Canopy Shade Research Articles

Arabidopsis FHY1 and FHY1-LIKE Are Not Required for Phytochrome A Signal Transduction in the Nucleus

Photoreceptors of the phytochrome family control a multitude of responses in plants. Phytochrome A (phyA) is essential for far-red light perception, which is important for germination and seedling establishment in strong canopy shade. Translocation of phyA from the cytosol into nucleus is a key step in far-red light signaling and requires FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) and FHY1-LIKE (FHL). FHY1/FHL bind to phyA downstream signaling components. Therefore, it has been suggested that FHY1/FHL also have a function in assembling phyA transcription factor complexes in the nucleus. Yet, in this study, we show that constitutively nuclear-localized phyA is active in the absence of FHY1 and FHL. Furthermore, an artificial FHY1, consisting of an SV40 NLS, a phyA binding site, and a YFP tag as spacer between them, complements the fhy1-3 fhl-1 double mutant. These findings show that FHY1 and FHL are not required for phyA downstream signaling in the nucleus. However, we found that lines expressing phyA-NLS-YFP are hypersensitive to red and far-red light and that slightly increased levels of constitutively nuclear-localized phyA result in photomorphogenic development in the dark. Thus, restricting phyA to the cytosol and inducing nuclear transport in light by interaction with FHY1/FHL might be important to suppress photomorphogenesis in the dark.

Thinning enhances stool resistance to an extreme drought in a Mediterranean Quercus ilex L. coppice: insights for adaptation

Mediterranean holm oak forests are subjected to chronic seasonal droughts coinciding with the warmest conditions during the summer. Importantly, climate change projections support increased frequency and intensity of droughts in the future. In order to evaluate whether thinning practices can be used as efficient adaptation strategies to climate change, we measured canopy cover as a surrogate of defoliation in 49 Quercus ilex L. subsp. ilex individual genets subjected to experimental ramet thinning. Canopy cover measurements were obtained before, during and after the exceptionally intense and prolonged drought of 2016. Our results show that intensity of basal area reduction determined higher resistance, but not resilience, to this intense-long drought period. Independently of shoot thinning intensity, every holm oak exhibited crown defoliation during the dry period but most of them recovered their leaves the next spring. Holm oaks subjected to thinning with more than over 50% of basal area removed, were less vulnerable to severe drought, however, and supported more leaves later on. Additionally, our results highlight the positive influence of canopy shading from neighbouring trees preventing defoliation after drought events. A greater canopy shading per stool led to a higher resistance in holm oak trees exposed to severe drought. These findings suggest that, in order to cope with concomitant climate change and to optimize genet-level stress tolerance, coppice selection should be done by removing shoots with fewer leaves per unit area, preferably those unexposed to shading from neighbouring trees until a reduction around 50% of basal area per stool is achieved.

UVR8 disrupts stabilisation of PIF5 by COP1 to inhibit plant stem elongation in sunlight

Alterations in light quality significantly affect plant growth and development. In canopy shade, phytochrome photoreceptors perceive reduced ratios of red to far-red light (R:FR) and initiate stem elongation to enable plants to overtop competitors. This shade avoidance response is achieved via the stabilisation and activation of PHYTOCHROME INTERACTING FACTORs (PIFs) which elevate auxin biosynthesis. UV-B inhibits shade avoidance by reducing the abundance and activity of PIFs, yet the molecular mechanisms controlling PIF abundance in UV-B are unknown. Here we show that the UV-B photoreceptor UVR8 promotes rapid PIF5 degradation via the ubiquitin-proteasome system in a response requiring the N terminus of PIF5. In planta interactions between UVR8 and PIF5 are not observed. We further demonstrate that PIF5 interacts with the E3 ligase COP1, promoting PIF5 stabilisation in light-grown plants. Binding of UVR8 to COP1 in UV-B disrupts this stabilisation, providing a mechanism to rapidly lower PIF5 abundance in sunlight.

EFFECTS OF SHADE TREE SPATIAL DISTRIBUTION AND SPECIES ON PHOTOSYNTHETIC RATE OF COFFEE TREES

The use of shade trees in coffee fields have been motivated by climatic changes. However, microclimatic conditions in shaded coffee fields differ due to shade tree spatial distribution and species, altering physiological responses of coffee trees. This study aimed to evaluate the effects of shade tree spatial distribution and species on coffee trees photosynthetic rate in two growth seasons, of high (HSD) and low (LSD) sink demand. The experimental design consisted of randomized blocks with three replicates in split-split-plots. Plots were the shade tree species: <em>Anadenanthera falcata</em>, <em>Cassia grandis</em> and <em>Peltophorum dubium</em>. Split plot was formed by five distances between coffee trees and shade tree trunks: coffee trees on planting row of shade trees, distancing one (D1L) and five (D5L) meters from shade trees trunk; coffee trees on inter-rows of shade trees, parallel to D1L and D5L (D1E and D5E); coffee trees distancing 77 meters from shade tree trunks, in a full-sun field (PS). The split-split-plots correspond to coffee tree canopy exposure to the sun: branches facing North or South. Shade trees canopy density and occupation was evaluated with a convex densiometer. Photosynthetic rate (Pn)and photosynthetic active radiation (PAR) were measured with an Infrared Gas Analyzer (IRGA) on two time-frames, between 7.00 and 9.00 solar hours and between 11.00 and 13.00. Shade tree canopy density and occupation was not homogenous during the change of seasons and shift due to spatial distribution, which also changes PAR levels. Shade trees reduce PAR to more suitable values for coffee tree exploitation, especially on D1L and D5L. During HSD, shading did not affect P<sub>n</sub>, which was greater in branches facing North. Yet, in LSD, between 11.00 and 13.00, coffee trees shaded with <em>A. falcata</em> showed greater P<sub>n</sub> than at PS. Coffee trees shaded with <em>C. grandis</em> at D5L and D1E had greater values of P<sub>n</sub> than PS.

Exploring the effects of pasture trees on plant community patterns

AbstractQuestionsWe aim to answer three questions: (a) what are the effects of canopy shading of different tree species on seed germination of eight understorey grassland species? (b) how is plant species’ occurrence in understorey communities affected by differences in canopy cover and does that depend on tree species composition? and (c) are there mechanistic links between the effects of trees on species’ germination and their occurrence in the understorey plant community?LocationSemi‐natural wooded pastures in the biosphere reserve Östra Vätterbranterna, southern Sweden.MethodsIn this study, we examined the germination of eight grassland plant species in a seed sowing experiment under natural conditions in the field. Seeds were sown beneath and outside the canopy of two tree species within 48 plots split up by four wooded pasture sites. We combined observed germination responses with a plant community survey to assess the effects of canopy cover in relation to tree species composition on plant community responses. We analysed these data in relation to species’ seed mass and vegetative shade tolerance.ResultsShade‐tolerant species germinated better beneath compared to outside tree canopies, without any clear advantage of large‐seeded over small‐seeded species. As expected, species’ shade tolerance was also positively related to canopy cover within the understorey plant community. Importantly, we found strong tree species‐specific effects of canopy shading on the species’ germination response, but not on their presence within the plant community. However, optimal canopy cover conditions for germination and for the mature plants differed across grassland species and depended on tree species.ConclusionsOur results show that different tree species play key ecosystem engineering roles in shaping wooded grassland plant community composition at the germination stage. Management practices favouring specific tree species may therefore be highly relevant for targeted biodiversity conservation of wooded semi‐natural grasslands.

Manipulation of vegetative growth and improvement of yield potential of cashew (Anacardium occidentale L.) by Paclobutrazol

Cashew (Anacardium occidentale L.) is a perennial tree crop that realizes yield after several years of planting due to its long gestation period. Therefore, canopy management by pruning in later stages of growth often affects orchard life and performance of trees. High density planting system (HDP) has been attempted in cashew to obtain early benefits in terms of yield during initial years of planting. Under HDP, maintenance of tree and canopy growth becomes important due to closer spacing and shading of canopy of trees. In cashew, due to non availability of dwarf clones and dwarfing rootstocks, use of growth retardants, paclobutrazol (PBZ), assumes importance. Hence, this study was aimed to evaluate the morpho-physiological responses of cashew to PBZ treatments under field trials. PBZ treatments resulted in reduced vegetative growth and enhanced reproductive growth with most striking responses at PBZ 3 g a.i./tree treatment. PBZ treatments altered cashew tree physiology by modifying tree size, canopy growth, internodal length, branching pattern and overall ground coverage of the tree. Higher total leaf chlorophyll content, better photo assimilation and enhanced leaf photosynthesis contributed in inducing early flowering and development of more flowering panicles with perfect flowers. Enhanced fruit set and increased number of nuts/m2 canopy contributed in yield increment. Regression analysis showed leaf pigments, nut number and number of inflorescence as the most contributing traits for yield enhancement under PBZ. These findings may highlight the exploitation of morpho-physiological traits for better canopy growth and yield maximization by PBZ in cashew under the HDP.

Effects of natural and artificial shade on human thermal comfort in residential neighborhood parks of Phoenix, Arizona, USA

This research studied the capacity of natural and artificial shade types to improve outdoor human comfort during normally hot, summer midday (1200 to 1400 h), desert conditions. Micrometeorological data were collected in full sun and under shade canopies of six landscape tree taxa and constructed ramadas in residential neighborhood parks of Phoenix, AZ, USA. The six tree taxa included Arizona ash (Fraxinus velutina Torr.), Mexican palo verde (Parkinsonia aculeata L.), Aleppo pine (Pinus halepensis Mill.), South American mesquite (Prosopis spp. L.), Texas live oak (Quercus virginiana for. fusiformis Mill.), and Chinese elm (Ulmus parvifolia Jacq.). Results showed that natural shading from live trees and artificial shading from constructed ramadas were not similarly effective at improving outdoor human thermal comfort, represented by physiologically equivalent temperature (PET). The difference in PET between full sun and under shade canopies of Fraxinus and Quercus trees was greater than under shade canopies of Parkinsonia, Prosopis, trees or constructed ramadas by 2.9 to 4.3 °C. Radiation intensity was the most significant driver of lowered PET (p < 0.0001, R2 = 0.69) and with the exception of ramadas, lower radiation intensities corresponded with lower PET. Our results suggest that selecting trees that attenuate the most solar radiation is the most effective urban design strategy for lowering PET during normally hot, summer midday, desert conditions.

Janzen-Connell effects in a forest BEF experiment: Strong distance-dependent seedling establishment of multiple species.

The Janzen-Connell (JC) hypothesis is a major ecological explanation for high species richness, in particular in tropical forest ecosystems. Central components of the JC hypothesis are noncompetitive effects of distance and density dependence, two drivers that contribute independently to species coexistence, but are ultimately linked in the field. However, although numerous studies provide evidence for either distance- or density-dependent effects based on observational data, experimental testing of simultaneous and interactive effects of distance and density has rarely been conducted, especially in a comprehensive multispecies approach. Here, we make use of the forest Biodiversity-Ecosystem Functioning project (BEF) -China to estimate distance- and density-dependent effects in a reciprocal tree seedling transplant experiment of 11 tree species. We deployed 13,490 juveniles of all 11 species in their own (home) and in all foreign monocultures (away), as well as at three different levels of planting density, thereby testing for distance and density effects, respectively. In addition, to quantify the amount to which density effects were brought about by potential additional effects of intraspecific competition, we set up a common garden experiment with different levels of planting density, where an additional "shadow" treatment controlled for effects of canopy shading. Although the "away" and "high-density" treatments significantly impaired the performance and productivity of seedlings, leaf damage and survival was exclusively affected by either the home/away or the density treatment, respectively. Negative density-dependent effects on leaf damage were less pronounced in the "home" treatment, showing that the effects were not additive. In addition, results obtained in the Common Garden Experiment showed that negative effects of high density may be also brought about by intraspecific competition as an alternative density-responsive mechanism and less by true JC effects. Overall, our results provide strong support on a multispecies basis for the influence of host-specific effects already operating in early stages of a forest plantation. However, they also emphasize the need to account appropriately for potential additional density-responsive mechanisms such as intraspecific competition or microenvironmental conditions when addressing the role of JC effects for species coexistence.

Status, conservation and ecology of Pallavicinia lyellii (Hook.) Carruth. in a key region of England

ABSTRACTIntroduction. Pallavicinia lyellii is recognised as being of principal importance for conservation in England and is threatened with extinction in Europe. The aims of this study were to investigate the current status, conservation and ecology of the species in S Hampshire, a key region for the plant.Methods. All recent and historic locations for Pallavicinia lyellii in S Hampshire were searched and information collected on distribution, abundance and ecology.Results. Pallavicinia lyellii was re-found at three sites. It is almost certainly extinct at two sites and may have been lost from a third. Whilst few colonies were sterile, most comprised a single sex. Colonies with both male and female plants were confined to Cadnam Bog, which supported 49 (91%) of the colonies found. Overall, female shoots occurred at 41 (76%) colonies and males at 26 (48%), producing a female sex bias (1.6:1). All colonies occur in boggy woodland, mostly on the sides of low mounds of damp, acidic, peaty soil developed, due to poaching by ponies and cattle, at the base of trees, usually I. aquifolium. The community mainly comprises a species-poor mix of acidophilous mosses and liverworts, most frequently Mnium hornum, Pseudotaxiphyllum elegans and Leucobryum juniperoideum.Conclusions. Cadnam Bog appears to support the largest sexually reproducing population of Pallavicinia lyellii in England. The site is specially protected, actively managed with consideration to P. lyellii and seemingly in favourable condition for the plant. Research is needed to quantify canopy shade favoured by the plant and assess implications for woodland management. Future monitoring should include re-survey of populations every 3 yr.

Composición y estructura del dosel de sombra en sistemas agroforestales con café de tres municipios de Cundinamarca, Colombia

Se estudió la composición y estructura del dosel de sombra en cafetales de los municipios de Tibacuy, Pacho y San Juan de Rioseco, Cundinamarca, Colombia. Se seleccionaron 15 fincas por municipio y en cada finca un lote de café (Coffea arabica) cv. Castillo en el que se estableció una parcela de 1000 m2 donde se registraron las especies arbóreas con diámetro a la altura del pecho mayor a 10 cm y todos los individuos de plátano (Musa AAB). De acuerdo al porcentaje de sombra en cada municipio las fincas se clasificaron en sombrío alto (SA), sombrío medio (SM) y sombrío bajo (SB). Se encontraron 43 especies arbóreas asociadas a los cafetales, donde el 16% de ellas estaban presentes en los tres municipios; la familia más representativa fue la Fabaceae. La cantidad de plátano fue mayor en cafetales de San Juan de Rioseco, siendo esta especie determinante en las interacciones por sombra en los sistemas evaluados. La abundancia absoluta de árboles fue mayor en fincas con SA y SM (p &lt; 0,05) en los tres municipios; no se registraron diferencias significativas entre niveles de sombrío para la riqueza de especies arbóreas y en Tibacuy la diversidad fue mayor en sistemas de SM (p &lt; 0,05). Citrus sinensis, Inga edulis y Cordia alliodora fueron las especies de mayor importancia ecológica en los cafetales de los tres municipios, de acuerdo al I.V.I. Finalmente, en los sistemas agroforestales (SAF) de los tres municipios no existe una distribución homogénea de la sombra en el terreno lo cual es más evidente en SAF de SB en Pacho; hay superposición de copas y el SAF de SA en Tibacuy tiene una mayor complejidad en la estructura vertical, con tres estratos bien diferenciados.

Model Based Study of Crop Evapotranspiration under Canopy Shading

California has some of the key agricultural regions in the United States. One of these key regions, San Joaquin Valley, frequently experiences severe droughts leading to shortage of irrigation water. This has a significant impact on the agricultural based economy of the region. It is imperative to develop new strategies to reduce overall water consumption in agriculture without affecting crop yield. A large fraction of irrigation water is lost due to the evapotranspiration (ET) process in the crops and the soil. The classical Penman-Monteith model has been used in the present work to analyze the effect of different environmental variables and water saving strategies on the ET. Some of the scenarios considered show potential for significant water savings without much reduction in the amount of sunlight available to facilitate crop growth. The central idea considered in this study is the use of canopy shading to cover the crop field resulting in reduction in the ET. Among the strategies considered, the most promising strategy is to partially cover the crop field for a certain part of the day by employing a partially covering retractable canopy. Based on numerical calculations, total reduction in ET is calculated to be 37% from June to August for the partially covering retractable canopy.

Field monitoring of suction in the vicinity of an urban tree: exploring termite infestation and the shading effects of tree canopy

The objective of this short communication is to explore spatial distribution of soil suction in the vicinity of an urban tree considering effects of termite infestation and also radiant energy interception by canopy. A site in an urban landscape containing a mix of species cover (grass cover in the vicinity of trees) was selected for monitoring. A field monitoring program was designed to monitor soil (soil suction, moisture), vegetation parameters (tree height, grass leaf area), and meteorological parameters during drying/wetting cycles. As expected, before termite infestation, suction magnitude and rate of change were highest near the tree stem and at shallower depths, reflecting the dominance of transpiration over evaporation. However, after termite infestation, soil suction diminished significantly near the tree stem and increased farther from the tree stem, a phenomenon accompanied by loss of canopy area, as captured by a color analysis technique (i.e., an image processing method). These findings reflected a reduction in stomatal conductance, itself an indicator of transpiration loss through the stomata—likely because reduced canopy shading effects caused increased evaporation. Soil suction at deeper depths seemed not to be significantly affected, generally due to canopy and termite infestation. In summary, the study sheds new light on issues of tree maintenance by showing how termite infestation can significantly affect the performance of green infrastructure.

A Genome-Wide Association Study of Non-Photochemical Quenching in response to local seasonal climates in Arabidopsis thaliana.

Field‐grown plants have variable exposure to sunlight as a result of shifting cloud‐cover, seasonal changes, canopy shading, and other environmental factors. As a result, they need to have developed a method for dissipating excess energy obtained from periodic excessive sunlight exposure. Non‐photochemical quenching (NPQ) dissipates excess energy as heat, however, the physical and molecular genetic mechanics of NPQ variation are not understood. In this study, we investigated the genetic loci involved in NPQ by first growing different Arabidopsis thaliana accessions in local and seasonal climate conditions, then measured their NPQ kinetics through development by chlorophyll fluorescence. We used genome‐wide association studies (GWAS) to identify 15 significant quantitative trait loci (QTL) for a range of photosynthetic traits, including a QTL co‐located with known NPQ gene PSBS (AT1G44575). We found there were large alternative regulatory segments between the PSBS promoter regions of the functional haplotypes and a significant difference in PsbS protein concentration. These findings parallel studies in rice showing recurrent regulatory evolution of this gene. The variation in the PSBS promoter and the changes underlying other QTLs could give insight to allow manipulations of NPQ in crops to improve their photosynthetic efficiency and yield.

Permafrost response to vegetation greenness variation in the Arctic tundra through positive feedback in surface air temperature and snow cover

The permafrost response to variations in Arctic vegetation remains controversial. We investigated the consequences of Arctic vegetation greenness variation over the past three decades using a coupled land-atmosphere model and found that it induces air temperature perturbation, which is further amplified by snow cover variation and eventually leaves a footprint on soil temperature. Compared to the atmospheric impacts of vegetation, local shading of vegetation canopy has relatively minor effects on soil temperature. Significant soil warming was observed along the summer snowline between the Low and High Arctic, indicating the direct impact of snow cover variation led by vegetation changes. In the Low Arctic, the winter snowpack insulates the soil from colder air, resulting in less permafrost. In the High Arctic, snow persists for more than 330 d per year and has a strong protection effect on the permafrost as it insulates soil from warmer summer air and reflects solar radiation.

Effects of daytime intra-canopy LED illumination on photosynthesis and productivity of bell pepper grown in protected cultivation

In the past decade, light-emitting diodes (LEDs) have been replacing most other types of light sources. One emerging use for LEDs in horticulture is ‘intra-canopy illumination’ or ‘LED-interlighting’, feasible owing to their low heat output and small physical size. The interlighting technique, typically implemented in environmentally-controlled greenhouses also supplemented with overhead lighting, is mostly relevant for high-wire vegetable cultivation, in which self-shading results in light limitations for a large fraction of the canopy. Interlighting has been shown to increase the yield and/or improve fruit quality in all-year round greenhouse crops such as tomato, cucumber and sweet pepper. In this work, we utilized daytime supplemental intra-canopy LED illumination for sweet pepper grown in high-density ‘Spanish’ trellis systems within passive high tunnels in the Jordan Valley, Israel (latitude ˜32 °N). While canopy top at these conditions is not light-limited, extensive deep shading of the inner canopy is a disadvantage. In two experiments carried out in two separate seasons, the supplemental lighting, which enhanced the photosynthetic rates of the inner canopy foliage by 3.5- to 5.7-fold, resulted in significant increase (˜30%) of the fruit yield during the spring season. The added yield was attained by higher fruit numbers, with no notable effects on fruit size or weight. Our results raise the prospect that LED-interlighting may be a useful practical tool for maximizing fruit production, even in geographical regions of ample sunlight.

How canopy shadow affects invasive plant species classification in high spatial resolution remote sensing

AbstractPlant invasions can result in serious threats for biodiversity and ecosystem functioning. Reliable maps at very‐high spatial resolution are needed to assess invasions dynamics. Field sampling approaches could be replaced by unmanned aerial vehicles (UAVs) to derive such maps. However, pixel‐based species classification at high spatial resolution is highly affected by within‐canopy variation caused by shadows. Here, we studied the effect of shadows on mapping the occurrence of invasive species using UAV‐based data. MaxEnt one‐class classifications were applied to map Acacia dealbata, Ulex europaeus and Pinus radiata in central‐south Chile using combinations of UAV‐based spectral (RGB and hyperspectral), 2D textural and 3D structural variables including and excluding shaded canopy pixels during model calibration. The model accuracies in terms of area under the curve (AUC), Cohen's Kappa, sensitivity (true positive rate) and specificity (true negative rate) were examined in sunlit and shaded canopies separately. Bootstrapping was used for validation and to assess statistical differences between models. Our results show that shadows significantly affect the accuracies obtained with all types of variables. The predictions in shaded areas were generally inaccurate, leading to misclassification rates between 65% and 100% even when shadows were included during model calibration. The exclusion of shaded areas from model calibrations increased the predictive accuracies (especially in terms of sensitivity), decreasing false positives. Spectral and 2D textural information showed generally higher performances and improvements when excluding shadows from the analysis. Shadows significantly affected the model results obtained with any of the variables used, hence the exclusion of shadows is recommended prior to model calibration. This relatively easy pre‐processing step enhances models for classifying species occurrences using high‐resolution spectral imagery and derived products. Finally, a shadow simulation showed differences in the ideal acquisition window for each species, which is important to plan revisit campaigns.

Evaluating a Coupled Phenology‐Surface Energy Balance Model to Understand Stream‐Subsurface Temperature Dynamics in a Mixed‐Use Farmland Catchment

AbstractStream temperature is a key variable that controls both physical and biogeochemical processes in aquatic ecosystems. Complex physical interactions between land surface and subsurface processes make accurate simulations of stream temperature dynamics at catchment scales a challenging task. In this study we propose an integrated, catchment‐scale framework to model stream, soil, streambed, and groundwater temperatures under the influence of hydrologic and vegetation dynamics in a mixed land use catchment in central England. The phenology and surface energy modules in the coupled model were used to quantify the impacts of vegetation processes on radiation fluxes (e.g., canopy shading and the effect of vegetation growth on optical parameters). The model enabled accurate simulations of the movement and partitioning of water and thermal fluxes in different hydrologic domains with R2 values of observed and simulated temperatures in the range 0.60–0.87. Simulated groundwater heads and stream stages allowed the identification of gaining and losing portions of stream reaches and the estimation of Darcy fluxes. Simulation results show significantly dampened diel streambed temperature fluctuations below 0.3 m in gaining reaches, while in losing reaches the diel fluctuations showed relatively strong fluctuations below 0.3 m. The model enabled evaluation of the relative contributions of different processes to the stream thermal budget. Results indicate that net radiation was the dominant heat source, while latent heat flux was the primary heat sink. The model provides a useful tool to explicitly simulate water and heat fluxes as well as temperature‐dependent reaction rates in biogeochemical analyses.

Chloroplasts Modulate Elongation Responses to Canopy Shade by Retrograde Pathways Involving HY5 and Abscisic Acid.

Plants use light as energy for photosynthesis but also as a signal of competing vegetation. Using different concentrations of norflurazon and lincomycin, we found that the response to canopy shade in Arabidopsis (Arabidopsis thaliana) was repressed even when inhibitors only caused a modest reduction in the level of photosynthetic pigments. High inhibitor concentrations resulted in albino seedlings that were unable to elongate when exposed to shade, in part due to attenuated light perception and signaling via phytochrome B and phytochrome-interacting factors. The response to shade was further repressed by a retrograde network with two separate nodes represented by the transcription factor LONG HYPOCOTYL 5 and the carotenoid-derived hormone abscisic acid. The unveiled connection among chloroplast status, light (shade) signaling, and developmental responses should contribute to achieve optimal photosynthetic performance under light-changing conditions.

Quantitative proteomic analyses identified multiple sugar metabolic proteins in soybean under shade stress.

Soybean-based intercropping is important for sustainable agricultural practice on a regional and global scale. However, most soybean varieties use shade avoidance strategy to acquire more light absorption when suffered in canopy shade in intercropping systems, thus reduced the yield of the whole population on a farmland. The mechanisms underlying early response of soybean in shade avoidance is still largely unknown. Here we report our identification of differentially accumulated proteins in shade-sensitive soybean seedlings by global quantitative proteome analysis under white light (WL) and shade conditions. By using Tandem Mass Tag (TMT) labelling and HPLC fractionation followed by high-resolution LC-MS/MS analysis, 29 proteins were found up-regulated and 412 proteins were found down-regulated in soybean seedlings by 2-h shade stress than that by 2-h WL treatment. Multiple differentially expressed proteins are enriched in carbohydrate metabolic process especially in the biosynthetic pathways of cell wall polysaccharides in soybean seedlings by shade stress comparing to those in WL growth conditions. Physiological assays showed that saccharides were rapidly declined in shoot apex of soybean seedlings under a short-term shading. Our results would provide new insights into the mechanisms of shade avoidance responses in soybean seedlings.

Comparing the differential effects of canopy shading by Dichrostachys cinerea and Terminalia sericea on grass biomass

Woody encroachment is occurring globally; however, the tropical grassy ecosystems, which dominate Africa, are particularly vulnerable to this phenomenon. Encroached ecosystems experience significant changes in biodiversity, ecosystem functioning and service provisioning. One such vital ecosystem service is the provisioning of grazing. As encroachment can reduce grass production through the shading out of shade-intolerant grasses, there is a need to better predict these impacts particularly, since multiple woody species act as encroachers and little is known on their differential effects. Encroacher species may affect grass production differently, depending on the architecture of their canopies. This study therefore aimed to compare the effects of two structurally different encroaching species (a shrub vs a tree) (Dichrostachys cinerea and Terminalia sericea) on grass biomass. We tested the effects of canopy architectural traits of these two species on grass biomass using field sampling in a savanna conservation area in southern Zimbabwe. Canopy cover was a strong predictor of grass biomass, where increasing canopy cover significantly reduced grass biomass under both species. However, the architecture of the shrub D.cinerea, typified by a large crown diameter and crown height and a small crown base-height, created more shade, which had a significantly greater negative effect on grass biomass than the canopies of T.sericea at the same stem density. Architectural traits are therefore considered useful in predicting impacts of encroaching species on grass biomass. The findings show that encroachment of D.cinerea holds the potential to cause a regime shift from an open system to a closed system as a result of its extensive canopy cover.