Foliar Surface Research Articles

Study on Thermal Environment of Sports Field in Different Materials

Natural lawn and artificial turf, which have a great difference on practical function and thermal environment characteristics, are widely used in sports field. In order to obtain the quantitative differences on thermal environment in summer, instrumental measurement and questionnaires are used in this paper to investigate the thermal environmental characteristics of natural lawn and artificial turf, respectively. Meanwhile human thermal sensation in the two lawns was also evaluated. The results show that the foliar surface temperature and mean air temperature in artificial turf is significantly higher than that of natural lawn in early summer. Due to thermal discomfort and the potential hurt for athletes on artificial turf field, cooling methods such as sprinkle are recommended.

Micromorfología foliar del género Quercus (Fagaceae) en México

México es el principal centro de diversidad del género Quercus en el Hemisferio Occidental. A pesar de los avances recientes en el conocimiento de los encinos mexicanos, aún existe cierto grado de confusión taxonómica, particularmente dentro de algunos complejos de especies. En este estudio se utilizó microscopía electrónica de barrido para describir las estructuras micromorfológicas foliares (tricomas, ceras epicuticulares y estomas) de ambas superficies foliares (haz y envés) en representantes seleccionados de encinos mexicanos, con el objetivo de evaluar la utilidad taxonómica de estos caracteres. En total se examinaron 27 especies, pertenecientes a las secciones Quercus (encinos blancos) y Lobatae (encinos rojos y negros), incluyendo varios grupos de plantas cercanamente relacionadas con problemas de delimitación taxonómica, así como especies que presentan hibridación. Se encontraron varios tipos de tricomas, tanto los de tipo glandular (simples y bulbosos) como los no glandulares (solitarios, multirradiados, estrellados, estrellados fusionados y fasciculado estipitados). Las ceras epicuticulares se observaron en forma de capas, capas fisuradas, costras, gránulos, placas y placas en rosetas. Los estomas fueron elípticos y se encontraron elevados con respecto a la superficie foliar o al mismo nivel que ésta. Entre los tres tipos de estructuras examinadas, los tricomas fueron los más útiles para propósitos taxonómicos, seguidos por las ceras epicuticulares. Todas las especies tuvieron diferentes combinaciones de estados de carácter para estas estructuras micromorfológicas, lo que permitió la elaboración de claves para identificar a las especies dentro de los grupos problemáticos.

Distribution of the Entomopathogenic Fungus Beauveria bassiana in Rice Ecosystems and Its Effect on Soil Enzymes

Fungal entomopathogens, especially Beauveria bassiana, are often studied within the context of their use in biological pest control; however, there is limited knowledge of their distributions in host plants and soil ecosystem. We examined the distribution of B. bassiana and its influence on rice plants and paddy soils. B. bassiana could only be detected on the foliar surfaces of rice plants within 15 days under Bb-4 (7.5 × 10(4) conidia/mL) and Bb-7 (7.5 × 10(7) conidia/mL) treatments. The endophytic colonization of B. bassiana could not be found in stems, roots, or seeds of rice plants under Bb-4 and Bb-7 treatments. The fungus was found only in the leaves of rice plants under Bb-4 and Bb-7 treatments at 15 days after inoculation. Moreover, B. bassiana was absent from paddy soils under Bb-4 and Bb-7 treatments at all times. Enzyme activity (urease and phosphatase) in the paddy soils of Bb-4 and Bb-7 treatments showed no significant difference from the control. It is possible that B. bassiana was not able to colonize paddy soil. Detailed understanding of distribution and ecological interactions of B. bassiana is helpful for understanding and predicting the effects of fungal entomopathogens on host populations, and the interactions among fungal entomopathogens and other organisms in the community.

Flammability of Some Ornamental Species in Wildland–Urban Interfaces in Southeastern France: Laboratory Assessment at Particle Level

Assessment of the flammability of ornamental vegetation (particularly hedges) planted around houses is necessary in light of the increasing urbanization of the wildland-urban interfaces (WUIs) and the high fire occurrence in such areas. The structure and flammability of seven of the species most frequently planted as hedges in Provence (southeastern France) were studied at particle level. Spatial repartition of the different types of fuel particles within plants was assessed by means of the cube method. The leaf flammability was assessed using an epiradiator as a burning device, and measurements of foliar physical characteristics and gross heat of combustion (GHC) helped to explain the results of burning experiments. Co-inertia analysis revealed that species with thin leaves were quick to ignite (Pyracantha coccinea, Phyllostachys sp.) and species with high leaf GHC burned the longest (Pittosporum tobira, Nerium oleander). Species presenting high ignitability (Photinia fraseri, Phyllostachys sp. and Pyracantha coccinea) were characterized by high foliar surface area-to-volume ratio, and species presenting lower ignitability were characterized by high GHC (Pittosporum tobira, Nerium oleander, Cupressus sempervirens). Hierarchical cluster analysis of the flammability variables (ignition frequency, time-to-ignition and flaming duration) categorized the relative flammability of the seven species (including dead Cupressus sempervirens) in five clusters of species from poorly flammable (Pittosporum tobira) to extremely flammable (dead Cupressus sempervirens).This study provides useful information for reducing fire risk in WUIs in the study area.

Two Cultivars of Oakleaf Hydrangea Respond to Ancymidol, Uniconazole, or Pinching

Shearing is an important cultural practice for maintaining plant size and appearance during nursery crop production. However, oakleaf hydrangea (Hydrangea quercifolia) is susceptible to dieback after shearing. The objective of this study was to determine whether foliar or substrate surface applications of ancymidol or uniconazole can reduce plant growth of oakleaf hydrangea similar to pinching, which was used to simulate shearing. ‘Alice’ or ‘Pee Wee’ oakleaf hydrangea plants were treated in 2002 or 2006, respectively, with ancymidol or uniconazole as a substrate surface application at 0, 1, 2, or 4 ppm; ancymidol as a foliar application at 0, 25, 50, or 100 ppm; or uniconazole as a foliar application at 0, 12.5, 25, or 50 ppm. Both cultivars received the same plant growth regulator treatments in 2012, and a pinched control was included in the 2012 experiment. Ancymidol and uniconazole had limited and inconsistent effects on growth of ‘Alice’ and ‘Pee Wee’ plants regardless of application method. Uniconazole was more effective at controlling growth of ‘Alice’ in 2002 when the study was conducted from October through December than in 2012 when the study was conducted during a more typical growing season of May through September. Plants treated with either ancymidol or uniconazole by either application method usually grew more during the first 2 weeks after application than those that were pinched. During the remainder of the growing season, little difference in growth between pinched plants and growth regulator-treated plants occurred. At harvest in 2012, pinched ‘Alice’ plants had more leaves but a smaller leaf area per leaf than plants treated with growth regulators resulting in no difference in total leaf area or in leaf, shoot, or root dry weight among the treatments. ‘Pee Wee’ treated with uniconazole using either application method or uniconazole as a foliar application had fewer leaves than pinched plants.

Norovirus Surrogate Survival on Spinach During Preharvest Growth

Produce can become contaminated with human viral pathogens in the field through soil, feces, or water used for irrigation; through application of manure, biosolids, pesticides, and fertilizers; and through dust, insects, and animals. The objective of this study was to assess the survival and stability of human noroviruses and norovirus surrogates (Murine norovirus [MNV] and Tulane virus [TV]) on foliar surfaces of spinach plants in preharvest growth conditions. Spinach plants were housed in a biocontrol chamber at optimal conditions for up to 7 days and infectivity was determined by plaque assay. Virus inoculation location had the largest impact on virus survival as viruses present on adaxial leaf surfaces had lower decimal reduction time (D values) than viruses present on abaxial leaf surfaces. Under certain conditions, spinach type impacted virus survival, with greater D values observed from survival on semi-savoy spinach leaves. Additional UVA and UVB exposure to mimic sunlight affected virus survival on adaxial surfaces for both semi-savoy and smooth spinach plants for both viruses. Human GII norovirus inoculated onto semi-savoy spinach had an average D value that was not statistically significant from MNV and TV, suggesting that these surrogates may have similar survival on spinach leaves compared with human noroviruses. An understanding of the behavior of enteric viruses on spinach leaves can be used to enhance growers' guidelines and for risk assessment with certain growing conditions.

Optical Method for Measuring Deposition Amount of Black Carbon Particles on Foliar Surface

To perform quick measurements of black carbon (BC) particles deposited on foliar surfaces of forest tree species, we investigated an optical method for measuring the amount of BC extracted from foliar surfaces and collected on quartz fiber filters. The seedlings of Fagus crenata, Castanopsis sieboldii, Larix kaempferi and Cryptomeria japonica were exposed to submicron BC particles for one growing season (1 June to 7 December 2009). At the end of the growing season, the leaves or needles of the seedlings were harvested and washed with deionized water followed by washing with chloroform to extract the BC particles deposited on the foliar surfaces. The extracted BC particles were collected on a quartz fiber filter. The absorption spectrum of the filters was measured by spectrophotometer with an integrating sphere. To obtain the relationship between the absorbance of the filter and the amount of BC particles on the filter, the amount of BC particles on the filter was determined as that of elemental carbon (EC) measured by a thermal optical method. At wavelengths below 450 nm, the absorption spectrum of the filter showed absorption by biological substances, such as epicuticular wax, resulting in the low coefficient of determination (<TEX>$R^2$</TEX>) in the relationship between the amount of EC on the filter (<TEX>$M_{EC}$</TEX>, <TEX>${\mu}g\;C\;cm^{-2}$</TEX> filter area) and the absorbance of the filter. The intercept of the regression line between <TEX>$M_{EC}$</TEX> and the absorbance of the filter at 580 nm (<TEX>$A_{580}$</TEX>) was closest to 0. There was a significant linear relationship between the <TEX>$A_{580}$</TEX> and <TEX>$M_{EC}$</TEX> (<TEX>$R^2$</TEX>=0.917, p<0.001), suggesting that the amount of BC particles collected on the filter can be predicted from the absorbance. This optical method might serve as a simple, fast and cost-effective technique for measuring the amount of BC on foliar surfaces.

Effects of Long-term Exposure to Black Carbon Particles on Growth and Gas Exchange Rates of Fagus crenata, Castanopsis sieboldii, Larix kaempferi and Cryptomeria japonica Seedlings

To clarify the effects of black carbon (BC) particles on growth and gas exchange rates of Asian forest tree species, the seedlings of Fagus crenata, Castanopsis sieboldii, Larix kaempferi and Cryptomeria japonica were exposed to BC particles with sub-micron size for two growing seasons from 1 June 2009 to 11 November 2010. The BC particles deposited after the exposure to BC were observed on the foliar surface of the 4 tree species. At the end of the experiment, the amount of BC accumulated on the foliar surface after the exposure to BC aerosols were 0.13, 0.69, 0.32 and 0.58 mg C <TEX>$m^{-2}$</TEX> total leaf area in F. crenata, C. sieboldii, L. kaempferi and C. japonica seedlings, respectively. In August 2010, the exposure to BC particles did not significantly affect net photosynthetic rate under any light intensity, stomatal diffusive conductance to water vapour (<TEX>$g_s$</TEX>), stomatal limitation of photosynthesis, response of <TEX>$g_s$</TEX> to increase in vapour pressure deficit and leaf temperature under light saturated condition in the leaves or needles of the seedlings. These results suggest that the BC particles deposited on the foliar surface did not reduce net photosynthesis by shading, did not increase leaf temperature by absorption of irradiation light, and did not induce plugging of stomata in the leaves or needles of the seedlings. There were no significant effects of BC particles on the increments of plant height and stem base diameter during the experimental period and the whole-plant dry mass at the end of the experiment. These results indicate that the exposure to BC particles with sub-micron size for two growing seasons did not significantly affect the growth and leaf or needle gas exchange rates of F. crenata, C. sieboldii, L. kaempferi and C. japonica seedlings.

A comparative study on the uptake and translocation of organochlorines by Phragmites australis

Organochlorines (OCs) are persistent chemicals found in various environmental compartments. The differences in the uptake of 14C-labeled 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB) and γ-hexachlorocyclohexane (γHCH) by Phragmites australis were investigated under hydroponic conditions. The first step in sorption appears to be correlated with the hydrophobic nature of the compounds, since log-linear correlations were obtained between root concentration factor and partition coefficient (LogKow). After 7 days of exposure, plant uptake of DCB, TCB, γHCH was significant with bioconcentration factors reaching 14, 19 and 15, respectively. Afterwards, uptake and translocation were seen to be more complex, with a loss of the simple relationship between uptake and LogKow. Linear correlations between the bioconcentration/translocation factors and the physico-chemical properties of OCs were shown, demonstrating that translocation from roots to shoots increases with solubility and volatility of the OCs. This suggests that OC-translocation inside plants might result from the combination of two processes, xylem sap flow and vapor fluxes. 14C-phytovolatilization was measured and was correlated with the volatility of the compounds; the more volatile OCs being most the likely to be phytovolatilized from foliar surfaces (p=0.0008). Thus, OC-uptake/translocation appears to proceed at a rate that depends mostly on the OCs hydrophobicity, solubility and volatility.

First Report of Magnaporthe poae, Cause of Summer Patch Disease on Annual Bluegrass, in Canada.

The ectotrophic, root-infecting fungus Magnaporthe poae Landschoot & Jackson, the causal agent of summer patch disease in the U.S. (2), is implicated in the damage and loss of annual bluegrass (Poa annua L.) on golf course greens. This pathogenic fungus, one of the important root pathogens of turfgrass, attacks and colonizes susceptible turfgrass roots suffering from environmental or cultural stresses. Over 100 turf samples that exhibited symptoms (chlorotic circular or irregular patches of ≥15 cm in diameter with necrotic crowns and discolored roots) reminiscent of summer patch were collected from 77 southwestern Ontario golf courses from July to August of 2009 and 2010. Roots and crowns were often covered with dark, ectotrophic runner hyphae, lobed hyphopodia, and growth cessation structures, characteristic of M. poae. Sections of root tissue were surface sterilized in 0.6% sodium hypochlorite (NaOCl) for 5 min. Sterilized root tissue was plated on potato dextrose agar (PDA) containing 50 mg L-1 streptomycin sulfate and incubated at 28°C for 7 to 10 days. A fungus with morphological characteristics (hyaline mycelium that appears gray or olive-brown when mature) similar to those of M. poae (1) was consistently isolated (≥100 isolates were obtained) and used to identify M. poae through molecular techniques and Koch's postulates. DNA was extracted from the fungal mycelium of the collected isolates using the PowerPlant DNA isolation kit (MO BIO Laboratories, Inc., Carlsbad, CA). The rDNA internal transcribed spacer (ITS) regions of the isolates (≥100 isolates) were amplified by PCR using universal fungal rDNA primers ITS 4 (5'-TCCTCCGCTTATTGATATGC-3') and ITS 5 (5'- GGAAGTAAAAGTCGTAACAAGG-3') (3). The purified PCR products were sequenced (GenBank Accession No. JX134588 through JX134601) and a BLAST search exhibited seven isolates with 99% (MAG3, MAG6, MAG13, MAG16, and MAG17) and 100% (MAG1 and MAG14) similarity to M. poae in the GenBank database. Pathogenicity of four isolates (MAG1, MAG3, MAG6, and MAG14) was confirmed with Koch's postulates. Sixteen healthy P. annua core samples (four replicates of each treatment/isolate) collected from an Ontario golf course were inoculated with 25 mg M. poae-infested Kentucky bluegrass seed (Poa pratensis L.; 12.5 mg inoculum applied at the surface of the potting medium and 12.5 mg inoculum applied on the foliar surface) and were placed in a growth chamber with 12-h day/night cycles at 30/25°C and approximate relative humidity. After 2 to 3 weeks, inoculated plants exhibited chlorotic foliage and necrotic roots covered with dark ectotrophic runner hyphae and lobed hyphopodia. Infected root sections from each replication were surface sterilized and placed on PDA containing 50 mg L-1 streptomycin sulfate. The fungal cultures exhibited morphological characteristics consistent with M. poae (1). To our knowledge, this is the first report of summer patch caused by M. poae in Canada.

The role of meta-topolins on the photosynthetic pigment profiles and foliar structures of micropropagated ‘Williams’ bananas

The effect of five topolins (meta-Topolin=mT; meta-Topolin riboside=mTR; meta-Methoxy topolin=MemT; meta-Methoxy topolin riboside=MemTR and 6-(meta-methoxy)-9-(tetrahydropyran-2-yl)-topolin=MemTTHP) on the photosynthetic pigments and leaf structures of micropropagated ‘Williams’ bananas was compared with the commonly used benzyladenine (BA). Surface-decontaminated explants were cultured for 70 d on modified Murashige and Skoog (MS) basal medium and supplemented with 10, 20 or 30μM cytokinins (CKs). At 10 d intervals, the photosynthetic pigments were quantified via spectrophotometric methods for 7 cycles. Generally, the maximum pigment content was attained between 40 and 50 d. The control plantlets had the highest pigment content (1150μg/g FW). Among the CKs, 10μM MemTTHP generally had the best pigment stimulatory effect at the same period. After 40 d, scanning electron microscopy (SEM) of the foliar surface showed that the stomata density was highest in 10μM MemTTHP-treated and lowest in 10μM MemTR-treated plantlets. The stomatal structure and pore area also varied with the type and concentration of CK added. Generally, prolonging culture duration as well as increasing CK concentrations reduced the pigment content. However, the drastic breakdown in chlorophyll pigments beyond 50 d was slightly inhibited by the presence of mT, mTR, MemTTHP and BA compared to the control. The CK-treated plantlets at equimolar concentration had comparable chlorophyll a/b and total chlorophyll/carotenoid ratios after 10 d; probably as an adaptive measure. At the end of the current study, 10μM mT and mTR plantlets remained green as reflected by the higher total chlorophyll/carotenoid ratio as well as by the visual observations. A well-developed photosynthetic apparatus enhances the survival of in vitro plantlets during the acclimatization stage. Current findings provide some insight into the role of meta-topolins on photosynthetic parameters in vitro, which inevitably partly contributed to the better acclimatization capability of meta-topolin-regenerants.

The morphological structure of leaves and the dust-retaining capability of afforested plants in urban Guangzhou, South China

Air pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. The mass artificial plantation is very helpful to absorb dust and reduce pollution for conservation of the urban environment. The foliar surface of plants is an important receptor of atmospheric pollutants. Therefore, selection of suitable plant species for urban environment is very important. The dust-retaining capability of urban trees in Guangzhou was determined at four different types of urban area, and the morphological traits of their leaves such as wax, cuticle, stomata, and trichomes were observed under a scanning electron microscope. It was determined that the dust-retaining capability of any given tree species is significantly different in the same place. Of the four studied tree species in the industrial area (IA) and commercial/traffic areas (CTA) type urban areas, the highest amounts of dust removed by Mangifera indica Linn was 12.723 and 1.482 g/m(2), respectively. However, in contrast, the equivalent maxima for Bauhinia blakeana is only 2.682 g/m(2) and 0.720 g/m(2), respectively. Different plant species have different leaf morphology. The leaf of M. indica has deep grooves and high stomata density which are in favor of dust-retained, and thus, their dust-retained capability is stronger, while B. blakeana has the cells and epicuticular wax with its stomata arranging regularly, resulting in poor dust catching capability. Leaf size was also shown to be related to dust capture for the four studied tree species. The dust removal capacity of individual tree species should be taken into account in the management of greening plantation in and around an urban area. It was also shown that temporal variation in dust accumulation occurred over the 28-day observation period and this was discussed. Furthermore, spatial contrasts in dust accumulation were evidenced by the data. This reflected the differing pollution loadings of the four urban-type areas. The highest amount of dust accumulation was associated with the industrial area in which shipyard and steelworks occurred whilst the lowest dust accumulation was associated with the grounds of the University which was the control area.

Improved Tolerance of Teak (Tectona grandis L.f.) Seedlings to Low-Temperature Stress by the Combined Effect of Arbuscular Mycorrhiza and Paclobutrazol

Low-temperature damage is a common problem for tropical and subtropical plants during their early-growth stage. In this study, an experiment with a L18 (21 × 37) mixed orthogonal array in a greenhouse was conducted to determine whether arbuscular mycorrhizal fungi (AMF) inoculation and paclobutrazol (PBZ) application through foliar spray would enhance the chilling tolerance of teak seedlings. One-month-old seedlings of clones 8301, 7544, and 7552 from a Myanmar provenance propagated by tissue culture techniques were inoculated with Glomus versiforme and cultivated for 6 months. The foliar surface of both mycorrhizal and nonmycorrhizal treated plants was sprayed with PBZ at concentrations of 0, 50, and 100 mg l−1 once a week for 3 weeks prior to exposure to low temperatures of 6, 3, and 0°C for 12 h in an artificial climate chamber, followed by 12 h of recovery at 20°C room temperature. AMF colonization significantly promoted height and RCD growth and dry biomass accumulation of shoot and root. Under low-temperature stress, AM symbiosis increased leaf chlorophyll content by 22.8%, soluble protein content by 19.6%, superoxide dismutase (SOD) activity by 10.6%, and peroxidase (POX) activity by 9.5%, whereas malondialdehyde content was decreased by 14.1%. Both AMF colonization and the foliar spray PBZ at 50 and 100 mg l−1 were capable of alleviating the damage caused by low-temperature stress on teak seedlings by increasing the photosynthetic pigments, accumulation of osmotic adjustment compounds, and antioxidant enzyme (SOD and POX) activity, and by decreasing membrane lipid peroxidation. AMF colonization and foliar spraying of PBZ at 50 mg l−1 produced a positive interaction and appears to be a good way to enhance chilling tolerance of teak seedlings experiencing stress at 6, 3 and 0°C for 12 h.

Microscopic and histochemical characterization of leaves of the medicinal plant Ocimum obovatum

Ocimum obovatum E. Mey. subsp. obovatum var. obovatum has been valued for its hair restorative properties for decades on the African continent. The member of the Lamiaceae is also traditionally prescribed as a remedy for infantile abdominal cramps and a hot water extract of the leaves is used to treat epigastric conditions in children. Commonly known as 'cat's whiskers', the aromatic plant can be seen growing along the KwaZulu-Natal coastline and the Western Cape of southern Africa. Ocimum obovatum is also common in Zimbabwe and Swaziland as well as northern and west Africa [1]. The medicinal properties of the plant are attributed to the essential oils supposedly produced and secreted by appendages on the foliar surfaces referred to as trichomes [2]. Traditional light and electron microscopy studies revealed the presence of two types of glandular trichomes and one type of non-glandular trichome across all stages of leaf development. The glandular trichomes were classified as large, four-celled peltate trichomes and smaller capitate trichomes. The latter were further classified into two subtypes; Type I capitate trichomes with a single basal cell and two head cells and Type II capitate trichomes with a single basal and stalk cell and an ovoid head cell. Histochemical and phytochemical studies showed that essential oils of a terpenoid nature were present in the head cells of glandular trichomes. Flavonoids, triterpenoids, tannins, saponins, fixed oils and fats, phenolics and cardiac glycosides were also detected in a crude ethanolic extract of the leaves using phytochemical test methods.

Effect of repeated irrigation with water containing varying levels of total organic carbon on the persistence of Escherichia coli O157:H7 on baby spinach.

The California lettuce and leafy greens industry has adopted the Leafy Greens Marketing Agreement (LGMA), which allows for 126 most-probable-number (MPN) Escherichia coli per 100 ml in irrigation water. Repeat irrigation of baby spinach plants with water containing E. coli O157:H7 and different levels of total organic carbon (TOC) was used to determine the epiphytic survival of E. coli O157:H7. Three irrigation treatments (0 ppm of TOC, 12 or 15 ppm of TOC, and 120 or 150 ppm of TOC) were prepared with bovine manure containing E. coli O157:H7 at either low (0 to 1 log CFU/100 ml) or high (5 to 6 log CFU/100 ml) populations, and sprayed onto baby spinach plants in growth chambers by using a fine-mist airbrush. MPN and direct plating techniques were used to determine the E. coli O157:H7 populations on the aerial plant tissue. Plants irrigated with high E. coli O157:H7 populations, regardless of TOC levels, showed a 3-log reduction within the first 24 h. Low levels of E. coli O157:H7 were observed for up to 16 days on all TOC treatments, ranging from 76.4 MPN per plant (day 1) to 0.40 MPN per plant (day 16). No viable cells were detected on spinach tissue 24 h after irrigation with water containing fewer than 126 CFU/100 ml E. coli O157:H7. Under growth chamber conditions in this study, E. coli O157:H7 populations in irrigation water that complies with the LGMA standards will not persist for more than 24 h when applied onto foliar surfaces of spinach plants.

CSM‐IXIM: A New Maize Simulation Model for DSSAT Version 4.5

The CERES‐Maize model is the most widely used maize (Zea mays L.) model and is a recognized reference for comparing new developments in maize growth, development, and yield simulation. The objective of this study was to present and evaluate CSM‐IXIM, a new maize simulation model for DSSAT version 4.5. Code from CSM‐CERES‐Maize, the modular version of the model, was modified to include a number of model improvements. Model enhancements included the simulation of leaf area, C assimilation and partitioning, ear growth, kernel number, grain yield, and plant N acquisition and distribution. The addition of two genetic coefficients to simulate per‐leaf foliar surface produced 32% smaller root mean square error (RMSE) values estimating leaf area index than did CSM‐CERES. Grain yield and total shoot biomass were correctly simulated by both models. Carbon partitioning, however, showed differences. The CSM‐IXIM model simulated leaf mass more accurately, reducing the CSM‐CERES error by 44%, but overestimated stem mass, especially after stress, resulting in similar average RMSE values as CSM‐CERES. Excessive N uptake after fertilization events as simulated by CSM‐CERES was also corrected, reducing the error by 16%. The accuracy of N distribution to stems was improved by 68%. These improvements in CSM‐IXIM provided a stable basis for more precise simulation of maize canopy growth and yield and a framework for continuing future model developments.

Deposição de calda de pulverização sobre plantas de salvínia em função de pontas de pulverização e arranjos populacionais entre plantas de Aguapé e Alface-D'Água

Este trabalho teve como objetivo avaliar o depósito de calda pulverizada por dois tipos de pontas de pulverização sobre plantas de Salvinia auriculata dispostas em diferentes arranjos populacionais com plantas de Eichhornia crassipes e Pistia stratiotes. Um experimento foi conduzido em condições de caixas-d'água em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 2 x 8, sendo dois tipos de pontas de pulverização (ConeJet TXVK-8 e TeeJet DG 11002 VS) e oito proporções entre as plantas aquáticas, a saber: dominância total da área de cobertura da caixa-d'água pelas plantas de salvínia (100%); e as proporções entre plantas de salvínia e de aguapé ou alface-d'água a 75%:25%, 50%:50% e 25%:75%. Também foi utilizada uma densidade tripla, na qual as três espécies estiveram igualmente dispostas na proporção de 33%. Soluções dos corantes Amarelo Tartrasina FDC-5 a 3.500 ppm e Azul Brilhante FDC-1 a 1.000 ppm foram utilizadas como traçadores para as pontas TXVK-8 e DG 11002VS, respectivamente. A pulverização das soluções foi efetuada na mesma unidade experimental, com intervalo de 30 minutos entre si, com auxílio de um pulverizador costal pressurizado com CO2, calibrado de modo que proporcionasse volume de aplicação aproximado de 200 L ha-1. Não foram observadas diferenças estatísticas entre os tipos de pontas de pulverização nas diferentes proporções estudadas, exceto para depósitos totais de calda de pulverização nas plantas na condição de dominância total da salvínia, uma vez que a ponta ConeJet TXVK-8 foi superior à TeeJet DG 11002 VS. Os valores dos depósitos diminuíram com o aumento da proporção de plantas de aguapé na associação e foram na condição em que 25% de plantas de salvínia estiveram associadas a 75% de plantas de aguapé. A presença da espécie alface-d'água não influenciou a deposição de gotas sobre as folhas de salvínia.

Genome sequencing and comparative analysis of the carrot bacterial blight pathogen, Xanthomonas hortorum pv. carotae M081, for insights into pathogenicity and applications in molecular diagnostics

Xanthomonas hortorum pv. carotae (Xhc) is an economically important pathogen of carrots. Its ability to epiphytically colonize foliar surfaces and infect seeds can result in bacterial blight of carrots when grown in warm and humid regions. We used high-throughput sequencing to determine the genome sequence of isolate M081 of Xhc. The short reads were de novo assembled and the resulting contigs were ordered using a syntenic reference genome sequence from X. campestris pv. campestris ATCC 33913. The improved, high-quality draft genome sequence of Xhc M081 is the first for its species. Despite its distance from other sequenced xanthomonads, Xhc M081 still shared a large inventory of orthologous genes, including many clusters of virulence genes common to other foliar pathogenic species of Xanthomonas. We also mined the genome sequence and identified at least 21 candidate type III effector genes. Two were members of the avrBs2 and xopQ families that demonstrably elicit effector-triggered immunity. We showed that expression in planta of these two type III effectors from Xhc M081 was sufficient to elicit resistance gene-mediated hypersensitive responses in heterologous plants, indicating a possibility for resistance gene-mediated control of Xhc. Finally, we identified regions unique to the Xhc M081 genome sequence, and demonstrated their potential in the design of molecular diagnostics for this pathogen.

Recherches préliminaires sur la mise en place d'une biosurveillance végétale de la pollution atmosphérique en zone industrielle complexe: applications du ray—grass dans la zone industrialo—portuaire de Dunkerque

Heavy metals are particularly present in industrial harbour areas, mainly under particle form. Three possible applications of rye—grass in heavy metals biomonitoring were studied in this work: bioaccumulation, observation of particle deposition on leaves and genotoxicity. Only lead and cadmium were detected on leaves, with higher concentrations in industrial site. This results show the application limits of French norm NF X43-901 when atmospheric concentrations of heavy metals are relatively low during the survey. However, size, composition, and quantity of particles microscopically observed on foliar surfaces (with SEM) change according to the sites. Moreover, comet assay, that was performed for the first time on rye—grass leaves, show genotoxic effects more important in road site.

Switching from a mechanistic model to a continuous model to study at different scales the effect of vine growth on the dynamic of a powdery mildew epidemic.

Epidemiological simulation models coupling plant growth with the dispersal and disease dynamics of an airborne plant pathogen were devised for a better understanding of host-pathogen dynamic interactions and of the capacity of grapevine development to modify the progress of powdery mildew epidemics. The first model is a complex discrete mechanistic model (M-model) that explicitly incorporates the dynamics of host growth and the development and dispersion of the pathogen at the vine stock scale. The second model is a simpler ordinary differential equations (ODEs) compartmental SEIRT model (C-model) handling host growth (foliar surface) and the ontogenic resistance of the leaves. With the M-model various levels of vine development are simulated under three contrasting climatic scenarios and the relationship between host and disease variables are examined at key periods in the epidemic process. The ability of the C-model to retrieve the main dynamics of the disease for a range of vine growth given by the M-model is investigated. The M-model strengthens experimental results observed regarding the effect of the rate of leaf emergence and of the number of leaves at flowering on the severity of the disease. However, it also underlines strong variations of the dynamics of disease depending on the vigour and indirectly on the climatic scenarios. The C-model could be calibrated by using the M-model provided that different parameters before and after shoot topping and for various vigour levels and inoculation time are used. Biologically relevant estimations of the parameters that could be used for its extension to the vineyard scale are obtained. The M-model is able to generate a wide range of growth scenarios with a strong impact on disease evolution. The C-model is a promising tool to be used at a larger scale.