Canopy structure and radiation regime in grapevine. 1. Spatial and angular distribution of leaf area in two canopy systems

Grapevine canopies are discontinuous and spatially heterogeneous. Thus, their geometrical structure is difficult to characterize. A method based on a three-dimensional discretion of the volume occupied by foliage elements was used to assess spatial and angular distribution of leaf area. The method was applied to two canopy systems (Open Lyre and Geneva Double Curtain) exhibiting different vigor levels. Leaf area density (LAD, m2·m-3), leaf inclination and leaf azimuth distributions were presented for the canopy systems, as are the distributions of lateral shoot leaves within the canopy. An attempt was made to determine the consequences of the canopy system on the grapevine canopy structure. The canopy structure parameters determined in this study were used in a companion paper as input parameters for a radiation model to describe the grapevine light microclimate

Canopy structure and radiation regime in grapevine. 2. Modeling radiation interception and distribution inside the canopy

A 3D version of the radiation model of SINOQUET and BONHOMME (1992) was used to simulate the light microclimate of grapevine. It was tested against measurements of radiation interception and distribution within two canopy systems (Open Lyre and Geneva Double Curtain) exhibiting different vigor levels. The agreement between the model and the measurements was generally good. Discrepancies may have arisen from incorrect assumptions concerning leaf azimuth distribution and leaf dispersion as well as a lack of accuracy in the description of the distribution of leaf area density inside the canopy. The model also permitted to assess light partitioning between main and lateral shoot leaves which can influence global canopy photosynthesis and berry ripening. As an example of application, the model was used to evaluate the consequences of lateral leaf removing on the interception efficiency of the canopy and the light environment of the fruit zone. The possible use of a geometrical approach to simulate the radiation interception at the canopy scale was also discussed

Optimal microchannel planar reactor as a switchable infrared absorber

This paper will propose methods to use leaf vasculature formations to advance a material to act as an infrared block. The research shows the use of microfluidics based flows to direct the structural assembly of a polymer into a thermally functional material. To manage IR radiation stop-band to lower a polymer device phase transition temperature. This paper will determine this functionality by hierarchical multi microchannel network scaling, to regulate laminar flow rate by analysis as a resistor circuit. Nature uses vasculature formations to modulate irradiance absorption by laminar fluidic flow, for dehydration and autonomous self-healing surfaces as a photoactive system. This paper will focus specifically on pressure drop characterization, as a method of regulating fluidic flow. This approach will ultimately lead to desired morphology, in a functional material to enhance its ability to capture and store energy. The research demonstrates a resistor conduit network can define flow target resistance, that is determined by iterative procedure and validated by CFD. This algorithm approach, which generates multi microchannel optimization, is achieved through pressure equalization in diminishing flow pressure variation. This is functionality significant in achieving a flow parabolic profile, for a fully developed flow rate within conduit networks. Using precise hydrodynamics is the mechanism for thermal material characterization to act as a switchable IR absorber. This absorber uses switching of water flow as a thermal switching medium to regulate heat transport flow. The paper will define a microfluidic network as a resistor to enhance the visible transmission and solar modulation properties by microfluidics for transition temperature decrease

Three-dimensional plant architecture and sunlit-shaded patterns: a stochastic model of light dynamics in canopies

Background and Aims Diurnal changes in solar position and intensity combined with the structural complexity of plant architecture result in highly variable and dynamic light patterns within the plant canopy. This affects productivity through the complex ways that photosynthesis responds to changes in light intensity. Current methods to characterise light dynamics, such as ray-tracing, are able to produce data with excellent spatio-temporal resolution but are computationally intensive and the resultant data are complex and high dimensional. This necessitates development of more economical models for summarising the data and for simulating realistic light patterns over the course of a day. Methods High-resolution reconstructions of field-grown plants are assembled in various configurations to form canopies, and a forward ray-tracing algorithm is applied to the canopies to compute light dynamics at high (1 minute) temporal resolution. From the ray-tracer output, the sunlit or shaded state for each patch on the plants is determined, and these data are used to develop a novel stochastic model for the sunlit-shaded patterns. The model is designed to be straightforward to fit to data using maximum likelihood estimation, and fast to simulate from. Key Results For a wide range of contrasting 3D canopies, the stochastic model is able to summarise, and replicate in simulations, key features of the light dynamics. When light patterns simulated from the stochastic model are used as input to a model of photoinhibition, the predicted reduction in carbon gain is similar to that from calculations based on the (extremely costly) ray-tracer data. Conclusions The model provides a way to summarise highly complex data in a small number of parameters, and a cost-effective way to simulate realistic light patterns. Simulations from the model will be particularly useful for feeding into larger-scale photosynthesis models for calculating how light dynamics affects the photosynthetic productivity of canopies

Mobile Regulatory Cassettes Mediate Modular Shuffling in T4-Type Phage Genomes

Coliphage phi1, which was isolated for phage therapy in the Republic of Georgia, is closely related to the T-like myovirus RB49. The ∼275 open reading frames encoded by each phage have an average level of amino acid identity of 95.8%. RB49 lacks 7 phi1 genes while 10 phi1 genes are missing from RB49. Most of these unique genes encode functions without known homologs. Many of the insertion, deletion, and replacement events that distinguish the two phages are in the hyperplastic regions (HPRs) of their genomes. The HPRs are rich in both nonessential genes and small regulatory cassettes (promoterearly stem-loops [PeSLs]) composed of strong σ70-like promoters and stem-loop structures, which are effective transcription terminators. Modular shuffling mediated by recombination between PeSLs has caused much of the sequence divergence between RB49 and phi1. We show that exchanges between nearby PeSLs can also create small circular DNAs that are apparently encapsidated by the virus. Such PeSL “mini-circles” may be important vectors for horizontal gene transfer

Assessment of the spatial distribution of light transmitted below young trees in an agroforestry system

Transmitted radiation under trees shows variability in space and time which may have implications for the understorey. Light measurements were made in a young agroforestry system to assess the radiation distribution below the tree canopy. Measurements show that the variability of the transmitted radiation is mostly due to the size of the tree shadow and to the irradiance distribution in the shaded area. The light measurements were used to test the predictive capacity of a three-dimensional radiative transfer model based on the turbid medium analogy. The model correctly simulates the fraction of sunlit area and the irradiance distribution in the shaded area. However, it underestimates low radiation values and fails in describing the fine spatial pattern of transmitted radiation because of the stochastic nature of the radiation field. To obtain a mean error less than 15 % of the incident radiation, the distribution of transmitted radiation has to be described by elementary soil surface areas over 0.08 m². / Répartition spatiale du rayonnement transmis sous de jeunes arbres en système agroforestier - Dans une plantation à large espacement, le rayonnement transmis disponible pour la strate inférieure est très variable dans l'espace et dans le temps. Cette hétérogénéité peut avoir des conséquences sur le fonctionnement de la strate inférieure. Des mesures de rayonnement utile à la photosynthèse ont été effectuées pour étudier la distribution du rayonnement sous les couronnes de jeunes merisiers plantés à faible densité. Ces mesures servent également à valider un modèle de transfert radiatif. Les mesures montrent que la variabilité du rayonnement transmis au niveau de la strate inférieure est essentiellement due à la taille de l'ombrage projeté par les arbres et à la distribution du rayonnement dans la surface ombragée. Le modèle simule correctement la proportion de surface ensoleillée ainsi que la distribution du rayonnement dans la surface ombragée. Cependant il sous-estime la valeur minimale du rayonnement transmis et ne permet pas de simuler sa répartition spatiale à une échelle fine à cause de la nature stochastique du rayonnement transmis. Pour une simulation correcte de la répartition spatiale du rayonnement transmis, la surface minimale de simulation doit être comprise entre 0.08 et 0.18 m²