Light Interception Efficiency Research Articles

Light competition drives species replacement during secondary tropical forest succession.

Light competition is thought to drive successional shifts in species dominance in closed vegetations, but few studies have assessed this for species-rich and vertically structured tropical forests. We analyzed how light competition drives species replacement during succession, and how cross-species variation in light competition strategies is determined by underlying species traits. To do so, we used chronosequence approach in which we compared 14 Mexican tropical secondary rainforest stands that differ in age (8-32year-old). For each tree, height and stem diameter were monitored for 2years to calculate relative biomass growth rate (RGR, the aboveground biomass gain per unit aboveground tree biomass per year). For each stand, 3D light profiles were measured to estimate individuals' light interception to calculate light interception efficiency (LIE, intercepted light per unit biomass per year) and light use efficiency (LUE, biomass growth per intercepted light). Throughout succession, species with higher RGR attained higher changes in species dominance and thus increased their dominance over time. Both light competition strategies (LIE and LUE) increased RGR. In early succession, a high LIE and its associated traits (large crown leaf mass and low wood density) are more important for RGR. During succession, forest structure builds up, leading to lower understory light levels. In later succession, a high LUE and its associated traits (high wood density and leaf mass per area) become more important for RGR. Therefore, successional changes in relative importance of light competition strategies drive shifts in species dominance during tropical rainforest succession.

Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory. In this study, we selected three stands typical in south China (a Cryptomeria japonica plantation, a Quercus acutissima plantation, and a mixed stand of both) and three thinning intensities to determine the best understory light environment for 3-year-old Phoebe bournei seedlings. The canopy structure, understory light environment, and photosynthesis and growth indicators were assessed following thinning. Thinning improved canopy structure and understory light availability of each stand; species composition was the reason for differences in the understory light environment. Under the same thinning intensity, the mixed stand had the greatest light radiation and most balanced spectral composition. P. bournei photosynthesis and growth were closely related to the light environment; all three stands required heavy thinning to create an effective and sustained understory light environment. In a suitable understory light environment, the efficiency of light interception, absorption, and use by seedlings was enhanced, resulting in a higher carbon assimilation the main limiting factor was stomatal conductance. As a shade-avoidance signal, red/far-red radiation is a critical factor driving changes in photosynthesis and growth of P. bournei seedlings, and a reduction increased light absorption and use capacity and height: diameter ratios. The growth advantage transformed from diameter to height, enabling seedlings to access more light. Our findings suggest that the regeneration of shade-tolerant species such as P. bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Incorporating dynamic schemes of canopy light extinction coefficient improves transpiration model performance for fruit plantations

The light extinction coefficient (C) describes the efficiency of light interception by a plant canopy, and is a key parameter commonly used to partition radiant energy between a vegetation canopy and the soil surface in several important transpiration models. The C has been observed to vary considerably in the field, but is often parametrized as a fixed constant value, resulting in large potential uncertainty in transpiration estimation. We hypothesized that C changes with leaf area index (LAI) and environments, and that accurate characterization of the C variation pattern would improve transpiration modelling. To test these hypotheses, the relationships between measured C and potential influencing factors were explored for three different fruit plantations in different climate zones in China. Based on these relationships, a new method was proposed to capture C dynamics that considered both LAI and environmental factors. Additionally, 16 C schemes (15 dynamic C schemes and one fixed C scheme) were individually embedded in the Penman-Monteith model, and comprehensive comparisons were made to determine the most effective C scheme for simulating transpiration based on a Bayesian framework. Results showed that C displayed clear variations across all sites, and that there were significant relationships of C with LAI and environmental factors. Compared with the model using a fixed C scheme, the model using the best dynamic C scheme significantly improved model performance by increasing estimation accuracy and decreasing model uncertainty. Specifically, the average coefficients of determination (R2) increased from 0.35 to 0.76, 0.82 to 0.85, and 0.90 to 0.93 for the orange orchard, the jujube orchard, and the grape greenhouse, respectively. Additionally, the average mean relative errors (MRE) decreased by 54.99%, 26.62%, and 13.95%, respectively, and the average uncertainty band widths (B) decreased by 46.81%, 21.74%, and 11.43%, respectively. Model performance improvement was more significant at sites with more serious environmental stresses. The results of our study emphasize the necessity for considering dynamic C patterns in water consumption estimation, particularly for regions facing severe abiotic stresses that are likely to occur in many regions under future climate conditions.

Branching responses to pruning in young cocoa trees

The branching pattern of a tree determines the efficiency of light interception and carbon assimilation. Pruning can modify the branching pattern, because of changes in physiological and environmental conditions, and ultimately pruning can have major effects on yield. For one of the major tropical tree crops, cocoa (Theobroma cacao), very little is known about branching response to pruning. To address this knowledge gap, we performed a pruning experiment on young cocoa trees in Côte d'Ivoire.We applied five treatments to two parcels planted with different genetic materials: two heading treatments (the removal of the terminal apex or 66% of a primary branch) and two thinning treatments (the removal of 1 or 2 primary branches) and one unpruned control. The secondary-branching pattern of the primary branches was described by the number, position, and length of secondary branches right after pruning, and the same observations were repeated after a cycle of leaf production. The probability of branching and the length of secondary branches along a primary branch, in pruned and unpruned conditions, was analyzed using generalized and linear mixed effect models, respectively.In unpruned conditions, the probability of secondary-branch presence was higher towards the middle of the primary branches and lower at the base and the tip. Secondary-branch length decreased from the base to the tip of a primary branch. After one cycle of leaf production, secondary branch emergence differed between the two parcels. In one parcel more branches emerged on the distal section of a primary branch, while in the other they emerged preferentially in the more proximal section. Pruning increased the probability of branch emergence mostly towards the tip of a primary branch, with heavy heading having the strongest effect. By contrast, heavy thinning increased branch emergence also toward the base of the primary branch.Our results can be applied to improve formation pruning, as this may trigger branching in different parts of the crown, depending on the form of pruning. Our study also assists the development of three-dimensional tree models that could further our understanding of the impact of pruning on cocoa growth and productivity.

Analyzing Changes in Maize Leaves Orientation due to GxExM Using an Automatic Method from RGB Images.

The sowing pattern has an important impact on light interception efficiency in maize by determining the spatial distribution of leaves within the canopy. Leaves orientation is an important architectural trait determining maize canopies light interception. Previous studies have indicated how maize genotypes may adapt leaves orientation to avoid mutual shading with neighboring plants as a plastic response to intraspecific competition. The goal of the present study is 2-fold: firstly, to propose and validate an automatic algorithm (Automatic Leaf Azimuth Estimation from Midrib detection [ALAEM]) based on leaves midrib detection in vertical red green blue (RGB) images to describe leaves orientation at the canopy level; and secondly, to describe genotypic and environmental differences in leaves orientation in a panel of 5 maize hybrids sowing at 2 densities (6 and 12 plants.m-2) and 2 row spacing (0.4 and 0.8 m) over 2 different sites in southern France. The ALAEM algorithm was validated against insitu annotations of leaves orientation, showing a satisfactory agreement (root mean square [RMSE] error = 0.1, R2 = 0.35) in the proportion of leaves oriented perpendicular to rows direction across sowing patterns, genotypes, and sites. The results from ALAEM permitted to identify significant differences in leaves orientation associated to leaves intraspecific competition. In both experiments, a progressive increase in the proportion of leaves oriented perpendicular to the row is observed when the rectangularity of the sowing pattern increases from 1 (6 plants.m-2, 0.4 m row spacing) towards 8 (12 plants.m-2, 0.8 m row spacing). Significant differences among the 5 cultivars were found, with 2 hybrids exhibiting, systematically, a more plastic behavior with a significantly higher proportion of leaves oriented perpendicularly to avoid overlapping with neighbor plants at high rectangularity. Differences in leaves orientation were also found between experiments in a squared sowing pattern (6 plants.m-2, 0.4 m row spacing), indicating a possible contribution of illumination conditions inducing a preferential orientation toward east-west direction when intraspecific competition is low.

Leaf, plant, to canopy: A mechanistic study on aboveground plasticity and plant density within a maize-soybean intercrop system for the Midwest, USA.

Plants have evolved to adapt to their neighbours through plastic trait responses. In intercrop systems, plant growth occurs at different spatial and temporal dimensions, creating a competitive light environment where aboveground plasticity may support complementarity in light-use efficiency, realizing yield gains per unit area compared withmonoculture systems. Physiological and architectural plasticity including the consequences for light-use efficiency and yield in a maize-soybean solar corridor intercrop system was compared, empirically, withthe standard monoculture systems of the Midwest, USA. The impact of reducing maize plant density on yield was investigated in the following year. Intercropped maize favoured physiological plasticity over architectural plasticity, which maintained harvest index (HI) but reduced light interception efficiency (ɛi ) and conversion efficiency (ɛc ). Intercropped soybean invested in both plasticity responses, which maintained ɛi , but HI and ɛc decreased. Reducing maize plant density within the solar corridor rows did not improve yields under monoculture and intercrop systems. Overall, the intercrop decreased land-use efficiency by 9%-19%and uncoordinated investment in aboveground plasticity by each crop under high maize plant density does not support complementarity in light-use efficiency. Nonetheless, the mechanistic understanding gained from this study may improve crop cultivars and intercrop designs for the Midwest to increase yield.

Dissection of canopy layer-specific genetic control of leaf angle in Sorghum bicolor by RNA sequencing

BackgroundLeaf angle is an important plant architecture trait, affecting plant density, light interception efficiency, photosynthetic rate, and yield. The “smart canopy” model proposes more vertical leaves in the top plant layers and more horizontal leaves in the lower canopy, maximizing conversion efficiency and photosynthesis. Sorghum leaf arrangement is opposite to that proposed in the “smart canopy” model, indicating the need for improvement. Although leaf angle quantitative trait loci (QTL) have been previously reported, only the Dwarf3 (Dw3) auxin transporter gene, colocalizing with a major-effect QTL on chromosome 7, has been validated. Additionally, the genetic architecture of leaf angle across canopy layers remains to be elucidated.ResultsThis study characterized the canopy-layer specific transcriptome of five sorghum genotypes using RNA sequencing. A set of 284 differentially expressed genes for at least one layer comparison (FDR < 0.05) co-localized with 69 leaf angle QTL and were consistently identified across genotypes. These genes are involved in transmembrane transport, hormone regulation, oxidation-reduction process, response to stimuli, lipid metabolism, and photosynthesis. The most relevant eleven candidate genes for layer-specific angle modification include those homologous to genes controlling leaf angle in rice and maize or genes associated with cell size/expansion, shape, and cell number.ConclusionsConsidering the predicted functions of candidate genes, their potential undesirable pleiotropic effects should be further investigated across tissues and developmental stages. Future validation of proposed candidates and exploitation through genetic engineering or gene editing strategies targeted to collar cells will bring researchers closer to the realization of a “smart canopy” sorghum.

Light Interception and Light Use Efficiency in Sorghum Based intercropping system

Light Interception and Light Use Efficiency in Sorghum Based intercropping system

Geographic Variation in the Petiole-Lamina Relationship of 325 Eastern Qinghai-Tibetan Woody Species: Analysis in Three Dimensions.

The petiole–lamina relationship is central to the functional tradeoff between photosynthetic efficiency and the support/protection cost. Understanding environmental gradients in the relationship and its underlying mechanisms remains a critical challenge for ecologists. We investigated the possible scaling of the petiole–lamina relationships in three dimensions, i.e., petiole length (PL) vs. lamina length (LL), petiole cross sectional area (PCA) vs. lamina area (LA), and petiole mass (PM) vs. lamina mass (LM), for 325 Qinghai–Tibetan woody species, and examined their relation to leaf form, altitude, climate, and vegetation types. Both crossspecies analysis and meta-analysis showed significantly isometric, negatively allometric, and positively allometric scaling of the petiole–lamina relationships in the length, area, and mass dimensions, respectively, reflecting an equal, slower, and faster variation in the petiole than in the lamina in these trait dimensions. Along altitudinal gradients, the effect size of the petiole–lamina relationship decreased in the length and mass dimensions but increased in the area dimension, suggesting the importance of enhancing leaf light-interception and nutrient transport efficiency in the warm zones in petiole development, but enhancing leaf support/protection in the cold zones. The significant additional influences of LA, LM, and LA were observed on the PL–LL, PCA–LA, and PM–LM relationships, respectively, implying that the single-dimension petiole trait is affected simultaneously by multidimensional lamina traits. Relative to simple-leaved species, the presence of petiolule in compound-leaved species can increase both leaf light interception and static gravity loads or dynamic drag forces on the petiole, leading to lower dependence of PL variation on LL variation, but higher biomass allocation to the petiole. Our study highlights the need for multidimension analyses of the petiole–lamina relationships and illustrates the importance of plant functional tradeoffs and the change in the tradeoffs along environmental gradients in determining the relationships.

Morpho-physiological bases of biomass production by energy cane and sugarcane: A comparative study

Using the same production system as sugarcane, energy cane (Saccharum spp. hybrid, as sugarcane) can produce more biomass, which can be associated with its high tillering and a vigorous root system with rhizomes. These traits enable energy cane to capture natural resources efficiently and convert more energy into biomass than sugarcane. Our aim is to understand the morpho-physiological bases of biomass production by energy cane. We evaluated the efficiencies of light interception and light conversion into biomass in a field experiment, measuring morphological and physiological traits of energy canes (Vertix 2 and Vertix 3) and sugarcane (IACSP95-5000). When plants have a low leaf area index (< 4 m2 m−2), the high tillering of energy cane increases the efficiency of light interception. High leaf insertion angles also favored light interception by canopies with high tiller density, as one found in Vertix 3. However, high tiller density likely caused excessive self-shading in energy cane canopy and then energy canes exhibited similar or lower photosynthetic activity than sugarcane, depending on environmental conditions. All three genotypes faced severe water stress during the ratoon cycle, but energy cane was less sensitive when considering light conversion efficiency and biomass yield.

Genetic Relationships Among Physiological Processes, Phenology, and Grain Yield Offer an Insight Into the Development of New Cultivars in Soybean (Glycine max L. Merr).

Soybean grain yield has steadily increased during the last century because of enhanced cultivars and better agronomic practices. Increases in the total biomass, shorter cultivars, late maturity, and extended seed-filling period are frequently reported as main contributors for better soybean performance. However, there are still processes associated with crop physiology to be improved. From the theoretical standpoint, yield is the product of efficiency of light interception (Ei), radiation use efficiency (RUE), and harvest index (HI). The relative contribution of these three parameters on the final grain yield (GY), their interrelation with other phenological–physiological traits, and their environmental stability have not been well established for soybean. In this study, we determined the additive–genetic relationship among 14 physiological and phenological traits including photosynthesis (A) and intrinsic water use efficiency (iWUE) in a panel of 383 soybean recombinant inbred lines (RILs) through direct (path analyses) and indirect learning methods [least absolute shrinkage and selection operator (LASSO) algorithm]. We evaluated the stability of Ei, RUE, and HI through the slope from the Finley and Wilkinson joint regression and the genetic correlation between traits evaluated in different environments. Results indicate that both supervised and unsupervised methods effectively establish the main relationships underlying changes in Ei, RUE, HI, and GY. Variations in the average growth rate of canopy coverage for the first 40 days after planting (AGR40) explain most of the changes in Ei. RUE is primarily influenced by phenological traits of reproductive length (RL) and seed-filling (SFL) as well as iWUE, light extinction coefficient (K), and A. HI showed a strong relationship with A, AGR40, SFL, and RL. According to the path analysis, an increase in one standard unit of HI promotes changes in 0.5 standard units of GY, while changes in the same standard unit of RUE and Ei produce increases on GY of 0.20 and 0.19 standard units, respectively. RUE, Ei, and HI exhibited better environmental stability than GY, although changes associated with year and location showed a moderate effect in Ei and RUE, respectively. This study brings insight into a group of traits involving A, iWUE, and RL to be prioritized during the breeding process for high-yielding cultivars.

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.

Voxel carving-based 3D reconstruction of sorghum identifies genetic determinants of light interception efficiency.

Changes in canopy architecture traits have been shown to contribute to yield increases. Optimizing both light interception and light interception efficiency of agricultural crop canopies will be essential to meeting the growing food needs. Canopy architecture is inherently three‐dimensional (3D), but many approaches to measuring canopy architecture component traits treat the canopy as a two‐dimensional (2D) structure to make large scale measurement, selective breeding, and gene identification logistically feasible. We develop a high throughput voxel carving strategy to reconstruct 3D representations of sorghum from a small number of RGB photos. Our approach builds on the voxel carving algorithm to allow for fully automatic reconstruction of hundreds of plants. It was employed to generate 3D reconstructions of individual plants within a sorghum association population at the late vegetative stage of development. Light interception parameters estimated from these reconstructions enabled the identification of known and previously unreported loci controlling light interception efficiency in sorghum. The approach is generalizable and scalable, and it enables 3D reconstructions from existing plant high throughput phenotyping datasets. We also propose a set of best practices to increase 3D reconstructions’ accuracy.

Is foliage clumping an outcome of resource limitations within forests?

Foliage clumping is a forest canopy structural feature influencing light interception, the inversion of light interception for estimating leaf area index, and photosynthesis rates. In this study we estimated clumping factor values at the branch level from different heights in broadleaf tree species at four sites in two climatic zones (two sites in dry climate and two sites in humid climate) using laser light. We found that branch level foliage distribution tends to be random at dry sites where water is the main limiting resource, and that foliage aggregation at the top of emergent canopy tops increases with branch height at humid site where competition for light is high. Our results suggest that high competition for light leads to the production of large amounts of leaves grouped together in high irradiance areas of the canopy, even though this significantly reduces the light interception efficiency on a per leaf area basis. A comparison of these results with foliage clumping factor values derived at larger spatial scales for two sites (one dry and one humid) revealed a crossover in the scales at which clumping arises: leaves are essentially clumped at the branch level but much less so at the plot level for the humid site, and leaves are clumped at the plot level but not at the branch level for the dry site. This suggests that the occurrence of foliage clumping may be related to the intensity of resource limitation (light or water in this case) and its availability in 3D space. Additional research is required to confirm the role of environmental conditions in determining foliage clumping across various forest biomes. Further confirmation and understanding of causal relations between abiotic stresses and canopy foliage clumping may lead to significant refinement in forest canopy radiative transfer modelling schemes.

Challenges for Simulating Growth and Phenology of Silage Maize in a Nordic Climate with APSIM

APSIM Next Generation was used to simulate the phenological development and biomass production of silage maize for high latitudes (i.e., &gt;55°). Weather and soil data were carefully specified, as they are important drivers of the development and growth of the crop. Phenology related parameters were calibrated using a factorial experiment of simulations and the minimization of the root mean square error of observed and predicted phenological scaling. Results showed that the model performed well in simulating the phenology of the maize, but largely underestimated the production of biomass. Several factors could explain the discrepancy between observations and predictions of above-ground dry matter yield, such as the current formalization of APSIM for simulating the amount of radiation absorbed by the crop at high latitudes, as the amount of diffuse light and intercepted light increases with latitude. Another factor that can affect the accuracy of the predicted biomass is the increased duration of the day length observed at high latitudes. Indeed, APSIM does not yet formalize the effects of extreme day length on the balance between photorespiration and photosynthesis on the final balance of biomass production. More field measurements are required to better understand the drivers of the underestimation of biomass production, with a particular focus on the light interception efficiency and the radiation use efficiency.

Effect of double rows plant system on plant growth, yield components and grain yield in prolific and non-prolific hybrid maize

Double row plant systems in corn plants theoretically can improve the efficiency of light interception in leaves, but their effect on grain yields is not consistent in each hybrid type. This research was conducted in the experimental garden of the Balai Penelitian Tanaman Serealia (Balitsereal) Maros Regency, South Sulawesi. This study aimed to evaluate the response of yields of prolific and nonprolific hybrid corn types to the double row and single row planting systems. Experimental design using Randomized Group Design in divided plot design that was carried out with three replications. The main plot was variety Nasa-29, Bisi-2 (prolific), Bima-19 (nonprolific), while subplot was a double row and single row. The double row planting system did not have a significant effect on plant height, number of leaves, and leaf area index (ILD), but a significant positive effect was found on the number of grains per row of ears, number of ears per plant, and percentage of the weight of the second ear’s grains to the total yield and grain yield. In this study, the significant effect of double rows on each variety tested was not seen on all parameters tested. The double row planting system significantly increases the grain yield and the grain yield was consistent with the increase in the number of ear rows, the number of ear per plant and the percentage of grain weight of the second ears on yield, but not on plant height. The leaf area index achieved in this study may be one of the determinants of increased grain yield. A double row system can be considered as an alternative planting system, especially in the type of prolific hybrid corn to increase the contribution of two ears to grain yield.

Asymmetric competition, ontogenetic growth and size inequality drive the difference in productivity between two-strata and one-stratum forest stands

Size inequality has been considered a key feature of plant population structure with impacts on ecosystem functions. In forest ecosystems, studies examining the relationship between tree size inequality and stand productivity have produced mixed outcomes. These studies found positive, neutral or negative relationships and discussed how this could be influenced by competition for light between trees (e.g. light interception efficiency), but far less attention has been paid to the role played by tree ontogenetic growth. In this article, we present a simple mathematical model that predicts the basal area growth of a two-strata stand as a function of tree basal areas and asymmetric competition. Comparing the growth of this stand to the growth of a spatially homogeneous one-stratum stand and a spatially heterogeneous one-stratum stand, we show that higher growth of the two-strata stand is achieved for concave shape, increasing functions of ontogenetic growth and for low intensities of absolute size-asymmetric competition. We also demonstrate that the difference in growth between the two-strata stand and the one-stratum stands depends on tree size inequality, mean tree basal area and total basal area in the two-strata stand. We finally found that the relationships between tree size inequality and productivity can vary from positive to negative and even non-monotonous. However, we highlight that negative relationships may be more frequent. As a conclusion, our results indicate that ontogenetic growth can have a major impact on the form and the magnitude of the size inequality–productivity relationship.

Large leaves in warm, moist environments confer an advantage in seedling light interception efficiency.

Leaf size varies conspicuously along environmental gradients. Small leaves help plants cope with drought and frost, because of the effect of leaf size on boundary layer conductance; it is less clear what advantage large leaves confer in benign environments. We asked if large leaves give species of warm climates an advantage in seedling light interception efficiency over small-leaved species from colder environments. We measured seedling leaf, architectural and biomass distribution traits of 18 New Zealand temperate rainforest evergreens; we then used a 3-D digitiser and the Yplant program to model leaf area display and light interception. Species associated with mild climates on average had larger leaves and larger specific leaf areas (SLA) than those from cold climates, and displayed larger effective foliage areas per unit of aboveground biomass, indicating higher light interception efficiency at whole-plant level. This reflected differences in total foliage area, rather than in self-shading. Our findings advance the understanding of leaf size by showing that large leaves enable seedlings of species with highly conductive (but frost-sensitive) xylem to deploy large foliage areas without increasing self-shading. Leaf size variation along temperature gradients in humid forests may therefore reflect a trade-off between seedling light interception efficiency and susceptibility to frost.

Changes in the vertical distribution of leaf area enhanced light interception efficiency in maize over generations of selection.

Breeders select for yield, thereby indirectly selecting for traits that contribute to it. We tested if breeding has affected a range of traits involved in plant architecture and light interception, via the analysis of a panel of 60 maize hybrids released from 1950 to 2015. This was based on novel traits calculated from reconstructions derived from a phenotyping platform. The contribution of these traits to light interception was assessed in virtual field canopies composed of 3D plant reconstructions, with a model tested in a real field. Two categories of traits had different contributions to genetic progress. (a) The vertical distribution of leaf area had a high heritability and showed a marked trend over generations of selection. Leaf area tended to be located at lower positions in the canopy, thereby improving light penetration and distribution in the canopy. This potentially increased the carbon availability to ears, via the amount of light absorbed by the intermediate canopy layer. (b) Neither the horizontal distribution of leaves in the relation to plant rows nor the response of light interception to plant density showed appreciable trends with generations. Hence, among many architectural traits, the vertical distribution of leaf area was the main indirect target of selection.

High efficiency sweet cherry orchard systems research

The large tree size, and delicate nature and small size of the fruit, makes production of sweet cherries Fig. 6 - Planar UFO sweet cherry canopy architectural orchard designs: A) vertical-trellis UFO with 18,725 upright leaders per ha or B) Vtrellis UFO with 24,996 inclined leaders per ha, in theory with 33% higher yield potential, but slightly less training, harvest and pruning efficiency. Fig. 6 - Progettazione dell’architettura della chioma in piano “UFO” su ciliegio dolce: A) sostegni verticali per UFO con 18725 fusti verticali per ha o B) sostegno a V per UFO con 24996 fusti inclinati per ha, in teoria con il 33% in più di potenziale produttivo, ma leggermente meno per quanto riguarda efficienza di allevamento, raccolta e potatura. A B Lang 34 among the most traditionally labor-intensive tree fruits. Great improvements in orchard efficiencies have been achieved over the past two decades, prompted by the development of precocious, vigorcontrolling rootstocks such as the Gisela (Gi) series. Recent training systems research has focused on canopy architectural designs that improve various orchard efficiencies, including: 1) light interception and distribution whit minimization of shade; 2) bloom, fruit development and ripening for more uniform fruit harvest; 3) balanced, quantifiable crop load management for achieving high fruit quality; 4) simplified strategies for fruitwood development and maintenance to reduce hand-pruning labor; 5) partial mechanization to reduce pruning and harvest labor; 6) utilization of protective orchard covers to mitigate the risk of crop damage from rain, hail, frost, and wind; and 7) better spray coverage for protection from insect pests and diseases. Across several sites in North America, the NC140 regional research project has evaluated the performance of three sweet cherry cultivars on dwarfing (Gi3), semi-dwarfing (Gi5), and semi-vigorous (Gi6) rootstocks trained to “threedimensional” and “two-dimensional” (planar) canopy architectures over nine years to date. The planar Super Slender Axe (SSA) training system had the highest early yields on a per tree and per orchard basis, but the planar Upright Fruiting Offshoots (UFO) training system sustained higher cumulative yields upon reaching maturity. The three-dimensional Tall Spindle Axe (TSA) trees had higher early yields than those trained to the three-dimensional Kym Green Bush (KGB) canopy architecture, but the KGB trees achieved nearly comparable cumulative yields. Fruitwood renewal strategies are critical for maintenance of yields and fruit quality. Profitable yields of high quality fruit are achievable for each of the canopy architectures, but each also has specific advantages and challenges, including suitability for specific rootstocks and cultivars. These are discussed, including comparisons of the two- vs. three-dimensional canopy architectures developed as single leader (SSA vs. TSA) and multiple leader (UFO vs. KGB) training systems. The advantages of utilizing the natural light interception efficiencies and growth habit of sweet cherry in the simplified structure of UFO-style planar canopy architectures is expanding beyond sweet cherries to many other major trees fruits around the world as well.