摘要:

Alyssum alyssoidesL. is an Eurasian winter annual that has become naturalized in the United States, where it grows in bare, disturbed habitats. In north-central Kentucky seeds germinate during summer and early autumn, and plants overwinter as semirosettes. Flowering and seed production occur in spring, and mature seeds are dispersed in late spring and early summer. At maturity seeds are conditionally dormant, but by early summer to midsummer they are capable of rapid germination in light and darkness at temperatures that occur in the habitat. Unlike other species of winter annuals from the same geographic area, seeds ofA. alyssoidescan germinate rapidly and to high percentages at field temperatures in July and August when the soil is sufficiently moist for a few days. However, plants from summer-germinating seeds are killed by droughts during July and August, and all plants that survive to maturity are from autumn-germinating seeds. On the basis of its germination characteristics and drought intolerance,A. alyssoidesis not well adapted to a warm, temperate climate with summer rainfall interspersed with periods of drought such as occurs throughout much of the southeastern United States. This may help to explain why the species has not been reported from states south of Kentucky in the eastern United States.

ISSN:0008-4026    

DOI:10.1139/b74-318

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Gas–liquid chromatographic analysis of the trimethylsilyl ethers of the ethanol (90%)-extracted carbohydrates (soluble carbohydrates) from soybean (Glycine max) plants demonstrated the presence of major quantities ofO-methylinositol, glucose, fructose, and sucrose, minor quantities ofmyo-inositol, and two unidentified components. In leaf blades and petioles of 6-vveek-old plants,O-methylinositol accounted for more than 50% of the total soluble carbohydrates present.

ISSN:0008-4026    

DOI:10.1139/b74-319

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Perithecial formation, the mechanism of ascospore release, and conidiogenesis inSubbaromyces splendensHesseltine are described from light microscopic and scanning electron microscopic investigations. Growth of the neck of the perithecium, which apparently involves elongation of hyphal cells, is pointed out as an unusual developmental feature in this fungus. The potential of usingS. splendensas an experimental organism in studies of fungal morphogenesis is discussed.

ISSN:0008-4026    

DOI:10.1139/b74-320

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

By using the soybean cotyledon callus bioassay for cytokinin-like compounds and two methods of extraction of cytokinins from plant tissues, the presence of growth-active compounds of a purine nature has been detected in soybean (Glycine max. L. cv. Mandarin) root cell suspension cultures growing in a medium containing NH4+. These compounds can be added to residual NH4+, glutamine, and an adequate supply of amino acids as conditioning substances in these cultures.

ISSN:0008-4026    

DOI:10.1139/b74-321

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A quantitative comparison of foliage display in two plots of corn, seeded differently, revealed that the plants in both have essentially the same architecture despite differences in planting procedure. No significant azimuth preferences were found. Investigations of leaf inclinations indicated that leaf distribution functions are very close to the theoretical spherical distribution, with the result that radiation interception calculations are independent of solar altitude. This greatly facilitates the incorporation of canopy structure variables into theoretical models of canopy radiation interception.

ISSN:0008-4026    

DOI:10.1139/b74-322

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The observation with the electron microscope of specimens during conidium initiation reveals the enteroblastic nature of the conidial prefiguration. The morphological characteristics expressed during the other stages of conidiogenesis (conidium maturation and propagule liberation) are also studied. The cytochemical techniques (showing the presence of polysaccharidic and proteinic substances) confirm our conclusions on the nature of the newly formed primary sporal envelope and show an identical wall structure whatever the organ studied.A comparison with the functioning of other types of phialides is made and a relationship between the phialoconidiogenesis (Phialophora richardsiae(Nannf.) Conant.) and the annello-conidiogenesis (Doratomyces purpureofuscus), based on the similarity of conidium initiation mechanisms, is accepted.

ISSN:0008-4026    

DOI:10.1139/b74-323

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Capsidiol, the phytoalexin from peppers, rishitin, the phytoalexin from potatoes, and 20 other derivatives or model compounds related to capsidiol were compared for fungitoxicity against a range of pathogenic and non-pathogenic fungi, using spore germination and growth assay procedures. Capsidiol was the most active compound tested (mean effective dose (ED50) vs.Phytophthora infestons, 1 × 10−5 M) and all derivatives examined had decreased activity. No correlations were found between sensitivity to capsidiol or rishitin and pathogenicity for peppers or potatoes, nor were there any clear correlations between structure and activity. Activity was greatly influenced by minor structural changes and such changes frequently had differential effects on different fungi. The results suggest that phytoalexins such as capsidiol, even if not primary determinants of disease resistance, could influence the progress of disease and the sequence of subsequent colonization.

ISSN:0008-4026    

DOI:10.1139/b74-324

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Gene-specific RNA directly involved in resistance of wheat (Triticum aestivumL.) to stem rust (Puccinia graminisPers. f. sp.triticiEriks. and E. Henn.) was produced only in interactions involving an avirulent race of stem rust. The genotype of the host did not affect the production of this RNA, suggesting that the RNA involved in the expression of resistance is a product of the gene for avirulence.Several parameters affecting the bioassay used for the detection of this active RNA were investigated. These included temperature, infection density, the time interval between infection and injection of extract, and the time interval between injection and harvest.A comparison between the number of necrotic sites produced after injection of active RNA into leaves of the resistant line and the number produced in the incompatible interaction showed that 2–7% of the potentially reactive sites respond in the bioassay by becoming necrotic.The active RNÀ isolated from a stem rust – wheat interaction involving a given gene for avirulence produced a response in bioassay plants only when both the corresponding gene for resistance and stem-rust haustoria were present.

ISSN:0008-4026    

DOI:10.1139/b74-325

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Application of different concentrations of the naturally occurring cytokinin zeatin 6(4-hydroxy-3-methyl trans-2-butenylamino)purine caused changes in one or more species of tRNAs. With the depletion of storage products from senescing cotyledons quantitative changes in tRNAleu1, 5, 6, tRNAser1–3, and tRNAtyr1–4were observed. Higher concentrations of zeatin applied as a single spray did not produce significant changes either in the cotyledon or the hypocotyl. The relationship of cytokinin activity to senescing soybean cotyledons is discussed.

ISSN:0008-4026    

DOI:10.1139/b74-326

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A rapid reconnaissance technique was used to sample montane vegetation in the Alsek River region, southwest Yukon. Twenty-one major community types are described from 223 sample stands. The forest vegetation of the region is interspersed with numerous shrub and herb vegetation types. This vegetation diversity is extraordinarily rich for a forest region and is due primarily to the variable climate (both local and regional) and the frequency of disturbance by fire and geomorphological processes.Ten communities, within four forest types, are distinguished in the region. The most widespread forest type is dominated byPicea glauea. The remaining three are dominated byPopulus tremuloides, P. balsamifera, andSalix scouleriana. Shrub communities recognized include theBetula glandulosa–Festuca altaica, Salix glauca, Juniperus communis–Arctostaphylos uva-ursi, Artemisia frigida–Poa glauca, Artemisia alaskana, andSalix setchelliana–Oxytropis campestristypes. Herb communities distinguished include theCarex sabulosa, Hedysarum boreale–Agropyron yukonense, Calamagrostis, andAgropyron yukonensetypes.Examination of diversity and its components during succession in the Alsek River region indicates that, in general, richness and general diversity increase and dominance decreases until the later stages of succession, when these trends are subsequently reversed. Evenness, while somewhat more variable, showed trends similar to that of the dominance component. Deviations from these trends occurred when the habitat was either extremely homogeneous or extremely heterogeneous.The flora of the region is relatively rich and derived from many North Temperate elements. The largest segment (64%) is derived from the more northern (Circumarctic-alpine, Circumboreal-montane, Amphi-beringian, Amphi-atlantic) elements.

ISSN:0008-4026    

DOI:10.1139/b74-327

出版商:NRC Research Press    

年代:1974

数据来源: NRC