Matt K. John

Bio: Matt K. John is an academic researcher. The author has contributed to research in topics: Ascorbic acid & Phosphorus. The author has an hindex of 2, co-authored 2 publications receiving 808 citations.

The structure and function of the vegetative mycelium of ectomycorrhizal plants

Abstract: SUMMARY Using perspex observation chambers, the uptake, translocation and distribution of 32P-labelled phosphorus was studied in ectomycorrhizal mycelial networks of Suillus bovinus (Fr.) O. Kuntze interconnecting plants of Pinus contorta Dougl. ex Loud and Pinus sylvestris L. Label was fed either directly to the cut ends of individual mycelial strands, to plant roots, or to the unsterile peat in the vicinity of advancing mycelial fans. Where 32P was fed to individual strands or mycelial fans it was taken up and translocated through the mycelium, over distances exceeding 40 cm, to all host plants connected to the mycelial network. Ectomycorrhizal roots acted as major sinks for phosphate but the label did not move exclusively towards the plant and was distributed throughout the mycelial system. Calculated translocation rates and flux rates suggest that transport is primarily by symplastic flow rather than turgor driven bulk flow. The amount of label accumulated by each plant was significantly related both to the size of the plant shoot and to the number of mycorrhizal root tips but did not appear to be influenced by the transpiration rates of individual plants. Phosphorus supplied directly to plant roots did not move to other plants via the mycelial connections suggesting that movement of phosphorus between the fungus and host is unidirectional.

Plant communities affect arbuscular mycorrhizal fungal diversity and community composition in grassland microcosms

Abstract: Summary • The diversity of arbuscular mycorrhizal (AM) fungi was investigated in an unfertilized limestone grassland soil supporting different synthesized vascular plant assemblages that had developed for 3 yr. • The experimental treatments comprised: bare soil; monocultures of the nonmycotrophic sedge Carex flacca; monocultures of the mycotrophic grass Festuca ovina; and a species-rich mixture of four forbs, four grasses and four sedges. The diversity of AM fungi was analysed in roots of Plantago lanceolata bioassay seedlings using terminal-restriction fragment length polymorphism (T-RFLP). The extent of AM colonization, shoot biomass and nitrogen and phosphorus concentrations were also measured. • The AM diversity was affected significantly by the floristic composition of the microcosms and shoot phosphorus concentration was positively correlated with AM diversity. The diversity of AM fungi in P. lanceolata decreased in the order: bare soil > C. flacca > 12 species > F. ovina. • The unexpectedly high diversity in the bare soil and sedge monoculture likely reflects differences in the modes of colonization and sources of inoculum in these treatments compared with the assemblages containing established AM-compatible plants.

Labile organic matter as an indicator of organic matter quality in arable and pastoral soils in New Zealand

Abstract: Labile organic matter fractions (light fraction C, microbial biomass C and water-soluble organic matter) were extracted from two soils (Lismore silt loam and Temuka clay loam) varying in cropping history from long-term (>9 yr) arable cropping to long-term (>9 yr) pasture in the Canterbury region of New Zealand. With increasing periods under pasture, soil organic C content increased and the amounts of labile organic matter extracted increased (microbial biomass C, 1.0–2.2% of organic C; light fraction, 1.8–4.6% organic C and water-soluble C, 0.7–1.2% organic C). Labile organic matter was more closely correlated with previous cropping history (R=0.89–0.96) than with soil organic C content (R=0.81–0.82). Alternating these soils under rotations of 2–5 yr of pasture followed by 2–5 yr arable resulted in soil organic C remaining unchanged while labile organic matter increased under pasture and declined under the arable phase. The three indices of labile organic matter were closely correlated suggesting they are interrelated properties. In the Lismore soil the mean proportion of total soil organic C, N and P present in water-soluble form differed widely being 0.28, 0.18 and 0.03% respectively for field-moist samples. This presumably reflects differences in chemical nature, solubility, biodegradability and affinity for soil colloids of soil organic C, N and P compounds. Water-soluble organic C, N and P was much greater when extracted from air-dried than field-moist soils and this difference was proportionately greater for soils with higher total soil organic matter contents. Water-soluble organic matter in air-dried soils was thought to have originated from soil solution, from lysed desiccated microbial cells and from labile humic material. It was concluded that inclusion of grazed pastures in a cropping system maintains labile organic C in higher amounts than is possible under annual cropping.

Accumulation and release of plant nutrients in decomposing Scots pine needle litter. Long-term decomposition in a Scots pine forest II

Abstract: Plant nutrient dynamics in decomposing needle litter were measured during a 5-year period in a Scots pine forest in central Sweden. As seen over the whole 5-year period, the nutrients were retained...