摘要:

Seedlings of resistant (Sr6) and susceptible (sr6) near-isogenic lines of wheat (Triticum aestivumL.) were inoculated with a race of stem rust (Puccinia graminisPers. f. sp.triticiEriks. & E. Henn.) that was avirulent on the line withSr6and they were kept at 19, 25, 26, and 27 °C. Fluorescence microscopy was used to detect autofluorescing necrotic host cells and rust colonies after these were stained with a fiuorochrome (Calcofluor White M2R New).In leaves containing theSr6gene, a smaller percentage of colonies grown at 25 °C had necrotic cells associated with them than those that were grown at 19 °C. The incidence of colony-associated necrosis in these leaves could be further reduced by increasing the temperature to 26 °C and 27 °C. Similarly, the number of necrotic host cells per colony decreased with an increase in temperature. Colonies in genotypically resistant leaves were usually smaller than those in genotypically susceptible leaves, but the differences in colony sizes between these two lines decreased at the higher temperatures.When infected plants containing theSr6gene were kept for varying times at 25 °C and then were transferred to 19 °C, there was significantly less fungal growth and more necrosis than in plants kept continuously at 25 °C. This necrosis occurred largely in those cells that were invaded after the transfer to 19 °C, when theSr6gene was activated.

ISSN:0008-4026    

DOI:10.1139/b77-169

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Seven freshwater algae were grown in the presence of Abate® 4-E (O,O,O′,O′-tetramethyl-O,O′-thiodi-p-phenylene phosphorothioate) and Dursban® M-3633 (O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) at 1,10, and 100 μg/ℓ active ingredient. The response of different algal groups to the insecticides was highly variable.The growth rate of the nitrogen-fixing blue-green algaAnabaena flos-aquaewas increased from 22% at 10 μg/ℓ Abate to 58% at 100 μg/ℓ Abate when grown on nitrogen-free medium. Dursban caused similar growth stimulation. The green algaChlamydomonas reinhardiishowed growth stimulation in response to 100 μg/ℓ Dursban.Significant decreases in growth rate were observed for the green algaChlorella pyrenoidosaafter treatment with 10 μg/ℓ Abate (8%) and 100 μg/ℓ Dursban (12%). The diatomNavicula pelliculosagave decreases in growth rate of the same order with 10 μg/ℓ Abate or Dursban.No significant effect on the growth rates of the diatomNavicula minimaor the blue-green algaeCoccochloris peniocystis, Oscillatoriasp., andAnabaena flos-aquaegrown in the presence of nitrate was detected after treatment with eithe

ISSN:0008-4026    

DOI:10.1139/b77-170

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

First trifoliate leaves of wax beans.Phaseolus vulgaris, were exposed to14CO2in light for periods of 15 to 75 s. Leaves were frozen in liquid N2and a chloroplast fraction was isolated nonaqueously. The chloroplast fraction contained a small amount of contaminating cytoplasm that could not be removed. Labelled photosynthetic compounds were separated from the whole leaves and from the corresponding chloroplast fractions and their radioactivity was measured.The compounds fell into two groups in their behaviour. Glyceric acid and ribulose, derived from photosynthetic 3-phosphoglyceric acid and ribulose diphosphate respectively, remained largely or exclusively in the chloroplast fraction. Labelled sucrose and serine and glycine, on the other hand, were located in the chloroplast fraction only during the first 15–30 s of14CO2supply, and appeared in the cytoplasmic fraction in increasing amounts thereafter. The results suggest that serine and glycine are produced in organelles in the layer of cytoplasm that closely surrounds the chloroplasts and is isolated with them in the non aqueous technique. Sucrose may also be synthesized from photosynthetic intermediates in this layer of cytoplasm. Sucrose was not formed from intermediates of the glycolate pathway in detached leaves.

ISSN:0008-4026    

DOI:10.1139/b77-171

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Four peroxidase (EC 1.11.1.7) isozymes were isolated from each of two flax genotrophs. All four isozymes were glycoproteins and all exhibited indoleacetic acid (IAA) oxidase activity. The percentage purity of two of the isozymes was very high; these isozymes differed in percentage carbohydrate and in peroxidase and IAA oxidase specific activities. Three of the isozymes displayed molecular weight values of about 43 000; for the fourth, molecular weight was considerably higher. Corresponding isozymes from the genotrophs and from two other flax genotypes displayed molecular weight differences which corresponded to electrophoretic relative mobility differences. Enzyme yield per unit fresh weight was higher for one genotroph than the other, and the balance between peroxidase activity and IAA oxidase activity between the genotrophs was different.

ISSN:0008-4026    

DOI:10.1139/b77-172

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Four woody angiosperm species representing an evergreen tree (Castanopsis chrysophylla(Dougl.) A.DC), a deciduous tree (Acer macrophyllumPursh), an evergreen shrub (Rhododendron macrophyllumG.Don), and a deciduous shrub (Acer circinatumPursh) were sampled to assess the relation of cross-sectional area of conducting tissue in the stem to leaf area. For the first three species listed, a linear relation between conducting area and leaf area was obtained withr2values ranging from 0.89 to 0.96. ForAcer circinatumthe relation only approached linearity with a log transformation of both axes withr2 = 0.80.

ISSN:0008-4026    

DOI:10.1139/b77-173

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The infection of susceptible cucumber leaves byPseudoperonospora cubensiswas investigated under controlled conditions in a 6 × 3 × 4 factorial experiment with 72 combinations of temperature, inoculum concentration, and leaf-wetness duration. The minimum, maximum, and optimum levels of each factor for symptom production were found to depend on one or both of the other factors. The minimal temperature for infection was 20 °C with 2 h of wetness and this decreased to 10–15 and 5–10 °C with 6 and 12 h of wetness, respectively, according to the inoculum load. The maximal temperature for infection was 25 °C, except for a single treatment in which some infection occurred at 28 °C. Optimal temperatures for infection were 20, 15–20, 10–20, and 5–20 °C at dew periods of 2, 6, 12, and 24 h, respectively. The shortest dew period needed to establish infection was 2 h. A sharp increase in infection was associated with extending the dew period to 6h. Further lengthening of the dew period resulted in more infection under unfavorable combinations of temperature and inoculum concentration. An inoculum load of 10 sporangia/cm2was minimal for infection under favorable combinations of temperature and wetness, and higher loads were needed under unfavorable combinations. The optimal inoculum concentration was 1000 sporangia/cm2under most inoculation circumstances. The implications of the variable behaviour of the pathogen to disease development in the field are discussed.

ISSN:0008-4026    

DOI:10.1139/b77-174

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Three groups of plants ofCelosia cristatawere grown in a 8-h, 12-h, or 16-h day. Histological studies of the shoot apex were performed during the vegetative and the prefloral phases.The apical meristems of the plants subjected to long-day conditions (16 h) flatten (fasciation). At the beginning of the fasciation, an activation of thecorpusand a restructuration of the meristem are observed. The transformed meristem shows four superficial layers which cover a group of differentiated cells. The zonation is always recognizable and the apex initiates numerous leaves. The broadening of the meristem is due to the high level of mitotic activity of two opposite regions in the ‘anneau initial’ which takes an elliptical shape and to the peculiar orientation of the mitoses. During this transformation the volumes of the lateral and medullary zones increase while the volume of the axial zone remains almost identical. The long vegetative phase ceases with the homogeneization of the meristematic state of the four superficial layers and with the edification of a prefloral crest.The apex of plants grown under an 8-h photoperiod remains small sized. They never undergo fasciation and reach the prefloral phase very quickly.The meristems of the plants cultivated under 12 h of light daily show an unstable state and sometimes evolve tardily towards fasciation.

ISSN:0008-4026    

DOI:10.1139/b77-175

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two new species ofRhizophydium(Phycomycetes, Chytridiales) are described, both with uniporous sporangia.Rhizophydium annulatumn.sp. is on pollen from northern Florida, the other,R. lenelangein.sp., was recovered from Guatemalan soil.

ISSN:0008-4026    

DOI:10.1139/b77-176

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A new genus and species of Xylariaceae,Pulveria porrecta, is described from wood of dead hardwood trees in New York and Ontario. It differs from other genera and species of the Xylariaceae in producing irregularly disposed, globose asci in nonostiolate ascocarps. A short discussion of its morphology and development is included.

ISSN:0008-4026    

DOI:10.1139/b77-177

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Observations have been made on the walls of the mesophyll cells in the leaves of hemlock,Tsuga canadensis, to determine if there were any structural features which would account for the relatively high resistance measured at the mesophyll cell surface in infiltrated leaves by Tyreeet al. (1975). There was no indication of an internal cuticle based on histochemical tests of fresh sections and the appearance of the wall in electron micrographs. Examination of Alcian-blue-stained fresh sections and thin sections of material treated with ruthenium red indicated that mesophyl) cell walls may be covered with a mucilaginous layer that retards the evaporation of water to intercellular spaces.

ISSN:0008-4026    

DOI:10.1139/b77-178

出版商:NRC Research Press    

年代:1977

数据来源: NRC