Leaf Layers Research Articles

Distribution of primary and secondary metabolites among the leaf layers of headed cabbage (Brassica oleracea var. capitata)

The present study investigated the distribution of several primary metabolites (soluble sugar, protein, and mineral) and secondary metabolites (carotenoids, vitamin C, anthocyanin, flavonoids, and total phenolic compounds) among the leaf layers of headed cabbage. The leaf layers of two cultivars were separated and numbered sequentially from the outer to the inner leaves. The fructose and glucose content of the inner leaf layers was significantly greater than that of the outer layers. Similarly, the level of glucosinolates increased gradually from the outer leaves to the umbilicus of the leaf head. However, the content of antioxidants decreased from the outer leaves to the core of the leaf head, in line with the antioxidant capacity. The levels of soluble protein and mineral shared the similar decreasing trend. These results provide a reference for consumers to choose optimal fractions of whole cabbage heads in order to cater to their particular dietary needs.

Leaflet shape analysis separates rose cultivars and estimates leaf area

Trying to use tip leaflet of rose plants as a sample to estimate leaf area and to separate rose cultivars, in an experiment we took leaf images from three different stem layers of four garden roses. After preliminary image pre-processing measures, some important leaf geometric features such as leaf and leaflet area, perimeter, circularity and leaflet length and width were measured or calculated. Analysis of variance showed that it would be possible to separate rose cultivars by including only two leaf properties, i.e., tip leaflet angle and leaflet area to leaf area ratio. It was also determined that three leaf layers along the rose stem can be recognized and categorized by implementing just angle of tip leaflet. Leaflet area was agreeably approximated by fitting a simple linear model to the product of leaflet minor and major axes. Further analyses indicated that some leaflet properties such as solidity, perimeter and circularity can be used as significant criteria to distinguish rose cultivars, however other features like leaflet elongation and rectangularity were quite poor and insignificant in this case. In conclusion, it was determined that rose leaflet tip angle not only has the ability of being as a good morphometric marker in separating rose stem leaf layers but also it is capable of identifying different rose cultivars.

Intensive Fruit-zone Leaf Thinning Increases Vitis vinifera L. ‘Cabernet Sauvignon’ Berry Temperature and Berry Phenolics without Adversely Affecting Berry Anthocyanins in Virginia

Selective leaf removal in the proximity of grape clusters is a useful practice to manage fruit diseases and otherwise improve fruit composition. The current recommendation in the eastern United States is to create a fruit zone with one to two leaf layers and to focus removal on the “morning sun” side of the canopy. We evaluated a more intense and an earlier application of fruit-zone leaf thinning relative to current recommendations to determine whether additional benefits could be obtained without a penalty of impaired berry pigmentation or other ill effects of abundant grape exposure. Fruit secondary metabolites and berry temperature were monitored in two different field experiments conducted with ‘Cabernet Sauvignon’ in the northern Shenandoah Valley American Viticultural Area (AVA) of Virginia. One experiment evaluated the effects of no leaf removal, prebloom removal of four basal leaves per shoot, and prebloom removal of eight basal leaves per shoot. The other experiment evaluated the effects of no leaf removal and postfruit set removal of six basal leaves per shoot. On average, exposed grapes heated to ≥30 °C for a 126% longer period (53 hours) than shaded grapes in the postveraison period (from color development through harvest). However, postveraison grape temperatures did not remain above provisional, critical temperature thresholds of either 30 or 35 °C for as long as they did in studies conducted in sunnier, more arid climates. There were minimal differences in berry temperature between east- and west-exposed grapes in the northeast/southwest-oriented rows of the experimental vineyard. Regardless of implementation stage, leaf removal consistently increased total grape phenolics measured spectrophotometrically, and either increased or had no impact on anthocyanins relative to no leaf removal. Grape phenolics and anthocyanins were unaffected by canopy side. Berry total phenolics were increased and anthocyanins were at least maintained in fruit zones void of leaf layers—a canopy attribute that reduces bunch rot in humid regions.

Effect of partial pesticide spraying on the number of major pests and damage to new shoots of tea plants

Abstract We studied the effects of partial spraying, targeting tea [Camellia sinensis (L.) O. Kuntze] plants' plucking surfaces, on the annual number of major pests and damage to new shoots. The prevention of feeding damage to shoots caused by Empoasca onukii Matsuda (Hemiptera: Cicadellidae) was more stable when spraying at high volumes. However, the annual number of E. onukii with conventional spraying (200 L/1000 m2) was similar to the control (No pesticide). On the other hand, the prevention effect on shoots and the annual number of Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) in partial spraying (40 L/1000 m2) was similar to conventional spraying. Moreover, although high volumes of spraying (1000 L/1000 m2) are usually needed to control Pseudaulacaspis pentagona (Targioni-Tozetti) (Hemiptera: Diaspididae), the male adult population of P. pentagona in the control and partially sprayed field tended to be lower than that in the conventional spraying. When using pesticides harmful to P. pentagona's natural enemies, partial spraying seems beneficial. Enough pesticide spraying to widely cover the leaf layer was thought necessary to protect the tea plants' new shoots. However, the spraying method targeting only the tea plants' plucking surfaces protects the new shoots with similar efficacy. Besides, partial spraying protects pests' natural enemies, allowing additional pest population control.

Temporal and Organ-specific Responses in NUE Traits to N Fertilization, Fungicide Intensity and Early Sowing in Winter Wheat Cultivars

Fungicide intensity and sowing time influence the N use efficiency (NUE) of winter wheat but the underlying mechanisms, interactions of plant traits, and the temporal effects are not sufficiently understood. Therefore, organ-specific responses in NUE traits to fungicide intensity and earlier sowing were compared at two nitrogen (N) levels for six winter wheat cultivars in 2017. Plants were sampled at anthesis and at maturity and separated into chaff, grain, culms, and three leaf layers to assess their temporal contribution to aboveground dry matter (DM) and N uptake (Nup). Compared to the control treatment, across cultivars, the treatment without fungicide mostly exerted stronger and inverse effects than early sowing, on grain yield (GY, −12% without fungicide, +8% n.s. for early sowing), grain Nup (GNup, −9% n.s., +5% n.s.) as well as on grain N concentration (+4%, −2% n.s.). Grain yield in the treatment without fungicide was associated with similar total DM, as observed in the control treatment but with lower values in harvest index, thousand kernel weight, N use efficiency for GY (NUE) and N utilization efficiency. Lower GNup was associated with similar vegetative N uptake but lower values in N translocation efficiency and N harvest index. In contrast, early sowing tended to increase total DM at anthesis and maturity as well as post-anthesis assimilation, at similar harvest index and increased the number of grains per spike and total N use efficiency. Total N uptake increased after the winter season but was similar at anthesis. Although the relative N response in many traits was lower without fungicide, few fungicide x interactions were significant, and the sowing date did not interact either with N fertilization for any of the N and DM traits. The results demonstrate the positive effects of fungicides and earlier sowing on various traits related to yield formation and the efficient use of nitrogen and are discussed based on various concepts.

A review of railway sanding system research: Wheel/rail isolation, damage, and particle application

This paper reviews the academic and industrial research conducted into the practical aspects of using abrasive particles in the wheel/rail contact, such as: wheel/rail isolation, surface damage, and the application of the particles into the contact. Abrasive particles are applied to the wheel/rail contact to restore traction when low adhesion situations exist on the rail head; this process is referred to as “sanding” because sand particles are the preferred particle type in the railway industry. This aspect of sanding was covered in another sanding review. Currently, particles are applied either by firing dry particles into the wheel/rail contact via an air stream or by suspending them in a gel which can be applied using train-borne or trackside methods. The papers looked at in this review were scrutinised using a gap analysis method which grades each paper based on seven criteria, these criteria assessed: whether the papers had been peer reviewed, whether the conclusions matched the results, the range of testing scales used, and the presence of fundamental modelling work. When the findings of the research in this review were analysed, it was apparent that the negative effects of sanding (damage and isolation) have not been researched in much depth compared to its positive effects (adhesion restoration and leaf layer removal). In addition, the academic research that has been conducted has not been taken forward by industry, and industry research has not been studied in more depth by academia, suggesting a communication gap between the two branches of research; this was also the case for research into application methods.

Precultivation of young seedlings under different color shades modifies the accumulation of phenolic compounds in Cichorium leaves in later growth phases

Manipulation of spectral composition has been found to be an efficient way to influence the growth and quality of plant production in protected or controlled environments. The aim of this study was to compare the short- and long-term effects of early pretreatment with different color shades on the composition of phenolic compounds and photosynthetic pigments in Cichorium leaves. The analyses conducted immediately after color shade pretreatments at ˜40 μmol m−²s−1 (blue, red orange, white) indicated lower values of chlorophyll, anthocyanin and flavonoid indices, as well as of the majority of flavonoids, compared to those in the same plants subsequently grown for 4 weeks under higher white light with an intensity of ˜320 μmol m−²s−1. However, we observed significant differences in the contents of phenolics and pigments depending on previous color shade pretreatment in plants grown for 4 weeks in the same environment and in leaves grown during this period. The most significant effect was observed in plants pretreated with orange light, in which levels of isorhamnetin, its derivatives and feruloyl malate were increased, and kaempferol-3-(6”-acetyl)-glucoside levels were significantly decreased. Blue light pretreatment led to lower values of chlorogenic acid, caftaric acid and isorhamnetin-3-(6”-acetyl)-glucoside but a higher content of isorhamnetin-3-glucoside. Red light led to an increase in quercetin derivatives. Compared to plants grown under constant conditions, low light in the early growth phases led to the upregulation of feruloyl malate, caffeoyl malate and kaempferol derivatives. Nondestructive measurements enabled the identification of significant effects of light pretreatment on the chlorophyll contents, as well as the accumulation of flavonoids and anthocyanins in the epidermal leaf layer. The induction of specific metabolites influenced by the acclimation of plants to colored light environments may emphasize the environment‐induced biochemical responses associated with the remarkable plasticity of phenylpropanoid metabolism.

The Effect of Plant Genotype, Growth Stage, and Mycosphaerella graminicola Strains on the Efficiency and Durability of Wheat-Induced Resistance by Paenibacillus sp. Strain B2.

Plant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>106 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55–94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71–79% of protection and reached 81–94% in association with half of the recommended dose of Cherokee® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field conditions.

Functional Crown Architecture of Five Temperate Broadleaf Tree Species: Vertical Gradients in Leaf Morphology, Leaf Angle, and Leaf Area Density

The morphology, inclination, and spatial distribution of leaves in different parts of tree crowns are important determinants of the radiation, momentum, and gas exchange between the canopy and the atmosphere. However, it is not well known how these foliage-related traits vary among species differing in successional status. We measured leaf size, leaf mass area (LMA), leaf inclination (angle to the horizontal), leaf area density (LAD), total leaf area (leaf area index, LAI), and leaf area distribution across the crown in adult trees of five common, early to late-successional tree species (Betula pendula Roth, Quercus petraea (Matt.) Liebl., Carpinus betulus L., Tilia cordata Mill., and Fagus sylvatica L.) using different canopy access techniques and the harvest of foliated trees (29 trees in total). Leaf size increased continuously with crown depth in B. pendula and T. cordata but peaked at mid-crown in Q. petraea, C. betulus, and F. sylvatica to decrease toward the shade crown. By contrast, LMA and leaf angle decreased continuously with crown depth in all species, but the pattern of vertical change varied. The mid/late- and late-successional species had higher LAI, lower shade-leaf LMA, lower leaf angles (shade and sun crown), and higher LAD in the uppermost sun crown in comparison to early successional B. pendula. We assume that the most peripheral sun leaf layer is partly acting as a shield against excess radiation, with foliage properties depending on the structure of the shade crown. We conclude that the vertical change in leaf morphology, inclination, and spatial distribution in tree crowns is highly species specific, with partial dependence on the species’ position in succession.

Partial replacement of red and blue by green light increases biomass and yield in tomato

Effects of green light on plant growth are relatively understudied, and published results are contradictory. Although per unit leaf area, green light drives photosynthesis less efficiently than does red light, on a whole-plant level green light may increase growth due to changes in vertical light distribution, leaf light acclimation and canopy architecture. As most studies were conducted on small plants with compact stems, positive effects may have remained unnoticed. In a greenhouse experiment, a tomato (Solanum lycopersicum) crop was exposed to 7, 20 or 39% of green light in a background of narrow bandwidth red and blue light, as well as sunlight, for 76 days. The intensity supplied by lamps (171 μmol m−2 s−1) and the red:blue ratio were similar between treatments. Adding green light (+32%) to the spectrum significantly and linearly increased plant biomass and yield (+6.5%). With increasing green light percentage, there were tendencies for linear increases in leaf biomass (P = 0.06), specific leaf area (P = 0.09), stem biomass (P = 0.07), stem length (P = 0.05) and number of internodes (P = 0.05). In the top and middle leaf layers of the canopy, net photosynthesis rate, stomatal conductance and leaf thickness were unaffected by the treatment while in leaves in the middle leaf layer, chlorophyll a:b ratio and carotenoid concentrations increased with the percentage of green light. This study shows that partial replacement of red by green light increases growth of plants in dense canopies and suggests that the combined effects of a light spectrum on plant growth are more than the sum of wavelength effects on photosynthetic efficiency.

“A Model for Simulating Photosynthesis in Plant Communities” by W.G. Duncan, R.S. Loomis, W.A. Williams, and R. Hanau, Hilgardia (1967) 38:181–205

This article is part of a series of brief commentaries to highlight papers that have resulted in important and distinctly new perspectives in crop science. A criterion for selection of papers is that they must have been published at least 20 yr ago to allow for a long‐range perspective in assessment of the papers. The current article briefly reviews the paper by W.G. Duncan, R.S. Loomis, W.A. Williams, and R. Hanau published in 1967 that provided original concepts about the interception of solar radiation by crop leaf canopies and the estimate of canopy photosynthesis rate based on the intercepted radiation. They developed a geometric description of beam penetration through leaf layers and calculation of canopy CO2 exchange by considering separately leaves in direct‐beam radiation and in the shade.

The response of three species of phytoseiid mite (Acari: Phytoseiidae) to synthetic pyrethroid pesticides in the laboratory and the field.

The Kanzawa spider mite, Tetranychus kanzawai Kishida, is a major pest in tea fields [Camellia sinensis (L.) O. Kuntze] in Japan. However, recently, there have been some instances where acaricides are no longer applied as a result of the low occurrence of T. kanzawai in tea fields in Japan. In the period of 2015-2017, surveys of predatory mites in the study tea field detected Amblyseius eharai Amitai and Swirski, Phytoseiulus persimilis Athias-Henriot, Euseius sojaensis (Ehara), Amblyseius obtuserellus Wainstein and Begljarov, and Typhlodromus vulgaris Ehara in tea fields, but not Neoseiulus womersleyi (Schicha), indicating that a major change in the composition of the phytoseiid mite population had occurred. In laboratory studies, we confirmed the ability to avoid synthetic pyrethroid insecticides of the major beneficial mites in tea fields, A. eharai and P. persimilis, but not of E. sojaensis, a predatory mite whose population declined heavily after pesticide application. Attempts are made in this study to associate the decrease in T. kanzawai frequency in Japan with changes in pesticide used, method of spraying, and composition of the phytoseiid mite population. By continuing the method of pesticide spraying ('partial surface'), which leaves refugia in the leaf layer with sub-lethal dosages of pesticide, phytoseiid mites are aided to evade pesticides, resulting in maintenance of the composition of the phytoseiid mite populations in terms of diversity and abundance. Maintaining the diversity and abundance of Phytoseiidae may have contributed to the stabilization of the T. kanzawai population at low densities in Japanese tea fields.

Effects of light intensity on growth, quality and antioxidant activities of Sedum sarmentosum

The present study was conducted to explore the effect of light intensity on growth, bioactivity compounds accumulation and anti-oxidative activity of Sedum sarmentosum. The growth, yield, contents of total flavonoids, total phenolic, quercetin, kaempferol and isorhamnetin, and antioxidant activities were assessed in S. sarmentosum under five light intensities, namely 100% full sunlight (G1), 77% full sunlight (G2), 60% full sunlight (G3), 38% full sunlight (G4), and 16% full sunlight (G5). The results showed that light intensity significantly affected the growth and the chemical compounds accumulation. With the decrease of light intensity, the maximum branch length and the average internode distance increased. G2 treatment greatly promoted the numbers of leaf layers and branches, and G3 treatment remarkably improved the yield. The highest total flavonoids and phenolic contents were obtained in G3 treatment. Meanwhile, the highest quercetin and isorhamnetin contents were obtained in G1 treatment. The difference of kaempferol content was not significant. In addition, based on DPPH, FTC and FRAP methods, the antioxidant activities of the aqueous extracts under G1 treatment were superior to the others. The results indicated that more than 60% full sunlight was the optimum light intensity condition to achieve high yield and quality of S. sarmentosum.

Optimal nitrogen regimes compensate for the impacts of seedlings subjected to waterlogging stress in summer maize.

A field experiment was performed to explore the compensation effects of different nitrogen (N) regimes on the growth and photosynthetic capacity in different leaf layers of the summer maize hybrid of LuYu9105 under waterlogging at the seedling stage. The results showed that waterlogging significantly decreased the maximum green leaf area (gLA) by 10.0~15.3% and 9.3~22.5%, mainly due to the reduction in the below-ear layer leaves at the silking stage in 2014 and 2015, respectively. Waterlogging also significantly decreased the ear leaf photosynthetic rate (PN), and Fv/Fm, Fv/Fo, ΦPSII and qP at the below-ear layer leaves at the mid- and late-filling stages, which was accompanied by a reduction in the duration of grain-filling (T) by 2.6~5.9%, thus resulting in a loss of grain yield by 7.0~18.5%. Interestingly, a shift in N from basal application to topdressing at the big flare stage was shown to compensate the adverse effects of waterlogging by through increased gLA and leaf photosynthetic capacity at the ear layer and the above-ear layer, as well as a greater grain-filling rate, resulting in an increase in grain yield by 9.9~27.0% and 17.8~25.8% compared to other N treatments. Therefore, this study showed that optimal nitrogen regimes during maize growth are capable of compensating for the impacts caused by waterlogging at the seedling stage.

Annual Under-Vine Cover Crops Mitigate Vine Vigor in a Mature and Vigorous Cabernet franc Vineyard

Excessive vine vegetative growth in wet, cool climates increases management costs and compromises grape quality. The standard practice of bare soil under vines exacerbates the vigor problem. This study examined the ability of under-vine cover crops to mitigate excessive vigor in a mature vineyard. A three-year study was conducted in a mature Cabernet franc vineyard in Ovid, NY. Under-vine cover crops of chicory (CHI), tall fescue (FES), tillage radish (TR), alfalfa (ALF), or natural vegetation (NV) were established annually since 2014 to compare with a control of glyphosate-maintained bare soil (GLY). Pruning weight was reduced 64% by CHI and 54% by FES or TR compared to GLY in 2015. Primary and lateral shoot growth was suppressed by CHI in 2016. Fruiting zone leaf layer number was reduced by all of the under-vine cover crops in 2015, and by CHI and FES in 2016. Yield per vine was not reduced by any of the under-vine cover crops in any year of the study. Under-vine cover crops had little impact on harvest parameters including soluble solids, titratable acidity, pH, or yeast assimilable nitrogen. Soil properties such as aggregate stability, microbial respiration rate, and carbon mineralizability were improved by some cover crops. Although NV, FES, and TR showed little, and ALF showed neutral, effect on vine growth or yield components, CHI effectively alleviated mature vine vigor without reducing yield in a cool climate. Since water or nutrient competition alone did not fully explain the mitigating effect of under-vine cover crops on vine vigor, other mechanisms such as microbial or allelopathic effects of under-vine cover crops should be examined.

Tender leaf and fully-expanded leaf exhibited distinct cuticle structure and wax lipid composition in Camellia sinensis cv Fuyun 6

The goal of the present study was to compare the structural and compositional differences of cuticle between tender leaf and fully-expanded leaf in Camellia sinensis, and provide metabolic base for the further characterization of wax biosynthesis in this economically important crop species. The tender second leaf and the fully-expanded fifth leaf from new twig were demonstrated to represent two different developmental stages, their cuticle thickness were measured by transmission electron microscopy. The thickness of the adaxial cuticle on the second and fifth leaf was 1.15 µm and 2.48 µm, respectively; the thickness of the abaxial cuticle on the second and fifth leaf was 0.47 µm and 1.05 µm, respectively. The thickness of the epicuticular wax layer from different leaf position or different sides of same leaf were similar. However, the intracuticular wax layer of the fifth leaf was much thicker than that of the second leaf. Total wax lipids were isolated from the second leaf and the fifth leaf, respectively. Gas chromatography-mass spectrometry analysis identified 51 wax constituents belonging to 13 chemical classes, including esters, glycols, terpenoids, fatty acids and their derivatives. Wax coverage on the second and fifth leaf was 4.76 µg/cm2 and 15.38 µg/cm2, respectively. Primary alcohols dominated in the tender second leaf. However, triterpenoids were the major components from the fully-expanded fifth leaf. The predominant carbon chains varied depending on chemical class. These data showed that the wax profiles of Camellia sinensis leaves are development stage dependent, suggesting distinct developmental dependent metabolic pathways and regulatory mechanisms.

Canopy management strategies to control yield and grape composition of Montepulciano grapevines

Background and Aims Higher temperature during the season is forcing growers in Central Italy to explore ways to reliably control vine yield and grape ripening, while maintaining grape composition. The most common approaches include altering winter pruning, shoot thinning (St), leaf removal and bunch thinning. These studies, however, rarely evaluated these practices in concert and over multiple seasons. Methods and Results From 2009 to 2013, five treatments were applied to Vitis vinifera L. cv. Montepulciano: winter pruning only (Wp, Control); Wp plus St; St plus pre-flowering defoliation (St + Dpa); St plus pre-veraison defoliation (St + Dpv); and St + Dpv plus bunch thinning (St + Dpv + Bt) applied prior to veraison. Effects on canopy architecture, yield, ripening and berry composition were measured. Compared to Wp, St, St + Dpv and St + Dpv + Bt treatments reduced leaf area and leaf layer number in the fruiting zone, while St + Dpv + Bt reduced yield. No treatment slowed ripening. The treatment St + Dpa reduced yield and the incidence of Botrytis cinerea, and improved fruit composition, but increased TSS in berries. All treatments were ceased after 2013 and the vines were pruned in winter only. The treatment St + Dpa imposed in 2013 had a strong carry-over effect on yield but not TSS in 2014. Conclusions Shoot thinning alone reduced canopy density but failed to reduce yield or improve fruit composition. Both the St + Dpv and St + Dpv + Ct treatments provided a more open fruit zone, had no effect on yield and increased TSS in fruit at harvest. Shoot thinning plus pre-flowering defoliation decreased yield and improved berry composition in a Mediterranean climate; however, given its observed carry-over effects on yield this approach should be applied only in alternate years, suggesting the need for further research exploring additional viticultural practices. Significance of the Study Despite some benefits of St, defoliation and bunch thinning on their own or even in concert, no combination tested was consistently effective for controlling vine yield and grape ripening, while maintaining grape composition.

Genetic Structure of Zymoseptoria tritici in Northern France at Region, Field, Plant, and Leaf Layer Scales.

Population genetic structure of the worldwide-distributed wheat pathogen Zymoseptoria tritici has been extensively studied at large geographical scales, but to a much less extent at small or local spatial scales. A total of 627 single-conidial fungal isolates were sampled from several locations in northern France (Hauts-de-France Region) to assess fungal genetic structure at region, field, plant, and leaf layer scales, using highly polymorphic microsatellite markers and mating type idiomorphs. Important and overall similar levels of both gene and genotype diversities (gene diversity values of ≥0.44 and haplotype frequencies of ≥94%) were found at all the examined scales. Such rates of diversity are likely due to an active sexual recombination in the investigated areas, as revealed by equal proportions of the two mating types scored in all sampled populations. Interestingly, a rare occurrence of clones among lesions from a same leaf, as well as among leaves from different plant leaf layers (e.g., upper versus lower leaves), was highlighted, indicating that ascospores contribute much more than expected to Z. tritici epidemics, compared with pycnidiospores. Population structure and analyses of molecular variance revealed significant genetic differentiation at the regional scale (GST = 0.23) and, as expected, not at the other more local scales (GST ≤ 0.01). Further analyses using Bayesian and unweighted neighbor-joining statistical methods detected six genetic clusters within the regional population, overall distributed according to the locations from which the isolates were sampled. Neither clear directional relative migration linked to the geographical distribution of the locations, nor isolation by distance, were observed. Separate evolutionary trajectories caused by selection and adaptations to habitat heterogeneity could be the main forces shaping such structuration. This study provides new insights into the epidemiology and the genetic structure of Z. tritici at small local and, for the first time, at single plant and leaf layer scales. Such findings would be helpful in implementing effective control strategies.

Partitioning of absorbed light energy within photosystem II in barley can be affected by chloroplast movement

Plants have developed many ways to protect reaction centres of photosystems against overexcitation. One of the mechanisms involves reduction of the leaf absorption cross-section by light-induced chloroplast avoidance reaction. Decrease in the probability of photon absorption by the pigments bound within photosystem II (PSII) complexes leads to the increase in quantum yield of PSII photochemistry (ΦPSII). On the other hand, the decrease of PSII excitation probability causes reduction of chlorophyll a fluorescence intensity which is manifested as the apparent increase of determined quantum yield of regulated light-induced non-photochemical quenching (ΦNPQ). Absorption of different light intensity by phototropins led to the different chloroplast distribution within barley leaves, estimated by measurement of the leaf transmittance. Due to a weak blue light used for transmittance measurements, leaves exposed to actinic light with wavelengths longer than 520 nm undergo chloroplast accumulation reaction, in contrast with leaves exposed to light with shorter wavelengths, that showed a different extent of chloroplast avoidance reaction. Based on the ΦNPQ action spectra measured simultaneously with the transmittance, the influence of different chloroplast distribution on ΦNPQ was assessed. The analysis of results showed that decrease in the leaf absorption cross-section due to increasing part of chloroplasts reaching profile position significantly affected the partitioning of excitation energy within PSII and such rearrangement also distorted measured ΦNPQ and cannot be neglected in its interpretation. When the majority of chloroplasts reached profile position, the photoprotective effect appeared to be the most prominent for strong blue light that has the highest absorption in the upper leaf layers in comparison with green or red ones.

A review on recent wheel/rail interface friction management

Traction is influenced greatly by the climatic conditions, especially under wet conditions induced by rain or snowfall which could cause the loss of adhesion and could reduce the coefficient of traction (COT) to a dangerous level. This is why good adhesion is needed to ensure safe and good traction of train. Poor adhesion between wheel and rail can cause various problems and it could be fatal. Friction modifiers are applied to the contact interface to control adhesion, whether to enhance friction or lubricates, to ensure safe running of the rolling stock. In handling poor adhesion issues, sand is the most popular and the main adhesion enhancer used globally on railway networks. Sand particles enhance adhesion dramatically in contaminated wheel/rail contacts such as rail covered by autumn leaf layers or oil stain, and in wet rails. In this review paper, a compilation of some of the research of over the last decade is presented. The topics that will be presented in this paper are the adhesion characteristics of wheel/rail contacts under wet and dry condition, and the influence of sanding on rails covered with leaf layers.