摘要:

Gray mold caused byBotrytis cinereaPers.:Fr. developed in seedlings of black spruce (Picea marianaBSP) that were subjected to high temperatures (30–45 °C) in darkness or to drought conditions immediately before inoculation with the pathogen (106 conidia/mL). Incidence and density of spore production ofB.cinereain needles of the treated seedlings increased, and chlorophyll content decreased, with duration of the preinoculation treatments. Gray mold did not develop in seedlings subjected to preinoculation high temperature in the light, and also failed to develop in seedlings that were kept at 1–20 °C in light or darkness with adequate water, inoculated with 103–107conidia ofB.cinerea/mL, then subjected to a range of postinoculation humid periods (0–48 h) at various constant temperatures (12, 20, and 28 °C) in light or darkness. Regression models were developed to describe the incidence and density of sporulation ofB.cinereaand chlorophyll content in seedling needles as functions of the level and period of preinoculation high temperature plus darkness, preinoculation drought period, and seedling age (R2 = 0.45–0.95;p ≤ 0.01). It was concluded that high temperature in combination with darkness, and drought stress, predisposed the seedlings to gray mold.Key words:Picea mariana,Botrytis cinerea, predisposition, disease models.

ISSN:0008-4026    

DOI:10.1139/b94-018

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Seed germinability of some common dwarf shrubs and seed-bank composition were studied in young pine forests along a pollution gradient from Severonickel smelter in Monchegorsk, northern Russia. Samples for seed germination and seed-bank trials were taken from sites representing different zones of pollution. Generally, germinability of dwarf shrub seeds was not affected by distance from pollution source, except forEmpetrum nigrumssp.hermaphroditium. The average density per site of seedlings that emerged from seed-bank samples varied between 278 and 416 seedlings/m2.Empetrum nigrumssp.hermaphroditumandBetulasp. dominated in seed banks.Calluna vulgariswas also numerous at one site. As a whole, seed-bank taxa were well represented in the above ground vegetation. There were no significant differences in seedling density between sites for dominant taxa. Our results indicate that seeds can retain viability even under a heavy pollution load and thus form a potential for vegetation recovery in polluted sites.Key words: seed germination, seed bank, recovery, pollution, coniferous forest.

ISSN:0008-4026    

DOI:10.1139/b94-019

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The activity and capacity of cyanide-resistant or alternative pathway respiration was examined inVicia fabaL. guard and mesophyll cell protoplasts maintained either in darkness (dark adapted) or illuminated with blue light. Respiration rates by dark-adapted guard cell protoplasts were unaffected by titrating with salicylhydroxamic acid (0.1–2.0 mM), an inhibitor of alternative pathway respiration, suggesting the lack of activity of this pathway. In combination with 0.1 mM KCN, an inhibitor of cytochrome pathway respiration, salicylhydroxamic acid was effective in inhibiting total respiration rates. In contrast with guard cell protoplasts, salicylhydroxamic acid reduced rates of O2consumption in dark-adapted mesophyll cell protoplasts by 25–30% of total respiration. Titrating the cytochrome pathway of guard cell protoplasts with KCN (10–140 μM) alone failed to reduce respiratory activity but was effective in combination with salicylhydroxamic acid. Addition of a proton ionophore, carbonyl cyanidem-chlorophenylhydraxone, to dark-adapted guard cell protoplast suspensions increased respiration by approximately 30 and 84% in the presence and absence of salicylhydroxamic acid, suggesting restriction of electron flow by adenylates. Illumination of guard cell protoplasts with blue light for 30 min increased the sensitivity of respiration to salicylhydroxamic acid and increased the activity of the alternative pathway over this time period to ~55% of total respiration. Blue light also increased the rate of uncoupled respiration by guard cell protoplasts treated with salicylhydroxamic acid compared with dark-adapted protoplasts. The results suggest that electron movement through either cytochrome or alternative pathways in guard cell mitochondria may be regulated during signal transduction of blue light.Key words:Vicia faba, guard cell protoplasts, alternative pathway, respiration, blue light.

ISSN:0008-4026    

DOI:10.1139/b94-020

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

This paper describes the anatomy and morphology of the complex nectary systems of the tropical treeGuarea macrophyllaVahl (Meliaceae) and presents the first record of extrafloral nectaries occurring on reproductive organs (fruits) of a member of the order Sapindales. The extrafloral nectaries ofG.macrophyllaoccur on petioles, petiolules, the abaxial surface of all leaflets, leaf buds, and over the surface of fruits. All extrafloral nectaries are distinctly raised above the surface. Foraging ants collect extrafloral nectar onGuareatrees both day and night. We suggest that the presence of extrafloral nectaries might be a useful taxonomic character for the identification ofGuareaspecies.Key words:Guarea, Meliaceae, extrafloral nectaries, ants.

ISSN:0008-4026    

DOI:10.1139/b94-021

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

In vitro production of trichothecene mycotoxins, deoxynivalenol, nivalenol, T-2 toxins, and their derivatives was studied in rice culture using 30 strains from sevenFusariumspecies. Six strains of threeFusariumspecies were selected for the evaluation of mycotoxin production and pathogenicity after artificial inoculation to seven wheat lines with different levels of resistance or susceptibility and their eight F1's. Three criteria were used for the evaluation: the reduction of seed set, the reduction of grain weight, and the concentration of mycotoxins in infected grain. Significant variability was observed amongFusariumstrains, wheat genotypes, and in the interaction between them. The contribution ofFusariumstrains, however, was far greater than that of the other two factors. The kinds and relative amounts of mycotoxins produced in rice culture were consistent with those present in infected grain with some exceptions. Significant correlations were found between the grain weight reduction and the mycotoxin concentration and between the level of resistance of the wheat genotypes under the artificial and natural conditions of infection. The biological role ofFusariummycotoxins in pathogenicity and wheat resistance to Fusarium head blight is discussed.Key words: Fusarium head blight (scab),Fusariummycotoxins,Fusariumpathogenicity, wheat resistance to Fusarium head blight.

ISSN:0008-4026    

DOI:10.1139/b94-022

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A replacement series experiment was used to investigate the effects of mycorrhizae, phosphorus availability, and plant density on competitive relationships between three tallgrass prairie species of varying mycorrhizal dependencies. Under mycorrhizal conditions, the obligately mycorrhizal dependent warm-season grassAndropogon gerardii(big bluestem) was a better competitor in mixture with the nonmycorrhiza-dependent cool-season grassKoeleria pyramidata(Junegrass). In the absence of mycorrhizae, however, competitive effects of big bluestem were greatly reduced and Junegrass experienced competitive release. Relative yield totals increased when mycorrhizae were suppressed, suggesting greater intensity of interspecific competition in the presence of mycorrhizae. Thus, the competitive dominance of big bluestem in tallgrass prairie is strongly related to its mycorrhizal status.Elymus canadensis(Canada wild rye) outcompeted big bluestem both with and without mycorrhizae. Relative yield totals of this species mixture were also lower under mycorrhizal conditions, indicating that mycorrhizae increase the intensity of interspecific competition between them. Relative yields of wild rye competing with big bluestem increased in the absence of mycorrhizae, suggesting that it also experiences competitive release when big blue-stem are not mycorrhizal. The outcomes of competition were generally similar among the three total plant density treatments and between P-fertilized and nonfertilized treatments. However, interactions between mycorrhizal effects and plant density confirm that outcomes of interspecific competitive interactions may be density dependent in some cases.Key words: arbuscular mycorrhizae, de Wit replacement series,Andropogon gerardii,Elymus canadensis,Koeleria pyramidata.

ISSN:0008-4026    

DOI:10.1139/b94-023

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone inZaluzania trilobaandIva microcephala) indicates that it acts as electron transport inhibitor. Since photosystem I and electron transport from DPC toQAwere not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxygen evolution level.Key words: oxygen evolution, ivalin, photosynthesis, sesquiterpene lactone.

ISSN:0008-4026    

DOI:10.1139/b94-024

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The host–fungus interaction between the achlorophyllous gametophyte ofBotrychium lunariaand its fungal endophyte was studied by means of light and electron microscopy. Aseptate hyphae with a multilayered cell wall formed intracellular coils. The interface consisted of a thick layer of fibrillar matrix material, an electron-translucent zone, and the host plasmalemma. Several vesicles that show different stages of development and degeneration occurred within one host cell. Degenerating vesicles were encased by large amounts of an electron-translucent material. Arbuscules were not observed. The fungus did not infect the young sporophyte but degenerated within intact gametophyte cells.Key words:Botrychium lunaria, gametophyte, mycorrhiza, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b94-025

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Nitrate uptake rates were determined for nonmycorrhizal and mycorrhizal maritime pine (Pinus pinaster) associated with the ectomycorrhizal basidiomyceteHebeloma cylindrosporumand for this fungal species grown in vitro. Different [NO3−] (0–1.3 and 10 mM) were supplied to nonmycorrhizal or mycorrhizalP.pinasterplants grown axenically in test tubes for 21 weeks. Uptake of NO3−by the plants was determined by measuring NO3−depletion from the medium that was added to the culture tubes without root pertubation. For all applied [NO3−] the uptake rates for NO3−in mycorrhizal plants were increased about twofold compared with nonmycorrhizal plants. The same range of [NO3−] was supplied to the fungus in pure culture, and uptake rates were calculated either from the measurement of NO3−depletion from the medium or by15N accumulation in the mycelium. For the same external nitrate concentrations the results obtained with these two methods were not significantly different. The amount of fungal biomass in mycorrhizal root systems was determined with the chitin assay. The contribution of each partner to nitrate uptake in the mycorrhizal plant was calculated from the kinetic parameters of nitrate uptake by the fungus and host plant alone given by the Lineweaver–Burk plots. For external [NO3−] higher than 0.1 mM the measured uptake rates for NO3−in mycorrhizal plants were greater than the calculated sum of the individual symbiotic partners. The significance of this excess nitrate uptake is discussed in relation to the role of ectomycorrhizae in nitrogen accumulation.Key words: NO3−uptake rates,Km,Vmax, ectomycorrhizal symbiosis,Hebeloma cylindrosporum,Pinus pinaster.

ISSN:0008-4026    

DOI:10.1139/b94-026

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Growth and antifungal activity of a sterile red fungus againstGaeumannomyces graminisvar.tritici(the take-all fungus) in vitro was greatly influenced by nutritional and environmental conditions. The utilization by the sterile red fungus of various carbon and nitrogen sources differed considerably at pH 5.5 and 6.5. Maximum growth of the sterile red fungus occurred when pectin was supplied as the carbon source at both pH levels. As nitrogen sources, NH4H2PO4supported maximum growth at pH 5.5, whereas Ca(NO3)2was the best at pH 6.5. Pectin strongly enhanced the antifungal activity of the sterile red fungus towards the take-all fungus as did Ca(NO3)2supplied as a N source. There was, however, little or no antagonism in the presence of calcium citrate, arabinose, leucine, or arginine. In general, antagonism was optimal at 20 °C and at pH 5.5.Key words: sterile red fungus,Gaeumannomyces graminisvar.tritici, biological control.

ISSN:0008-4026    

DOI:10.1139/b94-027

出版商:NRC Research Press    

年代:1994

数据来源: NRC