摘要:

AbstractNeedles of four spruce trees showing different degrees of novel kinds of forest decline were investigated by electron microscopy. Green needles appearing at least superficially still intact were selected for the present investigation. Most of the mesophyll appeared to be undamaged. However, groups of atypical mesophyll cells were found close to the endodermis or the hypodermis. The chloroplasts of the apparently damaged cells were particularly affected. Changes in the matrix of the chloroplasts, i.e,. increased affinity to osmium, occurrence of extensive nests of plastoglobuli, as well as damage to the membranes, i.e. lesions in the envelope and abnormal thylakoid membranes, were observed. Signs of decomposition of other cellular structures including mitochondria were also detectable. There appeared to be a close correlation between the degree of damage at the whole tree level and the degree of damage occurring at the cellular level. It is concluded that particularly the lipids and the proteinsof, the membranes are affected by anthropogenic air pollutants and natural stressors. The altered membrane structure may for instance cause abnormal osmotic conditions for the cellular compartments and may impair transport processes and thus lead to lossof function not only of the cells but also of the whole needle.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00985.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe intracellular localization of the radioactively labelled fungicide (3H)triadimenol A in thein vitrogrown sporidia ofUstilago avenaeand in the in vivo cultured powdery mildew (Erysiphe graminisf. sp.hordet) on barley (Hordeum vulgare) is described. The specimens were prepared by low temperature techniques: shock freezing, freeze substitution and embedding in Spurr's low viscosity resin. The localization of the fungicide was achieved by means of conventional electron microscopic autoradiography. The available experimental data allow a first qualitative analysis of the distribution of silver grains on freeze substituted sporidia ofU. avenaeand the infection structures ofErysiphe graminisf. sp.hordei.ConcerningU. avenaethe fungicide is detected preferentially over the vacuoles, the cytoplasm, and the cell walls after a six month exposure. The host pathogen system powdery mildew on barley exhibits an accumulation of silver grains in the host cell wall adjacent to the infection site and the papillae whereas decisively fewer grains occur inside the haustoria. Apart from this general localization pattern the haustoria show ultrastructural changes caused by the fungicide treatment: vesiculation and collapse of the sheath membrane as well as a diffuse appearance of the haustorial cytoplasm. Around the haustoria an aggregation of host cytoplasm material is observed.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00986.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA disease characterized by complete chlorosis of plant foliage was recently observed inCynodon dactylonL. naturally growing in central Sudan. Severely affected plants were stunted with short internodes and small inward folded leaves. Examination of sections from paraffin embedded leaf and rhizome fractions, stained with a DNA‐binding fluorochrome Bisbenzimid H 33258, and observed in a fluorescent microscope revealed abnormal amounts of DNA material in the phloem sieve tubes of diseased plants. More intense fluorescence was also observed in the xylem region and was shown to be due to the presence of a rod‐shaped bacterium. No such anomalies were observed in healthy plants. Electron microscopy of ultrathin sections prepared from phloem zones, reacting with fluorescence in light microscopy revealed the presence of pleomorphic prokaryotes in the sieve tube elements of such zones. No helical forms were observed in semi‐thin sections from the same plant material, suggesting the MLO nature of these prokar

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00987.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIsolates ofPhytophthora cactorumresistant to the systemic fungicide metalaxyl were obtained by exposing them to sequentially increased concentrations of metalaxyl. A linear relationship was observed between the concentrations of metalaxyl and percentage inhibition of mycelial growth ofP. cactorum.The stability of metalaxyl‐resistant isolates 150R and 250R was confirmed after six serial transfers on corn meal agar without fungicide. Thein vitrometalaxyl‐resistant isolate (Ph10) was less aggressive on apple rootstocks compared with the Ph07 isolated from metalaxyl‐treated trees and the Ph03 isolated from untreated trees. Metalaxyl‐resistant and sensitive isolates remained sensitive to the chemically unrelated fungicide fosetyl‐Al at high concentration (600 μg/ml), to mancozeb, and to a mixture of metalaxyl + mancozeb. Significant differences in resistance to metalaxyl existed amongP. cactorumfiel

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00988.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe variations over 7–8 day of peroxidase (PO) and polyphenoloxidase (PPO) activity have been investigated in tomato plants the roots of which had been subjected to stresses (heat, chloroform and a non‐pathogenic form ofFusarium oxysporum) that induce resistance toFusarium oxysporumf. sp.lycopersici.All treatments induced increase of PO and PPO activity that reached a maximum 3 days after the treatments in leaves, 4 days in stem and roots and were higher in leaves than in other parts. Activity decreased to levels for the control plants after 8 days.Inoculation withFusarium oxysporumf. sp.lycopersicifurther stimulated PO and PPO activity in all treated plants over that caused by the treatments alone. Again, activity of treated plants was lower than in controls 7 days after inoculation.It is concluded that 1. increased PO and PPO activity in tomato is a systemic response to cellular injury caused in the root by heat, chloroform and non‐pathogenicFusarium oxysporum, 2. these treatments do no prevent the pathogen from interacting with the plants and inducing further enzyme increase, 3. treated plants react more strongly to the challenge inoculation than untreated p

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00989.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractLiberation of HCN from cyanogenic plant tissue depends on cyanogen content (HCN‐potential), cyanogen splitting enzymes, cyanohydrin cleaving activity (hydroxynitrile lyase) and nonenzymatic cyanide detoxifying compounds. The maximal amount of HCN potentially set free is governed by the total cyanogen content, whereas the velocity of HCN liberation depends on enzymatic activities (β‐glucosidase [β‐G], hydroxynitrile lyase [HN]). Plants revealing a high HCN‐potential and a high β‐glucosidase activity generally are susceptible to infection withMicrocyclus ulei.Based on the data of HCN‐p and β‐G activity of differentHeveaspecies a proposal for future screening work inHevearesistance s

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00990.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA serum‐free medium (medium A6), supports the primary isolation and cultivationin vitroof corn stunt spiroplasma (CSS). The growth characteristics of CSS in A6medium are similar to those in the conventional serum dependent, ketoglutarate sorbitol medium (SMK

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00991.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractExtensive studies showed that no disease was caused when seeds of different forage grasses were inoculated withXanthomonas campestrispv.graminis.The disease could easily be induced by infecting the plants in the root system, leaves or flower. The inoculation site in the leaf proved to be of vital importance for the development of the disease. Wilting symptoms were quickly induced when the pathogen was inoculated near the leaf base. Plants in root‐contact with diseased plants showed disease symptoms. It is not known whether these symptoms were caused by the bacteria or by toxins released by nearby diseased plants. Cross inoculation trials on different grass varieties revealed that different pathovars exist in the group of xanthomonads, pathogenic to forage grasses. Some have a broad host range whereas others are more limited to a single plant genus. Field trials suggest that in Belgian climatic conditions, the losses caused by bacterial wilt are rather limite

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00992.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA simple procedure was developed to purify bean yellow mosaic virus from infected faba bean. The procedure included clarification of tissue homogenate by 25% chloroform followed by low‐speed centrifugation, virus concentration by polyethylene glycolprecipitation and further purification by agarose‐acrylamide gel electrophoresis. The partially purified virus preparation was electrophoresed in 0.5% agarose‐2% acrylamide gel for 4 h. Gel bands containing the virus were collected, homogenized, and mixed (1:1) with Freunds adjuvant. Four weekly intramuscular injections and a booster injection four weeks after the fourth injection were given to a rabbit. Antisera collected from the first five bleedings produced high A405readings in ELISA (0.47,5–0.790) with virus‐infected faba bean leaves and low readings (0.030–0.065) with healthy tissue. Plates were coated with 5μg/ml of gammaglobulins (IgG) fractionated from the different bleedings of the antiserum prepared and a 1: 1000 dilution ofthe IgG from the third bleeding conjugated to alkaline phosphat

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00993.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractBook Reviewed in this article:Haug, G., and H. Hoffmann (Manag. Eds.), W. S. Bowers, W. Ebing, T. R. Fukuto, D. Martin, R. Wegler, and Y. Yamamoto (Eds.):Chemistry of Plant Protection.Hofmeister, H., und E. Garve:Lebensraum Acker – Pflanzen der Äcker und ihre Ökologie.Plattner, H., und H. P. Zingsheim, Elektronenmikroskopische Methodik in der Zell‐ und Molekularbiologie.Horn, W., C. J. Jensen, W. Odenbach, and O. Schieder:Genetic Manipulation in Plant Breeding.Hanns Kreisel, undFrieder Schauer:Methoden des mykologischen Laborato

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00994.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY