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Palmerston North, New Zealand

von der Heide C.,Leibniz University of Hanover | Bottcher J.,Leibniz University of Hanover | Deurer M.,Plant and Food Research Palmerston North | Duijnisveld W.H.M.,Federal Institute for Geosciences and Natural Resources | And 2 more authors.
Nutrient Cycling in Agroecosystems | Year: 2010

The knowledge of the spatial and temporal variability of N2O concentrations in surface groundwater is the first step towards upscaling of potential indirect N2O emissions from the scale of localized samples to aquifers. This study aimed to investigate the spatial and the temporal variability of N2O concentrations at different scales in the surface groundwater of a denitrifying aquifer in northern Germany. The spatial variability of N2O concentrations in the surface groundwater was analysed at the plot (200 × 200 m) and at the transect scale (12 m). Twenty plots that were distributed across an area of 11 km2 and 6 transects were sampled. Sixty per cent of the spatial variance of N2O was located at the plot scale and 68-79% was located at the transect scale. This indicates that small-scale processes governed the spatial variability of N2O in the surface groundwater. A spatial upscaling of N2O from the transect to the aquifer scale might be possible with an adequate number of samples that represent important boundary conditions for N2O accumulation in the catchment (topography, groundwater level, land use). For the investigation of the temporal variability, 4 multilevel wells were sampled monthly over a period of 13 months. In two periods, a multilevel well was additionally sampled in 2-day intervals over 8 days. At the annual scale, N2O concentrations in the surface groundwater were higher during the vegetation period (median 87 μg N2O-N l-1) and could change rapidly on the day scale whereas the concentrations were smaller in winter (median 21 μg N2O-N l-1). Groundwater recharge events seemed to be crucial for the day scale variability. Capture of the temporal variations for upscaling might be achieved with a process-based sampling strategy with weekly sampling intervals during the vegetation period, the additional sampling after groundwater recharge events and monthly sampling intervals in winter. © 2009 Springer Science+Business Media B.V. Source

Scalzo J.,The New Zealand Institute for Plant and Food Research Ltd | Stevenson D.,Plant and Food Research Palmerston North | Hedderley D.,Plant and Food Research Palmerston North
Journal of Berry Research | Year: 2015

BACKGROUND: Blueberry fruit available in the market comes from cultivars that have been selected for specific traits and not necessarily for high concentrations of health-promoting phytochemicals in the fruit. OBJECTIVE: To identify and quantify the total and individual phenolic components and other quality traits from a combination of cultivars from two Vaccinium species (V. corymbosum and V. virgatum). The cultivar combination provided a continuous and extended fruit harvest. METHODS: Fruit samples were collected from cultivars growing in a randomized complete block design. The phenolic components were assessed on fruit extracts, the fruit weight and firmness were assessed on fresh fruit and the rest of the traits were assessed on fruit juice. RESULTS: For most traits the differences between Vaccinium species and cultivars were considerable. Strong and positive correlations were found between phenolic components and between fruit traits. For each cultivar the majority of the traits analysed in this work from a single year were highly correlated to the average across the three years of evaluation. Assessing traits from a single year of data should be mostly reliable for individual cultivars. CONCLUSIONS: The combination of cultivars in this study was designed to offer the widest possible harvest window; however, it gives high variation in fruit quality. © 2015 - IOS Press and the authors. Source

Foo E.,University of Tasmania | Ross J.J.,University of Tasmania | Jones W.T.,Plant and Food Research Palmerston North | Reid J.B.,Plant and Food Research Palmerston North
Annals of Botany | Year: 2013

Background and Aims Arbuscular mycorrhizal symbioses are important for nutrient acquisition in.80% of terrestrial plants. Recently there have been major breakthroughs in understanding the signals that regulate colonization by the fungus, but the roles of the known plant hormones are still emerging. Here our understanding of the roles of abscisic acid, ethylene, auxin, strigolactones, salicylic acid and jasmonic acid is discussed, and the roles of gibberellins and brassinosteroids examined. Methods Pea mutants deficient in gibberellins, DELLA proteins and brassinosteroids are used to determine whether fungal colonization is altered by the level of these hormones or signalling compounds. Expression of genes activated during mycorrhizal colonization is also monitored. Key Results Arbuscular mycorrhizal colonization of pea roots is substantially increased in gibberellin-deficient na-1 mutants compared with wild-type plants. This is reversed by application of GA3. Mutant la cry-s, which lacks gibberellin signalling DELLA proteins, shows reduced colonization. These changes were parallelled by changes in the expression of genes associated with mycorrhizal colonization. The brassinosteroid-deficient lkb mutant showed no change in colonization. Conclusions Biologically active gibberellins suppress arbuscule formation in pea roots, and DELLA proteins are essential for this response, indicating that this role occurs within the root cells. © 2013 The Author. Source

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