摘要:

The structural characteristics of the sporogenous and parietal tissues of healthy anthers ofSilene dioica(L.) Clairv. (Caryophyllaceae) are described as well as those of anthers infected byUstilago violacea(Pers.) Rouss. (Ustilaginales). In infected anthers, the invading dikaryotic mycelium grew intercellularly and very rarely penetrated the cells. The pathogen stopped stamen histogenesis at an early stage, causing necrosis specifically of the sporogenous tissue either directly or following hypertrophy. Five stages were distinguished during the histological modifications leading to anther destruction. (1) First, the mycelium developed in the anther filament and spread throughout the superficial tissues of the anther without causing histological changes in the anther. (2) Then, some sporogenous cells began to show necrosis and formed compact masses. (3) An increasing number of sporogenous cells became necrotic following strong vacuolisation and hypertrophy. (4) Hyphae grew profusely in the necrotic mass of sporogenic cells. (5) Finally, the fungus produced teliospores which filled the sporangial cavity.

ISSN:0008-4026    

DOI:10.1139/b80-045

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The relative contribution of different types of litter to the maintenance of soil organic matter and nitrogen levels cannot be determined from standard litter bag disappearance studies. By coupling measurements of weight loss with nitrogen dynamics and presenting results in a new format, estimates of both state of decay and percentage of material eventually transferred to lower soil horizons can be obtained.

ISSN:0008-4026    

DOI:10.1139/b80-046

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The abilities of 60 species of soil microfungi to decompose protein, xylan, cellulose, and chitin were tested with an agar diffusion technique. Proteolytic capacity was shown by 51 species; 35 were xylanolytic, 31 were cellulolytic, and 23 were chitinolytic. The importance of the physiological capacities of soil fungi in determining the communities in different soil horizons is discussed.

ISSN:0008-4026    

DOI:10.1139/b80-047

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The soil fungiMortierella pusilla, M. isabellina, andTrichoderma viride, and the aquatic fungusSaprolegnia parasiticawere chosen as test organisms to study the fungitoxicity of the pesticides methoxychlor and fenitrothion and some of their known metabolites and derivatives. The inhibition of mycelial growth on agar plates was used as a criterion for toxicity and it was established that the inhibiting effect was fungistatic rather than fungicidal. The results, which indicate that some metabolites are more toxic than the parent pesticides, are reported in the form of dosage response relationships and a novel method of reporting such relationships is proposed.

ISSN:0008-4026    

DOI:10.1139/b80-048

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Diheterospora rotiferorumandDiheterospora ovisporaare described as new species endoparasitic on bdelloid rotifers belonging toPhilodinaandAdineta. In both species resting spores (aleuriospores) are produced underwater and disseminative spores (phialoconidia) are produced from aerial conidiophores.Verticillium reniformisandAcrostalagmus tagenophorus, also endoparasites of rotifers, are transferred to the genusDiheterospora.

ISSN:0008-4026    

DOI:10.1139/b80-049

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A new species,Tolypocladium parasiticum, is described as endoparasitic on the rotifer hostAdineta. Unlike most other known Hyphomycetes parasitic on rotifers, conidia are produced underwater. Infection is initiated by conidia lodging in the lower gullet near the mastax of the host. Conidiogenous cells (phialides) arise either directly from the host body or in clusters from short, simple conidiophores. This species produces solitary terminal resting spores with an unusual nodular appearance.

ISSN:0008-4026    

DOI:10.1139/b80-050

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Pseudomeriais described as a new genus of Hyphomycetes recovered from soil. The type species,Pseudomeria mucosa, is parasitic on a bdelloid rotifer belonging to the genusAdineta. Conidia of this species are enveloped in mucus and initiate infection by lodging in or near the mastax of the host. Twenty-four hours after infection short, unbranched conidiophores radiate from the cuticle of the host. Conidiophores consist of up to eight cells and cease growth after about 48 h. On submerged conidiophores conidia are not produced. When conidiophores become exposed to air, in shallow water or as a result of drying, each cell of the conidiophore produces a narrow conidiogenous apex forming an acropetal succession of globose conidia.

ISSN:0008-4026    

DOI:10.1139/b80-051

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Harposporium arcuatumis described as a new endoparasitic nematode-destroying hyphomycete from soil. The conidia are long, very narrow, and semicircular in outline. Infection of the host is initiated by conidia germinating in the gut or lodging in the oesophagus. Resting spores were not found.

ISSN:0008-4026    

DOI:10.1139/b80-052

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The effects of 0.15 ppm sulphur dioxide and (or) 0.15 ppm ozone on membrane permeability, measured by electrical conductivity of solute leakage, were determined for soybean, white bean, cucumber, and radish. Solute leakage increased significantly prior to visible injury for soybean and white bean exposed to 0.15 ppm ozone alone. This results in water-soaked lesions on the upper leaf surface prior to visible coloured necrotic lesions and is representative of a "leaky" plasmalemma. The sulphur dioxide – ozone mixture did not increase solute leakage above that of the control for white bean and soybean. Therefore, the presence of sulphur dioxide, in combination with ozone, attenuates or reduces the effects of ozone on increasing membrane permeability of white bean and soybean. Ozone alone did not affect membrane permeability in cucumber and radish. The sulphur dioxide – ozone mixture, which produced more injury than ozone alone, did increase membrane permeability temporarily for radish and cucumber but this occurred only after visible injury symptoms appeared. Overall, the effects of the pollutants singly or in combination on membrane permeability appear to offer an explanation of differences in species responses.

ISSN:0008-4026    

DOI:10.1139/b80-053

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A qualitative examination of the recent sediments of 10 lakes spanning a wide range of limnological conditions indicated that synuracean scales were consistently well preserved in lake sediments. The stratigraphic distribution of the fossil scales of sixMallomonasspecies was then studied in the recent sediments of three Canadian Shield lakes. Two of these lakes (Found and Jake lakes) are adjacent to a major highway and have been subjected to moderate cultural disturbances. Delano Lake, isolated 4.5 km south of the road, was not subjected to these disturbances and hence was a control.Road construction coincided with the near extinction ofMallomonas allorgeiin Found Lake, whilstM. fastigataincreased in relative importance in both Found and Jake lakes following cultural disturbances. TheMallomonasstanding crop, estimated from the accumulation rate of scales, increased strikingly in Found Lake immediately following the 1933 road construction. No sudden changes inMallomonasspecies composition or standing crop were recorded in the control lake's recent history. These data suggest thatMallomonastaxa are sensitive to changes in water quality and are therefore potentially useful paleoindicators.

ISSN:0008-4026    

DOI:10.1139/b80-054

出版商:NRC Research Press    

年代:1980

数据来源: NRC