Yuntao Ma

Comparison of architecture among different cultivars of hybrid rice using a spatial light model based on 3-D digitising

Modification of plant types (i.e. plant architecture) is an important strategy to enhance the yield potential of crops. The aims of this study were to specify rice plant types using 3-D modelling methodology. The architecture of three typical hybrid rice cultivars were measured in situ in a paddy field using a 3-D digitiser at four development stages from the panicle initiation to the filling stage. The structural parameters of the rice canopies were calculated and their light capture and potential carbon gain were simulated based on a 3-D light model. The results confirmed that a plant type with steeper leaf angles let light penetrate more deeply with relatively uniform light distribution in the canopy at higher sun elevation angles, although this result was related to leaf area index. The variations of plant types, however, did not convert into differences of light distribution across rice varieties at lower sun elevation angles. Light use efficiency at the higher leaf area index could be enhanced by reducing mutual-shading. These results indicate that a promising approach to quantify the rice architecture in situ is to combine 3-D digitising and a 3-D light model to evaluate light interception and photosynthesis of rice plant types.

Estimating photosynthetically active radiation distribution in maize canopies by a three-dimensional incident radiation model

The three-dimensional (3-D) radiation distribution model in plant canopy is pivotal for understanding and modelling plant eco-physiological processes. Diffuse and direct radiations penetrate into plant canopies in different ways and may present different intensity and wavelength composition. Sunfleck (the canopy surfaces where the direct radiation reaches) distribution in the plant canopy is usually regarded as an important index for crop development, especially under dense canopy conditions. Distributions of direct and diffuse components of photosynthetically active radiation (PAR) in maize (Zea mays L.) canopies were estimated respectively using a 3-D incident radiation model (3DIRM). The 3DIRM model was set up for computing incident radiation in crop canopies by applying a parallel-projection based submodel for direct solar radiation and a central-projection based submodel for incident diffuse radiation simulation in crop canopy. It was well assessed with a field experiment with multi-point PAR measurement in maize canopies with relative errors of 2.6, 4.5 and 2.6%, respectively, for sunfleck area ratio, diffuse PAR and total PAR. The results suggest that the 3DIRM model could be used to estimate the direct, diffuse and total PAR at any specific surface part in the 3-D canopy space. The exponential distinction model for direct, diffuse and total PAR along with leaf area index in different heights in maize canopies was also evaluated based on the 3DIRM simulation results.

Image-based dynamic quantification and high-accuracy 3D evaluation of canopy structure of plant populations

Background and Aims Global agriculture is facing the challenge of a phenotyping bottleneck due to large-scale screening/breeding experiments with improved breeds. Phenotypic analysis with high-throughput, high-accuracy and low-cost technologies has therefore become urgent. Recent advances in image-based 3D reconstruction offer the opportunity of high-throughput phenotyping. The main aim of this study was to quantify and evaluate the canopy structure of plant populations in two and three dimensions based on the multi-view stereo (MVS) approach, and to monitor plant growth and development from seedling stage to fruiting stage. Methods Multi-view images of flat-leaf cucumber, small-leaf pepper and curly-leaf eggplant were obtained by moving a camera around the plant canopy. Three-dimensional point clouds were reconstructed from images based on the MVS approach and were then converted into surfaces with triangular facets. Phenotypic parameters, including leaf length, leaf width, leaf area, plant height and maximum canopy width, were calculated from reconstructed surfaces. Accurate evaluation in 2D and 3D for individual leaves was performed by comparing reconstructed phenotypic parameters with referenced values and by calculating the Hausdorff distance, i.e. the mean distance between two surfaces. Key Results Our analysis demonstrates that there were good agreements in leaf parameters between referenced and estimated values. A high level of overlap was also found between surfaces of image-based reconstructions and laser scanning. Accuracy of 3D reconstruction of curly-leaf plants was relatively lower than that of flat-leaf plants. Plant height of three plants and maximum canopy width of cucumber and pepper showed an increasing trend during the 70 d after transplanting. Maximum canopy width of eggplants reached its peak at the 40th day after transplanting. The larger leaf phenotypic parameters of cucumber were mostly found at the middle-upper leaf position. Conclusions High-accuracy 3D evaluation of reconstruction quality indicated that dynamic capture of the 3D canopy based on the MVS approach can be potentially used in 3D phenotyping for applications in breeding and field management.

Coupling individual kernel-filling processes with source–sink interactions into GREENLAB-Maize

Background and Aims Failure to account for the variation of kernel growth in a cereal crop simulation model may cause serious deviations in the estimates of crop yield. The goal of this research was to revise the GREENLAB-Maize model to incorporate source- and sink-limited allocation approaches to simulate the dry matter accumulation of individual kernels of an ear (GREENLAB-Maize-Kernel). Methods The model used potential individual kernel growth rates to characterize the individual potential sink demand. The remobilization of non-structural carbohydrates from reserve organs to kernels was also incorporated. Two years of field experiments were conducted to determine the model parameter values and to evaluate the model using two maize hybrids with different plant densities and pollination treatments. Detailed observations were made on the dimensions and dry weights of individual kernels and other above-ground plant organs throughout the seasons. Key Results Three basic traits characterizing an individual kernel were compared on simulated and measured individual kernels: (1) final kernel size; (2) kernel growth rate; and (3) duration of kernel filling. Simulations of individual kernel growth closely corresponded to experimental data. The model was able to reproduce the observed dry weight of plant organs well. Then, the source-sink dynamics and the remobilization of carbohydrates for kernel growth were quantified to show that remobilization processes accompanied source-sink dynamics during the kernel-filling process. Conclusions We conclude that the model may be used to explore options for optimizing plant kernel yield by matching maize management to the environment, taking into account responses at the level of individual kernels.

Assessment of light capture and carbon gain of two wheat canopies with 3-D modelling

Plant architecture is an important determinant of crop performance and agro-ecological adaptation. In this study, a field experiment was carried out during the 2008–2009 season to study the architecture of two winter wheat cultivars in situ with a 3-D digitizer at the grain filling stage. The parameters describing plant architecture were analyzed and 3-D light capture and potential carbon gain of the plant were calculated. Simulation results showed that light capture and potential carbon gain were more uniformly distributed for the cultivar with more erect leaves. At the grain filling stage, the photosynthetic contributions were about 55%, 49% and 30% for flag leaf, ear, and stem relative to total leaf photosynthesis.

Assessment of the Effects of Leaf Angle Combinations on Potential Photosynthesis Capacity of Rice with 3-D Models Using High Performance Computing

Improving plant structure is pivotal for increasing the potential yield of crops. The aim of this paper was to evaluate the influence of leaf angle and leaf area index (LAI) on light interception efficiency and capacity of biomass production of rice using 3-D models. A group of virtual plant types of rice, with different combinations of leaf angles, was designed based on the 3-D data of a real rice canopy which was digitized in situ in the field at the filling stage. The results indicated that plant types with excessively steep leaves could lead a significant decrease of photosynthesis at higher solar inclination angle. An optimum LAI corresponding to the peak photosynthetic rate can be found for each of the plant type. To overcome the obstacle of heavy computing in this study, computer cluster and message passing interface were used to provide an efficient and economical way for simulating the 3-D light distribution and photosynthetic rate in rice canopies.