Influence of UV radiation on chlorophyll, and antioxidant enzymes of wetland plants in different types of constructed wetland

A surface- and vertical subsurface-flow-constructed wetland were designed to study the response of chlorophyll and antioxidant enzymes to elevated UV radiation in three types of wetland plants (Canna indica, Phragmites austrail, and Typha augustifolia). Results showed that (1) chlorophyll content of C. indica, P. austrail, and T. augustifolia in the constructed wetland was significantly lower where UV radiation was increased by 10 and 20 % above ambient solar level than in treatment with ambient solar UV radiation (p < 0.05). (2) The malondialdehyde (MDA) content, guaiacol peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities of wetland plants increased with elevated UV radiation intensity. (3) The increased rate of MDA, SOD, POD, and CAT activities of C. indica, P. australis, and T. angustifolia by elevated UV radiation of 10 % was higher in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland. The sensitivity of MDA, SOD, POD, and CAT activities of C. indica, P. austrail, and T. augustifolia to the elevated UV radiation was lower in surface-flow-constructed wetland than in the vertical subsurface-flow-constructed wetland, which was related to a reduction in UV radiation intensity through the dissolved organic carbon and suspended matter in the water. C. indica had the highest SOD and POD activities, which implied it is more sensitive to enhanced UV radiation. Therefore, different wetland plants had different antioxidant enzymes by elevated UV radiation, which were more sensitive in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland.

Relationships between Oak powdery mildew incidence and severity and commensal fungi

Oak (Quercus robur) powdery mildew is a common and damaging fungal disease. In a local survey at Reading, UK, oak powdery mildew was common on trees of all height classes but was most common on trees of 3-9m. A variety of other fungal species were commonly found growing in association with oak powdery mildew colonies. The abundance of such fungi was estimated through stratified sample surveys for 2.5 years. The taxa most commonly associated with oak powdery mildew were Acremonium sp., Trichoderma sp., Ampelomyces/Phoma sp. and Leptosphaerulina australis. Nearly 90% of mildew colonies were associated with L. australis, which is not generally considered as a mycoparasite or antagonist, in contrast with the other three fungi. Abundance varied between June and October surveys. Acremonium sp. abundance was greater in summer samplings whereas L. australis and Trichoderma sp. abundances were greater in autumn samplings. Ampelomyces/Phoma sp. was never observed in the absence of powdery mildew. Relationships between the mildew-associated fungi and oak powdery mildew appeared curved and differed significantly between sampling years. L. australis was positively correlated with the other three associated fungi studied when powdery mildew was also present. The variety and high population densities of the mildew associated fungi suggest that they may be important in determining the final density of oak mildew and the damage caused by it.

Global patterns of plant root colonization intensity by mycorrhizal fungi explained by climate and soil chemistry

Aim Most vascular plants on Earth form mycorrhizae, a symbiotic relationship between plants and fungi. Despite the broad recognition of the importance of mycorrhizae for global carbon and nutrient cycling, we do not know how soil and climate variables relate to the intensity of colonization of plant roots by mycorrhizal fungi. Here we quantify the global patterns of these relationships. Location Global. Methods Data on plant root colonization intensities by the two dominant types of mycorrhizal fungi world-wide, arbuscular (4887 plant species in 233 sites) and ectomycorrhizal fungi (125 plant species in 92 sites), were compiled from published studies. Data for climatic and soil factors were extracted from global datasets. For a given mycorrhizal type, we calculated at each site the mean root colonization intensity by mycorrhizal fungi across all potentially mycorrhizal plant species found at the site, and subjected these data to generalized additive model regression analysis with environmental factors as predictor variables. Results We show for the first time that at the global scale the intensity of plant root colonization by arbuscular mycorrhizal fungi strongly relates to warm-season temperature, frost periods and soil carbon-to-nitrogen ratio, and is highest at sites featuring continental climates with mild summers and a high availability of soil nitrogen. In contrast, the intensity of ectomycorrhizal infection in plant roots is related to soil acidity, soil carbon-to-nitrogen ratio and seasonality of precipitation, and is highest at sites with acidic soils and relatively constant precipitation levels. Main conclusions We provide the first quantitative global maps of intensity of mycorrhizal colonization based on environmental drivers, and suggest that environmental changes will affect distinct types of mycorrhizae differently. Future analyses of the potential effects of environmental change on global carbon and nutrient cycling via mycorrhizal pathways will need to take into account the relationships discovered in this study.

Thermal and pressure stability of myrosinase enzymes from black mustard (Brassica nigra L. W.D.J Koch. var. nigra), brown mustard (Brassica juncea L. Czern. var. juncea) and yellow mustard (Sinapsis alba L. Subsp Maire) seeds

This study investigates the effects of temperature and pressure on inactivation of myrosinase extracted from black, brown and yellow mustard seeds. Brown mustard had higher myrosinase activity (2.75 un/mL) than black (1.50 un/mL) and yellow mustard (0.63 un/mL). The extent of enzyme inactivation increased with pressure (600-800 MPa) and temperature (30-70 °C) for all the mustard seeds. However, at combinations of lower pressures (200-400 MPa) and high temperatures (60-80 °C), there was less inactivation. For example, application of 300 MPa and 70 °C for 10 minutes retained 20%, 80% and 65% activity in yellow, black and brown mustard, respectively, whereas the corresponding activity retentions when applying only heat (70 °C, 10min) were 0%, 59% and 35%. Thus, application of moderate pressures (200-400 MPa) can potentially be used to retain myrosinase activity needed for subsequent glucosinolate hydrolysis.

Autoclaving kills soil microbes yet soil enzymes remain active

Biocidal treatment of soil is used to remove or inhibit soil microbial activity, and thus provides insight into the relationship between soil biology and soil processes. Chemical (soil pH, phosphodiesterase, protease) and biological (substrate induced respiration) characteristics of three contrasting soils from tropical savanna ecosystems in north Queensland, Australia were measured in field fresh samples and following autoclaving (121 °C/103 kPa for 30 min on two consecutive days). Autoclaving treatment killed the active soil microbial biomass and significantly decreased protease activity (∼90%) in all three soils. Phosphodiesterase activity in kaolinitic soils also significantly decreased by 78% and 92%. However, autoclave treatment of smectitic soil only decreased phosphodiesterase activity by 4% only. This study demonstrates phosphodiesterase can remain stable in extreme conditions. This might be a characteristic vital to the cycling of phosphorus in shrink–swell clays in Australian tropical savanna ecosystems.

Phosphate supply and arsenate toxicity in ectomycorrhizal fungi

Three species of ectomycorrhizal fungi (Hebeloma crustuliniforme, Suillus variegatus and Cenococcum geophilum) were grown in axenic culture amended with range of AsO43– concentration under three different PO43– regimes. The fungi exhibited different growth responses to AsO43– that varied with PO43– concentration. Suillus variegatus showed the greatest sensitivity to AsO43–, with growth almost completely inhibited in the presence of AsO43– under the lower two PO43– treatments. Under the highest PO43– treatment however, growth was enhanced and S. variegatus was able to persist at AsO43– concentrations of up to 4 mM. Hebeloma crustuliniforme also showed high sensitivity to AsO43– especially at low PO43– concentration. The two higher PO43– treatments had an ameliorating effect on AsO43– toxicity in H. crustuliniforme. This demonstrates the ability of PO43– to alleviate AsO43– toxicity. The response from S. variegatus and H. crustuliniforme, both basidiomycetes, was in contrast to the ascomycete C. geophilum. This fungus demonstrated tolerance to AsO43– when grown in culture solution and PO43– did not have an ameliorating effect on AsO43– toxicity in C. geophilum.

Mushrooms and taphonomy: the fungi that mark woodland graves

Two closely related chemoecological groups of fungi, the ammonia fungi and the postputrefaction fungi, have been associated with the decomposition by-products of cadavers. Sporocarps have been observed in disparate woodlands across the world and often mark sites of graves. These groups of fungi provide visible markers of the sites of cadaver decomposition and follow repeated patterns of successional change as apparent decomposition proceeds. We suggest these phenomena may become a useful tool for crime scene investigation, forensic archaeology and forensic taphonomy.

Considerations on the use of the p-nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi

The p-nitrophenyl phosphomonoesterase assay (p NPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. p NPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of monoester organic P sources in the soil. The importance of the assay to the P nutrition of soil fungi is considered based on the evidence currently available including the consistency of methodological approach. The nature of organic P in the soil and the relevance of the assay to some specific soil substrates is discussed, particularly the chemistry and bioavailability of myo-inositol hexakisphosphate and the lower inositol phosphates. The evidence for the long-term stability of p NPPases in the soil is examined in the light of the persistence of p NPPase in soils. The role of persistent extracellular fungal p NPPases in the soil P cycle is discussed. Conclusions from p NPPase based studies must be based upon an appreciation of the constraints of the assay and the complex chemistry of organic P and p NPPase in the soil.

Some potential inaccuracies of the p -nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi

The p-nitrophenol phosphomonoesterase assay (pNPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. pNPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of organic P sources in the soil. We report here on a series of experiments with the ectomycorrhizal basidiomycete Hebeloma cylindrosporum that highlight components of accepted methodology that might impinge on the reliability of the assay. These include the loss of pNPPase after filtration, inaccuracies in measuring wall-associated enzyme and the ample pool of intracellular pNPPase can be mistakenly measured as external pNPPase if cells are accidentally damaged.

Temperature regulation of extracellular proteases in ectomycorrhizal fungi (Hebeloma spp.) grown in axenic culture

Strains of Hebeloma representative of different climatic zones were grown in axenic culture at either 2 °C and 22° or 6° and 22°. Culture filtrates were assayed for proteolytic activity using FITC labelled BSA as a substrate. Assays were run between 0–37°. Growth at low temperature induced greater proteolytic activity (g−1 D.W. mycelium). Many of the strains produced protease(s) which retained significant activity at temperatures as low as 0°, and a thermal optimum between 0–6° with a second optimum at higher temperature. The results are discussed in relation the nutrient acquisition potential of ectomycorrhizal fungi at low temperature and the contribution such cold active proteases might make to the soil enzyme pool.