Mutual Shading Research Articles

Interactions between Diffuse Light and Cucumber (Cucumis sativus L.) Canopy Structure, Simulations of Light Interception in Virtual Canopies

Plant photosynthesis and biomass production are associated with the amount of intercepted light, especially the light distribution inside the canopy. Three virtual canopies (n = 80, 3.25 plants/m2) were constructed based on average leaf size of the digitized plant structures: ‘small leaf’ (98.1 cm2), ‘medium leaf’ (163.0 cm2) and ‘big leaf’ (241.6 cm2). The ratios of diffuse light were set in three gradients (27.8%, 48.7%, 89.6%). The simulations of light interception were conducted under different ratios of diffuse light, before and after the normalization of incident radiation. With 226.1% more diffuse light, the result of light interception could increase by 34.4%. However, the 56.8% of reduced radiation caused by the increased proportion of diffuse light inhibited the advantage of diffuse light in terms of a 26.8% reduction in light interception. The big-leaf canopy had more mutual shading effects, but its larger leaf area intercepted 56.2% more light than the small-leaf canopy under the same light conditions. The small-leaf canopy showed higher efficiency in light penetration and higher light interception per unit of leaf area. The study implied the 3D structural model, an effective tool for quantitative analysis of the interaction between light and plant canopy structure.

Effect of Stomatal Morphology on Leaf Photosynthetic Induction Under Fluctuating Light in Rice.

Plants are often confronted with light fluctuations from seconds to minutes due to altering sun angles, mutual shading, and clouds under natural conditions, which causes a massive carbon loss and water waste. The effect of stomatal morphology on the response of leaf gas exchange to fluctuating light remains disputable. In this study, we investigated the differences in leaf stomatal morphology and photosynthetic induction across twelve rice genotypes after a stepwise increase in light intensity. A negative correlation was observed between stomatal size and density across rice genotypes. Smaller and denser stomata contributed to a faster stomatal response under fluctuating light. Plants with faster stomatal opening also showed faster photosynthetic induction and higher biomass accumulation but lower intrinsic water use efficiency (iWUE) under fluctuating light. Moreover, stomatal morphology seemed to have less effect on the initial and final stomatal conductance, and there was a minimal correlation between steady-state and non-steady-state stomatal conductance among different rice genotypes. These results highlight the important role of stomatal morphology in regulating photosynthetic efficiency and plant growth under fluctuating light conditions. To simultaneously enhance leaf iWUE when improving the photosynthetic efficiency under fluctuating light, it may be necessary to take biochemical processes into account in the future.

Productivity of Eugenol from Clove (Syzygium aromaticum L.) Under Different Light and Soil Water Conditions

We examined the effect of watering and shading treatments on eugenol productivity of clove seedlings in order to provide the information of the suitable site conditions for eugenol production. After a six-month experiment growing clove seedlings under twelve treatments (3 shading treatments (0%, 60% and 80%) x 4 watering treatments (1.0, 0.75, 0.5 and 0.25 l/m2/day), the total leaf mass per tree (LM), the eugenol content per unit leaf mass (EL) and the eugenol yield per tree (EY) were measured and compared between treatments. As the results, the low watering rates reduced LM slightly; however, this effect was counteracted by the drastically increased EL under the same conditions, resulting in the highest EY in the least watered treatment (0.25 l/m2/day). Heavy shading consistently reduced LM and EL, resulting in the lowest LY under the 80% shading treatment. The relatively dryer site condition where moderate water stress is likely to occur is more suitable for planting clove trees from the aspect of the for long-term high productivity of eugenol, and that the high tree density which may cause a severe competition and a heavy mutual shading among clove trees should be avoided to maintain long term high productivity.

Machine learning-informed and synthetic biology-enabled semi-continuous algal cultivation to unleash renewable fuel productivity

Algal biofuel is regarded as one of the ultimate solutions for renewable energy, but its commercialization is hindered by growth limitations caused by mutual shading and high harvest costs. We overcome these challenges by advancing machine learning to inform the design of a semi-continuous algal cultivation (SAC) to sustain optimal cell growth and minimize mutual shading. An aggregation-based sedimentation (ABS) strategy is then designed to achieve low-cost biomass harvesting and economical SAC. The ABS is achieved by engineering a fast-growing strain, Synechococcus elongatus UTEX 2973, to produce limonene, which increases cyanobacterial cell surface hydrophobicity and enables efficient cell aggregation and sedimentation. SAC unleashes cyanobacterial growth potential with 0.1 g/L/hour biomass productivity and 0.2 mg/L/hour limonene productivity over a sustained period in photobioreactors. Scaling-up the SAC with an outdoor pond system achieves a biomass yield of 43.3 g/m2/day, bringing the minimum biomass selling price down to approximately $281 per ton.

Optimization of PV array tilt angle for minimum levelized cost of energy

This paper studies the effects of PhotoVoltaic (PV) tilt angle variation over the cost efficiency of PV networks. The monthly modification of the tilt angle β conducted by this study, decreased the levelized cost of energy (LCOE), thus enhancing the system's economical status, by reducing its capital investment's payback period. The intended outcome of this work is twofold: it corresponds to a generalized novel mathematical model which enables the maximum number of PV panels to be fit into a square shaped area without any mutual shading, plus it investigates the monthly tilt angle values based on a specific selection, and their effects on the LCOE. The application of the obtained results (i.e., numerical values of β) has diminished both the LCOE as well as the power cost, while increasing power production for a PV system located in Tripoli-Lebanon (latitude: 34.38°), Belfort-France (latitude: 47.63°) and Tantan-Morocco (latitude: 28.38°).

Field microenvironments regulate crop diel transcript and metabolite rhythms.

Most research in plant chronobiology has been done in laboratory conditions. However, laboratories usually fail to mimic natural conditions and their slight fluctuations, highlighting or obfuscating rhythmicity. High-density crops, such as sugarcane (Saccharum hybrid), generate field microenvironments with specific light and temperature regimes resulting from mutual shading. We measured the metabolic and transcriptional rhythms in the leaves of 4-month-old (4mo) and 9mo field-grown sugarcane. Most of the assayed rhythms in 9mo sugarcane peaked >1h later than in 4mo sugarcane, including rhythms of the circadian clock gene, LATE ELONGATED HYPOCOTYL (LHY). We hypothesized that older sugarcane perceives dawn later than younger sugarcane as a consequence of self-shading. As a test, we measured LHY rhythms in plants on the east and the west sides of a field. We also tested if a wooden wall built between lines of sugarcane plants changed their rhythms. The LHY peak was delayed in the plants in the west of the field or beyond the wall; both shaded at dawn. We conclude that plants in the same field may have different phases resulting from field microenvironments, impacting important agronomical traits, such as flowering time, stalk weight and number.

Growth Rate, Dry Matter Accumulation, and Partitioning in Soybean (Glycine max L.) in Response to Defoliation under High-Rainfall Conditions.

The frequency of heavy rains is increasing with climate change in regions that already have high annual rainfall (i.e., Sichuan, China). Crop response under such high-rainfall conditions is to increase dry matter investment in vegetative parts rather than reproductive parts. In the case of soybean, leaf redundancy prevails, which reduces the light transmittance and seed yield. However, moderate defoliation of soybean canopy could reduce leaf redundancy and improve soybean yield, especially under high-rainfall conditions. Therefore, the effects of three defoliation treatments (T1, 15%; T2, 30%; and T3, 45% defoliation from the top of the soybean canopy; defoliation treatments were applied at the pod initiation stage of soybean) on the growth and yield parameters of soybean were evaluated through field experiments in the summer of 2017, 2018, and 2019. All results were compared with nondefoliated soybean plants (CK) under high-rainfall conditions. Compared with CK, treatment T1 significantly (p < 0. 05) improved the light transmittance and photosynthetic rate of soybean. Consequently, the leaf greenness was enhanced by 22%, which delayed the leaf senescence by 13% at physiological maturity. Besides, compared to CK, soybean plants achieved the highest values of crop growth rate in T1, which increased the total dry matter accumulation (by 6%) and its translocation to vegetative parts (by 4%) and reproductive parts (by 8%) at physiological maturity. This improved soybean growth and dry matter partitioning to reproductive parts in T1 enhanced the pod number (by 23%, from 823.8 m−2 in CK to 1012.7 m−2 in T1) and seed number (by 11%, from 1181.4 m−2 in CK to 1311.7 m−2 in T1), whereas the heavy defoliation treatments considerably decreased all measured growth and yield parameters. On average, treatment T1 increased soybean seed yield by 9% (from 2120.2 kg ha−1 in CK to 2318.2 kg ha−1 in T1), while T2 and T3 decreased soybean seed yield by 19% and 33%, respectively, compared to CK. Overall, these findings indicate that the optimum defoliation, i.e., T1 (15% defoliation), can decrease leaf redundancy and increase seed yield by reducing the adverse effects of mutual shading and increasing the dry matter translocation to reproductive parts than vegetative parts in soybean, especially under high-rainfall conditions. Future studies are needed to understand the internal signaling and the molecular mechanism controlling and regulating dry matter production and partitioning in soybean, especially from the pod initiation stage to the physiological maturity stage.

A new kinetics model to predict the growth of micro-algae subjected to fluctuating availability of light

Light is a key environmental factor for the growth of micro-algae, and optimizing the capture of light is critical for high efficiency production systems. As the density of the population of micro-algae increases, the availability of light decreases, leading to a reduction in the growth rate because of mutual shading, while other effects, such as photo-inhibition, might be especially frequent when the population density is low. Several models in the literature have been developed to take into account light phenomena and predict micro-algal growth, particularly in a mono-culture. With the help of a simple expression for the attenuation of the light, we propose and justify a new growth function that incorporates both photo-inhibition and photo-limitation. In agreement with the experimental data, this new formulation describes the micro-algal response to a wide range of situations of excessive or insufficient light intensities through an explicit dependence on both the incident light and the biomass concentration. While simple, the proposed expression can be satisfactorily applied to practical cases under nutrient replete conditions in photo-bioreactors with different sizes and geometries. It extends naturally to the growth of different species, providing a dynamic model which can simulate experiments in a mono-culture as well as in poly-cultures. The investigation of the competition for light-limited growth shows that the model predicts competitive exclusion, which has also been experimentally demonstrated. This leads to new perspectives for the control and optimization of mixed micro-algal cultures.

Photovoltaic Module Efficiency Optimizing Techniques: A Review

The solar irradiation falling on PV-module that converted into heat hence the reducing efficiency. The dust deposition decreases efficiency and resist the amount of solar radiation interacting on surface of PV-panel. The mismatch position placed of PV string can make the mutual shading between the PV-Module, Due to this reason of shading the totally efficiency of PV system falls. To overcome all mentioned problem, in this paper the review of environmental factor and their latest minimizing techniques for optimizing performance of PV-Module is discussed. This paper merely focused on the review of cooling, Cleaning and shading effect techniques.

Photovoltaic Module Efficiency Optimizing Techniques: A Review

The solar irradiation falling on PV-module that converted into heat hence the reducing efficiency. The dust deposition decreases efficiency and resist the amount of solar radiation interacting on surface of PV-panel. The mismatch position placed of PV string can make the mutual shading between the PV-Module, Due to this reason of shading the totally efficiency of PV system falls. To overcome all mentioned problem, in this paper the review of environmental factor and their latest minimizing techniques for optimizing performance of PV-Module is discussed. This paper merely focused on the review of cooling, Cleaning and shading effect techniques.

Assessment of the Urban Heat Island Impact on Building Energy Performance at District Level with the EUReCA Platform

In recent decades, the cooling energy demand in urban areas is increasing ever faster due to the global warming and the growth of developing economies. In this perspective, the urban building energy modelling community is focusing its research activities on innovative tools and policy actions to improve cities’ sustainability. This work aims to present a novel module of the EUReCA (Energy Urban Resistance Capacitance Approach) platform for evaluating the effects of the interaction between district’s buildings in the cooling season. EUReCA predicts the urban energy demand using a bottom-up approach and low computational resources. The new module allows us to evaluate the mutual shading between buildings and the urban heat island effects, and it is well integrated with the calculation of the energy demand of buildings. The analysis was carried out considering a real case study in Padua (Italy). Results show that the urban heat island causes an average increase of 2.2 °C in the external air temperature mainly caused by the waste heat rejected from cooling systems. This involves an increase in urban cooling energy and electricity demand, which can be affected between 6 and 8%. The latter is the most affected by the urban heat island (UHI), due to the degradation it causes on the HVAC systems’ efficiency.

Effects of Different Planting Densities on Photosynthesis in Maize Determined via Prompt Fluorescence, Delayed Fluorescence and P700 Signals.

The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.

Modeling canopy photosynthesis and light interception partitioning among shoots in bi-axis and single-axis apple trees (Malus domestica Borkh.)

Bi-axis training increased vegetative shoot light interception and modeled photosynthetic rate, and reduced fruiting shoot mutual shading and vegetative growth by optimizing canopy structure compared to single-axis in young apple trees. Improving light interception and distribution within canopy are constant objectives of training through manipulating tree architecture. A bi-axis training system with two primary scaffolds has been proposed to improve flowering and dry matter production in apple trees. In this study, ‘Fuji’ apple trees trained using a bi-axis or single-axis training system were compared. Twelve three-dimensional (3D) virtual apple trees were reconstructed by combining 3D digitizing and allometric relationships for three shoot types (vegetative long shoot, VL; fruiting shoot, FS; vegetative short shoot, VS), to evaluate canopy structure impacts on light interception. Light interception efficiency was evaluated by silhouette to total area ratio (STAR). The potential canopy photosynthetic rate was evaluated by the eco-physiological RATP model. The leaf area of VL in bi-axis trained trees was approximately 40% lower than that in single-axis trees. Lower leaf area and more uniform spatial distribution were noted in VL in bi-axis than in single-axis trees. This led to more even spatial light distribution and more shoots having higher STAR in bi-axis than in single-axis trees, regardless of the whole tree or shoot type. In the virtual orchard, bi-axis trees had a 25% and 10% STAR increase in VS and VL, respectively, but a similar STAR for FS compared to single-axis trees. Mutual shading between neighboring trees in the virtual orchard made of bi-axis trees was significantly lower than that with single-axis trees for FS. The modeled canopy net photosynthetic rate was 26% higher in bi-axis than in single-axis trees. With the increase in tree age, the projected leaf area increased, but the porosity of the canopy decreased, and mutual shading increased for the whole canopy and all shoot types, irrespective of training systems. These results indicated that manipulating scaffolds in apple trees can regulate canopy structure, light interception, and vegetative growth during the early developmental stages.

Effect of Planting Density and Fertilizer Rate on Some Physiological Parameters of Arabica Coffee Seedlings

Planting high density can reduce photosynthetic active radiation due to mutual shading or low light interception. The nature of the canopy and utilization of solar radiation influence the performances of coffee genotype. This study was designed to evaluate the effect of planting density and fertilizer rate on physiological parameters of Arabica coffee seedlings under nursery conditions. It was conducted at the Jimma Agricultural Research Center in southwest Ethiopia in 2018 season. A factorial experimentation in a completely randomized design with three replications was used for the study. The treatments consisted of combinations of two Arabica coffee cultivars (compact-74110 and open-75227), four population densities per polythene tube (one, two, three and four) and three compound NPK fertilizer (22:6:12 + Te) rates (control, 5g and 10g). The most common plant physiological parameters including NAR, AGR, RGR and CGR were estimated and analyzed using standard procedures. The results showed that interaction between cultivar, population density and fertilizer significantly (P ≤0.05) influenced NAR and CGR, and highly significantly (P ≤0.01) influenced AGR and RGR. The highest values of NAR, AGR, RGR and CGR were recorded from the lowest population density (PD1) and increased in the order of PD1 > PD2 > PD3 > PD4 for each parameter. Application of 5g of NPK significantly enhanced NAR, AGR, RGR and CGR as compared with other fertilizer rates, while these parameters were observed to decrease for 10g of NPK perhaps due to toxicity problem. In general, high planting density decrease physiological parameters of the coffee plant, so more attention like intensive coffee tree management practices as well as optimization of population density should be done under field conditions to increase physiological parameters of the coffee plant.

Towards zero-energy residential complexes in high-density conditions

Carbon dioxide is the largest component of the human footprint and one of the major components of all greenhouse gases. The expected increase in population will lead to growth in energy consumption and greenhouse gas emissions. The building industry has the highest potential for reducing greenhouse gas emissions. Therefore, buildings should become not only efficient consumers but also energy producers, not a simple task in dense cities. The paper describes the feasibility and limitations of near zero energy design in highly dense urban conditions. The study was carried out by examination and comparison of various density design, alternatives of an existing urban plot in the coastal climate zone of Israel. Increased dwelling units’ number leads to higher total energy use on the one hand and mutual shading of new high-rise residential buildings on the other. Preserving solar rights for PV systems installation become more complex. The relation between urban density and solar rights in urban design, energy consumption and energy generation within plot borders and their implications are presented and discussed in the paper.

Optimal Layout for Façade-Mounted Solar Photovoltaic Arrays in Constrained Fields

AbstractA method for optimizing the geometrical layout for a façade-mounted solar photovoltaic array is presented. Unlike conventional studies, this work takes into account the finite height of the façade, which is more realistic. The proposed analytical relationships and optimization routine evaluate the best tilt angle and the number of panels such that the whole layout receives the maximum solar radiation, year-round. This is achieved while ensuring that the panels are at a safe minimum distance to avoid mutual shading issues. Validation was performed by simulating the scenarios and comparing the results with manual measurements taken in a three-dimensional drafting program. The method was then used to evaluate designs for facades with a variety of orientations, hypothetically located in Auckland, New Zealand. For this case study, the per-panel and total year-round energy accumulation associated with the number of panels were determined. The results showed that more panels can be integrated into constrained fields by sacrificing the year-round best value of the tilt angle. Therefore, increasing the number of panels may decrease the energy accumulation performance.

Differences in grain yield responses to planting density in twin and narrow row cultivation between early and late maize cultivars

AbstractWe investigated how two planting patterns, twin row (TR) and narrow row (NR), affected maize grain yield compared with conventional row (CR) cultivation at five different planting densities, ranging from 7 to 12 plants/m2, over 2 years using early and late cultivars. For all the planting patterns, the relationship between grain yield and planting density could be fit using the quadratic curve Y = a (X − b)2 + c at the &lt;1% level of significance, where a represents grain yield response to planting density, and c represents the maximum yield. Regardless of the cultivar’s maturation period, the magnitude of a was smaller for TR than for NR and CR. Although the late cultivar had a higher c value than the early cultivar, the a value and annual difference were larger. For the early and late cultivars, TR at 10.8 and 9.9 plants/m2, respectively, easily achieved stable high grain yields. The large magnitude of the grain yield response to planting density for the late cultivar was caused by the large decrease in the number of grains per ear and the harvest index at an above optimum planting density. This large decrease and instability in yield‐related traits resulted from a high maximum leaf area index, the frequent mutual shading of leaf blades and the large differences between the years.

Effect of colony formation on light absorption by Botryococcus braunii

This study elucidates the effect of colony formation on light absorption by Botryococcus braunii microalgae cells. The spectral average mass absorption cross-section of suspensions of B. braunii cultures with free-floating cells or colonies was measured experimentally across the photosynthetically active radiation region. The average mass absorption cross-section was found to decrease significantly across the spectrum in the presence of colonies. This observation could be attributed to (i) reduced pigment concentrations due to nutrient limitations, (ii) mutual shading of the aggregated cells, and/or (iii) the presence of the colonies' extracellular matrix. The Monte Carlo ray tracing method was used to elucidate the contribution of each of these phenomena on the mass absorption cross-section of cells in colonies. Colonies were modeled either as fractal aggregates of monodisperse cells or as an ensemble of monodisperse cells regularly arranged at the periphery of a hollow sphere embedded in a spherical extracellular matrix or as a volume and average projected area equivalent coated sphere. The change in pigment concentrations due to nutrient limitation was found to be the most important factor. In addition, the mass absorption cross-section of cells in colonies was found to decrease due to mutual shading among cells. This effect was stronger with increasing number of cells in the colony and increasing cell absorption index. The effect of extracellular matrix on the mass absorption cross-section was found to be negligible. Finally, good agreement was found between the equivalent coated sphere approximation and the colonies modeled as fractal aggregates comprised of monodisperse cells. This study also established that the Monte Carlo ray tracing method can be used for a variety of microalgae species and colony configurations, whose absorption cross-section are not readily calculated by standard methods due to their complex geometry, inhomogeneous nature, and large size compared to the wavelength of the incident light.

Comparative Analysis of Ground-Mounted vs. Rooftop Photovoltaic Systems Optimized for Interrow Distance between Parallel Arrays

The aim of this research is to perform an in-depth performance comparison of ground-mounted and rooftop photovoltaic (PV) systems. The PV modules are tilted to receive maximum solar irradiance. The efficiency of the PV system decreases due to the mutual shading impact of parallel tilted PV modules. The mutual shading decreases with the increasing interrow distance of parallel PV modules, but a distance that is too large causes an increase in land cost in the case of ground-mounted configuration and a decrease in roof surface shading in the case of rooftop configuration, because larger sections of roof are exposed to sun radiation. Therefore, an optimized interrow distance for the two PV configurations is determined with the aim being to minimize the levelized cost of energy (LCoE) and maximize the energy yield. The model of the building is simulated in EnergyPlus software to determine the cooling load requirement and roof surface temperatures under different shading scenarios. The layout of the rooftop PV system is designed in Helioscope software. A detailed comparison of the two systems is carried out based on energy output, performance ratio, capacity utilization factor (CUF), energy yield, and LCoE. Compared to ground-mounted configuration, the rooftop PV configuration results in a 2.9% increase in CUF, and up to a 23.7% decrease in LCoE. The results of this research show that installing a PV system on a roof has many distinct advantages over ground-mounted PV systems such as the shading of the roof, which leads to the curtailment of the cooling energy requirements of the buildings in hot regions and land cost savings, especially for urban environments.

Spectrum of Light as a Determinant of Plant Functioning: A Historical Perspective.

The significance of the spectral composition of light for growth and other physiological functions of plants moved to the focus of “plant science” soon after the discovery of photosynthesis, if not earlier. The research in this field recently intensified due to the explosive development of computer-controlled systems for artificial illumination and documenting photosynthetic activity. The progress is also substantiated by recent insights into the molecular mechanisms of photo-regulation of assorted physiological functions in plants mediated by photoreceptors and other pigment systems. The spectral balance of solar radiation can vary significantly, affecting the functioning and development of plants. Its effects are evident on the macroscale (e.g., in individual plants growing under the forest canopy) as well as on the meso- or microscale (e.g., mutual shading of leaf cell layers and chloroplasts). The diversity of the observable effects of light spectrum variation arises through (i) the triggering of different photoreceptors, (ii) the non-uniform efficiency of spectral components in driving photosynthesis, and (iii) a variable depth of penetration of spectral components into the leaf. We depict the effects of these factors using the spectral dependence of chloroplast photorelocation movements interlinked with the changes in light penetration into (light capture by) the leaf and the photosynthetic capacity. In this review, we unfold the history of the research on the photocontrol effects and put it in the broader context of photosynthesis efficiency and photoprotection under stress caused by a high intensity of light.