Testing the Performance of Two Maize Simulation Models with a Range of Cultivars of Maize (Zea mays) in Diverse Environments

Maize production is increasing in importance in Australia, and has potential for substantial further expansion. Additional production areas and/or more intensive use of existing production areas will be needed. Simulation models offer the capacity to rapidly assess the suitability of a range of genotypes and phenotypes, and to predict yield and yield reliability over a range of environmental conditions. However, they must be validated and be sufficiently robust to provide reliable predictions. The performance of two maize simulation models, a complex mechanistic one, AUSIM-Maize, and a simpler one, the Muchow - Sinclair model, was evaluated against experimental data from field trials at Gatton, South East Queensland and Katherine, Northern Territory. AUSIM-Maize predicts phenological and canopy development, total dry matter and grain yield. The Muchow - Sinclair model concentrates on total dry matter and grain yield. Sensitivity analysis indicated that the output of the models was most affected by the values used for the duration of the basic vegetative period, photoperiod sensitivity and leaf initiation rate (in AUSIM - Maize), radiation use efficiency, leaf appearance rate (in both models) and one coefficient that affects leaf area senescence (in the Muchow - Sinclair model). AUSIM - Maize consistently overpredicted the time from emergence to tassel initiation (especially with short season cultivars, and when environmental conditions favoured rapid plant development to TI), silking and physiological maturity. Leaf number was consistently overpredicted by AUSIM - Maize. Neither model predicted total dry matter or grain yield satisfactorily over the range in the experimental data, though each tended to be more accurate than the other on one measure of model performance (regression or root mean square deviation). Both provided sound predictions within a limited range of conditions and genotypes that resulted in relatively short crop durations, but were inaccurate when the data extended over a greater range of environmental conditions and genotypes. Several areas of the models where modification is needed to improve predictions and to make the models more generally applicable are identified

Plant Development and Leaf Area Production in Contrasting Cultivars of Maize Grown in a Cool Temperate Environment in the Field

Crop models need accurate simulation of the interdependent processes of crop development and leaf area production. Crop development proceeds according to genotype characteristics and environmental influences, specifically temperature and photoperiod. It can be partly described by thermal requirements for development intervals and coefficients that describe genotype adaptation. The objectives of this study were to (a) quantify (i) time of tassel initiation, tasselling and silking; (ii) thermal intervals for initiation, appearance and expansion of successive leaves (iii) thermal duration from initiation to tip appearance and from tip appearance to collar appearance, and (iv) leaf area and canopy cover as measured by leaf area index (LAI) in contrasting cultivars of maize grown in the field in a cool environment; and (b) relate these to plant characteristics and environmental variables, particularly temperature. For these purposes, three cultivars of maize were grown in three and four cultivars in two serial plantings from 18 April to 24 June in field experiments at Wageningen, The Netherlands, in 1997, and detailed data on crop development, leaf production and environmental variables were collected. The base temperature (Tb) for maize was confirmed as 8 degrees C, but thermal time calculation needs to be re-examined to explore a recovery period after chilling injury. Equations that relate foliar properties to total leaf number and ordinal leaf position were derived. Individual leaf area can be described by the modified bell curve, and differences in temporal increase in LAI were related to parameters of leaf initiation, appearance and expansion

Cation disorder and phase transitions in the structurally complex solar cell material Cu2ZnSnS4

Cu2ZnSnS4 (CZTS) is a technologically important and complex quaternary semiconductor and a highly promising material for the absorber layer in sustainable thin film solar cells. Its photovoltaic performance is currently limited by low open-circuit voltage, thought to be due to a range of point defects such as disorder between the copper and zinc lattice sites. This is the highest-resolution neutron diffraction study reported for CZTS, which unambiguously identifies the crystal symmetry and accurately quantifies precise values for the disorder on all cation symmetry sites as a function of temperature. Two samples of CZTS were fabricated by solid state reaction and their compositions were measured by inductively-coupled plasma mass spectroscopy, which identified significant tin loss during growth, leaving the samples Sn-poor, Cu-rich and Sn-poor, Zn-rich respectively. Both samples were found exclusively to adopt the tetragonal kesterite crystal structure with significant cation disorder, which is investigated in detail over the range 4–1275 K. Importantly, and in contrast to previous reports, the 2a Wyckoff site shows disorder equal to or greater than the 2c site. The order–disorder phase transition was observed at different temperatures for the two compositions, 489 and 501 K respectively, lower than previously reported. The kesterite–sphalerite transition was observed between 1250 and 1275 K for the Sn-poor, Cu-rich sample, significantly higher than previously reported. These results provide new insights into the high levels of disorder present in CZTS and confirm that composition and cation disorder have a significant effect on the phase transition mechanism. This work will enable the development of routes to the fabrication of higher-efficiency photovoltaic devices

Predicting Broccoli Development: I. Development Is Predominantly Determined By Temperature Rather Than Photoperiod

Predictive models of broccoli (Brassica oleracea L. var. italica Plenck) ontogeny will aid farmers who need to forecast changes in crop maturity arising from variable climatic conditions so that their forward marketing arrangements can match their anticipated supply. The objective of this study was to quantify the temperature and photoperiod responses of development in a sub-tropical environment from emergence to floral initiation (EFI), and from floral initiation to harvest maturity (FIHM). Three cultivars, ('Fiesta', 'Greenbelt' and 'Marathon') were sown on eight dates from 11 March to 22 May 1997 and grown under natural and extended (16 h) photoperiods at Gatton College, south-east Queensland, under non-limiting conditions of water and nutrient supply. Climatic data, dates of emergence, floral initiation and harvest maturity were obtained. The estimated base (Tbase) and optimum (Topt) temperatures of 0 and 20 degrees C, respectively were consistent across cultivars, but thermal time requirements were cultivar specific. Differences in thermal time between cultivars during FIHM were small and of little practical importance, but differences in thermal time during EFI were large. Sensitivity to photoperiod and solar radiation was low in the three cultivars used. When the thermal time models were tested on independent data for five cultivars ('Fiesta', 'Greenbelt', 'Marathon', 'CMS Liberty' and 'Triathlon') grown as commercial crops over two years, they adequately predicted floral initiation and harvest maturity

Modeling the Subsurface Structure of Sunspots

While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

Simulating maize yield in sub-tropical conditions of southern Brazil using Glam model

The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales (greater than 100,000 km2), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small spatial scales (lower than 10,000 km2). Large area models can contribute to monitoring or forecasting regional patterns of variability in maize production in the region, providing a basis for agricultural decision making, and Glam‑Maize is one of the alternatives

Recent Developments in Helioseismic Analysis Methods and Solar Data Assimilation

MR and AS have received funding from the European Research Council under the European Union’s Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 307117

Assessment of systemic AAV-microdystrophin gene therapy in the GRMD model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by the absence of dystrophin, a membrane-stabilizing protein encoded by the DMD gene. Although mouse models of DMD provide insight into the potential of a corrective therapy, data from genetically homologous large animals, such as the dystrophin-deficient golden retriever muscular dystrophy (GRMD) model, may more readily translate to humans. To evaluate the clinical translatability of an adeno-associated virus serotype 9 vector (AAV9)–microdystrophin (μDys5) construct, we performed a blinded, placebo-controlled study in which 12 GRMD dogs were divided among four dose groups [control, 1 × 1013 vector genomes per kilogram (vg/kg), 1 × 1014 vg/kg, and 2 × 1014 vg/kg; n = 3 each], treated intravenously at 3 months of age with a canine codon-optimized microdystrophin construct, rAAV9-CK8e-c-μDys5, and followed for 90 days after dosing. All dogs received prednisone (1 milligram/kilogram) for a total of 5 weeks from day-7 through day 28. We observed dose-dependent increases in tissue vector genome copy numbers; μDys5 protein in multiple appendicular muscles, the diaphragm, and heart; limb and respiratory muscle functional improvement; and reduction of histopathologic lesions. As expected, given that a truncated dystrophin protein was generated, phenotypic test results and histopathologic lesions did not fully normalize. All administrations were well tolerated, and adverse events were not seen. These data suggest that systemically administered AAV-microdystrophin may be dosed safely and could provide therapeutic benefit for patients with DMD