, but not with glaucoma. Ultraviolet radiation is a probable causative factor and prophylaxis using appropriately filtering glass a possibilty.

Some effects on the blood vessels of the human forearm of local exposure to pressures below atmospheric.

1. Measurements were made of the initial rate of change of volume of the forearm when the limb was suddenly exposed to various pressures below atmospheric; this was taken to indicate the arterial inflow under these conditions.2. The relationship between arterial inflow and the change in external pressure was curvilinear, with the convexity towards the pressure axis. At -90 mm Hg inflow was increased more than fivefold.3. With short repeated exposures to negative pressure the inflow to the limb showed a progressive decrease for successive exposures until a steady value was obtained.4. The relationship between arterial inflow and the reduction of external pressure during short repeated periods of exposure (6th-10th exposures) was linear from ambient to -80 mm Hg.5. Measurements of forearm blood flow after one, four and ten exposures to reduced external pressure showed that vasoconstriction developed within 20 sec of the end of the exposure and took about 60 sec to disappear. There were only slight differences in the degree of vasoconstriction induced by the different numbers of exposures.