Research Articles (Plant Production and Soil Science)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1729

A collection containing some of the full text peer-reviewed/ refereed articles published by researchers from the
Department of Plant Production and Soil Science

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Now showing 1 - 20 of 1043

IMA GENOME-F20 a draft genome assembly of Agroathelia rolfsii, Ceratobasidium papillatum, Pyrenopeziza brassicae, Neopestalotiopsis macadamiae, Sphaerellopsis filum and genomic resources for Colletotrichum spaethianum and Colletotrichum fructicola
(Pensoft Publishers, 2025-02) D’Angelo, Davide; Sorrentino, Roberto; Nkomo, Tiphany; Zhou, Xianzhi; Vaghefi, Niloofar; Sonnekus, Byron; Bose, Tanay; Cerrato, Domenico; Cozzolino, Loredana; Creux, Nicky; D'Agostino, Nunzio; Fourie, Gerda; Fusco, Giovanna; Hammerbacher, Almuth; Idnurm, Alexander; Kiss, Levente; Hu, Yanping; Hu, Hongli; Lahoz, Ernesto; Risteski, Jason; Steenkamp, Emma Theodora; Viscardi, Maurizio; Van der Nest, Magrieta Aletta; Wu, Yuan; Yu, Hao; Zhou, Jianjin; Dewage, Chinthani S. Karandeni; Kotta-Loizou, Loly I.; Stotz, Henrik U.; Fitt, Bruce D.L.; Huang, Yong-Ju; Wingfield, Brenda D.; brenda.wingfield@up.ac.za
Evaluating undergrowth species pattern and soil seed banks mode for monitoring conservation in a protected forest of Nigeria
(Springer, 2025) Omomoh, Bernard Eromosele; Aigbe, Precious Daniel; Alli, Busayo Janet; Ogunsanwo, Gbenga Elijah; Akomolafe, Gbenga Festus; Adeniji, Oluwafemi Adebayo; Agbede, Isaac Kolawole
As most trees enter senescence, the assessment of undergrowth species and seedling outcomes from soil seed banks becomes imminent research and an essential tool to checklist an area prioritized for tree conservation. The procedure to ascertain senescent trees are not underrepresented is uncommon research, specifically for a buffer zone of a Strict Nature Reserve (SNR) in the Akure Forest Reserve. This study evaluates the species richness of the undergrowth patterns that are prioritized for conservation and also examines the effective soil depths for seedling outcomes. However, four (4) sample plots (50 × 50 m2) from lowlands were established at the buffer zone of a protected forest to measure the population size of the undergrowth species pattern. Similarly, twenty (20) 1 × 1 m2 quadrats of 60 samples were collected at different soil depths (0–3 cm, 3–6 cm, 6–9 cm) and were warm stratified at about 21–39 °C in a greenhouse for seedling outcome. A total of 97 undergrowth species were encountered aboveground, while a total of 18 plant species were distributed at 0–3 cm, 16 at 3–6 cm, and 8 at 6–9 cm seedling emergence. The results from the statistical analysis showed the observed differences among the soil depths from the seedling outcome are significant, and there is a strong dissimilarity between the seedling outcome and the undergrowth species. The undergrowth species pattern is more diverse, and the species richness is higher, which implies a stable community with little or no disturbance. Regrettably, some aging trees were still underrepresented, despite the undergrowth species richness and diversity. More so, the IUCN red list assessment showed that numerous plants, i.e., 34 plants out of 97 undergrowth species, fall into the category of Not Evaluated (NE), which showed that many plants in this typical forest are still going through IUCN evaluation. The current evaluation will assist the IUCN assessment and also help government agents in the conservation allotment of underrepresented aging trees in the protected forest. In the meantime, public education will be used to manage the unsustainable gathering of wild fruit and forest food in the buffer zone. This will be followed by support for home gardens as a means of preventing the overuse of aging tree fruit and plants throughout the ecosystem. It was advised that research be done in protected areas of the forest on soil depths suitable for seedling recruitment and soil seed banks potential that would support conservation action allocation.
Reinstatement of Aloe mutans (Asphodelaceae subfam. Alooideae), a distinctive, endemic, maculate aloe from the central Limpopo province of South Africa
(Magnolia Press, 2024-03-12) Smith, Gideon F.; Figueiredo, Estrela; Klopper, Ronell Renett
Until 1987, Aloe mutans (Asphodelaceae subfam. Alooideae) was accepted as a distinctive species of maculate aloe from South Africa’s Limpopo province. However, this species thereafter often has been included in the synonymy of A. greatheadii var. davyana. Recently, A. davyana was separated from A. greatheadii at the rank of species, which requires reconsideration of the taxonomic status of A. mutans. It is shown that A. mutans differs from A. davyana in several vegetative and reproductive morphological characters so warranting its recognition at the rank of species. Aloe mutans is therefore here reinstated as an accepted species. Both A. mutans and A. davyana are illustrated and an amplified description is provided for A. mutans.
Petalidium namibense (Acanthaceae), a new species from Namibia
(Magnolia Press, 2024-11-12) Swanepoel, Wessel; Van Wyk, Abraham Erasmus (Braam)
Petalidium namibense, hitherto confused with P. englerianum, P. rossmannianum, and the widespread P. variabile, is here described as a new species. It is a range-restricted species, only known from the area to the southwest, west and northwest of Puros in the Kaokoveld Centre of Endemism, northwestern Namibia, where it grows at the base of rocky outcrops, on arid hillsides, and along ephemeral riverbeds and drainage lines. Diagnostic characters for P. namibense include the pale grey appearance of the plants, corky bark on older stems, vegetative parts with a dense white indumentum of relative long dendritic trichomes appearing lanate, flowers borne in short few-flowered dichasia, and bracteoles narrowly ovate. The flowers of P. namibense are distinctive in having the two upper corolla lobes discolorous, abaxially light brown, adaxially vermillion, without nectar guides, and connate towards the base for 25–40% of their length. The anterior lobe is adaxially magenta with two relative long, narrowly triangular yellow nectar guides. The two lateral lobes are adaxially vermillion, or distally magenta, grading to vermillion towards the throat, and lack conspicuous nectar guides. A comparison of key morphological features distinguishing P. namibense from P. sesfonteinense, its closest relative in appearance, as well as from P. englerianum, P. rossmannianum, and P. variabile, is provided. Based on IUCN Red List criteria, a provisional conservation assessment of Vulnerable (VU) is recommended for the new species.
Petalidium etendekaense (Acanthaceae), a new species from Namibia, with notes on the taxonomic identity of P. glutinosum
(Magnolia Press, 2024-02-01) Swanepoel, Wessel; Manzitto-Tripp, Erin A.; Dexter, Kyle G.; Van Wyk, Abraham Erasmus (Braam)
Petalidium etendekaense, previously mistaken for P. glutinosum and P. variabile, is now described as a new species. The name P. pilosibracteolatum is considered synonymous with the older P. glutinosum, the latter of which is also lectotypified. The newly described species is currently only known from the vicinity of Bergsig and slightly further west towards the Skeleton Coast National Park in the Kaokoveld Centre of Endemism, northwestern Namibia. It typically grows on hillsides and along ephemeral riverbeds, primarily in soils derived from Etendeka Group basalt. Diagnostic characters for P. etendekaense include its tomentose-strigulose indumentum, the inflorescence main axis and secondary branches that invariably become spiny with age, and a corolla with an ovate front lobe that is longer than it is wide. Additionally, all lobes of the corolla exhibit similar colours, ranging from dark burgundy to carmine to pink towards the apices. A comparison of some morphological features is provided to differentiate Petalidium etendekaense from P. glutinosum and P. variabile. Based on the IUCN Red List categories and criteria, we conducted a conservation assessment, resulting in the new species being classified as of Least Concern (LC).
Clarifying the placement of Trifolium capense in leobordea (Fabaceae)
(Magnolia Press, 2024-01-24) Le Roux, M. Marianne; Klopper, Ronell Renett; Boatwright, James S.
No abstract available.
Cyphia deliae (Campanulaceae: Cyphioideae), a new species from South Africa and Eswatini
(Magnolia Press, 2024-01-09) Steyn, Hester Maria; Van Wyk, Abraham Erasmus (Braam)
Cyphia deliae, previously confused with C. bolusii, is described here as a new species. It is a range-restricted species known only from the Barberton Centre of Endemism, a biogeographical region that spans the border between South Africa and Eswatini. This species grows on rocky outcrops in montane grassland. Cyphia deliae can be differentiated from its morphologically most similar relative, C. bolusii, primarily by floral characters. A comparison of specific morphological features distinguishing Cyphia deliae from C. bolusii is provided. In accordance with IUCN Red List categories and criteria, a conservation assessment of Vulnerable B1ab(iii); C2a(i) is recommended for the new species.
Aloe burgersfortensis (Asphodelaceae subfam. Alooideae): a distinctive, winter-flowering maculate aloe endemic to the southeastern Limpopo and northwestern Mpumalanga provinces of South Africa
(Magnolia Press, 2024-02-01) Smith, Gideon F.; Figueiredo, Estrela; Klopper, Ronell Renett
Aloe burgersfortensis (Asphodelaceae subfam. Alooideae), which generally has been included in the synonymy of A. parvibracteata since 2000, is formally reinstated as an accepted species that is endemic to the southeastern Limpopo and northwestern Mpumalanga provinces of South Africa. Aloe burgersfortensis differs from A. parvibracteata in several vegetative and reproductive morphological characters so warranting its recognition at the rank of species; the differences are quantified and discussed. The typification of the name A. burgersfortensis is reinterpreted and corrected. Both A. burgersfortensis and A. parvibracteata are illustrated and an amplified description is provided for A. burgersfortensis.
Plant community responses to climate change : the importance of ecological context dependencies
(Wiley, 2025-03) Michalet, Richard; Dolezal, Jiri; Lenoir, Jonathan; Le Roux, Peter Christiaan; Rumpf, Sabine; Wipf, Sonja
No abstract available.
Fine scale patterns and drivers of plant species richness on a sub-Antarctic island
(Wiley, 2025-03) Tsamba, Joshua; Le Roux, Peter Christiaan; Pertierra, Luis R.; Kuhlase, Bongekile Sinenhlanhla Nontokozo; Greve, Michelle
AIMS : Cold environments, such as polar systems, are highly vulnerable to global change drivers such as climate change and invasive species. Therefore, it is essential to assess what drives the diversity of native and invasive species in these systems. LOCATION : We investigated what drives native and alien plant species richness on sub-Antarctic Marion Island and determined the scale-dependence of these drivers. METHODS : Native and alien plant species richness was surveyed at “small” (1 m2) and “large” (9 m2) sampling grains. Difference in richness between the two sampling grains was calculated to assess how local turnover contributes to species assemblage. The factors driving richness at both grains, and the differences in richness between the two grains, were analysed using simultaneous auto-regressive models. Drivers related to energy and environmental heterogeneity were correlated with native richness, whilst drivers related to productivity were related to alien richness. RESULTS : Biotic interactions with a cushion plant facilitated native richness, but restricted alien richness at low elevations. Further, some drivers of richness depended on spatial grain. Native richness was positively related to northness at large, but not small grain size, suggesting that higher northness increases local turnover at a grain size > 1 m2. On the other hand, topographical wetness index (TWI) boosted native richness at small but not large grains, implying that competition for water limits coexistence at low TWI (i.e., low moisture availability) only at small grain. Differences in native species richness between large and small grain sizes were more pronounced at low elevations, suggesting higher compositional heterogeneity at low altitudes. CONCLUSIONS : Our study highlights that drivers of plant species richness in a polar ecosystem differ between native and alien plant species. Additionally, the effects of some drivers on richness differ between sampling grains, and considering these differences provides insight into drivers of local patterns of species assemblage.
Antitubercular activity of 7-methyljuglone-loaded poly-(lactide co-glycolide) nanoparticles
(MDPI, 2024-11-20) Diedericks, B.; Kok, Anna-Mari; Mandiwana, Vusani; Gordhan, Bhavna Gowan; Kana, Bavesh Davandra; Ray, Suprakas Sinha; Lall, Namrita
BACKGROUND/OBJECTIVES : Loading of natural products into poly-(lactide-co-glycolic) acid (PLGA) nanoparticles as drug delivery systems for the treatment of diseases, such as tuberculosis (TB), has been widely explored. The current study investigated the use of PLGA nanoparticles with 7-methyljuglone (7-MJ), an active pure compound, isolated from the roots of Euclea natalensis A. DC. METHODS : 7-MJ as well as its respective PLGA nanoparticles were tested for their antimycobacterial activity against Mycobacterium smegmatis (M. smegmatis), drug-susceptible Mycobacterium tuberculosis (M. tuberculosis) (H37Rv), and multi-drug-resistant M. tuberculosis (MDR11). The cytotoxicity of 7-MJ as well as its respective PLGA nanoparticles were tested for their cytotoxic effect against differentiated human histiocytic lymphoma (U937) cells. Engulfment studies were also conducted to determine whether the PLGA nanoparticles are taken up by differentiated U937 cells. RESULTS : 7-MJ has been shown to have a minimum inhibitory concentration (MIC) value of 1.6 μg/mL against M. smegmatis and multi-drug-resistant M. tuberculosis and 0.4 μg/mL against drug-susceptible M. tuberculosis. Whilst promising, 7-MJ was associated with cytotoxicity, with a fifty percent inhibition concentration (IC50) of 3.25 μg/mL on differentiated U937 cells. In order to lower the cytotoxic potential, 7-MJ was loaded into PLGA nanoparticles. The 7-MJ PLGA nanoparticles showed an 80-fold decrease in cytotoxic activity compared to free 7-MJ, and the loaded nanoparticles were successfully taken up by differentiated macrophage-like U937 cells. CONCLUSIONS : The results of this study suggested the possibility of improved delivery during TB therapy via the use of PLGA nanoparticles.
Survey of farmers' knowledge of yam pests and diseases and management practices in southern Ethiopia
(Oxford University Press, 2024-11) Gogile, Ashebir; Kebede, Misrak; Wada, Eyasu; Kidanemariam, Dawit B.; Abraham, Adane
Yam is a widely consumed food in the tropics and subtropics. Determination of pests (pathogens and insects) and diseases (developed pest invasions and symptoms) and the appropriate management practices are critical in existing crop production systems. This study aimed to document farmers’ knowledge about yam pests and diseases and their management practices in southern Ethiopia. Data were collected from 342 systematically selected farmers and 96 yam fields in 5 major yam-growing zones (Dawuro, Gofa, Gamo, Kembata-Tembaro, and Wolaita) in southern Ethiopia using a semi-structured interview guide. The results showed that 54.1% of the farmers saved their planting materials for the next growing season, while 39.2% of the farmers purchased the planting materials from the local market every year. Most farmers (63.5%) reported that the cultivation of yam has been declining annually due to pests and diseases. White yam (Dioscorea rotundata) (Poir, Dioscoreales, Dioscoreaceae) and water yam (Dioscorea alata) are severely damaged by pests and diseases, as perceived by 33.9% and 24.9% of farmers, respectively. Farmers use healthy-looking pest- and disease-free tubers (39.5%), remove infected plants (24.0%), practice crop rotations (17.3%), and use animal manure (7.0%) to manage yam pests and diseases. Farmers’ knowledge can be a starting point for seeking solutions to yam pests and disease risks. This study could play an important role in improving yam cultivation by identifying strategies to improve the recent decline in yam production to meet future food needs for a rapidly growing population.
Downscaling and validating GLDAS groundwater storage anomalies by integrating precipitation for recharge and actual evapotranspiration for discharge
(Elsevier, 2024-08) Viviers, Cindy; Van der Laan, Michael; Gaffoor, Zaheed; Dippenaar, Matthys Alois; cindy.viviers@tuks.co.za
STUDY REGION : The Steenkoppies Catchment is located approximately 75 km southwest from Pretoria, South Africa (RSA). STUDY FOCUS : This study tested a framework for downscaling Global Land Data Assimilation System (GLDAS-2.2) groundwater storage anomaly (GWSA) estimates from 0.25◦ to 0.05◦. This was achieved in Google Earth Engine using the Random Forest algorithm with only precipitation and actual evapotranspiration (ETa) as input variables. Additionally, the study assessed whether accounting for temporal lags could minimise residuals and enhance model performance. NEW HYDROLOGICAL INSIGHTS FOR THE REGION : The greater range of downscaled GWSA values indicated that the product effectively captured local recharge (precipitation) and discharge (ETa) variations while maintaining conservation of mass. Optimising the temporal correlation (r) between input variables resulted in lower residuals and fewer outliers. Groundwater level measurements and downscaled estimates for the hard rock aquifer showed larger amplitudes and seasonality and yielded the highest r (0.6) and lowest RMSE (40 mm) and MAE (31 mm). Measurements near the spring and in the karst aquifer showed less evident amplitude and seasonality. The in situ derived and downscaled GWSA comparison demonstrated the effectiveness of the product for monitoring storage declines. When applied over aquifers experiencing significant land use change or belowaverage precipitation, the approach could monitor groundwater storage changes, even with limited in situ observations. The adaptable code is available for application in other study areas.
The influence of different tree species and age on the surface water balance of a small commercial forestry catchment
(Elsevier, 2024-08) Kaptein, Nkosinathi D.; Clulow, Alistair D.; Everson, Colin Stuart; Toucher, Michele L.; Germishuizen, Ilaria
Acacia mearnsii and Eucalyptus dunnii plantations play an important role in the South African economy as a source for a variety of wood products. However, these species are commonly associated with high evapotranspiration (ET) which may cause streamflow reduction, affecting downstream water users who are reliant on the stream for survival. The potential future increase in exotic plantations worldwide necessitates understanding the impact of these different species on the water balance, hence the streamflow. At the Two Streams research catchment in South Africa, intense hydrological observations (streamflow, ET and weather) have been conducted on A. mearnsii for almost two decades. In 2018, the catchment was clear-felled with subsequent replanting of E. dunnii and hydrological measurements continued. This provided an opportunity to present observations of the surface water balance of the catchment. However, gaps in the data at various times prevented a compilation of a continuous hydrological record. Therefore, three window periods, with complete records of streamflow, ET and precipitation, and with similar weather conditions, were compared. Only the interception loss (Il) was estimated using the Von Hoyningen-Huene method. First window, A. mearnsii trees were three years old (Amear3), second window, A. mearnsii trees were seven years old (Amear7) and the third window, E. dunnii trees were three years old (Edun3). Results indicated a negative catchment surface water balance for all window periods. During the Amear7 window period, the Il was highest compared to the young crops, which reduced effective precipitation, in turn contributing to the lowest measured streamflow. The negative surface water balance and high ET, suggests that trees were accessing water not quantified in the surface water balance. Crops of all three window periods were found to have the potential to significantly reduce the streamflow, which may in turn affect downstream water users. Further research using isotopes to trace the sources of water used by trees in the system is suggested.
Knowledge, attitude, and practice (KAP) analysis of agricultural biologicals among smallholder farmers across three counties in Kenya
(Elsevier, 2025-03) Mweke, Allan; Alexandersson, Erik; Mulugeta, Tewodros; Ilomo, Mesia; Kritzinger, Quenton; Matsuanyane, Lerato; Onyango, Cecilia Moraa
Agricultural biologicals (agrobiologicals) can be sustainable options to manage plant pests and diseases and enhance growth. This can reduce reliance on synthetic inputs, which often come from non-renewable sources and pose risks to the environment and farmers. However, the use of agrobiologicals in Sub-Saharan Africa (SSA) is low. To understand factors leading to low adoption of Agrobiologicals in Kenya, we performed a Knowledge, Attitude and Practice (KAP) analysis among smallholder farmers in three counties in Kenya regarding agrobiologicals. 275 farmers were interviewed in Kajiado, Kiambu and Machakos counties. The farmers’ knowledge on agrobiologicals was low and varied across the counties; 18–47 % of respondents were deemed knowledgeable. The main source of knowledge was neighbours (32–57 % depending on the county). Regarding the information flow, agro-dealers were the main source of information for agricultural inputs in general. More than 70 % of the farmers were not trained in employing agrobiologicals, and 70 % of the farmers stated that agrobiologicals are not effective. Still, between 46 % (Kajiado) and 18 % (Machakos) used agrobiologicals in their farming practices. The number of years in farming positively correlated with knowledge of agrobiologicals, but not attitude and practice. Possibly, the low knowledge regarding agrobiologicals influenced attitude and practice; however perceived sufficient knowledge of agrobiologicals did not translate into an increased use, indicating that knowledge alone is not sufficient to ensure use among smallholder farmers. These findings call for new strategies to promote agrobiologicals to smallholder farmers in SSA.
Using indicators to assess the status of biological invasions and their management on islands─the Prince Edward Islands, South Africa as an example
(Springer, 2025-03) Fernandez Winzer, Laura; Greve, Michelle; Le Roux, Peter Christiaan; Faulkner, Katelyn T.; Wilson, John R.U.
Addressing the challenge biological invasions pose to island biodiversity is pivotal to achieving Target 6 of the Kunming–Montreal Global Biodiversity Framework. Using a suite of 24 indicators, we evaluated the current status of biological invasions and their management on the Prince Edward Islands, South Africa’s sub-Antarctic territories, and provide recommendations for management. There are 45 established alien taxa on Marion Island, of which 25 are invasive, and nine invasive taxa on the less frequently visited Prince Edward Island. However, despite stringent biosecurity, new alien taxa continue to arrive, potentially through ten introduction pathways, but particularly as contaminants on goods and stowaways on transport vectors. Not all detected taxa have been systematically recorded or identified—identifying incursions to species level may help pinpoint gaps in biosecurity. Three invasive plant species have caused Major environmental impacts (as per the Environmental Impact Classification for Alien Taxa categories), and Massive impacts have been recorded for the house mouse. An ambitious plan to eradicate the house mouse is being developed. A further eight taxa are controlled and four monitored to determine whether they have been eradicated. We argue that systematically tracking and documenting biological invasions is vital to improve the appropriateness, adaptability, and responsiveness of management; and we recommend a dedicated, integrated reporting process involving all stakeholders. Such monitoring is particularly important for remote sites given competing demands to reduce the human footprint, manage biological invasions, and allow access. This article is part of the theme issue ‘Managing biological invasions in protected areas: moving towards the new Global Biodiversity Framework targets’.
Antifungal effect of metabolites from bacterial symbionts of entomopathogenic nematodes on Fusarium head blight of wheat
(MDPI, 2024-02-12) Kgosiemang, Julius Leumo; Ramakuwela, Tshimangadzo; Figlan, Sandiswa; Cochrane, Nicolene; tshimangadzo.ramakuwela@up.ac.za
Fungal diseases such as Fusarium head blight (FHB) are significant biotic stressors, negatively affecting wheat production and quality. This study explored the antifungal activity of the metabolites produced by the bacterial symbionts of entomopathogenic nematodes (EPNs) against FHB-causing Fusarium sp. Fusarium graminearum. To achieve this, the symbiotic bacteria of nine EPN isolates from the EPN collection at the Agricultural Research Council-Small Grains (ARC-SG) were isolated from the cadavers of Galleria mellonella (Lepidoptera: Pyralidae) larvae after infection with EPNs. Broth cultures (crude) and their supernatants (filtered and autoclaved) of each bacterial isolate were used as bacterial metabolite treatments to test their inhibitory effect on the mycelial growth and spore germination of F. graminearum. Mycelial growth inhibition rates varied among both bacterial isolates and treatments. Crude metabolite treatments proved to be more effective than filtered and autoclaved metabolite treatments, with an overall inhibition rate of 75.25% compared to 23.93% and 13.32%, respectively. From the crude metabolite treatments, the Xenorhabdus khoisanae SGI 197 bacterial isolate from Steinernema beitlechemi SGI 197 had the highest mean inhibition rate of 96.25%, followed by Photorhabdus luminescens SGI 170 bacteria isolated from Heterorhabditis bacteriophora SGI 170 with a 95.79% mean inhibition rate. The filtered metabolite treatments of all bacterial isolates were tested for their inhibitory activity against Fusarium graminearum spore germination. Mean spore germination inhibition rates from Xenorhabdus spp. bacterial isolates were higher (83.91 to 96.29%) than those from Photorhabdus spp. (6.05 to 14.74%). The results obtained from this study suggest that EPN symbiotic bacterial metabolites have potential use as biological control agents of FHB. Although field efficacy against FHB was not studied, the significant inhibition of mycelial growth and spore germination suggest that the application of these metabolites at the flowering stage may provide protection to plants against infection with or spread of F. graminearum. These metabolites have the potential to be employed as part of integrated pest management (IPM) to inhibit/delay conidia germination until the anthesis (flowering stage) of wheat seedlings has passed.
Leveraging historic streamflow and weather data with deep learning for enhanced streamflow predictions
(IWA Publishing, 2024-04-01) Schutte, Christiaan E.; Van der Laan, Michael; Van der Merwe, Barend Jacobus
Streamflow information is crucial for effectively managing water resources. The declining number of active gauging stations in many rivers is a global concern, necessitating the need for reliable streamflow estimates. Deep learning techniques offer potential solutions, but their application in southern Africa remains largely underexplored. To fill this gap, this study evaluated the predictive performance of gated recurrent unit (GRU) and long short-term memory (LSTM) networks using two headwater catchments of the Steelpoort River, South Africa, as case studies. The model inputs included rainfall, maximum, and minimum temperature, as well as past streamflow, which was utilized in an autoregressive sense. The inclusion of streamflow in this way allowed for the incorporation of simulated streamflow values into the look-back window for predicting the streamflow of the testing set. Two modifications were required to the GRU and LSTM architectures to ensure physically consistent predictions, including a change in the activation function of the GRU/LSTM cells in the final hidden layer, and a non-negative constraint that was used in the dense layer. Models trained using commercial weather station data produced reliable streamflow estimates, while moderately accurate predictions were obtained using freely available gridded weather data.
The ascorbate-glutathione cycle coming of age
(Oxford University Press, 2024-05-03) Foyer, Christine H.; Kunert, Karl J.
Concepts regarding the operation of the ascorbate–glutathione cycle and the associated water/water cycle in the processing of metabolically generated hydrogen peroxide and other forms of reactive oxygen species (ROS) are well established in the literature. However, our knowledge of the functions of these cycles and their component enzymes continues to grow and evolve. Recent insights include participation in the intrinsic environmental and developmental signalling pathways that regulate plant growth, development, and defence. In addition to ROS processing, the enzymes of the two cycles not only support the functions of ascorbate and glutathione, they also have ‘moonlighting’ functions. They are subject to post-translational modifications and have an extensive interactome, particularly with other signalling proteins. In this assessment of current knowledge, we highlight the central position of the ascorbate– glutathione cycle in the network of cellular redox systems that underpin the energy-sensitive communication within the different cellular compartments and integrate plant signalling pathways.
A review of the potential of poly-(lactide-co-glycolide) nanoparticles as a delivery system for an active antimycobacterial compound, 7-methyljuglone
(MDPI, 2024-02) Diedericks, B.; Kok, Anna-Mari; Mandiwana, Vusani; Lall, Namrita; namrita.lall@up.ac.za
7-Methyljuglone (7-MJ) is a pure compound isolated from the roots of Euclea natalensis A. DC., a shrub indigenous to South Africa. It exhibits significant promise as a potential treatment for the highly communicable disease tuberculosis (TB), owing to its effective antimycobacterial activity against Mycobacterium tuberculosis. Despite its potential therapeutic benefits, 7-MJ has demonstrated in vitro cytotoxicity against various cancerous and non-cancerous cell lines, raising concerns about its safety for consumption by TB patients. Therefore, this review focuses on exploring the potential of poly-(lactide-co-glycolic) acid (PLGA) nanoparticles as a delivery system, which has been shown to decrease in vitro cytotoxicity, and 7-MJ as an effective antimycobacterial compound.

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