Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Reducing ventilation requirements in semi-closed greenhouses increases water use efficiency
    Katsoulas, N. ; Sapounas, A. ; Zwart, H.F. de; Dieleman, J.A. ; Stanghellini, C. - \ 2015
    Agricultural Water Management 156 (2015). - ISSN 0378-3774 - p. 90 - 99.
    closed greenhouses - climate conditions - plant-compounds - tomato yield - crop - evapotranspiration - irrigation - simulation - quality - leaf
    We explore an under-appreciated side effect of semi-closed greenhouses: the ability to recover transpired water, thereby increasing water use efficiency. Semi-closed greenhouses are fit with cooling equipment, to limit natural ventilation requirements for temperature and humidity control. We assess the effect of cooling system capacity on ventilation needs of semi-closed greenhouses under different climate conditions and provide a general framework to evaluate potential water savings using the semi-closed greenhouse concept in different regions. We simulate greenhouse climate and crop yields for various cooling system capacities in Central Europe (The Netherlands) and Mediterranean (Greece and Algeria) by implementing a "cooling module" into an existing greenhouse model (KASPRO) and validating it using concurrent experimental data. Increasing the capacity of the cooling system has a double effect on water use efficiency (WUE): increase of fruit yield due to improved microclimate and lower water use, due to collection and reuse of vapour condensed in the heat exchanger and, to a lesser extent, lower crop transpiration. Thus WUE is strongly associated to the capacity of the cooling system. Finally, we show that there is a unique relationship between water use efficiency and the coupling of greenhouse environment to the outside air (an indicator of ventilation requirements), for all regions studied.
    Sustainable harvesting of non-timber forest products based on ecological and economic criteria
    Hernandez-Barrios, J.C. ; Anten, N.P.R. ; Martinez-Ramos, M. - \ 2015
    Journal of Applied Ecology 52 (2015)2. - ISSN 0021-8901 - p. 389 - 401.
    lacandona rain-forest - understorey palm - extraction systems - defoliation - growth - reproduction - population - impact - leaf - exploitation
    1. Harvesting of highly valuable non-timber forest products (NTFPs) has been considered a win-win strategy where local people profit while conserving forest biodiversity ecosystem services. Nevertheless the sustainability of NTFP harvesting has been debated as the nature of NTFPs harvesting regimes scale of commercialization are highly heterogeneous, few studies have evaluated the cumulative ecological economic effects of such regimes. Here we assessed the medium-term (10 years) sustainability of NTFP harvesting using Chamaedorea palm leaves a major NTFP from Mesoamerica that is highly valued in the international floral industry as a case study. 2. We used an experimental ecological study and an economic assessment to analyse the sustainability of leaf harvesting in C. ernesti-augustii. A 4-year leaf removal experiment was conducted to assess effects of increasing levels of defoliation (0%, 25%, 50%, 75%, 100% leaf removal, biannually) on palm survivorship, leaf production and leaf quality. Results of this experiment were combined with estimations of harvest economic value to make projections of the availability of leaves and profit per unit area. Finally, we determined harvesting regimes that maximize profit while maintaining medium-term viability of exploited populations. 3. Palms tolerated up to 50% chronic defoliation, but higher defoliation levels reduced survivorship, leaf production and leaf quality. In the long term, this 50% defoliation level maximized harvest volume and profit without significantly affecting palm survival and leaf quality. Our results show that harvesters face the dilemma of either maximizing short-term income leading to rapid exhaustion of stocks, or maintaining exploited populations but maximizing income in the long term. 4. Synthesis and applications. Our study shows that intermediate harvesting levels (=50% leaf removal) are needed to achieve long-term sustainability of Chamaedorea palm leaves. Results of this study have an immediate application for the amendment of the official Mexican law, which enables higher harvesting intensities of Chamaedorea leaves, and for the design of sustainable management strategies. Applications of such strategies should consider communitybased management, fair markets, regulating norms, as well as a thorough communication among stakeholders. Key-words: Chamaedorea ernesti-augustii, defoliation, Mexico, plant demography, socioecological sustainability, tropical rain forest
    Growth dynamics of tree nursery seedlings: The case of oil palm
    Akpo, E. ; Stomph, T.J. ; Kossou, D. ; Struik, P.C. - \ 2014
    Scientia Horticulturae 175 (2014). - ISSN 0304-4238 - p. 251 - 257.
    plant-growth - field performance - feeding damage - pot size - leaf - fertilization - plantations - populations - attributes - management
    Tree seedling survival in the field partly depends on management during seedling production. Insight into how nursery practices affect seedling growth dynamics would generate understanding in how to optimise tree seedling production. The objective of this study was to analyse the growth dynamics of oil palm seedlings to evaluate the effects of bag size, substrate type, and fertiliser supply, and their interactions. An experiment was run in 2011 (March to November 2011) and repeated in 2012 (April to October 2012) using three bag sizes, four substrates, and three levels of fertiliser supply (3 × 4 × 3 factorial design). Seedling height, collar diameter and number of leaves were measured over time. Seedling growth was analysed by comparing treatment effects at monthly intervals. Data were also fitted to growth curves to analyse treatment effects on absolute and relative rates of increase in seedling height, collar diameter and number of leaves. While substrate and fertiliser supply effects were fairly constant over time, bag size effects increased with larger variance explained over time. We observed that bag size effects overtook substrate, fertiliser and interaction effects from about two months onwards. Seedling height and collar diameter followed an exponential growth while number of leaves increased linearly over time. Analysis of generated data with the different growth models indicated that seedling growth rates were mainly under the influence of bag size, followed by substrate. Interactions between nursery practices, although significant sometimes, did not account for a large part of experimental error. Implications for tree seedling management are further discussed.
    Genetic mapping of gummy stem blight (Didymella bryoniae) resistance genes in Cucumis sativus-hystrix introgression lines
    Lou, L. ; Wang, H.Y. ; Qian, C.T. ; Liu, J. ; Bai, Y. ; Chen, J.F. - \ 2013
    Euphytica 192 (2013)3. - ISSN 0014-2336 - p. 359 - 369.
    interspecific hybridization - north-carolina - field-tests - genome - rearrangements - cucurbitaceae - tomato - crops - leaf - dna
    Gummy stem blight (GSB, Didymella bryoniae (Auersw.) Rehm) is a devastating disease occurring worldwide in cucumber (Cucumis sativus L.) production and causing considerable yield loss. No commercially available cultivars are resistant to GSB. By screening 52 introgression lines (ILs) derived from the cross of C. hystrix x C. sativus and eight cucumber cultivar/lines through a whole plant assay, three ILs (HH1-8-1-2, HH1-8-5, HH1-8-1-16) were identified as GSB resistant lines. Six common introgression regions in these three ILs were on Chromosomes 1, 4, and 6. To further map the resistance in the ILs, three mapping populations (2009F(2), 2009F(2)' and 2010F(2)) from a cross between resistant IL HH1-8-1-2 and susceptible 8419 were constructed and used for QTL mapping with SSR markers. Two quantitative trait loci (QTLs) were identified; one on Chromosome 4 and the other on Chromosome 6. The interval for Chromosome 4 QTL is 12 cM spanning 3.569 Mbp, and the interval for Chromosome 6 QTL is 11 cM covering 1.299 Mbp. The mapped QTLs provide a foundation for map-based cloning of the genes and establishing an understanding of the associated mechanisms underlying GSB resistance in cucumber.
    Feeding behaviour and performance of different populations of the black currant-lettuce aphid, Nasonovia ribisnigri, on resistant and susceptible lettuce
    Broeke, C.J.M. ten; Dicke, M. ; Loon, J.J.A. van - \ 2013
    Entomologia Experimentalis et Applicata 148 (2013)2. - ISSN 0013-8703 - p. 130 - 141.
    host-plant resistance - myzus-persicae - potato aphid - tissue localization - lactuca-sativa - gene mi - tomato - leaf - homoptera - biotypes
    When crops are bred for resistance to herbivores, these herbivores are under strong selection pressure to overcome this resistance, which may result in the emergence of virulent biotypes. This is a growing problem for crop species attacked by aphids. The Nr-gene in lettuce confers near-complete resistance against the black currant-lettuce aphid, Nasonovia ribisnigri (Mosely) (Hemiptera: Aphididae). Since 2007, populations of N.ribisnigri have been reported in several locations in Europe to infest resistant lettuce varieties that possess the Nr-gene. The objective of this study was to analyse the behaviour and level of virulence of several N.ribisnigri populations observed to have colonized Nr-locus-containing lettuce lines. We analysed the stylet penetration and feeding behaviour, and the performance of these N.ribisnigri populations on resistant and susceptible lettuce lines. Large variation in the degree of virulence to the Nr-locus-containing lettuce lines was found among populations of the Nr:1 biotype. The German population was highly virulent on the Nr-containing resistant lettuce lines, and showed similar feeding behaviour and performance on both the susceptible and resistant lettuces. The French population from Paris was the second most virulent, though reproduction on the resistant lines was reduced. The French population from Perpignan and a population from Belgium, however, showed reduced performance and feeding rate on the resistant compared to the susceptible lettuces. The lettuce background in which the Nr-gene is expressed influences the level of resistance to the various Nr:1 aphid populations, because the performance and feeding behaviour differed between the aphids on the cultivars (romaine lettuce) compared to the near-isogenic lines (butterhead/iceberg lettuce). This study also shows that being able to feed on a plant not automatically implies that a population can successfully develop on that plant, because aphids showed phloem ingestion during the 8-h recording period on resistant lettuce, but were not able to survive and reproduce on the same lettuce line.
    Changes in plant defense chemistry (pyrrolizidine alkaloids) revealed through high-resolution spectroscopy
    Almeida De Carvalho, S. ; Macel, M. ; Schlerf, M. ; Moghaddam, F.E. ; Mulder, P.P.J. ; Skidmore, A.K. ; Putten, W.H. van der - \ 2013
    ISPRS Journal of Photogrammetry and Remote Sensing 80 (2013). - ISSN 0924-2716 - p. 51 - 60.
    near-infrared spectroscopy - senecio-jacobaea - red edge - nitrogen - leaf - reflectance - forest - regression - vegetation - prediction
    Plant toxic biochemicals play an important role in defense against natural enemies and often are toxic to humans and livestock. Hyperspectral reflectance is an established method for primary chemical detection and could be further used to determine plant toxicity in the field. In order to make a first step for pyrrolizidine alkaloids detection (toxic defense compound against mammals and many insects) we studied how such spectral data can estimate plant defense chemistry under controlled conditions. In a greenhouse, we grew three related plant species that defend against generalist herbivores through pyrrolizidine alkaloids: Jacobaea vulgaris, Jacobaea erucifolia and Senecio inaequidens, and analyzed the relation between spectral measurements and chemical concentrations using multivariate statistics. Nutrient addition enhanced tertiary-amine pyrrolizidine alkaloids contents of J. vulgaris and J. erucifolia and decreased N-oxide contents in S. inaequidens and J. vulgaris. Pyrrolizidine alkaloids could be predicted with a moderate accuracy. Pyrrolizidine alkaloid forms tertiary-amines and epoxides were predicted with 63% and 56% of the variation explained, respectively. The most relevant spectral regions selected for prediction were associated with electron transitions and CH, OH, and NH bonds in the 1530 and 2100 nm regions. Given the relatively low concentration in pyrrolizidine alkaloids concentration (in the order of mg g-1) and resultant predictions, it is promising that pyrrolizidine alkaloids interact with incident light. Further studies should be considered to determine if such a non-destructive method may predict changes in PA concentration in relation to plant natural enemies. Spectroscopy may be used to study plant defenses in intact plant tissues, and may provide managers of toxic plants, food industry and multitrophic-interaction researchers with faster and larger monitoring possibilities
    Estimating salinity stress in sugarcane fields with spaceborne hyperspectral vegetation indices
    Hamzeh, S. ; Naseri, A.A. ; Alavi Panah, S.K. ; Mojaradi, B. ; Bartholomeus, H. ; Clevers, J.G.P.W. ; Behzad, M. - \ 2013
    International Journal of applied Earth Observation and Geoinformation 21 (2013). - ISSN 0303-2434 - p. 282 - 290.
    salt-affected soils - difference water index - spectral reflectance - precision agriculture - chlorophyll content - canopy reflectance - plant-leaves - fresh-water - hyperion - leaf
    The presence of salt in the soil profile negatively affects the growth and development of vegetation. As a result, the spectral reflectance of vegetation canopies varies for different salinity levels. This research was conducted to (1) investigate the capability of satellite-based hyperspectral vegetation indices (VIs) for estimating soil salinity in agricultural fields, (2) evaluate the performance of 21 existing VIs and (3) develop new VIs based on a combination of wavelengths sensitive for multiple stresses and find the best one for estimating soil salinity. For this purpose a Hyperion image of September 2, 2010, and data on soil salinity at 108 locations in sugarcane (Saccharum officina L.) fields were used. Results show that soil salinity could well be estimated by some of these VIs. Indices related to chlorophyll absorption bands or based on a combination of chlorophyll and water absorption bands had the highest correlation with soil salinity. In contrast, indices that are only based on water absorption bands had low to medium correlations, while indices that use only visible bands did not perform well. From the investigated indices the optimized soil-adjusted vegetation index (OSAVI) had the strongest relationship (R2 = 0.69) with soil salinity for the training data, but it did not perform well in the validation phase. The validation procedure showed that the new salinity and water stress indices (SWSI) implemented in this study (SWSI-1, SWSI-2, SWSI-3) and the Vogelmann red edge index yielded the best results for estimating soil salinity for independent fields with root mean square errors of 1.14, 1.15, 1.17 and 1.15 dS/m, respectively. Our results show that soil salinity could be estimated by satellite-based hyperspectral VIs, but validation of obtained models for independent data is essential for selecting the best model.
    Local auxin biosynthesis regulation by PLETHORA transcription factors controls phyllotaxis in Arabidopsis.
    Pinon, V. ; Prasad, K. ; Grigg, S.P. ; Sanchez Perez, G.F. ; Scheres, B. - \ 2013
    Proceedings of the National Academy of Sciences of the United States of America 110 (2013)3. - ISSN 0027-8424 - p. 1107 - 1112.
    shoot apical meristem - stem-cell fate - signaling network - homeobox gene - transport - growth - maize - thaliana - apex - leaf
    Lateral organ distribution at the shoot apical meristem defines specific and robust phyllotaxis patterns that have intrigued biologists and mathematicians for centuries. In silico studies have revealed that this self-organizing process can be recapitulated by modeling the polar transport of the phytohormone auxin. Phyllotactic patterns change between species and developmental stages, but the processes behind these variations have remained unknown. Here we use regional complementation experiments to reveal that phyllotactic switches in Arabidopsis shoots can be mediated by PLETHORA-dependent control of local auxin biosynthesis.
    Mapping spatio-temporal variation of grassland quantity and quality using MERIS data and the PROSAIL model
    Si, Y. ; Schlerf, M. ; Zurita-Milla, R. ; Skidmore, A.K. ; Wang, T. - \ 2012
    Remote Sensing of Environment 121 (2012). - ISSN 0034-4257 - p. 415 - 425.
    radiative-transfer models - remote-sensing data - chlorophyll content - vegetation indexes - reflectance data - hyperspectral measurements - heterogeneous grassland - canopy reflectance - leaf - lai
    Accurate estimates of the quantity and quality of grasslands, as they vary in space and time and from regional to global scales, furthers our understanding of grassland ecosystems. The Medium Resolution Imaging Spectrometer (MERIS) is a promising sensor for measuring and monitoring grasslands due to its high spectral resolution, medium spatial resolution and a two- to three-day repeat cycle. However, thus far the multi-biome MERIS land products have limited consistency with in-situ measurements of leaf area index (LAI), while the multi-biome canopy chlorophyll content (CCC) has not been validated yet with in-situ data. This study proposes a single-biome approach to estimate grassland LAI (a surrogate of grass quantity) and leaf chlorophyll content (LCC) and CCC (surrogates of grass quality) using the inversion of the PROSAIL model and MERIS reflectance. Both multi-biome and single-biome approaches were validated using two-season in-situ data sets and the temporal consistency was analyzed using time-series of MERIS data. The single-biome approach showed a consistently better performance for estimating LAI (R 2=0.70, root mean square error (RMSE)=1.02, normalized RMSE (NRMSE)=16%) and CCC (R 2=0.61, RMSE=0.36, NRMSE=23%) compared with the multi-biome approach (LAI: R 2=0.36, RMSE=1.77, NRMSE=28%; CCC: R 2=0.47, RMSE=1.33, NRMSE=84%). However, both single-biome and multi-biome approaches failed to retrieve LCC. The multi-biome LAI was overestimated at lower LAI values (
    Soil biotic impact on plant species shoot chemistry and hyperspectral reflectance patterns
    Carvalho, S. de; Macel, M. ; Schlerf, M. ; Skidmore, A.K. ; Putten, W.H. van der - \ 2012
    New Phytologist 196 (2012)4. - ISSN 0028-646X - p. 1133 - 1144.
    borne pathogens - spectroscopy - community - leaf - accumulation - herbivores - prediction - invader - quality - forest
    Recent studies revealed that plant-soil biotic interactions may cause changes in above-ground plant chemistry. It would be a new step in below-ground-above-ground interaction research if such above-ground chemistry changes could be efficiently detected. Here we test how hyperspectral reflectance may be used to study such plant-soil biotic interactions in a nondestructive and rapid way. The native plant species Jacobaea vulgaris and Jacobaea erucifolius, and the exotic invader Senecio inaequidens were grown in different soil biotic conditions. Biomass, chemical content and shoot reflectance between 400 and 2500 nm wavelengths were determined. The data were analysed with multivariate statistics. Exposing the plants to soil biota enhanced the content of defence compounds. The highest increase (400%) was observed for the exotic invader S. inaequidens. Chemical and spectral data enabled plant species to be classified with an accuracy > 85%. Plants grown in different soil conditions were classified with 50-60% correctness. Our data suggest that soil microorganisms can affect plant chemistry and spectral reflectance. Further studies should test the potential to study plant-soil biotic interactions in the field. Such techniques could help to monitor, among other things, where invasive exotic plant species develop biotic resistance or the development of hotspots of crop soil diseases.
    Frankincense tapping reduced photosynthetic carbon gain in Boswellia papyrifera (Burseraceae) trees
    Mengistu, T. ; Sterck, F.J. ; Anten, N.P.R. ; Bongers, F. - \ 2012
    Forest Ecology and Management 278 (2012). - ISSN 0378-1127 - p. 1 - 8.
    tropical dry forest - rain-forest - leaf - leaves - deciduousness - allocation - woodlands - exchange - thailand - ethiopia
    Whole-crown carbon gain depends on environmental variables and functional traits, and in turn sets limits to growth sinks of trees. We estimated the annual whole-crown carbon gain of trees of the species Boswellia papyrifera, which are tapped for frankincense, by integrating leaf photosynthetic rates over the total leaf area and leaf life span. We examined the effect of tapping on total leaf area and leaf photosynthesis and, in turn, on carbon gain and resin yield for trees of a dry highland population and a wetter lowland population. Highland and lowland trees had similar total leaf area, but highland trees had higher photosynthetic rates per unit leaf area than lowland trees since they received more light and had higher photosynthetic capacities. Highland trees therefore achieved a higher annual carbon gain than lowland trees, despite a shorter rainy season and shorter leaf lifespan. Intensive tapping reduced crown leaf area and the carbon gain in the lowland trees, but not in highland trees. These results highlight how the interplay between local conditions and functional traits determine regional variation in tree productivity. However, such differences in productivity and carbon gain did not influence frankincense yield across sites. We conclude that tapping B. papyrifera trees reduces annual carbon gain but the extent differs among different populations
    The role of roots in the resource economics spectrum
    Mommer, L. ; Weemstra, M. - \ 2012
    New Phytologist 195 (2012)4. - ISSN 0028-646X - p. 725 - 727.
    life-span - leaf - plant - growth - leaves - grassland - increase - traits - stands
    Simulation of Organ Patterning on the Floral Meristem Using a Polar Auxin Transport Model
    Mourik, S. van; Kaufmann, K. ; Dijk, A.D.J. van; Angenent, G.C. ; Merks, R.M.H. ; Molenaar, J. - \ 2012
    PLoS ONE 7 (2012)1. - ISSN 1932-6203 - 9 p.
    flower development - arabidopsis-thaliana - phyllotaxis - efflux - flux - canalization - initiation - leaf
    An intriguing phenomenon in plant development is the timing and positioning of lateral organ initiation, which is a fundamental aspect of plant architecture. Although important progress has been made in elucidating the role of auxin transport in the vegetative shoot to explain the phyllotaxis of leaf formation in a spiral fashion, a model study of the role of auxin transport in whorled organ patterning in the expanding floral meristem is not available yet. We present an initial simulation approach to study the mechanisms that are expected to play an important role. Starting point is a confocal imaging study of Arabidopsis floral meristems at consecutive time points during flower development. These images reveal auxin accumulation patterns at the positions of the organs, which strongly suggests that the role of auxin in the floral meristem is similar to the role it plays in the shoot apical meristem. This is the basis for a simulation study of auxin transport through a growing floral meristem, which may answer the question whether auxin transport can in itself be responsible for the typical whorled floral pattern. We combined a cellular growth model for the meristem with a polar auxin transport model. The model predicts that sepals are initiated by auxin maxima arising early during meristem outgrowth. These form a pre-pattern relative to which a series of smaller auxin maxima are positioned, which partially overlap with the anlagen of petals, stamens, and carpels. We adjusted the model parameters corresponding to properties of floral mutants and found that the model predictions agree with the observed mutant patterns. The predicted timing of the primordia outgrowth and the timing and positioning of the sepal primordia show remarkable similarities with a developing flower in nature
    Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence
    Damm, A. ; Erler, A. ; Hillen, W. ; Meroni, M. ; Schaepman, M.E. ; Verhoef, W. ; Rascher, U. - \ 2011
    Remote Sensing of Environment 115 (2011)8. - ISSN 0034-4257 - p. 1882 - 1892.
    atmospheric absorption features - vegetation fluorescence - canopy reflectance - resolution - field - leaf - spectrometers - calibration - scattering - principle
    Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy scale. The commonly used Fraunhofer Line Depth (FLD) principle exploits spectrally narrow atmospheric oxygen absorption bands and relates Fs to the difference of the absorption feature depth of a fluorescensing and a non-fluorescensing surface. However, due to the nature of these narrow bands, Fs retrieval results depend not only on vegetation species type or environmental conditions, but also on instrument technology and processing algorithms. Thus, an evaluation of all influencing factors and their separate quantification is required to further improve Fs retrieval and to allow a reproducible interpretation of Fs signals. Here we present a modeling study that isolates and quantifies the impacts of sensor characteristics, such as spectral sampling interval (SSI), spectral resolution (SR), signal to noise ratio (SNR), and spectral shift (SS) on the accuracy of Fs measurements in the oxygen A band centered at 760 nm (O2-A). Modeled high resolution radiance spectra associated with known Fs were spectrally resampled, taking into consideration the various sensor properties. Fs was retrieved using the three most common FLD retrieval methods, namely the original FLD method (sFLD), the modified FLD (3FLD) and the improved FLD (iFLD). The analysis investigates parameter ranges, which are representative for field and airborne instruments currently used in Fs research (e.g., ASD FieldSpec, OceanOptics HR, AirFLEX, AISA, APEX, CASI, and MERIS). Our results show that the most important parameter affecting the retrieval accuracy is SNR, SR accounts for = 40% of the error, the SSI for = 12%, and SS for = 7% of the error. A trade-off study revealed that high SR can partly compensate for low SNR. There is a strong interrelation between all parameters and the impact of specific parameters can compensate or amplify the influence of others. Hence, the combination of all parameters must be considered by the evaluation of sensors and their potential for Fs retrieval. In general, the standard FLD method strongly overestimates Fs, while 3FLD and iFLD provide a more accurate estimation of Fs. We conclude that technical sensor specifications and the retrieval methods cause a significant variability in retrieved Fs signals. Results are intended to be one relevant component of the total uncertainty budget of Fs retrieval and have to be considered in the interpretation of retrieved Fs signals.
    A novel expression cassette for the efficient visual selection of transformed tissues in florists' chrysanthemum (Chrysanthemum morifolium Ramat.).
    Mao, J. ; Stoopen, G.M. ; Jongsma, M.A. ; Wang, C.Y. - \ 2011
    African journal of biotechnology 10 (2011)51. - ISSN 1684-5315 - p. 10537 - 10542.
    agrobacterium-mediated transformation - green fluorescent protein - plant transformation - transgenic plants - gene-expression - stem segments - gfp - reporter - marker - leaf
    Constructs carrying visual reporter genes coupled with efficient promoters could facilitate the process of identification and selection of stable transformants in recalcitrant crops. Here, a novel construct utilizing a ribulose-1,5-bisphosphate carboxylase (RbcS) promoter combined with the green fluorescent protein (GFP) reporter gene to initiate very high expression of GFP in florist's chrysanthemum (Chrysanthemum morifolium Ramat.) was described. Based on this expression cassette, a new regeneration protocol using leaf discs as explants was developed for the Agrobacterium-mediated transformation of Chrysanthemum genotype ‘1581’, and a transformation efficiency of 7% was obtained. The expression of two different GFP constructs targeted to either cytosol or plastids was compared in transgenic lines. Both GFP constructs were expressed at such a high level that the green fluorescence dominated red fluorescence in the leaf tissues, allowing easy observation and microdissection of transformed tissues even without a GFP filter. Under normal light, plants with GFP targeted to plastids had a light green phenotype deriving from the high GFP expression. Quantitative reverse transcriptional PCR analysis showed that the plastid targeted construct with intron had significantly higher steady state transcript levels of GFP mRNA. This novel expression cassette may allow direct visual selection of transformed tissues independent of antibiotic selection in a wide range of plant species
    Functional traits determine trade-offs and niches in a tropical forest community
    Sterck, F.J. ; Markesteijn, L. ; Schieving, F. ; Poorter, L. - \ 2011
    Proceedings of the National Academy of Sciences of the United States of America 108 (2011)51. - ISSN 0027-8424 - p. 20627 - 20632.
    rain-forest - dry forest - habitat associations - species coexistence - plant-communities - amazonian forest - shade tolerance - neutral theory - leaf - light
    question in community ecology. Whereas neutral theory assumes that species are adapted to common field conditions and coexist by chance, niche theory predicts that species are functionally different and coexist because they are specialized for different niches. We integrated biophysical principles into a mathematical plant model to determine whether and how functional plant traits and trade-offs may cause functional divergence and niche separation of tree species. We used this model to compare the carbon budget of saplings across 13 co-occurring dry-forest tree species along gradients of light and water availability. We found that species ranged in strategy, from acquisitive species with high carbon budgets at highest resource levels to more conservative species with high tolerances for both shade and drought. The crown leaf area index and nitrogen mass per leaf area drove the functional divergence along the simulated light gradient, which was consistent with observed species distributions along light gradients in the forest. Stomatal coordination to avoid low water potentials or hydraulic failure caused functional divergence along the simulated water gradient, but was not correlated to observed species distributions along the water gradient in the forest. The trait-based biophysical model thus explains how functional traits cause functional divergence across species and whether such divergence contributes to niche separation along resource gradients.
    How plant architecture affects light absorption and photosynthesis in tomato: towards an ideotype for plant architecture using a functional-structural plant model
    Sarlikioti, V. ; Visser, P.H.B. de; Buck-Sorlin, G.H. ; Marcelis, L.F.M. - \ 2011
    Annals of Botany 108 (2011)6. - ISSN 0305-7364 - p. 1065 - 1073.
    carbon gain - leaf - interception - canopy - morphology - yield - assimilation - efficiency - avoidance - capture
    Background and Aims - Manipulation of plant structure can strongly affect light distribution in the canopy and photosynthesis. The aim of this paper is to find a plant ideotype for optimization of light absorption and canopy photosynthesis. Using a static functional structural plant model (FSPM), a range of different plant architectural characteristics was tested for two different seasons in order to find the optimal architecture with respect to light absorption and photosynthesis. Methods - Simulations were performed with an FSPM of a greenhouse-grown tomato crop. Sensitivity analyses were carried out for leaf elevation angle, leaf phyllotaxis, leaflet angle, leaf shape, leaflet arrangement and internode length. From the results of this analysis two possible ideotypes were proposed. Four different vertical light distributions were also tested, while light absorption cumulated over the whole canopy was kept the same. Key Results Photosynthesis was augmented by 6 % in winter and reduced by 7 % in summer, when light absorption in the top part of the canopy was increased by 25 %, while not changing light absorption of the canopy as a whole. The measured plant structure was already optimal with respect to leaf elevation angle, leaflet angle and leaflet arrangement for both light absorption and photosynthesis while phyllotaxis had no effect. Increasing the length : width ratio of leaves by 1·5 or increasing internode length from 7 cm to 12 cm led to an increase of 6–10 % for light absorption and photosynthesis. Conclusions - At high light intensities (summer) deeper penetration of light in the canopy improves crop photosynthesis, but not at low light intensities (winter). In particular, internode length and leaf shape affect the vertical distribution of light in the canopy. A new plant ideotype with more spacious canopy architecture due to long internodes and long and narrow leaves led to an increase in crop photosynthesis of up to 10 %.
    The effect of intracanopy lighting on cucumber fruit yield-Model analysis
    Trouwborst, G. ; Schapendonk, A.H.C.M. ; Rappoldt, K. ; Pot, S. ; Hogewoning, S.W. ; Ieperen, W. van - \ 2011
    Scientia Horticulturae 129 (2011)2. - ISSN 0304-4238 - p. 273 - 278.
    photosynthesis - leaf - canopy - leaves - responses - growth - plants
    Intracanopy lighting is a recently developed supplementary lighting technique for high-wire grown vegetable production in greenhouses where a part of the lamps is mounted within instead of above the canopy. A potentially higher yield using intracanopy lighting compared with top-lighting, is based on three assumptions: (1) increased light-absorption by the crop; (2) a higher photosynthetic light use efficiency due to a more homogeneous vertical light distribution; (3) a preserved photosynthetic capacity of leaves deeper in the canopy. We used an explanatory crop model to quantify the relative importance of these assumptions for a cucumber crop during an experiment in winter in the Netherlands (Trouwborst et al., 2010). Photosynthesis and yield data of this intracanopy lighting experiment with light-emitting diodes (34% of supplemental PAR) in combination with top-lighting (66% of supplemental PAR) were used to parameterise our model. In that study intracanopy lighting did not result in an increased yield compared with 100% top-lighting due to extreme leaf curling and a lower dry matter partitioning to the fruits. Our model predicted an 8% increase in fruit yield for the intracanopy lighting treatment if there were to be no leaf curling and no lower dry matter partitioning. This increase can be largely explained by the change in light distribution and light absorption. The model further revealed unexpectedly large consequences of the lower dry matter partitioning to the fruits whereas the negative effect of leaf curling was small. The direct effect of a greater Amax at deeper canopy layers was slightly positive. The last however might have indirectly caused the greater partitioning to the leaves as the greater Amax was associated with a preserved leaf mass per area. Solutions for this problem are discussed. Our explanatory model allowed us to disentangle the interacting effects of intracanopy lighting on fruit yield. Overall, intracanopy lighting has been shown here to potentially increase the assimilation light use efficiency
    Impact of multiangular information on empirical models to estimate canopy nitrogen concentration in mixed forest
    Huber, S. ; Koetz, B. ; Psomas, A. ; Kneubuehler, M. ; Schopfer, J.T. ; Itten, K.I. ; Zimmermann, N.E. - \ 2010
    Journal of Applied Remote Sensing 4 (2010)1. - ISSN 1931-3195
    hyperspectral brdf data - imaging spectroscopy - bidirectional reflectance - spectral measurements - absorption features - ecosystem processes - chlorophyll content - carbon - leaf - photosynthesis
    Directional effects in remotely sensed reflectance data can influence the retrieval of plant biophysical and biochemical estimates. Previous studies have demonstrated that directional measurements contain added information that may increase the accuracy of estimated plant structural parameters. Because accurate biochemistry mapping is linked to vegetation structure, also models to estimate canopy nitrogen concentration (C-N) may be improved indirectly from using multiangular data. Hyperspectral imagery with five different viewing zenith angles was acquired by the spaceborne CHRIS sensor over a forest study site in Switzerland. Fifteen canopy reflectance spectra corresponding to subplots of field-sampled trees were extracted from the preprocessed CHRIS images and subsequently two-term models were developed by regressing C-N on four datasets comprising either original or continuum-removed reflectances. Consideration is given to the directional sensitivity of the C-N estimation by generating regression models based on various combinations (n=15) of observation angles. The results of this study show that estimating canopy C-N with only nadir data is not optimal irrespective of spectral data processing. Moreover adding multiangular information improves significantly the regression model fits and thus the retrieval of forest canopy biochemistry. These findings support the potential of multiangular Earth observations also for application-oriented ecological monitoring.
    High-resolution methods for fluorescence retrieval from space
    Mazzoni, M. ; Falorni, P. ; Verhoef, W. - \ 2010
    Optics Express 18 (2010)15. - ISSN 1094-4087 - p. 15649 - 15663.
    chlorophyll fluorescence - leaf - reflectance - vegetation - prospect - canopy
    The retrieval from space of a very weak fluorescence signal was studied in the O2A and O2B oxygen atmospheric absorption bands. The accuracy of the method was tested for the retrieval of the chlorophyll fluorescence and reflectance terms contributing to the sensor signal. The radiance at the top of the atmosphere was simulated by means of a commercial radiative-transfer program at a high resolution (0.1 cm-1). A test data set was generated in order to simulate sun-induced chlorophyll fluorescence at the top of the canopy. Reflectance terms were spectrally modeled using cubic splines and fluorescence by means of the sum of two Voigt functions. Sensor radiance residual minimization was performed in the presence of a multiplicative noise, thus ensuring that the sensor simulations were realistic. The study, which focused on the possibility of retrieving fluorescence with an accuracy better than 10%, was performed for instrument resolutions ranging from about 0.4 cm-1 to 2 cm-1 in order to test the algorithm for the characteristics of existing and planned hyper-spectral sensors. The algorithm was also used to retrieve fluorescence in the single O2A band at the OCO and TANSO-FTS instrument spectral resolutions
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