摘要:

The percentage of ectomycorrhizal short roots onQuercus albaandQ.rubrainoculated withPisolithus tinctoriusfollowed a nearly matching pattern among fertilizer treatments, supporting the hypothesis that there may be an optimal amount of N or P for maximum mycorrhizal formation. Several cycles of low and high fertilizations could produce well-balanced seedlings with adequate growth and percentage of ectomycorrhizal short roots for planting.

ISSN:0008-4026    

DOI:10.1139/b85-233

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Both host plant water stress during sporulation and low relative humidity during germination caused decreased germination and germ tube elongation ofLeveillula taurica(Lev.) Am. conidia on glass. This may explain the low incidence of powdery mildew disease of pepper plants (Capsicum annuumL.) caused byL.tauricaduring the harmattan (dry) season in Ghana.

ISSN:0008-4026    

DOI:10.1139/b85-234

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Flavonoid characters are presented for seven "phases" (sensuBarkley 1962) ofSenecio streptanthifoliusGreene and four related species,SeneciopauperculusMichx.,Senecio multilobatusT. & G.,Senecio canusHook., andSenecio neomexicaiiusA. Gray. Evidence from the study of flavonoid characters supports the division ofS.streptanthifoliusinto two subgroups; the subgroup composed of thesuksdorfiiandlaetiflorusphases is apparently related toS.pauperculus. In the other subgroup, three of five phases have apparently arisen through a combination of hybridization and polyploidy or introgression. While the two subgroups are thought to have originated during the Pliocene, the within-subgroup hybridization events are hypothesized to have occurred in Pleistocene or post-Pleistocene times.

ISSN:0008-4026    

DOI:10.1139/b85-235

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A study of the initiation and propagation of cell divisions in the epidermis of flax hypocotyl segments culturedin vitrowas made using surface observations (light and scanning electron microscopes) as well as transverse and longitudinal sections. Epidermal cells were of two types: long, narrow cells and short, wide cells. The latter, less numerous, rarely participated in cell division. Nuclear activation and the first mitoses appeared very early (after 4–8 h of culture). Cell division began in isolated cells and spread progressively to surrounding cells arranged transversely. At 24 h, approximately 50 cells in division or newly divided were observed on an epidermal strip of 10 × 2 mm composed of about 8000 original cells. At 48 h, about 110 cells had divided forming 22 division centers; 26 prophase, 10 metaphase, and 7 telophase figures were observed. The mean number of original cells which participated in the formation of a cell division center was three at 12 h, five at 72 h, with no increase thereafter. The percentage of cells in mitosis or already divided remained low (1.9%) in relation to the total number of epidermal cells. For 22 division centers, only 7 would participate in vegetative bud formation.

ISSN:0008-4026    

DOI:10.1139/b85-236

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The localizationin situof phosphoenolpyruvate carboxylase was studied in maize leaves, at the ultrastructural level, by an indirect immunocytochemical method using colloidal gold particles as a probe. It is shown unambiguously that the enzyme is located in the hyaloplasm of mesophyll cells.

ISSN:0008-4026    

DOI:10.1139/b85-237

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Mature leaves ofColeus blumeiBenth. were tested for their ability to import14C assimilate, to unload and metabolize it, and to transfer it to the mesophyll. To enhance the potential for import, plants were preconditioned by removal of shoot tips and axillary branches, by 48 h of darkness, and by removal of roots. One mature leaf on each plant was isolated in a CO2-free chamber and kept in the light or dark while the rest of the plant was exposed for 5 h to light and 7.4 MBq14CO2, followed by 7 h of12CO2. Autoradiographs showed that label imported into sink leaves exposed to the light was most concentrated in the major veins, but that considerable activity also occurred in the mesophyll at the base of the lamina and adjacent to the major veins. In general, sink leaves kept in the dark imported much less label, but in one case mesophyll labeling was observed in such a leaf. Microautoradiography of sink leaf midveins indicated that14C was always translocated in the phloem. Low concentrations of sucrose and glucose accumulated in intercostal regions of both lighted and darkened sink leaves within 12 h of plant illumination. Chromatography of intercostal areas of the sink leaves showed that the imported assimilate was unloaded and metabolized into a number of other compounds, which indicates that mature leaves ofColeuscan be converted into genuine sinks.

ISSN:0008-4026    

DOI:10.1139/b85-238

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Variegated leaves ofColeus blumeiBenth. were exposed for 4 h to 1.85 MBq14CO2to study the movement of14C assimilate from green to albino portions of the lamina. Autoradiographs showed considerable14C activity in both veins and mesophyll of the central albino regions, whether the lamina was left intact or various parts of it were severed or removed prior to14CO2exposure. However, when all of the photosynthetic tissue was removed, virtually no label appeared in the albino tissue. Autoradiographs of chromatographed extracts of albino regions from intact leaves showed that sucrose was the most abundant labeled compound and that imported assimilate was unloaded and metabolized into a number of other compounds. The albino region is therefore a genuine sink. No label was imported into any part of mature leaves when lower leaves were fed14CO2, and young developing leaves ceased to import in the tip-to-base progression typical of dicotyledonous leaves.

ISSN:0008-4026    

DOI:10.1139/b85-239

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Walls of intercellular hyphae and haustorium mother cells of the stem rust fungus in wheat leaves were studied cytochemically using lectin probes, periodate – thiocarbohydrazide – silver proteinate or periodate–chromate–phosphotungstate staining, and protease treatment. Up to six possible layers in the haustorium mother cell walls and four in the hyphal walls were resolved. Three outer layers of the haustorium mother cell walls were continuous with the three outer layers of the hyphal walls. The two innermost layers of the haustorium mother cell walls were not continuous with the hyphal walls but formed part of the septum. These two layers differed from the other layers of the haustorium mother cell walls in having no affinity to concanavalin A. In both hyphal and haustorium mother cell walls, components with an affinity for concanavalin A were extractable with protease treatment. Wheat-germ lectin binding occurred throughout the fungal walls except in the two outermost layers. Periodate-sensitive glycosubstances were also common, but the amounts varied among layers. Although some of these glycosubstances were confirmed as polysaccharides containing sugars with vicinal hydroxyl groups, much of the glycosubstances present in the walls was sensitive to protease treatment, indicating a possible glycoprotein composition.

ISSN:0008-4026    

DOI:10.1139/b85-240

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Resistance in sunflower (Helianthus annuusL.) to downy mildew (Plasmopara halstedii(Farl.) Berl. et de Toni) is conditioned by a series ofPl. genes. Races 1 (European race), 2 (Red River race), and 3 (a new North American race encountered in the Red River valley in 1980) formed similar infection structures on inoculated seedlings whether susceptible or resistant to races 1 and 2; all cultivars tested were susceptible to race 3. The zoospores encysted and produced germ tubes and appressoria on the roots and hypocotyls. Penetration occurred and mycelium and haustoria developed in both compatible and incompatible host–pathogen combinations. Resistance did not appear to involve a hypersensitive reaction occurring prior to penetration.

ISSN:0008-4026    

DOI:10.1139/b85-241

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A form ofPhoma tracheiphila(Petri) Kant. & Gik., newly designated as f. sp.chrysanthemiBaker et al., massively invades the phloem and xylem and to a lesser extent the cortex and pith of chrysanthemum plants but causes only slight injury in the first season. However, infected plants either produce weak shoots the following year or commonly fail to resume growth. Injury appears to result from depletion of photosynthates and nutrients rather than from vascular plugging or toxins. Infection occurs through intact roots or through wounds of roots or stems, and the pathogen spreads to the top of 120-cm stems in 3 months. Infection occurs readily from 10–29.4 but most abundantly at 10–21° C. Mycelial development in the stems is retarded at 10 and is optimal at 21° C. ThisPhomadecline disease was prevalent in commercial and home chrysanthemum plantings in California in 1948–1956, but it has since been controlled by the annual planting of healthy cuttings in fumigated soil, as practiced for control of verticillium wilt. In home gardens the disease may cause severe losses if plants are grown as perennials, but if healthy cuttings are planted annually, the disease will be minimal even in plants grown in infested soil. The pathogen is indistinguishable morphologically fromPhoma tracheiphilaf. sp.tracheiphilaBaker et al., cause of "mal secco" of citrus, but will not infect sour orange or rough lemon plants.

ISSN:0008-4026    

DOI:10.1139/b85-242

出版商:NRC Research Press    

年代:1985

数据来源: NRC