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Majola T.,Vegetable and Ornamental Plant Institute | Kelly J.,Plant Protection Research Institute
Journal of the Canadian Society of Forensic Science | Year: 2013

A preliminary study was conducted to investigate the effect of direct sunlight and shade on carcass decomposition and arthropod succession in the central region of South Africa. Three pig carcasses (Sus scrofa) were used in this study and were placed in full sunlight, partially in the shade, and in fully shaded conditions. This research was done during the spring season of 2003, from 23 September to 11 November. Internal carcass temperatures, as well as environmental temperatures, were recorded daily and the decomposition rates were compared between direct sunlight versus the partially and fully shaded carcasses. The carcass placed in direct sunlight attracted more arthropods and the decomposition rate was faster compared to those carcasses placed in the shade. Chrysomya chloropyga and Lucilia spp. were the most dominant species on these carcasses. Dermestes maculatus De Geer (Coleoptera, Dermestidae), followed by Necrobia rufipes De Geer (Coleoptera, Cleridae), were present in high numbers during the active decay stage. This study illustrates that shade has an effect on physical decomposition stages. The preliminary results showed that shaded or partly shaded carcasses decompose slower than carcasses exposed to full sunlight. There was no effect on arthropod species succession or development, although the numbers of individuals varied. Source

Mampholo B.M.,Tshwane University of Technology | Sivakumar D.,Tshwane University of Technology | Beukes M.,University of Pretoria | van Rensburg W.J.,Vegetable and Ornamental Plant Institute
Journal of the Science of Food and Agriculture | Year: 2013

BACKGROUND: The perishability of Brassica chinensis poses a major challenge to distribution and marketing. The aim of this work was to select a suitable modified atmosphere packaging to retain the overall quality and bioactive compounds during storage. RESULTS: Four types of biorientated polypropylene packaging (BOPP) - BOPP03, BOPP04, BOPP05 and BOPP06 - with different perforations were evaluated regarding the maintenance of quality parameters (weight loss, leaf yellowing, colour L*, C*, h°), decay, chlorophyll a, chlorophyll b, bioactive compounds (carotenoids, ascorbic acid, total phenolic compounds), antioxidant scavenging activity, overall appearance and odour evaluation, at 10°C at 2, 4, 6, 8 and 10 days. Leaves were packed in BOPP (two 2-mm holes) and packed and unpacked leaves were included for comparison. The modified atmosphere created (2% O2 and 7% CO2) inside the BOPP05 reduced leaf yellowing (higher h°), improved the overall appearance with acceptable odour, moderately maintained chlorophyll a and b, bioactive compounds and antioxidant scavenging activity, and remained marketable for up to 10 days at 10°C. Gas composition within the packages influenced the retention of bioactive compounds and overall quality. CONCLUSION: Application of BOPP05 is a promising method for extending the shelf life of B. chinensis leaves in order to promote its utilisation and commercialisation via urban fresh-produce markets. © 2012 Society of Chemical Industry. Source

Fessehazion M.K.,University of Pretoria | Fessehazion M.K.,Vegetable and Ornamental Plant Institute | Annandale J.G.,University of Pretoria | Everson C.S.,University of Pretoria | And 4 more authors.
Agricultural Water Management | Year: 2015

Poor management of irrigation water and nitrogen (N) fertiliser in ryegrass cropping systems reduces forage yield, and quality, N-use efficiency, and potentially leads to atmospheric and water pollution. The objective of this study was to calibrate and validate the soil water balance (SWB-Sci) model for annual ryegrass (. Lolium multiflorum) pasture and assess the impact of different irrigation strategies on forage yield, irrigation water use and N use efficiency. Field trials were conducted using annual ryegrass under a range of irrigation and N application strategies to calibrate and test the SWB-Sci model. Once calibrated and validated, the model was used to investigate and compare the impact of different irrigation strategies on forage yield, unproductive water loss due to drainage and runoff and N leaching. Using the moderate deficit (irrigating to 60-80% of the field capacity) irrigation strategy, reduced water loss due to drainage and runoff by 54-66%, irrigation water by 37-63%, and N leaching by 69-72% compared to the common farmers' practice of 25. mm irrigation per week, without significant forage yield reduction. The SWB-Sci model showed ways of improving water and N fertilisation use efficiency using moderate deficit irrigation approaches in high rainfall areas. © 2014 Elsevier B.V. Source

Slabbert R.M.,Vegetable and Ornamental Plant Institute | Kruger G.H.J.,North West University South Africa
Plant Physiology and Biochemistry | Year: 2011

The present study describes the behaviour of photosystem II (PSII) in Amaranthus hypochondriacus and Amaranthus hybridus under water stress conditions, assessed by the analyses of the polyphasic rise in chlorophyll a fluorescence (O-J-I-P). We determined the adaptive behaviour in relation to the regulation of the different functional and structural parameters of PSII, which was a direct and rapid response due to changes in soil water status indicated by a decrease in leaf water potential and relative water content. It allows for the identification of specific key or limiting chlorophyll fluorescence parameters which could be used to identify traits conveying tolerance. For the above partial processes of PSII function studied, it seems that A. hybridus remained the more stable upon water stress (after 17 days of withholding water), concerning the specific energy fluxes of absorption/reaction centre (ABS/RC) apparent (antenna size) and trapping/reaction centre (TR/RC) (maximum trapping flux), as well as the density of the reaction centres/cross section (RC/CS) and the phenomenological trapping flux/cross section (TR o/CS). It was clear that amaranth adjusts the non-photochemical (k n) deactivation constant of PSII and to a less extend also the photochemical (k p) deactivation constant by means of photoregulation, which forms the basis of the quenching of chlorophyll a fluorescence. Although drought stress caused the deactivation of RCs leading to a decrease in the density of active RCs, the plants compensated by increasing the efficiency of the conversion of trapped excitation energy to electron transport beyond Q A (efficiency of exciton trapping/reaction centre: ET o/TR o). Subsequent damage to PSII might be the reason for the slow, or lack of recovery, for most of the parameters measured. © 2011 Elsevier Masson SAS. Source

Mabhaudhi T.,University of KwaZulu - Natal | Modi A.T.,University of KwaZulu - Natal | Beletse Y.G.,Vegetable and Ornamental Plant Institute
Water SA | Year: 2013

Bambara groundnut is a protein-rich legume, with food-security potential. Effects of irrigation levels and seed coat colour on growth, development, yield and water-use efficiency of local bambara groundnut landrace selections were evaluated under a rain shelter. Emergence was slow, although variation was indicated between landraces. Limited water availability was shown to lower stomatal conductance, although chlorophyll content index was shown to be unaffected. Additionally, growth indices of plant height, leaf number and leaf area index were shown to be lower in response to decreasing water availability. Furthermore, landraces generally flowered and matured earlier while also demonstrating higher water-use efficiency at lower water availability. Seed yield was lower under limited water availability resulting from lower pod mass and pod number. Drought tolerance in bambara groundnut landraces was achieved by reduced canopy size, early flowering and maturity, and maintaining high water use efficiency under stress. 'Brown' and 'Red' landraces responded to water stress better than the 'Light-brown' landrace, suggesting an effect of seed colour on possible drought tolerance. Source

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