Effects of Shade on Microclimate, Canopy Characteristics and Light Integrals in Dry Season Field-Grown Cocoa (Theobroma cacao L.) Seedlings

Effect of shade regimes on gradients of microclimate, canopy extent (leaf area index: LAI) and light integrals in dry season field-grown cocoa (cacao) seedlings was investigated in a rainforest zone of Nigeria. The shade regimes tested were: unshaded/open-to-sun, dense shade and moderate shade. Shade intensity affected solar radiation transmission through cacao canopy, photosynthetic active radiation (PAR) and canopy light attenuation (extinction coefficient, k). Intensity of transmitted radiation below the canopy from incident radiation was highest for open-to-sun, followed by moderate and dense shade, respectively. The temporal trend of intercepted radiation showed that intercepted radiation increased from December to May, and, the values were highest for open-to-sun, followed by moderate and dense shade. The ratio of transmitted (Io) to incident (I) radiation (IO/I) was higher for open sun. Significant differences were found between open-to-sun (unshaded) and moderate and dense shade intensity for value of canopy extinction coefficient (k). The association of growing degree days (GDD), and, total leaf number (TLN) and leaf area index (LAI), were characterized by high coefficient of determination (R2) for the respective open, dense and moderate shade treatments. Inverse of the slope of the regression of relationship between estimated thermal time (°Cdays) and corresponding total leaf number (TLN) denotes leaf appearance rate (phyllochron, in °Cdays/leaf). Rate of leaf appearance was faster in open sun compared with to that in moderate or dense shade intensity. Characteristics of the cacao canopy development were measured by leaf area index (LAI), a parameter which affects the intercepted photosynthetic active radiation (PAR). Higher LAI was obtained in no shade (open sun) compared to that in moderate or dense shade treatments. Unshaded plants had a higher radiation use efficiency (RUE) and RUE values were significantly higher compared to the other two treatments. Low light intensity and LAI for under-storey cacao had negative implications for growth and biomass development. Air temperatures within the cacao field were highest for open sun cacao, followed by moderate and dense shade, respectively; the values increased from December to April, with peak values seen in April

Assessing crop model improvements through comparison of sorghum (sorghum bicolor L. moench) simulation models: A case study of West African varieties

Better defining niches for the photoperiod sensitive sorghum (Sorghum bicolor L. Moench) varieties of West Africa into the local cropping system might help to improve the resilience of food production in the region. In particular, crop models are key tools to assess the growth and development of such varieties against climate and soil variability. In this study, we compared the performance of three process-based crop models (APSIM, DSSAT and Samara) for prediction of diverse sorghum germplasm having widely varying photoperiod sensitivity (PPS) using detailed growth and development observations from field trials conducted in West Africa semi-arid region. Our results confirmed the capability of each selected model to reproduce growth and development for varieties of diverse sensitivities to photoperiod. Simulated phenology and morphology organs during calibration and validation were within the closet range of measured values with the evaluation of model error statistics (RMSE and R2). With the exception of highly sensitive variety (IS15401), APSIM and Samara estimates indicate the lowest value of RMSE (<7days) against the observed values for phenology events (flowering and maturity) compared to DSSAT model. Across the varieties, there was over-estimation for simulated leaf area index (LAI) while total leaf number (TLN) fitted well with the observed values. Samara estimates were found to be the closet with the lowest RMSE values (<3 leaves for TLN and <1.0 m2/m2 for LAI) followed by DSSAT and APSIM respectively. Prediction of grain yield and biomass was less accurate for both calibration and validation. The predictions using APSIM were found to be closest to the observed followed by DSSAT and Samara models respectively. Based on detailed field observations, this study showed that crop models captured well the phenology and leaf development of the photoperiod sensitive (PPS) varieties of West Africa, but failed to estimate accurately partitioning of assimilates during grain filling. APSIM and SAMARA as more mechanistic crop models, have a higher sensitivity of the adjustment of key parameters, notably the specific leaf area for APSIM in low PPS varieties, while SAMARA shows a higher response to parameters changes for high PPS varieties

Twelve-month observational study of children with cancer in 41 countries during the COVID-19 pandemic

Introduction Childhood cancer is a leading cause of death. It is unclear whether the COVID-19 pandemic has impacted childhood cancer mortality. In this study, we aimed to establish all-cause mortality rates for childhood cancers during the COVID-19 pandemic and determine the factors associated with mortality. Methods Prospective cohort study in 109 institutions in 41 countries. Inclusion criteria: children &lt;18 years who were newly diagnosed with or undergoing active treatment for acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin lymphoma, retinoblastoma, Wilms tumour, glioma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, medulloblastoma and neuroblastoma. Of 2327 cases, 2118 patients were included in the study. The primary outcome measure was all-cause mortality at 30 days, 90 days and 12 months. Results All-cause mortality was 3.4% (n=71/2084) at 30-day follow-up, 5.7% (n=113/1969) at 90-day follow-up and 13.0% (n=206/1581) at 12-month follow-up. The median time from diagnosis to multidisciplinary team (MDT) plan was longest in low-income countries (7 days, IQR 3-11). Multivariable analysis revealed several factors associated with 12-month mortality, including low-income (OR 6.99 (95% CI 2.49 to 19.68); p&lt;0.001), lower middle income (OR 3.32 (95% CI 1.96 to 5.61); p&lt;0.001) and upper middle income (OR 3.49 (95% CI 2.02 to 6.03); p&lt;0.001) country status and chemotherapy (OR 0.55 (95% CI 0.36 to 0.86); p=0.008) and immunotherapy (OR 0.27 (95% CI 0.08 to 0.91); p=0.035) within 30 days from MDT plan. Multivariable analysis revealed laboratory-confirmed SARS-CoV-2 infection (OR 5.33 (95% CI 1.19 to 23.84); p=0.029) was associated with 30-day mortality. Conclusions Children with cancer are more likely to die within 30 days if infected with SARS-CoV-2. However, timely treatment reduced odds of death. This report provides crucial information to balance the benefits of providing anticancer therapy against the risks of SARS-CoV-2 infection in children with cancer

Within Plant Resistance to Water Flow in Tomato and Sweet Melons

Efficient water resource management in relation to water use and crop yields is premised on the knowledge of plant resistance to water flow. However, such studies are limited and for most crops, the within plant resistance to water flow remains largely unknown. In this study, within plant resistance to water transport (hydraulic conductance) was monitored in tomato ( Lycopersicum esculuntum ) and sweet melon ( Citrullus lanatus ) using the high pressure flow meter (HPFM) and evaporative flux (EF) methods. In the evaporative flux method, measurements of transpiration flux and leaf water potential were used to calculate the total resistance to water flow using Ohm&apos;s law analogy. Measurements of tranpiration flux (Q) relationship, plant resistance calculated from the slope of their relationship, ranged from 6.57x10-01 to 2.27x10-03 Mpa m-2s-1 for tomato and sweet melon, respectively. The magnitude of whole plant hydraulic conductance calculated by the evaporative flux method and measured on the HPFM were not significantly different. This is probably due to that fact that Kp includes the hydraulic conductance of the root system, which offers the highest resistance to water flow in a plant, and the frictional resistance of the proximal part of the crown. Day time course of water relation parameters were monitored in melon and tomato (predawn, 1100 to 1400 h). The effect of time of day was pronounced on the dynamics of water relations, particularly around mid-day when sharp differences in the magnitudes of the measured water relation parameters were obtained. Minimum (predawn) leaf water potential (ψl) ranged from 0.135 to 0.207 MPa for both crops. The greatest conductance was found in the leaf and the lowest in the root in both crops. While the highest within plant resistance to the flow is contained in the root system, the stem component constitutes the least resistance (greatest conductance) to within plant flow of water in tomato. Repeated measurement analysis showed the existence of significant species effects on plant water relations (leaf water potential, evaporative/transpiration flux, xylem hydraulic conductance). Superiority within plant xylem transport and evaporative losses were obtained in tomato, from the relations of EF and Kh; this crop showed a higher hydraulic sufficiency than melon. The expression of hydraulic conductance of the root and shoot system relative to plant attributes did not eliminate differences in the magnitudes of conductance elements in tomato and melon. Differences obtained between melon and tomato in whole plant leaf and stem area specific hydraulic conductance (KI) indicate the carbon efficiency and, hence, the cost of resource allocation to areas of root surface and leaves for enhanced scavenging for water and mineral nutrients. Thus, application of mineral nutrients to enhance crop productivity should take into consideration the hydraulic conductance for specific plants.La gestion efficace de ressource d&apos;eau en relation avec son utilisation et son rendement est une prémisse de la connaissance de la résistance des plantes au flux d&apos;eau. Cependant, de telles études sont limitées et pour la plupart des récoltes, la résistance interne de la plante sur le flux d&apos;eau reste principalement inconnue. Dans cette étude, la résistance de plantes sur le flux (la conductance hydraulique) a été contrôlée dans la tomate ( Lycopersicum esculuntum ) et le melon doux ( Citrullus lanatus ) utilisant la méthode de forte pression (HPFM) et le flux d&apos;évaporation (EF). Dans la méthode de flux d&apos;évaporation, les mesures de flux de transpiration et de potentiel d&apos;eau de feuille ont été utilisées pour calculer la résistance totale en utilisant l&apos;analogie de loi d&apos;Ohm. La relation entre les mesures de flux de transpiration (Q) et la résistance des plantes a été calculé, la pente de cette relation, était entre 6.57x10-1 à 2.27x10-3 MPa m-2s-1 pour la tomate et le melon doux, respectivement. La grandeur de la conductance hydraulique de la plante entière prédite par la méthode de flux d&apos;évaporation et mesuré sur le HPFM n&apos;était pas significativement différente. Ceci est probablement en raison du fait que Kp inclut la conductance hydraulique du système fondamental, qui offre la plus haute résistance au le flux dans une plante, et la résistance de friction de la partie proche de la couronne. L&apos;effet du temps de la journée sur les paramètres d&apos;eau a été contrôlé dans le melon et la tomate (de 11.00 à 14.00 h). L&apos;effet du temps a été prononcé sur la dynamique de relations d&apos;eau, particulièrement autour du midi quand les différences tranchantes en grandeur des paramètres de relation d&apos;eau mesurés ont été obtenues. Le potentiel d&apos;eau minimal de feuille était compris entre 0,135 et 0,207 MPa pour les deux récoltes. La plus grande conductance a été trouvée dans la feuille et le plus bas dans la racine dans les deux récoltes. Pendant que la plus grande la résistance interne de la plante au flux est contenue dans le système fondamental, le composant de tige présentait la moindre résistance (la plus grande conductance) au flux d&apos;eau dans la tomate. L&apos;analyse répétée de mesure a montré l&apos;existence d&apos;effets d&apos;espèce significatifs sur les relations d&apos;eau des plantes (le potentiel d&apos;eau de feuille, le flux de d&apos;évaporation transpiration, la conductance hydraulique du xylem). La supériorité dans le transport de xylem de plante et dans les pertes d&apos;évaporation a été obtenue dans la tomate, concernant EF et de Kh; cette récolte a montré une efficacité hydraulique supérieure au melon. L&apos;expression de la conductance hydraulique de la racine et le système relatif aux attributs de la plante n&apos;a pas éliminé les différences dans les grandeurs de la conductance dans la tomate et le melon. Les différences ont été obtenu entre le melon et la tomate dans la feuille de la plante entière et le secteur de tige pour la conductance hydraulique spécifique (KI) indiquant l&apos;efficacité du carbone et, donc, le coût d&apos;allocation de ressource aux secteurs de surface et de feuilles fondamentales pour améliorer la récupération de l&apos;eau et de nutriments minéraux. Ainsi, l&apos;application de nutriments minéraux pour améliorer la productivité de récolte doit prendre en considération la conductance hydraulique des plantes

Effects of season of sowing on water use and yield of tomato in the humid south of Nigeria

Soil water availability is a major constraint to crop production in the post-rainy season period in the humid tropics. The seasonal pattern of water use was, therefore, studied in field-grown tomato (Lycopersicum esculentum   ) during two consecutive rainy and post-rainy seasons in a humid zone of Nigeria. Soil moisture content was monitored by the gravimetric method. Drainage micro-lysimeters were installed to monitor maximum evapotranspiration (ETM). For the post-rainy season sowing, the relative water use (ETa/Eo) values (the ratio of actual evapotranspiration, ETa to open water evaporation, Eo) varied from 1.14 at the beginning of the growing season to 0.04 at crop maturity. The values of ETa/Eo and evapotranspiration deficit (ETd) indicated that during the crop cycle, there were increasing intensities of soil moisture deficits, decreased transpiring leaf area and canopy developments and shortened vegetative and reproductive phases. The vertical profile of root distribution revealed significantly larger depths of roots and higher root mass and values of root length to maximum leaf area in the post-rainy season crop of tomato