Biological synthesis of gold nanoparticles using Magnolia kobus and Diopyros kaki leaf extracts

Leaf extracts of two plants, Magnolia kobus and Diopyros kaki, were used for ecofriendly extracellular synthesis of metallic gold nanoparticles. Stable gold nanoparticles were formed by treating an aqueous HAuCl₄ solution using the plant leaf extracts as reducing agents. UV–visible spectroscopy was used for quantification of gold nanoparticle synthesis. Only a few minutes were required for >90% conversion to gold nanoparticles at a reaction temperature of 95 °C, suggesting reaction rates higher or comparable to those of nanoparticle synthesis by chemical methods. The synthesized gold nanoparticles were characterized with inductively coupled plasma spectrometry (ICP), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and particle analysis using a particle analyzer. SEM and TEM images showed that a mixture of plate (triangles, pentagons, and hexagons) and spherical structures (size, 5–300 nm) were formed at lower temperatures and leaf broth concentrations, while smaller spherical shapes were obtained at higher temperatures and leaf broth concentrations.     

Assessing photosystem I and II distribution in leaves from C4 plants using confocal laser scanning microscopy

Images of chlorophyll fluorescence emitted at wavelengths above and below 700 nm were recorded from leaf sections of C₄ species using confocal laser scanning microscopy (LSM). We investigated species exhibiting both NAD-malic enzyme (NAD-ME) C₄ photosynthesis and NADP-malic enzyme (NADP-ME) C₄ photosynthesis. Comparing LSM fluorescence of leaf sections with flow-cytometrically determined fluorescence from individual chloroplasts revealed that LSM fluorescence was distorted by the optical properties of leaf sections. Leaf section fluorescence, when corrected by transmission data derived from light transmission images, agreed with flow cytometry data. The corrected LSM fluorescence yielded information on the distribution of the individual photosystems in the C₄ leaf sections: PSII concentrations in bundle sheath cells were elevated in NAD-ME species but diminished in most of the NADP-ME species investigated. The NADP-ME species, Arundinella hirta, however, showed normal PSII and increased PSI concentration in bundle sheath chloroplasts. Finally, a gradient of PSI was observed within the bundle sheath cells from Euphorbia maculata.     

Micromechanics of smooth adhesive organs in stick insects: pads are mechanically anisotropic and softer towards the adhesive surface

Animals have evolved adhesive structures on their legs to cling to the substrate during locomotion. Here we characterise the ultrastructure and mechanical properties of adhesive pads in Carausius morosus (Phasmatodea) using atomic force microscopy (AFM) as well as transmission and scanning electron microscopy (TEM, SEM). The smooth adhesive arolium has a soft cuticle consisting of principal rods, which branch into finer fibres near the surface. Indentation experiments showed that the pad material consists of distinct layers with different mechanical properties. The 100–300 nm thick outermost layer consisting of the cuticulin envelope and the epicuticle is extremely soft and resilient (mean effective Young’s modulus 12 kPa), while the subjacent procuticle is a much stiffer material (mean effective Young’s modulus 625 kPa). AFM contact mode imaging revealed that the cuticle is mechanically anisotropic, which can be explained by its fibrillar inner structure. We propose that the described layered structure of smooth adhesive pads, consisting of materials decreasing in stiffness towards the outer surface, represents a superior design to conform and adhere to substrates with roughnesses at different length scales. This design principle could be easily implemented in technical adhesives, and thus has a potential to inspire biomimetic applications.     

Stomatal characteristics,conductance ratios,and drought-induced leaf modifications of semiarid grassland species

Seventeen greenhouse-grown grasses from the Nebraska Sandhills region were surveyed for foliar stomatal density and distribution, closed guard cell lengths, open stomatal apertures, and surface characteristics (using scanning electron microscopy), surface conductance (using a steady-state porometer), and drought-induced leaf modifications. Leaves of C₃ species exhibited a proclivity toward being amphistomatic or hyperstomatic, while C₄ species tended to be more hypostomatic. Leaf modification, when it occurred, resulted in the enshrouding of the adaxial surface. Conductance data showed functional amphistomaty in most species, revealing differential functioning of adaxial and abaxial stomata. Conductance patterns were not closely related to stomatal aperture per unit area leaf surface or to stomatal distribution patterns. Lowered adaxial: abaxial conductance ratios, increased stomatal density, reduced stomatal size, and less drought-induced leaf modification were seen in C₄ grasses as compared with C₃ grasses. C₃ range and C₃ meadow species did not differ in conductance ratios, density ratios, or stomatal size, although meadow species exhibited much greater drought-induced leaf modification. Postulations involving correlation of adaxial: abaxial conductance ratios to stomatal distribution patterns, and assumptions of stomatal distribution based upon habitat and/or photosynthetic pathway may be erroneous. These characteristics may be of limited usefulness as morphological indicators in the search for drought-tolerant ecotypes of prairie grasses.     

Modelling sugar diffusion across plant leaf cuticles: the effect of free water on substrate availability to phyllosphere bacteria

We present a continuous model for the diffusion of sugars across intact plant leaf cuticles. It is based on the flow of sugars from a source, representing the leaf apoplast, to a sink, in the shape of a hemispherical drop of water on the outside of the cuticle. Flow is a function of the difference between sugar concentrations C_Source and C_Sink, permeability P of the cuticle, volume V_Sink of the water drop, as well as its contact angle α with the cuticle surface. Using a bacterial bioreporter for fructose, and a two‐compartment experimental set‐up consisting of isolated cuticles of walnut (Juglans regia) carrying water droplets while floating on solutions with increasing concentrations of fructose, we determined a value of 1 × 10^?6 m h^?1 for P. Using this value, we explored different scenarios for the leaching of sugars across plant leaf cuticles to reveal in quantitative terms how diffusion takes longer when V_Sink increases, P decreases or α increases. Bacterial growth was modelled as a function of changes in P, α and V_Sink and was consistent with observations or suggestions from the literature in relation to the availability of free water on leaves. These results are discussed in the light of bacteria as ecosystem engineers, i.e. with the ability to modify the plant leaf surface environment in favour of their own survival, e.g. by increasing cuticle leakage or leaf wetness. Our model represents a first step towards a more comprehensive model which will enhance our quantitative understanding of the factors that play a role in nutrient availability to bacterial colonizers of the phyllosphere, or plant leaf surface.     

Leaf wax n‐alkane patterns of six tropical montane tree species show species‐specific environmental response

It remains poorly understood how the composition of leaf wax n‐alkanes reflects the local environment. This knowledge gap inhibits the interpretation of plant responses to the environment at the community level and, by extension, inhibits the applicability of n‐alkane patterns as a proxy for past environments. Here, we studied the n‐alkane patterns of five Miconia species and one Guarea species, in the Ecuadorian Andes (653–3,507 m a.s.l.). We tested for species‐specific responses in the average chain length (ACL), the C₃₁/(C₃₁ + C₂₉) ratio (ratio), and individual odd n‐alkane chain lengths across an altitudinally driven environmental gradient (mean annual temperature, mean annual relative air humidity, and mean annual precipitation). We found significant correlations between the environmental gradients and species‐specific ACL and ratio, but with varying magnitude and direction. We found that the n‐alkane patterns are species‐specific at the individual chain length level, which could explain the high variance in metrics like ACL and ratio. Although we find species‐specific sensitivity and responses in leaf n‐alkanes, we also find a general decrease in “shorter” (<C₂₉) and an increase in “longer” (>C₃₁) chain lengths with the environmental gradients, most strongly with temperature, suggesting n‐alkanes are useful for reconstructing past environments.     

Effect of soil drying on growth,biomass allocation and leaf gas exchange of two annual grass species

Influence of short-term water stress on plant growth and leaf gas exchange was studied simultaneously in a growth chamber experiment using two annual grass species differing in photosynthetic pathway type, plant architecture and phenology:Triticum aestivum L. cv. Katya-A-1 (C₃, a drought resistant wheat cultivar of erect growth) andTragus racemosus (L.) All. (C₄, a prostrate weed of warm semiarid areas). At the leaf level, gas exchange rates declined with decreasing soil water potential for both species in such a way that instantaneous photosynthetic water use efficiency (PWUE, mmol CO₂ assimilated per mol H₂O transpired) increased. At adequate water supply, the C₄ grass showed much lower stomatal conductance and higher PWUE than the C₃ species, but this difference disappeared at severe water stress when leaf gas exchange rates were similarly reduced for both species. However, by using soil water more sparingly, the C₄ species was able to assimilate under non-stressful conditions for a longer time than the C₃ wheat did. At the whole-plant level, decreasing water availability substantially reduced the relative growth rate (RGR) ofT. aestivum, while biomass partitioning changed in favour of root growth, so that the plant could exploit the limiting water resource more efficiently. The change in partitioning preceded the overall reduction of RGR and it was associated with increased biomass allocation to roots and less to leaves, as well as with a decrease in specific leaf area. Water saving byT. racemosus sufficiently postponed water stress effects on plant growth occurring only as a moderate reduction in leaf area enlargement. For unstressed vegetative plants, relative growth rate of the C₄ T. racemosus was only slightly higher than that of the C₃ T. aestivum, though it was achieved at a much lower water cost. The lack of difference in RGR was probably due to growth conditions being relatively suboptimal for the C₄ plant and also to a relatively large investment in stem tissues by the C₄ T. racemosus. Only 10% of the plant biomass was allocated to roots in the C₄ species while this was more than 30% for the C₃ wheat cultivar. These results emphasize the importance of water saving and high WUE of C₄ plants in maintaining growth under moderate water stress in comparison with C₃ species.     

Endophytic Colonisation of Opium Poppy, Papaver somniferum, by an Entomopathogenic Beauveria bassiana Strain

Beauveria bassiana strain EABb 04/01-Tip isolated from stem-borer larvae of Timaspis papaveris (Hymenoptera: Cynipidae), a serious pest of opium poppy in Spain, was shown to be able to become established endophytically in this pharmaceutical crop. Microbiological, molecular and light and electron microscopic methods were used to study fungal colonisation and to describe its mode of penetration. After inoculation with a foliar spray of conidia, microbiological methods showed 100% of plants examined 24, 48, 72 and 144 h after treatment to be colonised endophytically by the fungus, although the percentage of previously surface sterilised leaf pieces showing fungal growth was 100% at 24 and 48 h, and 80 and 75% at 72 and 144 h after treatment, respectively. The fungus was also observed in leaf pieces obtained from newly formed leaves, indicating that it could spread from treated leaves to leaves formed after fungal application. For molecular studies, a polymerase chain reaction (PCR) protocol was used to amplify the ITS1-5.8S-ITS2 regions of the rDNA of the plant and the fungus. This procedure allowed the detection of the fungus on the surface of the leaves and also endophytically, but only at 72 h after treatment. A nucleotide BLAST search revealed that the ITS1-5.8S-ITS2 sequence of strain EABb 04/01-Tip showed 100% homology with a similar sequence from Cordyceps bassiana. SEM images revealed that although numerous conidia were observed on the leaf surface, few germinated and penetrated. Intracellular colonisation by B. bassiana was not observed, but hyphae were detected growing into the xylem vessels. The fungus was found to colonise 40.5 ± 4.3% of seedlings (with two cotyledons and the two first real leaves) from seeds dressed with a fungal spore suspension. These results may have implications in the biological control of T. papaveris, including the possible systemic protection of the plant against this cynipid.     

Composition,structure, and biological properties of lipopolysaccharides from different strains of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">atrofaciens</Emphasis>

The composition, structure, and certain biological properties of lipopolysaccharides (LPS) isolated from six strains of bacteria Pseudomonas syringae pv. atrofaciens pathogenic for grain-crops (wheat, rye) are presented. The LPS-protein complexes were isolated by a sparing procedure (extraction from microbial cells with a weak salt solution). They reacted with the homologous O sera and contained one to three antigenic determinants. Against the cells of warm-blooded animals (mice, humans) they exhibited the biological activity typical of endotoxins (stimulation of cytokine production, mitogenetic activity, etc.). The LCD of the biovar type strain was highly toxic to mice sensitized with D-galactosamine. The structural components of LPS macromolecules obtained by mild acidic degradation were characterized: lipid A, core oligosaccharide, and O-specific polysaccharide (OPS). Fatty acids 3-HO-C_10:0, C_12:0, 2-HO-C_12:0, 3-HO-C_12:0, C_16:0, C_16:1, C_18:0, and C_18:1 were identified in lipid A of all the strains, as well as the components of the hydrophilic part: glucosamine (GlcN), ethanolamine (EtN), phosphate, and phosphoethanolamine (EtN-P). In the core LPS, glucose (Glc), rhamnose (Rha), L-glycero-D-manno-heptose (Hep), GlcN, galactosamine (GalN), 2-keto-3-deoxy-D-mannooctonoic acid (KDO), alanine (Ala), and phosphate were present. The O chain of all the strains consisted of repeated elements containing a linear chain of three to four L-(two strains) or D-Rha (four strains) residues supplemented with a single residue of 3-acetamido-3,6-dideoxy-D-galactose (D-Fucp3Nac), N-acetyl-D-glucosamine (D-GlcpNAc), D-fucose (D-Fucf), or D-Rhap (strain-dependent) as a side substituent. In different strains the substitution position for Rha residues in the repeated components of the major rhamnan chain was also different. One strain exhibited a unique type of O-chain heterogeneity. Immunochemical investigation of the LPS antigenic properties revealed the absence of close serological relations between the strains of one pathovar; this finding correlates with the differences in their OPS structure. Resemblance between the investigated strains and other P. syringae strains with similar LPS structures was revealed. The results of LPS analysis indicate the absence of correlation between the OPS structure and the pathovar affiliation of the strains.     

Gas Exchange,Leaf Structure,and Hydraulic Features in Relation to Sex,Shoot Form,and Leaf Form in An Evergreen Shrub Sabina vulgaris in the Semi-Arid Mu Us Sandland in China

We examined differences in net photosynthetic rate (P _N), transpiration rate (E), water use efficiency (WUE), ratio of substomatal to atmospheric CO₂ concentration (C _i/C _a), cuticle thickness (CT), epidermis cell size (ECS), mesophyll cell size (MCS), vascular bundle size (VBS), tissue density (TD), and coefficient of water loss (k) in Sabina vulgaris as related to sex, shoot form, and leaf form. P _N, E, WUE, C _i/C _a, MCS, VBS, and k varied with sex, whereas CT, ECS, and TD did not. These differences in physiology and anatomy between the female and male plants may be closely related with their reproduction behaviour. P _N, E, C _i/C _a, CT, ECS, MCS, and VBS were significantly smaller in the erect shoots than in the prostrate shoots, WUE was just opposite; TD and k did not vary with shoot form. These changes in physiology with shoot form indicate that erect shoots may be more tolerant of water stress than prostrate shoots. P _N, E, C _i/C _a, TD, and k were significantly greater in the spine leaves than in the scale leaves, whereas WUE, CT, ECS, MCS, and VBS followed the opposite trends. The changes in physiology and anatomy with leaf form suggest that scale leaves have higher drought-resistant and water-holding capacities than spine leaves. Measurements of field gas exchange showed that three-year-old seedlings had lower drought-resistance and higher water loss than five-year-old seedlings, which provides some evidence that seedling survival decreases with decreasing plant age.     

Genotype differences in 13C discrimination between atmosphere and leaf matter match differences in transpiration efficiency at leaf and whole‐plant levels in hybrid Populus deltoides ×nigra

¹³C discrimination between atmosphere and bulk leaf matter (Δ¹³C_lb) is frequently used as a proxy for transpiration efficiency (TE). Nevertheless, its relevance is challenged due to: (1) potential deviations from the theoretical discrimination model, and (2) complex time integration and upscaling from leaf to whole plant. Six hybrid genotypes of Populus deltoides×nigra genotypes were grown in climate chambers and tested for whole‐plant TE (i.e. accumulated biomass/water transpired). Net CO₂ assimilation rates (A) and stomatal conductance (g_s) were recorded in parallel to: (1) ¹³C in leaf bulk material (δ¹³C_lb) and in soluble sugars (δ¹³C_ss) and (2) ¹⁸O in leaf water and bulk leaf material. Genotypic means of δ¹³C_lb and δ¹³C_ss were tightly correlated. Discrimination between atmosphere and soluble sugars was correlated with daily intrinsic TE at leaf level (daily mean A/g_s), and with whole‐plant TE. Finally, g_s was positively correlated to ¹⁸O enrichment of bulk matter or water of leaves at individual level, but not at genotype level. We conclude that Δ¹³C_lb captures efficiently the genetic variability of whole‐plant TE in poplar. Nevertheless, scaling from leaf level to whole‐plant TE requires to take into account water losses and respiration independent of photosynthesis, which remain poorly documented.     

Plant response to drought stress simulated by ABA application: Changes in chemical composition of cuticular waxes

Plant cuticles form the interface between epidermal plant cells and the atmosphere. The cuticle creates an effective barrier against water loss, bacterial and fungal infection and also protects plant tissue from UV radiation. It is composed of the cutin matrix and embedded soluble lipids also called waxes. Chemical composition of cuticular waxes and physiological properties of cuticles are affected by internal regulatory mechanisms and environmental conditions (e.g. drought, light, and humidity). Here, we tested the effect of drought stress simulation by the exogenous application of abscisic acid (ABA) on cuticular wax amount and composition. ABA-treated plants and control plants differed in total aboveground biomass, leaf area, stomatal density and aperture, and carbon isotope composition. They did not differ in total wax amount per area but there were peculiar differences in the abundance of particular components. ABA-treated plants contained significantly higher proportions of aliphatic components characterized by chain length larger than C₂₆, compared to control plants. This trend was consistent both between and within different functional groups of wax components. This can lead to a higher hydrophobicity of the cuticular transpiration barrier and thus decrease cuticular water loss in ABA-treated plants. At both ABA-treated and control plants alcohols with chain length C₂₄ and C₂₆ were predominant. Such a shift towards wax compounds having a higher average chain length under drought conditions can be interpreted as an adaptive response of plants towards drought stress.     

Penetration of chemicals into the Malus leaf cuticle

The adaxial leaf cuticle of Malus pumila was examined by electron microscopy to determine possible avenues for transcuticular movement of foliarly applied chemicals. Cutin-embedded polysaccharide microfibrils originated at the outer epidermal cell wall and occasionally extended to the cuticle surface. Lamellae, ca. 4 nm wide, usually were oriented parallel to the cuticle surface. When oriented perpendicular to the surface, they extended nearly to the subjacent wall layer from the surface. Aqueous solutions of uranyl acetate, silver nitrate and phenyl mercuric acetate applied to the cuticle surface of leaf segments floated on solutions of phosphate salts or thiocarbohydrazide (TCH) reacted within the cuticle to form insoluble electron-opaque deposits indicative of their avenues of transcuticular movement. Uranyl phosphate deposits were observed only in the polysaccharide microfibrils of chloroform: methanolextracted leaves. Silver-TCH deposits were observed in the microfibrils of both extracted and nonextracted leaf cuticles. Phenyl mercuric acetate-TCH deposits were randomly dispersed throughout the extracted cuticle and not associated with the polysaccharide microfibrils.Abbreviations TCH thiocarbohydrazide - PMA phenyl mercuric acetate     

Characterization of the NADP malic enzyme gene family in the facultative,single-cell C<Subscript>4</Subscript> monocot <Emphasis Type="Italic">Hydrilla verticillata</Emphasis>

Hydrilla verticillata has a facultative single-cell system that changes from C₃ to C₄ photosynthesis. A NADP⁺-dependent malic enzyme (NADP-ME) provides a high [CO₂] for Rubisco fixation in the C₄ leaf chloroplasts. Of three NADP-ME genes identified, only hvme1 was up-regulated in the C₄ leaf, during the light period, and it possessed a putative transit peptide. Unlike obligate C₄ species, H. verticillata exhibited only one plastidic isoform that may perform housekeeping functions, but is up-regulated as the photosynthetic decarboxylase. Of the two cytosolic forms, hvme2 and hvme3, the latter exhibited the greatest expression, but was not light-regulated. The mature isoform of hvme1 had a pI of 6.0 and a molecular mass of 64 kD, as did the recombinant rHVME1m, and it formed a tetramer in the chloroplast. The recombinant photosynthetic isoform showed intermediate characteristics between isoforms in terrestrial C₃ and C₄ species. The catalytic efficiency of rHVME1m was four-fold higher than the cytosolic rHVME3 and two-fold higher than recombinant cytosolic isoforms of rice, but lower than plastidic forms of maize. The K _m (malate) of 0.6 mM for rHVME1 was higher than maize plastid isoforms, but four-fold lower than found with rice. A comprehensive phylogenetic analysis of 25 taxa suggested that chloroplastic NADP-ME isoforms arose from four duplication events, and hvme1 was derived from cytosolic hvme3. The chloroplastic eudicot sequences were a monophyletic group derived from a cytosolic clade after the eudicot and monocot lineages separated, while the monocots formed a polyphyletic group. The findings support the hypothesis that a NADP-ME isoform with specific and unusual regulatory properties facilitates the functioning of the single-cell C₄ system in H. verticillata. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf surface wax is a source of plant methane formation under UV radiation and in the presence of oxygen

The terrestrial vegetation is a source of UV radiation‐induced aerobic methane (CH₄) release to the atmosphere. Hitherto pectin, a plant structural component, has been considered as the most likely precursor for this CH₄ release. However, most of the leaf pectin is situated below the surface wax layer, and UV transmittance of the cuticle differs among plant species. In some species, the cuticle effectively absorbs and/or reflects UV radiation. Thus, pectin may not necessarily contribute substantially to the UV radiation‐induced CH₄ emission measured at surface level in all species. Here, we investigated the potential of the leaf surface wax itself as a source of UV radiation‐induced leaf aerobic CH₄ formation. Isolated leaf surface wax emitted CH₄ at substantial rates in response to UV radiation. This discovery has implications for how the phenomenon should be scaled to global levels. In relation to this, we demonstrated that the UV radiation‐induced CH₄ emission is independent of leaf area index above unity. Further, we observed that the presence of O₂ in the atmosphere was necessary for achieving the highest rates of CH₄ emission. Methane formation from leaf surface wax is supposedly a two‐step process initiated by a photolytic rearrangement reaction of the major component followed by an α‐cleavage of the generated ketone.     

Two sides of a leaf blade: <Emphasis Type="Italic">Blumeria graminis</Emphasis> needs chemical cues in cuticular waxes of <Emphasis Type="Italic">Lolium perenne</Emphasis> for germination and differentiation

Plant surface characteristics were repeatedly shown to play a pivotal role in plant–pathogen interactions. The abaxial leaf surface of perennial ryegrass (Lolium perenne) is extremely glossy and wettable compared to the glaucous and more hydrophobic adaxial surface. Earlier investigations have demonstrated that the abaxial leaf surface was rarely infected by powdery mildew (Blumeria graminis), even when the adaxial surface was densely colonized. This led to the assumption that components of the abaxial epicuticular leaf wax might contribute to the observed impairment of growth and development of B. graminis conidia on abaxial surfaces of L. perenne. To re-assess this hypothesis, we analyzed abundance and chemical composition of L. perenne ab- and adaxial epicuticular wax fractions. While the adaxial epicuticular waxes were dominated by primary alcohols and esters, the abaxial fraction was mainly composed of n-alkanes and aldehydes. However, the major germination and differentiation inducing compound, the C₂₆-aldehyde n-hexacosanal, was not present in the abaxial epicuticular waxes. Spiking of isolated abaxial epicuticular Lolium waxes with synthetically produced n-hexacosanal allowed reconstituting germination and differentiation rates of B. graminis in an in vitro germination assay using wax-coated glass slides. Hence, the absence of the C₂₆-aldehyde from the abaxial surface in combination with a distinctly reduced surface hydrophobicity appears to be primarily responsible for the failure of normal germling development of B. graminis on the abaxial leaf surfaces of L. perenne.     

Characterization of mycolic acids from the pathogen Rhodococcus equi by tandem mass spectrometry with electrospray ionization

We describe a simple tandem mass spectrometric approach toward structural characterization of mycolic acids, the long-chain α-alkyl-β-hydroxy fatty acids unique to mycobacteria and related taxa. On collisionally activated dissociation in a linear ion trap or tandem quadrupole mass spectrometer, the [M−H]⁻ ions of mycolic acid generated by electrospray ionization undergo dissociation to eliminate the meroaldehyde residue, leading to formation of carboxylate anions containing α-alkyl chains. The structural information from these fragment ions affords structural assignment of the mycolic acids, including the lengths of the meromycolate chain and the α-branch. This study revealed that the mycolic acids isolated from pathogenic Rhodococcus equi 103 contained a series of homologous ions having C₃₀ to C₅₀ chain with 0–2 double bonds. The α-branch ranged from C₁₀ to C₁₈ with 0 to 1 double bond, in which 16:0 and 14:0 are the most prominent, whereas the meromycolate chain ranged from C₁₄ to C₃₄ with 0 to 2 double bonds. The major molecular species consisted of more than 3 isomers that differ by the lengths of the α-branch or meromycolate chain, and up to 10 isobaric isomers were identified for some minor ions. We also employed tandem quadrupole mass spectrometry with precursor ion and neutral loss scans for profiling mycolic acid with specific structure in mixtures. The tandem spectra obtained from precursor ion scans of m/z 255 (16:0-carboxylate anion) and m/z 227 (14:0-carboxylate anion) may provide a simple specific means for classification of Rhodococci species, whereas tandem spectra from neutral loss of meroaldehyde residue scans provided a simple approach to reveal the mycolic acid molecules with specific meromycolate chain in mixtures.     

Effect of varying environments on photosynthetic parameters of C3, C3-C4 and C4 species of Panicum

Summary CO₂ exchange characteristics and the activity of the carboxylating enzymes phosphoenolpyruvate carboxylase (PEP-C, E.C. 4.1.1.31) and ribulose 1,5-bisphosphate carboxylase (RuBP-C, E.C. 4.1.1.39) during one year in the greenhouse and at two levels of light and temperature in growth chambers were determined in the C₃-C₄ intermediate species P. milioides Nees ex. Trin. These results were compared with those of P. bisulcatum Thumb. (C₃) and P. maximum Jacq. (C₄). Under all tested conditions, and even when the influence of leaf surface temperature on photosynthetic rates and CO₂ compensation points were measured, the biochemical and physiological behaviour of the C₃-C₄ intermediate was more similar to that of the C₃ plant than the C₄ species. The C₄ plant P. maximum, however, responded positively, mainly in terms of PEP-C activity and photosynthetic rate, to the regime of high light and temperature. The results presented indicate that in the C₃-C₄ Panicum grown in high light and temperature no direct relationships between a low CO₂ compesation point and superior growth are evident. It has still to be clarified why in nature a photosynthetic-photorespiratory pathway leading to an intermediate CO₂ compensation value has evolved in P. milioides.     

Monitoring and visualising plant cuticles by confocal laser scanning microscopy

The present work shows the visualisation of phenolics and flavonoids of plant cuticles by confocal laser scanning microscopy (CLSM). Selected isolated fruit and leaf cuticles were monitored on the basis of autofluorescent phenolics and flavonoids which, in most cases, permitted us to obtain three-dimensional images of the cuticular membranes. The utility of this technique in investigations of cuticular translocation and diffusion of exogenous applied chemicals and cuticle degradation has also been explored.     

Fatty Acid Composition of Lipids from Leaves and Strobila of Cycas Revoluta (<Emphasis Type="Italic">Cycas revoluta</Emphasis>)

Fatty acid (FA) composition of lipids from leaves and differentiated fleshy strobila tissues and sporangia with spores of Cycas (Cycas revoluta Thumb.) after their step quantitative extraction from plant material was investigated. Quantitative content and qualitative composition of FAs of extractable and nonextractable leaf lipids were determined. It was established that flesh lipids of sporophylls are characterized by a high saturation level and contain a considerable proportion of saturated FAs with the usual chain length (C₁₂–C₁₈, 53–57%). At the same time, total amount of etherified FAs with a very long chain in lipids not extractable by the method of Zhukov and Vereshchagin exceeds several times that found in extractable lipids (~15 and ~4%, respectively). Neutral lipids of Cycas spores were represented by triacylglycerols, the lower-alkyl esters of FAs, free FAs, and sterol esters.