Leaf Halves Research Articles

Leaf unfolding and lamina biomechanics in Syngonium podophyllum and Pilea peperomioides

In nature, leaves and their laminae vary in shape, appearance and unfolding behaviour. We investigated peltate leaves of two model species with peltate leaves and highly different morphology (Syngonium podophyllum and Pilea peperomioides) and two distinct unfolding patterns via time-lapse recordings: we observed successive unfolding of leaf halves in S. podophyllum and simultaneous unfolding in P. peperomioides. Furthermore, we gathered relevant morphological and biomechanical data in juvenile (unfolding) and adult (fully unfolded) leaves of both species by measuring the thickness and the tensile modulus of both lamina and veins as a measure of their stiffness. In S. podophyllum, lamina and veins stiffen after unfolding, which may facilitate unfolding in the less stiff juvenile lamina. Secondary venation highly contributes to stiffness in the adult lamina of S. podophyllum, while the lamina itself withstands tensile loads best in direction parallel to secondary veins. In contrast, the leaf of P. peperomioides has a higher lamina thickness and small, non-prominent venation and is equally stiff in every region and direction, although, as is the case in S. podophyllum, thickness and stiffness increase during ontogeny of leaves from juvenile to adult. It could be shown that (changes in) lamina thickness and stiffness can be well correlated with the unfolding processes of both model plants, so that we conclude that functional lamina morphology in juvenile and adult leaf stages and the ontogenetic transition while unfolding is highly dependent on biomechanical characteristics, though other factors are also taken into consideration and discussed.

Tomato Disease Fusion and Classification using Deep Learning

Tomato plants' susceptibility to diseases imperils agricultural yields. About 30% of the total crop loss is attributable to plants with disease. Detecting such illnesses in the plant is crucial to avoid significant output losses.This study introduces "data fusion" to enhance disease classification by amalgamating distinct disease-specific traits from leaf halves. Data fusion generates synthetic samples, fortifying a TensorFlow Keras deep learning model using a diverse tomato leaf image dataset. Results illuminate the augmented model's efficacy, particularly for diseases marked by overlapping traits. Enhanced disease recognition accuracy and insights into disease interactions transpire. Evaluation metrics (accuracy 0.95, precision 0.58, recall 0.50, F1 score 0.51) spotlight balanced performance. While attaining commendable accuracy, the intricate precision-recall interplay beckons further examination. In conclusion, data fusion emerges as a promising avenue for refining disease classification, effectively addressing challenges rooted in trait overlap. The integration of TensorFlow Keras underscores the potential for enhancing agricultural practices. Sustained endeavours toward enhanced recall remain pivotal, charting a trajectory for future advancements.

PM 3/66 (3) Guidelines for the management of plant health risks of biowaste of plant origin

<scp>PM</scp> 3/66 (3) Guidelines for the management of plant health risks of biowaste of plant origin

ОСОБЕННОСТИ ИЗМЕНЕНИЯ ПРИЗНАКОВ ПРИ СЕЗОННОМ РАЗВИТИИ ЛИСТЬЕВ БЕРЕЗЫ ПОВИСЛОЙ (BETULA PENDULA ROTH)

The paper presents the results of studying the variability of the leaves of the hanging birch (Betula pendula Roth), which were carried out during the growing season of 2018 on permanent test areas in the pollution zone and in the residential area of the Ufa industrial Center. 10 trees were identified and numbered on the trial areas. The relative vital condition of the studied trees is characterized as "healthy". From each tree in the summer-autumn period (June, July, August, September, October), 10 leaves were selected from brachiblasts. For each sheet, 5 parameters were measured on the left and right half and an integral indicator of fluctuating asymmetry was calculated. When comparing the features of the seasonal development of birch leaves in the industrial and residential zones, morphological differences were established. According to Fischer's criterion, during the growing season, the 2nd feature was the most informative (the length of the second vein of the second order from the base of the leaf). In July, the greatest variability of leaves was revealed by a set of signs (2, 3, 4, 5). It should be noted that the 1st feature (the width of the leaf halves) weakly reflects deviations in the formation of asymmetry of birch leaves. The data obtained indicate the uneven seasonal development of birch leaves in the Ufa industrial Center against the background of the temperature regime during 2017-2018.

First report of Colletotrichum gloeosporioides causing leaf spot on Cyclobalanopsis glauca in China.

Cyclobalanopsis glauca (Thunb.) Oerst. is one of the most widely distributed species of evergreen broad-leaved tree in subtropical areas of China. It is also grown in Korea, Japan, and India. Because of its beautiful shape, C. glauca is commonly used for greening gardens and walkways. In July 2018, leaf spots on C. glauca were observed in Zhejiang province (Lishui, N: 28°26' 6.75";E: 119°54'11.22), China. About 70% of the trees were found to be diseased, with approximately 50% of leaves showing symptoms. The symptoms on C. glauca leaves initially appeared as small brown-yellow spots which gradually expanded, developing a light brown central and dark brown to black margin. The spots ranged from 4 to 15 mm in diameter. Ten symptomatic fragments measuring approximately 5×5 mm from each leaf were surface disinfested with 70% ethanol for 30 s, and then they were rinsed in sterile distilled water and placed on potato dextrose agar (PDA) medium at 25 °C in the dark for five days. Segments of colony perimeters were then transferred to new plates. The colonies initially produced white mycelia that later turned gray-white with pink and occasionally black dots scattered on the surface of the mycelium. Spores were aseptate, cylindrical, 8 to 15 μm in length, and 3 to 5 μm wide, most with rounded ends, a few with one apex round and the other fusiform, as described for Colletotrichum gloeosporioides (Penz.) Sacc. (Agostini et al. 1993). The internal transcribed spacer rDNA (ITS: MK758005) and two nuclear protein-coding genes (CHS: MK784770, ACT: MK784769) were amplified with ITS1/ITS4, CHS-79F/CHS-345, and ACT-512F/ACT-783R, respectively (Weir et al. 2012). The sequence had 99.61% identity to GQ485605 for ITS, 99.56% to GQ856782 for ACT, and 100% to GQ856733 for CHS of C. gloeosporioidesCBS 953.97 in GenBank, respectively. To fulfill Koch's postulates, spores (1×108) of the isolate were sprayed onto leaves of twelve 2-year-old C. glauca plants (at least six leaves per plant). The fungus was inoculated on one side of each leaf, and distilled water was used as a mock inoculated control on the other side. The plants were cultivated in the greenhouse to maintain high humidity and a temperature near 25 °C. After 9 days, 100% of the leaf halves that had been inoculated had symptoms identical to those observed onaffected C. glaucaleaves in the field, while no symptoms were observed on the mock inoculated half of each leaf. The fungus was reisolated from the symptoms and identified as C. gloeosporioides using techniques previously described. To our knowledge, this is the first report ofC. gloeosporioidesinfecting C. glauca in China. This study will establish a foundation for the further study of C. gloeosporioides to address the disease effectively.

Learning from plant movements triggered by bulliform cells: the biomimetic cellular actuator.

Within the framework of a biomimetic top-down approach, our study started with the technical question of the development of a hinge-free and compliant actuator inspired by plant movements. One meaningful biological concept generator was the opening and closing movements of the leaf halves of grasses. Functional morphological investigations were carried out on the selected model plant Sesleria nitida. The results formed the basis for further clarifying the functional movement principle with a particular focus on the role of turgor changes in bulliform cells on kinetic amplification. All findings gained from the investigations of the biological model were incorporated into a finite-element analysis, as a prerequisite for the development of a pneumatic cellular actuator. The first prototype consisted of a row of single cells positioned on a plate. The cells were designed in such a way that the entire structure bent when the pneumatic pressure applied to each individual cell was increased. The pneumatic cellular actuator thus has the potential for applications on an architectural scale. It has subsequently been integrated into the midrib of the facade shading system Flectofold in which the bending of its midrib controls the hoisting of its wings.

МОРФОЛОГИЧЕСКАЯ ИЗМЕНЧИВОСТЬ ЛИСТЬЕВ КАК ПОКАЗАТЕЛЬ АДАПТИВНОСТИ BETULA PENDULA ROTH К ЭКСТРЕМАЛЬНЫМ ЛЕСОРАСТИТЕЛЬНЫМ УСЛОВИЯМ

The results of research in 2019, which were performed on the territory of the Ufa industrial centre in contrasting forest conditions, are presented. On the same sample area, the same plant species may have a similar leaf shape, but different sizes (large-leaved trees and small-leaved trees). This paper presents the results of research on large-leaved trees. We determined the integral parameters of asymmetry of birch leaf plates and performed a dispersion analysis based on five characteristics. We determined that July is the most informative month. It was during this period that the Fisher test revealed differences in three features: the 1st feature (width of the leaf halves), the 3rd feature (distance between the bases of the first and second veins of the second order), and the 4th feature (distance between the ends of the first and second veins of the second-order). The obtained results indicate the seasonal dynamics of indicators of fluctuating asymmetry of leaves of hanging birch trees. This results should be taken into account when monitoring the state of the environment.

The impact of rainfall in remobilising particulate matter accumulated on leaves of four evergreen species grown on a green screen and a living wall

Green walls have recently been identified as a green infrastructure (GI) solution to the problem of particulate matter (PM) air pollution. Green wall systems mostly use evergreen plants as the leaves are retained throughout the year; however, researchers have argued that evergreen foliage becomes saturated with PM and fails to capture more due to a long retention time on the leaves. This study evaluated the potential of (simulated) rainfall to remobilise these captured PM and renew the capture ability of the leaf surfaces of four evergreen species (Heuchera villosa Michx, Helleborus × sternii Turrill, Bergenia cordifolia (Haw.) Sternb., Hedera helix L.) used in a living wall and a green screen located along a busy road in Stoke-on-Trent, UK. The approach used compared PM densities on pre- and post-rain exposed leaf surfaces (using leaf halves of the same leaf) and using a paired t-test to identify any significant reduction in PM due to the rainfall. An Environmental Scanning Electron Microscope (ESEM) and ImageJ image analysis software were employed to quantify the PM densities on leaves. The reduction of PM on leaves, following exposure to 16 mm hr−1 simulated rain in six different rainfall durations was estimated in all four species in order to evaluate any variable impact of rainfall on different species of plants. PM wash-off levels on leaves of H. helix by 41 mm hr−1 rain was also evaluated, using the same rainfall durations, to assess any differential impact of rainfall intensity on PM wash-off. This study revealed a significant impact of rainfall in washing the particles off the leaves in all rainfall durations used. A one-way Anova in a Generalised Linear Model showed a differential impact of rainfall in remobilising PM on different species of plants. The rainfall with higher intensity (41 mm hr−1) showed a significantly higher impact on PM wash-off compared to 16 mm hr−1 rain. The results of this study demonstrated the potential of green walls to act as good PM traps throughout the year by recycling their capture surfaces.

Towards More Realistic Leaf Shapes in Functional-Structural Plant Models

Fluctuating asymmetry in plant leaves is a widely used measure in geometric morphometrics for assessing random deviations from perfect symmetry. In this study, we considered the concept of fluctuating asymmetry to improve the prototype leaf shape of the functional-structural plant model L-Cucumber. The overall objective was to provide a realistic geometric representation of the leaves for the light sensitive plant reactions in the virtual plant model. Based on three-dimensional data from several hundred in situ digitized cucumber leaves comparisons of model leaves and measurements were conducted. Robust Bayesian comparison of groups was used to assess statistical differences between leaf halves while respecting fluctuating asymmetries. Results indicated almost no directional asymmetry in leaves comparing different distances from the prototype while detecting systematic deviations shared by both halves. This information was successfully included in an improved leaf prototype and implemented in the virtual plant model L-Cucumber. Comparative virtual plant simulations revealed a slight improvement in plant internode development against experimental data using the novel leaf shape. Further studies can now focus on analyses of stress on the 3D-deformation of the leaf and the development of a dynamic leaf shape model.

Fluctuating asymmetry of birch leaves did not increase with pollution and drought stress in a controlled experiment

Fluctuating asymmetry (FA), defined as small, non-directional deviations from perfect symmetry in morphological characters, is often recommended as a handy indicator of environmental stress. A reliance on observational data to provide empirical evidence for the effects of different stressors on FA, in combination with increasing attempts to use FA in environmental research, underscore the need for careful examination of the relationships between environmental stress and FA. We experimentally tested the hypotheses that (i) heavy metal and drought stress increase the leaf FA in plants, and that (ii) plants persisting in heavily polluted sites possess greater stress tolerance and therefore show smaller increases in leaf FA in response to heavy metals than do plants from unpolluted sites. We collected mountain birch, Betula pubescens subsp. czerepanovii, seeds from eight polluted and ten unpolluted sites and reared the seedlings in a sophisticated greenhouse (phytotron). We compared leaf FA between control seedlings, seedlings irrigated with water containing copper and nickel sulphates, and seedlings exposed to drought. Leaf FA showed no response to either heavy metals or drought, despite significant impacts of these treatments on seedling height, leaf size and photosynthetic efficiency. This FA result was independent of the level of pollution at the site of seed origin and consistent for FA values based on low and high accuracy measurements of leaf width, as well as for FA values based on measurements of the widths and areas of leaf halves. Our findings add to accumulating evidence regarding inconsistent relationships between FA and abiotic stress, thereby questioning the indicatory value of FA. We strongly recommend that the use of FA as an indicator of environmental stress be limited to study systems for which the existence of cause-and-effect relationship between the stressing impact and the changes in FA is confirmed by controlled, blinded experiments.

A simplified technique to detect variations of leaf chlorogenic acid levels between and within plants caused by maturation or biological stress

Most methods used for the quantification of chlorogenic acids (CGA) in plant tissue use a multi-step organic solvent extraction, which improves accuracy but is laborious and time-consuming. We needed a simpler technique that would allow us to compare the effects of various bacterial treatments on leaf tissue CGA levels over time. Here we describe such a technique that was rapid, used less tissue, and was highly reproducible. The final technique involved grinding a small amounts of leaf tissue in acidified water, which helped stabilize the phenolics, and after clarification by centrifugation could directly be analyzed by Ultra High Performance Liquid Chromatography with Ultraviolet and Mass spectrophotometer detectors (UHPLC-UV-MS). Using this method, we found that CGA levels can vary greatly with leaf age, location on the leaf, and between plants. Therefore in order to observe the more subtle changes caused by bacterial treatments, it was essential to first be aware of the CGA variations in plants to find the most homogenous tissue to use. Ultimately, we found that leaf halves were most homogenous and adjacent panels on a same side of the midrib could be used for multiple sampling of a treatment over time. During this study we also found some interesting relationships regarding CGA distribution in the plant.

Reproducibility of fluctuating asymmetry measurements in plants: Sources of variation and implications for study design

Fluctuating asymmetry (FA), i.e. small, non-directional deviations from perfect symmetry in morphological characters, increases under genetic and/or environmental stress. Ecological and evolutionary studies addressing FA became popular in past decades; however, their outcomes remain controversial. The discrepancies might be at least partly explained by inconsistent and non-standardised methodology. Our aim was to improve the methodology of these studies by identifying factors that affect the reproducibility of FA measurements in plant leaves. Six observers used a highly standardised measurement protocol to measure FA using the width, area and weight of the same set of leaves of 10 plant species that differed in leaf size, shape of the leaf margin and other leaf traits. On average, 24% of the total variation in the data was due to measurement error. Reproducibility of measurements varied with the shape of leaf margin, leaf size, the measured character and the experience of the observer. The lowest reproducibility of the width of leaf halves was found for simple leaves with serrate margins and the highest for simple leaves with entire margins and for compound pinnate leaves. The reproducibility was significantly lower for the weight of leaf halves than for either their width or area, especially for plants with small leaves. The reproducibility was also lower for measurements made by experienced observers than by naïve observers. The size of press-dried leaves decreased slightly but significantly relative to fresh leaves, but the FA of press-dried leaves adequately reflected the FA of fresh leaves. In contrast, preservation in 60% ethanol did not affect leaf size, but it decreased the width-based values of FA to 89.3% of the values measured from fresh leaves. We suggest that although reproducibility of leaf FA measurements depends upon many factors, the shape of the leaf margin is the most important source of variation. We recommend, whenever possible, choosing large-leaved plants with entire leaf margins as model objects for studies involving measurements of FA using the width of leaf halves. These measurements should be conducted with high accuracy from images of fresh or press-dried leaves.

Blueberry necrotic ring blotch virus in Southern Highbush Blueberry: Insights into In Planta and In-Field Movement.

Blueberry necrotic ring blotch virus (BNRBV) causes an emerging disease of southern highbush blueberry (SHB) in the southeastern United States. Disease incidence and severity vary considerably from year to year within the same planting. Experiments were conducted to determine how the virus spreads in the field. Leaf tissue from symptomatic field plants tested positive for BNRBV in 2011, whereas the same plants were asymptomatic in 2012 and tested negative for the virus. Symptomatic and asymptomatic leaves from individual shoots were tested for the presence of the virus, and symptomatic leaves tested positive (100%), whereas 65.4% of the asymptomatic leaves from the same shoots tested negative. Leaves were selected in which half the leaf blade was symptomatic and the other half was not; symptomatic leaf halves tested positive (100%), whereas 76.0% of the asymptomatic halves from the same leaf tested negative for the virus. When virus-free, potted trap plants were interspersed in the field among established plants that had shown disease symptoms the previous year, disease onset in trap plants was observed 2 to 3 weeks after disease onset in field plants. In a separate experiment, asymptomatic softwood cuttings were collected from mother plants symptomatic for BNRBV, rooted, and monitored for symptom development for a period of 12 to 27 months. No BNRBV symptoms were observed in the progeny, whereas disease incidence was high for cuttings taken at the same time from plants infected with Blueberry red ringspot virus used as a control. Collectively, these studies suggest that BNRBV does not infect SHB plants systemically and is not transmitted through vegetative propagation, and that the virus likely does not persist in plants after natural defoliation in the fall.

Increased size of epidermal cells in Syringa josikaea Jacq. smaller leaf side as an adaptive mechanism for reducing its asymmetry

Comparative study of quantitative anatomy of the epidermis in Syringa josikaea Jacq. leaf halves of different width was conducted in order to analyze the possible mechanism of formation of the value of fluctuating leaf asymmetry. A regular decrease in the density of main epidermal cells in the smaller leaf half compared with the bigger one was traced during leaf ontogeny. Stomatal index was equal in different-sized leaf halves. Adaptive response was found in fully formed leaves; it was aimed at reducing leaf blade fluctuating asymmetry by 23% on average and consisted of compensatory growth--further elongation of main epidermal cells in the smaller half of the leaf. It was concluded that the level of fluctuating leaf asymmetry in Hungary lilac is mainly due to a lower rate of cell division, as well as due to their greater elongation in the smaller half of adult leaf compared with the bigger half.

Clonal variation and stability assay of chimeric Pinot Meunier (Vitis vinifera L.) and descending sports

This project studied the genetic variation of the periclinal grape chimera Pinot Meunier, its natural occurring mutations (loss of trichomes on leaf surfaces) and the German Pinot noir clone Samtrot. Eleven Pinot Meunier clones of French, Italian and foremost German origin, Pinot Meunier mutations of differing ages and with various dispersions of hairless sectors as bud-, shoot- and complete vine mutations and six Samtrot clones were investigated with amplified fragment length polymorphisms (AFLPs) and microsatellites (SSRs). SSR-analysis proved chimerism of all Pinot Meunier clones tested and confirmed identical genotype for all hairless mutations and Samtrot clones at the analyzed loci. Clonal variation was shown by AFLP-analysis yielding a total of 670 bands out of 18 primer combinations of which 161 were polymorphic. Pinot Meunier, Samtrot and the naturally occurring hairless Pinot Meunier mutations could be significantly differentiated. Most of interclonal varying AFLP fragments (mean 1.5% per sample) originated within the groups of Samtrot or Pinot Meunier mutations, whereas intraclonal identity was highest within the Pinot Meunier clones. According to the analysis of molecular variance (AMOVA), variation among wild type and mutated Pinot Meunier leaf halves is significantly smaller than between phenotypically identical Samtrot and Pinot Meunier mutants. Average gene diversity calculated on variability of loci reduced from Samtrot (0.040 ± 0.023) towards Pinot Meunier (0.025 ± 0.013) clones.

Thidiazuron-induced high-frequency plant regeneration from leaf explants of Paulownia tomentosa mature trees

Attempts were made to study the effect of thidiazuron (TDZ) on adventitious shoot induction and plant development in Paulownia tomentosa explants derived from mature trees. Media with different concentrations of TDZ in combination with an auxin were used to induce adventitious shoot-buds in two explant types: basal leaf halves with the petiole attached (leaf explant) and intact petioles. Optimal shoot regeneration was obtained in leaf explants cultured on induction medium containing TDZ (22.7 or 27.3 μM) in combination with 2.9 μM indole-3-acetic acid (IAA) for 2 weeks, and subsequent culture in TDZ-free shoot development medium including 0.44 μM BA for a further 4-week period. The addition of IAA to the TDZ induction medium enhanced the shoot-forming capacity of explants. The caulogenic response varied significantly with the position of the explant along the shoot axis. The highest regeneration potential (85–87%) and shoot number (up to 17.6 shoots/explant) were obtained in leaf explants harvested from the most apical node exhibiting unfolded leaves (node 1). An analogous trend was also observed in intact petiole explants, although shoot regeneration ability was considerably lower, with values ranging from 15% for petioles isolated from node 1 to 5% for those of nodes 2 and 3. Shoot formation capacity was influenced by the genotype, with regeneration frequencies ranging from 50% to 70%. It was possible to root elongated shoots (20 mm) in basal medium without growth regulators; however, rooting frequency was significantly increased up to 90% by a 7-day treatment with 0.5 μM indole-3-butyric acid, regardless of the previous culture period in shoot development medium (4 or 8 weeks). Shoot quality of rooted plantlets was improved not only by IBA treatment but also by using material derived from the 4-week culture period. Regenerated plantlets were successfully acclimatized in the greenhouse 8 weeks after transplanting.

Modelling leaf phototropism in a cucumber canopy.

Leaf phototropism might have significant effects on the light interception, dry matter production and yield of cucumber (Cucumis sativus L.). The objective of the present study was to model the phototropism of leaves in a greenhouse cucumber canopy. The dynamic structural model of cucumber using a parametric L-system was extended to mimic the leaf movement induced by gradients in the local light environment of each leaf. The red to far-red (R : FR) ratio is known to be a driving force in shade avoidance reactions of plants. In the model, R : FR ratios on the left and right leaf half of each individual leaf lamina were calculated and the change in tropism angle per phyllochron was based on the R : FR gradient across the leaf halves. The tropism angle of a leaf describes the deviation of the present leaf azimuth from the initial leaf orientation, which is predefined by the phyllotaxis of the plant. Even in its simple form, the model simulated photo-morphogenic canopy responses.

Three-dimensional lamina architecture alters light-harvesting efficiency in Fagus: a leaf-scale analysis.

Modification of foliage exposition and morphology by seasonal average integrated quantum flux density (Qint) was investigated in the canopies of the shade-tolerant late-successional deciduous tree species Fagus orientalis Lipsky and Fagus sylvatica L. Because the leaves were not entirely flat anywhere in the canopy, the leaf lamina was considered to be three-dimensional and characterized by the cross-sectional angle between the leaf halves (theta). Both branch and lamina inclination angles with respect to the horizontal scaled positively with irradiance in the canopy, allowing light to penetrate to deeper canopy horizons. Lamina cross-sectional angle varied from 170 degrees in the most shaded leaves to 90-100 degrees in leaves in the top of the canopy. Thus, the degree of leaf rolling increased with increasing Qint, further reducing the light-interception efficiency of the upper-canopy leaves. Simulations of the dependence of foliage light-interception efficiency on theta demonstrated that decreases in theta primarily reduce the interception efficiency of direct irradiance, but that diffuse irradiance was equally efficiently intercepted over the entire range of theta values in our study. Despite strong alteration in foliage light-harvesting capacity within the canopy and greater transmittance of the upper crown compared with the lower canopy, mean incident irradiances varied more than 20-fold within the canopy, indicating inherent limitations in light partitioning within the canopy. This extensive canopy light gradient was paralleled by plastic changes in foliar structure and chemistry. Leaf dry mass per unit area varied 3-4-fold between the canopy top and bottom, providing an important means of scaling foliage nitrogen contents and photosynthetic capacity per unit area with Qint. Although leaf structure versus light relationships were qualitatively similar in all cases, there were important tree-to-tree and species-to-species variations, as well as evidence of differences in investments in structural compounds within the leaf lamina, possibly in response to contrasting leaf water availability in different trees.

Effect of Figaren, an Antiviral Protein from Cucumis figarei, on Cucumber mosaic virus Infection

Local lesion formation on cowpea leaves was more than 50% inhibited by treatment with a 23 kDa RNase-like glycoprotein from Cucumis figarei, figaren, from 24 hr before to 1 hr after inoculation with Cucumber mosaic virus (CMV). CMV accumulation detected by ELISA in tobacco leaves treated with figaren 6 or 0 hr before inoculation with CMV was suppressed. When upper leaves of tobacco plants were treated with figaren and inoculated 10 min later with CMV, mosaic symptoms were delayed for 5–7 days on most of the tobacco plants, and some plants remained asymptomatic. From fluorescence in situ hybridization, infection sites were present in figaren-treated cowpea or melon leaves after inoculation with CMV, though the sites were reduced in number and size compared with those in water-treated control leaves. The amount of CMV RNAs and CMV antigen in melon protoplasts inoculated with CMV and subsequently incubated with figaren similarly increased with time as did that in the control. ELISA and local lesion assays indicated that CMV infection on the upper surfaces of the leaves of tobacco, melon, cowpea and C. amaranticolor whose lower surfaces had been treated with figaren 5–10 min before CMV inoculation was almost completely inhibited. Figaren did not inhibit CMV infection on the opposite untreated leaf halves of melon, cowpea and C. amaranticolor, whereas it almost completely inhibited CMV infection on the untreated halves of leaves of tobacco. CMV infection was not inhibited in the untreated upper or lower leaves of the four plants. These data suggest that figaren does not completely prevent CMV invasion but does inhibit the initial infection processes. It may also induce localized acquired resistance in host plants.

Involvement of lipoxygenase, lipoxygenase pathway volatiles, and lipid peroxidation during the hypersensitive reaction of pepper leaves to Xanthomonas campestris pv. vesicatoria

Lipoxygenase activity and protein, production of lipid-derived volatiles, and lipid peroxidation levels were determined in pepper (Capsicum annuum L., cv. Early Calwonder-10R) leaves during the hypersensitive reaction induced by avirulent race 2 of Xanthomonas campestris pv. vesicatoria. Lipoxygenase activity increased during the collapse phase of the hypersensitive reaction (8 to 12 h after inoculation), and an increase in electrolyte leakage occurred. However, Western blot analysis revealed that lipoxygenase proteins decreased during the same period. When only one longitudinal half of a pepper leaf was inoculated with the avirulent bacterium race, a significant increase in lipoxygenase activity was observed in both inoculated and noninoculated leaf halves, 10 h after inoculation. In addition, lipoxygenase protein decreased in inoculated leaf halves, but remained unchanged in noninoculated ones. The evolution of some volatile compounds derived from the lipoxygenase pathway [(E,E)-2,4-hexadienal, 1-hexanol, 3-hexen-1-ol, 2,4-hexadienal and 2,4-eptadienal] and carotenoid degradation (α- and β-ionone) increased in the incompatible interaction during the collapse phase of the hypersensitive reaction. The level of the oxidative index (A235/A205) of leaf lipid extracts, determined to estimate lipid peroxidation, significantly increased in the advanced stage of the hypersensitive reaction. Furthermore, determination of the oxidative index in neutral lipid, glycolipid and phospholipid fractions showed that the oxidative index was significantly increased only in the glycolipid fraction. Lipoxygenase activity and protein, electrolyte leakage, volatiles and lipid peroxidation were not changed in pepper leaves inoculated with the virulent race 1 of X. campestris pv.vesicatoria during the time interval considered (2–12 h after inoculations). The hypothesis that a lipoxygenase with chloroplastic location is induced in the incompatible interaction, and which is responsible for the increase in lipid peroxidation is advanced.