Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value lateseason cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm–2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm–2), and was lowest in the young orchards (~137 cm3∙cm–2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with  large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress  coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation. Keywords: cultivar canopy cover transpiration reduction xylem water potentia

A new species of Urodacus from Western Australia, with additional descriptive notes for Urodacus megamastigus (Scorpiones)

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An investigation of Clostridium species present in nutraceutical preparations of Arthrospira platensis (Spirulina) for human consumption

The presence of the anaerobic spore former Clostridium in Arthrospira platensis destined for human consumption is generally not assessed during quality assurance procedures. As this nutraceutical is administered as complementary medicine to the immunocompromised, this study aimed to investigate the presence of these potential pathogens. Anaerobic counts performed on tablets from a single manufacturer indicated an excess of 105 CFU/endospores g−1 tablet for three different A. platensis batches. Tests for coliforms for use as “indicators” of pathogens in the tablets were negative. Using classic culture techniques, five species of Clostridium were isolated. Subsequent use of PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting of tablets showed a divergent microbial population, with a predominance of anaerobic endospore formers, including Clostridium. Sequencing of a 1.5 kb 16S rDNA clone library and phylogenetic analyses of prominent operational taxonomic units confirmed the presence of an additional five Clostridium spp. and other genera in the tablets. A composite molecular ladder, using 16S rRNA DGGE amplicons of 17 representative bacterial species was constructed to assist in identifying anaerobes present in tablets sourced from three different A. platensis manufacturers. Results indicated that commercial A. platensis preparations were contaminated with potentially hazardous clostridia and other anaerobic species. Results suggest that certain commercial A. platensis preparations require stringent microbial quality assurance measures to ensure safe use as a nutraceutical for the immunocompromised and the general public.National Research Foundation and the Cape Peninsula University of Technology Research Fun

The influence of interfacial bonding on the response of lightweight aluminium and glass fibre metal laminate panels subjected to air-blast loading

This paper examines the effects of glass fibre configuration and epoxy resin type on the response of glass fibre epoxy-based fibre metal laminate panels. These lightweight materials are excellent candidates for use in transportation applications, where mass is a major factor in design and materials selection. Interfacial bond strength was characterised through single leg bend testing and revealed varying failure characteristics for different epoxy configurations and surface treatments. A combination of bead blasting and silane treatment provided the best surface treatment for the aluminium, while SE84 epoxy resin gave superior adhesion properties compared to Prime 20ULV. Blast tests were performed to investigate the effect of bond strength on panel response under localised and more uniformly distributed air-blast loading conditions. Dimensionless analysis and failure mode identification were used to show that both fibre configuration and bond strength played a role in blast response but the bond strength (and particularly resin type) was more prominent

Identification of the gene for β-fructofuranosidase from Ceratocystis moniliformis CMW 10134 and characterization of the enzyme expressed in Saccharomyces cerevisiae

Publication of this article was funded by the Stellenbosch University Open Access Fund.The original publication is available at :Van Wyk, N. et al. 2013. Identification of the gene for β-fructofuranosidase from Ceratocystis moniliformis CMW 10134 and characterization of the enzyme expressed in Saccharomyces cerevisiae. BMC Biotechnology. 13:100, doi:10.1186/1472-6750-13-100.The original publication is available at http://www.biomedcentral.com/bmcbiotechnol/Background: β-Fructofuranosidases (or invertases) catalyse the commercially-important biotransformation of sucrose into short-chain fructooligosaccharides with wide-scale application as a prebiotic in the functional foods and pharmaceutical industries. Results: We identified a β-fructofuranosidase gene (CmINV) from a Ceratocystis moniliformis genome sequence using protein homology and phylogenetic analysis. The predicted 615 amino acid protein, CmINV, grouped with an existing clade within the glycoside hydrolase (GH) family 32 and showed typical conserved motifs of this enzyme family. Heterologous expression of the CmINV gene in Saccharomyces cerevisiae BY4742Δsuc2 provided further evidence that CmINV indeed functions as a β-fructofuranosidase. Firstly, expression of the CmINV gene complemented the inability of the Δsuc2 deletion mutant strain of S. cerevisiae to grow on sucrose as sole carbohydrate source. Secondly, the recombinant protein was capable of producing short-chain fructooligosaccharides (scFOS) when incubated in the presence of 10% sucrose. Purified deglycosylated CmINV protein showed a molecular weight of ca. 66 kDa and a Km and Vmax on sucrose of 7.50 mM and 986 μmol/min/mg protein, respectively. Its optimal pH and temperature conditions were determined to be 6.0 and 62.5°C, respectively. The addition of 50 mM LiCl led to a 186% increase in CmINV activity. Another striking feature was the relatively high volumetric production of this protein in S. cerevisiae as one mL of supernatant was calculated to contain 197 ± 6 International Units of enzyme. Conclusion: The properties of the CmINV enzyme make it an attractive alternative to other invertases being used in industry.Stellenbosch UniversityPublishers' Versio

Measurement and modelling of water use by high yielding apple orchards and orchards of different age groups in the winter rainfall areas of South Africa

Apple production for the export market is in South Africa entirely dependent on irrigation. In recent years, high performing orchards yielding up to 120 t of fruit ha-1 are becoming common in a country where the average yield is between 60 and 80 t ha-1. This raises important questions regarding the sustainability of the exceptionally high yields given the limited availability of water for irrigation. Moreover, there is also no accurate quantitative information published on water use by apple orchards of different age groups and this compromises efficient irrigation scheduling. The aim of this study was to quantify water use by high yielding apple orchards and orchards of different age groups. Data were collected in four commercial orchards, two planted to non-bearing ‘Cripps’ Pink’ and ‘Golden Delicious’ apples and another two highyielding full-bearing orchards of these cultivars. Transpiration in the full-bearing orchards was measured using the heat pulse velocity sap flow method. Granier probes were used on the young non-bearing trees. Orchard evapotranspiration (ET) was measured using eddy covariance systems during selected periods. Ancillary data which included the orchard microclimate, stomatal resistance, soil water content and soil evaporation were also collected. The full-bearing ‘Golden Delicious’ orchard (22- year-old) had the highest seasonal transpiration of 785 mm, followed by the fullbearing ‘Cripps’ Pink’ (9-year-old) which transpired 587 mm. The non-bearing ‘Cripps’ Pink’ (3-year-old) transpired 272 mm compared to 198 mm for the nonbearing ‘Golden Delicious’ (2-year-old). The data were used to validate a dual source ET model based on the Shuttleworth-Wallace method. Transpiration of full-bearing orchards was accurately predicted by the model with the RMSE of 0.55 mm d-1 for ‘Cripps’ Pink’ and 0.70 mm d-1 for the ‘Golden Delicious’ orchards. Improvements to the substrate evaporation sub-model are required to account for various orchard floor management practices.The research reported here formed part of a bigger project entitled “Quantifying water use by high performing apple orchards in the winter rainfall areas of South Africa” project no WRC K5/2398.The Water Research Commission (WRC), with additional funding from Hortgro Science, through the South African Apple and Pear Producers Association (SAAPPA) in South Africa.http://www.actahort.orgam2017Plant Production and Soil Scienc

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm-2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm-2), and was lowest in the young orchards (~137 cm3∙cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation