The fungitoxicities of plant furocoumarins

A mixture of the furocoumarins pimpinellin, isopimpinellin, isobergapten and sphondin isolated from Heracleum sphondylium root was toxic to Gloeosporium limetticola, Botryis cinerea, Sclerotinia fructigena and Stereum purpureum at 200 p.p.m. or less in nutrient medium. The extractive of the leaves of plants that contain furocoumarins suppressed in vivo growth of G. limetticola and B. cinerea at concentrations lower than the contents of the extractive in the leaves. Furocoumarins may form an important class of natural defensive agents against fungi; this possibility is discussed.     

Exploring the thiazole scaffold for the identification of new agents for the treatment of fluconazole resistant Candida

Cyclohexyliden- and 2-methylcyclohexyliden-hydrazo-4-arylthiazoles were synthesized and tested as antifungal agents. All compounds exhibited minimal inhibitory concentration (MIC) values comparable with those of fluconazole (FLC). Moreover, some compounds showed fungicidal activity at low concentration. Worth noting five out of nine compounds were active towards Candida albicans 25 FLC resistant isolated from clinical specimens. The cellular toxicity was evaluated and none of the compounds is toxic at the MIC. On the basis of our data we can conclude that these derivatives are promising agents for the treatment of resistant C. albicans.     

The Heterogeneity of Structural and Functional Photosynthetic Characteristics of Mesophyll Chloroplasts in Various Parts of Mature or Senescing Leaf Blade of Two Maize (Zea Mays L.) Genotypes

Differences in ultrastructural parameters of mesophyll cell (MC) chloroplasts, contents of photosynthetic pigments, and photochemical activities of isolated MC chloroplasts were studied in the basal, middle, and apical part of mature or senescing leaf blade of two maize genotypes. A distinct heterogeneity of leaf blade was observed both for structural and functional characteristics of chloroplasts. In both mature and senescing leaves the shape of MC chloroplasts changed from flat one in basal part of leaf to nearly spherical one in leaf apex. The volume density of granal thylakoids decreased from leaf base to apex in both types of leaves examined, while the amount of intergranal thylakoids increased in mature leaves but decreased in senescing leaves. The most striking heterogeneity was found for the quantity of plastoglobuli, which strongly increased with the increasing distance from leaf base. The differences in chloroplast ultrastructure were accompanied by differences in other photosynthetic characteristics. The Hill reaction activity and activity of photosystem 1 of isolated MC chloroplasts decreased from leaf base to apex in mature leaves. Apical part of senescing leaf blade was characterised by low contents of chlorophyll (Chl) a and Chl b, whereas in mature leaves, the content of Chls as well as the content of total carotenoids (Car) slightly increased from basal to apical leaf part. This was reflected also in the ratio Chl (a+b)/total Car; the ratio of Chl a/b did not significantly differ between individual parts of leaf blade. Both genotypes examined differed in the character of developmental gradient observed along whole length of leaf blade.     

Leaf Cuticular Waxes of Bermudagrass Response to Environment-Driven Adaptations of Climate Effect Inferred from Latitude and Longitude Gradient in China

Bermudagrass (Cynodon dactylon) is a widely used warm season lawn grass. Cuticular wax covering the surface of plant leaves plays an important role in helping plants resist biotic and abiotic stresses. We analyzed the changes of cuticle wax in 25 bermudagrass populations from different longitude and latitude gradients, in order to verify how environmental conditions affect the structure and chemical composition of cuticle wax. Five wax components were identified, including alkanes, esters, alkenes, aldehydes and primary alcohols. The wax characteristics were divided into two principal components, explaining 58.2 % and 66.7 % of the total variability in latitude and longitude, even some populations had a certain correlation with each other. Pearson correlation analysis further showed that the total wax coverage, wax component content and antioxidant enzyme activity of bermudagrass populations on the latitudinal gradient had different responses to environmental factors. Finally, nineteen key genes involved in wax biosynthesis, redox and photosynthesis were identified and verified by RT-qPCR. The results showed that the responses of bermudagrass in different populations to climate change were quite different, which was of great significance for the evolution of bermudagrass populations.     

Determination of diffusion coefficients of octadecanoic acid in isolated cuticular waxes and their relationship to cuticular water permeabilities

Transport properties of cuticular waxes from 40 different plant species were investigated by measuring desorption rates of ¹⁴C-labelled octadecanoic acid from isolated and subsequently reconstituted wax. Diffusion coefficients (D) of octadecanoic acid in reconstituted waxes, calculated from the slopes of the regression lines fitted to the linearized portions of desorption kinetics, ranged from 1.2 × 10^?19 m² s^?1 (Senecio kleinia leaf) to 2.9 × 10^?17 m² s^?1 (Malus cf. domestica fruit). Cuticular water permeabilities (cuticular transpiration) measured with intact cuticular membranes isolated from 24 different species varied from 1.7 × 10^?11 m s^?1 (Vanilla planifolia leaf) up to 2.1 × 10^?9 m s^?1 (Malus cf. domestica fruit), thus covering a range of more than 2 orders of magnitude. Cuticular water permeabilities were highly correlated with diffusion coefficients of octadecanoic acid in isolated cuticular wax of the same species. It is therefore possible to estimate cuticular barrier properties of stomatous leaf surfaces or of leaves where isolation of the cuticle is impossible by measuring D of octadecanoic acid in isolated waxes of these leaves.     

Feeding site selection of first-instar larvae of Cnaphalocrocis medinalis on susceptible and resistant rice plants

More first-instar larvae of the rice leaffolder, Cnaphalocrocis medinalis (Guenée), were recovered from susceptible IR36 and Roxoro rice varieties than resistant TKM6 and Oryza perennis, 24 h after infestation. Within a rice plant, a higher proportion of larvae was recovered from young whorl leaf, followed by mature leaves and leafsheaths on all the four rice varieties tested. However, differences were observed between susceptible and resistant varieties in the distribution of larvae on these three plant parts. In laboratory choice tests, first-instar larvae preferred to settle on the young leaves of IR36 and TKM6 when presented with their respective mature leaves. No such preference was observed in tests with Rexoro and O. perennis. Larval survival was similar on young and mature leaves of Rexoro. Young leaves of IR36 and TKM6 were more suitable for survival in comparison with their respective mature leaves while the reverse was true for O. perennis. Larval movement was slower on the mature leaves and larvae took longer to reach the whorl leaf of TKM6 than on IR36. The density of trichomes of the abaxial surface of TKM6 was higher than that of the other varieties tested. Adaptive significance of feeding in the leafwhorl to young larvae is discussed.     

Lognormal distribution of water permeability and organic solute mobility in plant cuticles

It is shown that water permeabilities and organic solute mobilities in plant cuticles have a lognormal distribution. Seven-hundred and fifty values for rate constants of desorption (～mobility) of 2,4-D from isolated Citrus aurantium L. cuticles from a population of leaves were pooled and analysed. A histogram of the rate constants of individual cuticles showed a skew distribution with a strong tail to higher values. Cuticular membranes with high values did not differ from others in visual appearance and were not leaky. After log-transformation of original data an almost perfect normal distribution was obtained. Statistical tests showed that a normal distribution of original values is not acceptable. Inspection of older data for water permeability in the same species and experiments using large samples of cuticles from leaves of Pyrus communis L. and Stephanotis floribunda Brongn. and from fruits of Capsicum annuum L. showed a similar distribution, as did inspection of data for experiments with organic solutes. A lognormal distribution was found for cuticles of plants from growth chambers, glasshouses and outdoors as well as for water permeability of intact leaves of Hedera helix L. For small samples the overestimation from using the arithmetic mean of original data can be high, but use of the geometric mean or the median leads to smaller deviations. Removing cuticular waxes from cuticles produced normally distributed samples. A normal distribution was also obtained when organic compounds which increase solute mobility were sorbed into cuticles.     

Developmental and seasonal changes of stress responsiveness in beech leaves (Fagus sylvatica L.)

The development of beech leaves (Fagus sylvatica L.) was characterized by determination of the pigment and electrolyte concentrations as well as the accumulation of dry mass and specific leaf mass from bud break to senescence. To test the hypothesis that stress tolerance and responsiveness of defences show developmental and/or seasonal changes, leaf discs were either incubated in the absence (control) or presence of paraquat to induce oxidative stress. Controls displayed developmental changes in stress susceptibility ranging from less than 15% of maximum electrolyte leakage in mature leaves to more than 20% leakage in senescent and 36–46% in immature leaves. Paraquat concentrations were chosen to result in about 95% of maximum electrolyte conductivity within 24 h in all developmental stages. Paraquat accumulation was about two‐fold lower in senescent as compared with immature leaves, whereas stress susceptibility, as characterized by the kinetics of the increase in relative leakage, was similar in these developmental stages with 50% of maximum electrolyte conductivity (EC₅₀) = 6·5 h in immature and 7·5 h in senescent leaves. In mature leaves with intermediate paraquat accumulation rates, two classes of stress‐sensitivity were distinguished, namely stress‐resistant and stress‐susceptible leaves with EC₅₀= 9·5 and 5·2 h, respectively. Stress‐resistance of mature leaves was accompanied by a rapid, approximately two‐fold induction of superoxide dismutase activity. Stress‐sensitive mature leaves initially contained high superoxide dismutase activities but showed a rapid, more than six‐ fold loss in activity in 24 h. Correlation of meteorological data with leakage rates suggested that high air temperatures and low precipitation might have been predisposing for loss of resistance against oxidative stress in beech leaves.     

Population Tendencies of Pseudomonas cichorii and P. syringae pv. garcae in Young and Mature Coffee Leaves

The population tendencies of Pseudomonas cichorii and P. syringae pv. garcae in young and mature coffee leaves were determined by inoculating streptomycin resistant bacterial cells from 24 h cultures into young and mature coffee leaves. The leaves were then sampled daily for 5 days and the number of bacterial cells per g of leaf tissue was determined. Pseudomonas cichorii increased in mature leaves only while P. syringae pv. garcae increased in young leaves. Symptom development was dependent on the presence of a large number of bacterial cells in the host tissue and coincided with the maximum content of bacterial cells in the leaf.     

Isolation and characterization of a marine algicidal bacterium against the harmful raphidophyceae <Emphasis Type="Italic">Chattonella marina</Emphasis>

A bacterial strain named AB-4 showing algicidal activity against Chattonella marina was isolated from coastal water of ULjin, Republic of Korea. The isolated strain was identified as Bacillus sp. by culture morphology, biochemical reactions, and homology research based on 16S rDNA. The bacterial culture led to the lysis of algal cells, suggesting that the isolated strain produced a latent algal-lytic compound. Amongst changes in algicidal activity by different culture filtrate volumes, the 10% (100 μl/ml) concentration showed the biggest change in algicidal activity; there, estimated algicidal activity was 95%. The swimming movements of Chattonella marina cells were inhibited because of treatment of the bacterial culture; subsequently, Chattonella marina cells became swollen and rounded. With longer exposure time, algal cells were disrupted and cellular components lost their integrity and decomposed. The released algicide(s) were heat-tolerant and stable in pH variations, except pH 3, 4, and 5. Culture filtrate of Bacillus sp. AB-4 was toxic against harmful algae bloom (HAB) species and nontoxic against livefood organisms. Bacillus sp. AB-4 showed comparatively strong activity against Akashiwo sanguinea, Fibriocapsa japonica, Heterosigma akashiwo, and Scrippsiella trochoidea. These results suggest that the algicidal activity of Bacillus sp. AB-4 is potentially useful for controlling outbreaks of Chattonella marina.     

Contrasting mechanisms of secondary metabolite accumulation during leaf development in two tropical tree species with different leaf expansion strategies

Young leaves of most species experience remarkably higher herbivore attack rates than mature leaves. Considerable theoretical effort has focused on predicting optimal defense and tradeoffs in defense allocation during leaf expansion. Among others, allocation to secondary chemistry may be dependent on growth constraints. We studied flavanoid production during leaf development in two species of Inga (Fabaceae: Mimosoideae) with different expansion strategies: Inga goldmanii, a species with slowly expanding young leaves, and Inga umbellifera, a species with fast-expanding young leaves. In these two species, the most abundant and toxic class of defensive compounds is flavanoids (which include tannins). We measured their concentration by leaf dry weight, their total content per leaf, their HPLC chemical profile and their toxicity to a generalist herbivore at different expansion levels. Although in both species the flavanoid concentration decreased with increasing leaf expansion, that decrease was twice as pronounced for I. umbellifera as it was for I. goldmanii. I. umbellifera leaves produced flavanoids only during the first half of their development while I. goldmanii leaves continued production throughout. The changes in flavanoid HPLC profiles and toxicity were also more dramatic for I. umbellifera, which had different flavanoids in young than in mature leaves. Relative to I. umbellifera, I. goldmanii showed smaller changes in both flavanoid composition and toxicity in the transition from young to mature leaves. These results indicate that, even though young leaves suffer higher rates of attack and are predicted to have better chemical defenses than mature leaves, growth constraints may modulate defense allocation and thus, evolution of defense strategies.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Distribution and immunolocalization of stachyose synthase in Cucumis melo L.

Indirect evidence for the site of stachyose biosynthesis has been provided by determining the occurrence and distribution of stachyose, raffinose and galactinol, the donor of the galactosyl moiety for stachyose synthesis, in Cucumis melo L. cv. Ranjadew. Studies of enzyme activities for the synthesis of these sugars and their distribution in different plant organs and isolates has led to the conclusion that stachyose is synthesized mainly in mature leaves and seeds. Nevertheless, stachyose-synthase activity varied with leaf age, the developmental stage of a plant, the growing season and the plant cultivar used. No stachyose or stachyose-synthase activity could be detected in isolated mesophyll protoplasts and chloroplasts, whereas both were found in a minor-vein-enriched fraction isolated from mature leaves. The conclusion that stachyose biosynthesis is associated with minor veins was confirmed by immunolocalization of the enzyme. Positive specific immunoreactivity of stachyose synthase with polyclonal anti-stachyose-synthase antibodies, labeled with protein A-gold, was detected in intermediary cells of leaf minor veins. The implication of this local synthesis of the main transport sugar for phloem loading in mature leaves of Cucumis melo is discussed.Abbreviation RUBPCase ribulose-1,5-bisphosphate carboxylase This work was supported by Deutsche Forschungsgemeinschaft. The excellent assistance of Ms. B. Müller in preparing the samples for electron microscopy is gratefully acknowledged. The authors thank Professor H.J. Schneider-Poetsch for anti-RuBPCase antibodies.     

Non-glaucousness, a probable aphid-resistance character of wheat

Cuticular waxes from wheat cultivars that have a bluish-green waxy bloom under field conditions were compared with those of non-glaucous (NG) variants that appeared dark green and glossy in the field. Cuticular wax from NG variants was deficient in diketones and hydroxydiketones, and did not form the micro-spicules of epicuticular wax which were characteristic of the normal bloom. Typically, NG wheats were resistant to Sitobion avenae in the field, but in environments where wax secretion was diminished, resistance was reduced or absent. Possible causes of this resistance, which appears likely to be easy to exploit, are discussed.     

Isolation and Characterization of Cuticular Polyester from the Leaf of Nicotiana tabacum

Cuticular membranes (ca.0.04mg/cm²) were isolated from fresh and flue-cured tobacco leaves (Nicotiana tabacum) as clear, colorless and thin films by oxalic ammonium treatment and successive cellulase-pectinase digestion. GC-MS analyses, after hydrogenolysis and trimethylsilylation, revealed that the membranes are mainly built up of 10,16-dihydroxy hexadecanoic acid in a polyester network structure which survives postharvest-treatments.

The fruit skins of solanaceaes; sweet pepper (Capsicum annuum), eggplant (Solanum melongena) and tomato (Solanum lycopersicum), have similar membranes which are essentially composed of 9,16- and 10,16-dihydroxy hexadecanoic acid.     

Mechanical freeze-thaw damage and frost hardening in leaves and isolated thylakoids from spinach. II. Frost hardening reduces solute permeability and increases extensibility of thylakoid membranes

Abstract Thylakoids isolated from cold-acclimated spinach (Spinacia oleracea L.) leaves were more resistant against mechanical freeze-thaw injury measured as plastocyanin release, than thylakoids from non-acclimated leaves. They were more resistant against solute influx during freezing and they were able to re-expand to a larger volume in comparison to non-hardy controls. Likewise, plastocyanin was released from thylakoids of non-acclimated but not of frost-hardy leaves under conditions of mild in situ freezing stress for several days.     

The pathogenicity of six strains of Helminthosporium sativum to three cereals with special reference to barley

Summary The pathogenicity of 6 strains ofHelminthosporium sativum P.K. & B. isolated from either oats, wheat or barley was studied. Oats was resistant to all strains followed by wheat while barley was susceptible. Barley variety Balder was the most resistant while Piroline was the most susceptible. Susceptibility of Piroline was manifested by higher percentage infection, bigger necrotic areas and wilting of the infected leaf. Toxic filtrates of the different strains could reproduce necrosis, wilting or chlorosis on cut leaves. Response of Balder and Piroline was similar in the filtrates of three strains, while in those of the other three Balder was more resistant. Formation of at least 2 toxic substances in the host tissues, one responsible for wilting and the other for necrosis, was suggested. No correlation was found between the dimensions of the spore or the number of its constituent cells and the virulence of the strain.     

Effect of Ustilago maydis (DC) Corda and its Toxin on Some Maize Cultivars

The pathogenic effects of Ustilago maydis (DC) Corda to five maize cultivars and four other plants were studied. It was found that none of the maize cultivars tested was resistant to the common smut disease whereas cultivars Balady was slightly susceptible. Only Sorghum rulgare from the other tested plants showed moderate susceptibility to the disease. With respect to gall formation only cultivars Giza 2 and single cross hybrid 10 formed galls after 2 weeks. The pure toxic material (Ustizeain) from Ustilago maydis was obtained, it caused chlorosis and necrosis on detached maize leaves, but it had no effect on growth of some fungi tested. Sporidia treatment showed also chlorosis on detached maize leaves.     

苹果中磷酸蔗糖合酶家族基因的表达特性及其与蔗糖含量的关系

磷酸蔗糖合酶(sucrose phosphate synthase,SPS)是植物中蔗糖合成的主要限速酶,影响植物的生长发育和果实中蔗糖的含量。为探明苹果中SPS基因家族特性及其在蔗糖合成中的作用,该研究从苹果基因组中分离了MdSPS家族基因,分析了它们的进化关系以及mRNA表达特性与酶活性和蔗糖含量的关系。结果显示:(1)在苹果基因组中有8个SPS家族基因表达,它们分别属于双子叶植物的3个SPS亚家族。(2)荧光定量PCR分析显示,苹果C类的MdSPS6基因和A类的MdSPS1a/b基因是苹果中表达丰度最高的SPS基因成员,其中MdSPS6在苹果成熟果中表达丰度最高,其次是成熟叶片,而MdSPS1a/b在不积累蔗糖的幼果中表达丰度最高。(3)在果实发育过程中,除MdSPS1a/b之外,其它5个苹果MdSPS家族基因均随果实的生长表达丰度增加,与SPS活性和蔗糖含量明显呈正相关关系。研究表明,C类家族MdSPS6是苹果果实发育后期和叶片中蔗糖合成的主要SPS基因。     

Isolation of scopoletin from leaves of Hevea brasiliensis and the effect of scopoletin on pathogens of H. brasiliensis

Scopoletin (7-hydroxy-6-methoxy coumarin) which inhibited the conidial germinationof Corynespora cassiicola was isolated from the uninfected mature leaves ofHevea brasiliensis. Scopoletin was not detected in uninfected immature rubber leaves. The immature leaves produced scopoletin after being infected with C. cassiicola. The concentration of scopoletin in infected leaves was higher than in uninfected mature leaves. Scopoletin also inhibited the conidial germination of other fungal pathogens of H. brasiliensis. However, no correlation was observed between scopoletin accumulation and clonal resistance. This revised version was published online in June 2006 with corrections to the Cover Date.