摘要:

Granulation of juice sacs in pummelo (Citrus grandisL.) fruit was found to occur upon ripening. The juice sac tissue consisted of epidermal and subepidermal cell layers, an elongated cell layer, and juice cells. The granulation was accompanied by the appearance of opaque white regions inside transparent tissue. The subepidermal cells of the granulated tissue were disordered and the cell walls of the elongated and the juice cells were distinctly thickened. An ultrastructural study has shown that the subepidermal cell walls of granulated juice sacs were distorted and had swollen regions. The cell walls of both the elongated and the juice cells had secondary thickening with pits. The total dry weight, cellulose (as glucose), lignin, and hemicellulose (as xylose) were significantly higher and insoluble proteins were lower in granulated juice sacs than in non-granulated ones. The content of insoluble neutral sugars such as rhamnose, arabinose, mannose, and galactose decreased as a result of granulation, as did that of soluble sugars glucose, fructose, sucrose, and organic acids. Thus, it seems that granulation of pummelo fruit juice sacs is a result of lignification of the juice cells, which leads to the formation of sclerenchyma.

ISSN:0008-4026    

DOI:10.1139/b89-084

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Clones of the gynodioecious herbGlechoma hederaceaL. produce ramets which flower and bear seed, ramets which flower but fail to bear seed, and sterile ramets. Performance and survivorship of these subsets of ramets were compared for hermaphrodite and male sterile clones in contrasting grassland and woodland habitats for 2 consecutive years. For all clones, ramet densities on given dates were comparable between years. Winter survival of ramets exceeded 95% and mortality during the growing season was exponential. No genet recruitment was recorded throughout the study. For all clones, flowering ramets were larger than nonflowering ramets. Both flowering and nonflowering ramets of hermaphrodite clones, from grassland and woodland, were significantly larger than corresponding types of ramets from male sterile clones. A higher proportion of ramets of hermaphrodite clones flowered and set seed than ramets of male sterile clones. Flowering ramets of hermaphrodite clones produced more flowers than flowering ramets of male sterile clones. For all clones, half-lives of subsets of ramets declined in the order: seed-bearing > flowering but not seed-bearing > nonflowering. Within the grassland habitat, ramet subsets from hermaphrodite clones had longer half-lives than corresponding subsets from the male sterile clones. In the absence of greater flowering and seed set by male sterile clones, self-incompatibility of hermaphrodite flowers, which has been reported previously forG.hederacea, is crucial for the maintenance of clones of both sexes in populations.

ISSN:0008-4026    

DOI:10.1139/b89-085

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A study of herbarium specimens ofDicranodontiumwas undertaken to facilitate the identification of the taxa present in Canada and to document their occurrence in the country. Keys, descriptions, illustrations, and distribution maps are provided for the four species in Canada, namelyD.asperulum(Mitt.) Broth.,D.denudatum(Brid.) Britt. in Williams,D.subporodictyonBroth., andD.uncinatum(Harv.) laeg. & Sauerb. One species,D.denudatum, has a disjunct distribution, being known from western British Columbia and southern Québec and Newfoundland. The other three species are known only from western British Columbia, predominantly the Queen Charlotte Islands. The rarity and restricted occurrence of these species is apparently due to the low sporophyte production resulting from the sterility of the majority of plants and to their preference for oceanic habitats. Only two species,D.asperulumandD.uncinatum, were seen with sporophytes.

ISSN:0008-4026    

DOI:10.1139/b89-086

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Thin cell layer explants of tobacco were floatedin vitroon the surface of liquid culture media. The initial exogenous concentrations of indolyl-3-butyric acid, and kinetin, the initial medium pH, and the explant density were varied. Various patterns ofde novoand direct differentiation without any intermediate callus (flower, vegetative bud, root) as well as the absence of morphogenesis and callus formation without any subsequent organogenesis were separately controlled on 100% of the explants. On the same exogenous combination of glucose, indolyl-3-butyric acid, and kinetin, changes in initial medium pH changed the pattern of morphogenesis. For a given initial exogenous indolyl-3-butyric acid concentration, vegetative buds were obtained at either pH 6.1 or 7.8, whereas a mixture of flowers and vegetative buds was obtained at pH 6.8. Furthermore, changes in explant density changed the morphogenetic response. It is suggested that the effects of the initial medium pH and explant density on morphogenesis may be related partially to modifications of the physicochemical properties of the cell wall and (or) plasmalemma.

ISSN:0008-4026    

DOI:10.1139/b89-087

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Immunofluorescence microscopy, azur A staining of viral inclusion bodies, and ELISA tests revealed differences between resistant and susceptible decapitated plants of pepper for virus distribution through the plant but not for virus multiplication and spread in the artificially inoculated leaves. Within 7 to 10 days after inoculation, viral antigens were detected with ELISA tests in all organs of the susceptible plants; only in inoculated leaves of highly resistant plants; and in inoculated leaves, primary stems, and primary roots of partially resistant plants. Immunofluorescence microscopy revealed that infection in petioles, stems, and roots of resistant varieties was restricted to one or two phloem bundles and did not spread to neighbouring tissues or to other plant organs. However, in some partially resistant plants the virus spread lately to other tissues and organs, resulting in a delayed systemic infection and mosaic symptoms on one or two axillary shoots.

ISSN:0008-4026    

DOI:10.1139/b89-088

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Germination, penetration, and subsequent growth of four saprophytic and five parasitic fungi nonpathogenic on French bean (Phaseolus vulgarisL. cv. Pinto) were examined on, or in, killed, untreated, and heat-treated or blasticidin S treated leaves in the presence (saprophytes only) or absence of additional nutrients. The saprophytes required either an external supply of nutrients or a diffusate from autoclaved leaves to germinate, and they subsequently did not attempt to penetrate untreated or heat-treated living leaves. In contrast, the parasites germinated well, and penetrated untreated tissue almost exclusively through stomata. For some parasites, preinoculation heat treatment increased the incidence of direct penetration and the degree of fungal growth in the tissue. The saprophytes and nonbiotrophic parasites all penetrated and grew well in leaves that had been killed by autoclaving or freezing. The data suggest that living, intact bean leaves are resistant to the fungal saprophytes tested because these fungi lack pathogenicity factors necessary for germination on, and penetration of, the leaf. Resistance to the parasites, in contrast, appears to reside in heat-sensitive and heat- or blasticidin S insensitive defenses in the leaf that may differ with the fungus.

ISSN:0008-4026    

DOI:10.1139/b89-089

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Germination and growth of four saprophytic and five parasitic fungi nonpathogenic on French bean (Phaseolus vulgarisL. cv. Pinto) were examined in leaves after the epidermis was bypassed by injection or wounding. In unheated leaves, only the parasites had the ability to spread from the wound site and to germinate and grow inside the tissue after injection. The saprophytes behaved similarly only after the leaves were given a preinoculation heat treatment, suggesting a sensitivity to heat-sensitive inhibitors. For two of the saprophytes, evidence for the presence of heat-insensitive inhibitors also was found. Unlike the intercellular growth following stomatal penetration, growth of all of the parasites was affected by heat-sensitive defenses once the epidermis was bypassed. The greater intercellular growth after injection as compared with stomatal penetration suggested that the guard cells play a significant role in the resistance of intact, unheated leaves toCladosporium fulvumCooke. Of the saprophytes examined,Neurospora crassaShear & Dodge appeared to posses a number of attributes that might be considered as potential pathogenicity factors.

ISSN:0008-4026    

DOI:10.1139/b89-090

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Cytologically detectable responses of the nonhost French bean (Phaseolus vulgarisL. cv. Pinto) to saprophytic and parasitic fungi were examined when fungal spores were introduced into heated or unheated leaves via wounds or by injection. Although similar types of responses were observed in interactions with all the fungi, some of these responses were characteristic of each group (saprophytes vs. parasites) in the frequency and (or) extent with which they were elicited. Differences in responses between and within each of these groups of fungi were more related to their degree of adaptation for parasitism than to their taxonomic relationships. Certain responses that were typically elicited by the saprophytes occurred to a lesser extent in tissue responding to the parasites, suggesting that the ability to not trigger, or suppress, these responses may be a general feature of parasitic fungi. None of the fungi elicited significant levels of plant cell necrosis, and for two of the saprophytes, dead spores elicited a lower frequency of responses than live ones. The data indicate that many of the responses of a nonhost plant to living fungi may be the result of reactions to fungal activity rather than to constitutive recognition molecules such as components of the fungal cell wall.

ISSN:0008-4026    

DOI:10.1139/b89-091

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The roots of 37 crop and pasture species were assessed for vesicular–arbuscular mycorrhizae in a vertisol containing spores of vesicular–arbuscular mycorrhizal fungi mainlyGlomus mosseae, and of the pathogenic fungus,Bipolaris sorokiniana. The level of mycorrhizal colonization of different hosts is an important aspect of managing crop sequences to reduce "long fallow disorder." All species except rapeseed in the Cruciferae and lupin in the Leguminosae were hosts, although perennial rye grass in the Gramineae had only very slight colonization. The percent root length colonized as assessed by the grid-intersect method ranged up to 60.5% for wheat in the winter series and up to 98.4% for mungbean in the summer series. Greatest weights of mycorrhizal roots were produced by phalaris grass, chickpea, safflower, cocksfoot, lucerne, and barley in the winter series and by lucerne, maize, canary seed, Sudan grass, grain sorghum, and buffel grass in the summer series. Although Gramineae as a group tends to have fine roots with a low percentage of mycorrhizal colonization, the total weight of mycorrhizal roots can be large, and they should be at least equal to legumes in effectiveness for breaking long fallow disorder. Percentages of mycorrhizal colonization determined by the grid-intersect and three slide methods were generally well correlated with one another, but all were less strongly correlated with weight of mycorrhizal roots for winter crops and were entirely uncorrelated with weight of mycorrhizal roots for summer crops. Significant inverse-regression relationships were obtained between infection of root segments (but not of stem bases) byB.sorokinianaand root colonization with vesicular–arbuscular mycorrhizae, indicating that vesicular–arbuscular mycorrhizal fungi antagonise root infection byB.sorokiniana.

ISSN:0008-4026    

DOI:10.1139/b89-092

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A synopsis of the genusSaniculain eastern Canada is presented. Four species and two varieties of these native woodland umbellifers are recognized. A key to the taxa, pertinent synonymy, comparative descriptions of diagnostic characters, and notes on the taxonomy, distribution, habitat, and rare status are provided. Illustrations of umbellet and fruit morphology, eastern Canadian dot maps, and North American range maps are also included for each taxon. The nameS.canadensisL. var.grandisFem. is revived, but it now represents a differently circumscribed taxon from that described by Femald.Sanicula odorata(Raf.) Pryer & Phillipe, which is neotypified here, must replace the long-accepted nameS.gregariaE. P. Bicknell.

ISSN:0008-4026    

DOI:10.1139/b89-093

出版商:NRC Research Press    

年代:1989

数据来源: NRC