摘要:

The incorporation of caffeine in standard transmission electron microscope fixation procedures has allowed good preservation and embedment of ectomycorrhizal short roots of English oak (Quercus roburL.). In the mantle the most conspicuous structures are cystidia which radiate outwards from the surface. These conically shaped cells have knobs at their tips and thickened cell walls. The cystidia and other outer mantle cells contain many cytoplasmic constituents, whereas the inner mantle cells are nearly devoid of cytoplasm. The mantle cells are held together by an intercellular slime network. The Hartig net cells are filled with cytoplasm and contain numerous lipid droplets. Typical dolipore septa separate the cells; however, these cells have irregularly branched shapes. The host root tissue appears little altered by the presence of the fungal symbiont. However, the root cap consists of only a few cell layers. The apical meristem is functional as evidenced by the presence of newly divided cells and microtubules lining enlarging cells.

ISSN:0008-4026    

DOI:10.1139/b84-180

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Previous observations onTrichomaneswith thick stems and axillary buds are compared with those recently obtained from species with slender stems and extraaxillary buds and also fromCardiomanes. In all species, leaves arise from typical two-sided apical cells and buds are initiated adjacent to them in cauline tissues, laterally on the apical meristem. Three different localizations of buds occur (axillary, extraaxillary, and intermediate) and result in different orientations of the whole lateral system (= leaf + bud). Each different arrangement is visible as early as the initiation stage. The leaf apical cell faces the bud initials in all cases. Growth does not interfere with relative orientation of the organs but greatly changes the vertical position of the buds, which may be borne on the stem near leaf insertion or at the leaf base. These results illustrate the necessity of accurate observation of the ontogenetic origin of lateral organs to define them.

ISSN:0008-4026    

DOI:10.1139/b84-181

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Water use efficiency (WUE, the ratio of dry matter produced to water used in transpiration) was studied in 17 poplar clones and hybrids. Although WUE could not be predicted from the poplar group alone, water efficiency was found to vary in different poplar genotypes. For example, a balsam poplar,Populus maximowicziiM-4 (sectionTacamahaca), and a white poplar clone,P.albaA-499 (sectionLeuce), had twice the dry matter production per unit of water transpired compared with another clone ofP.maximowiczii(M-13) and a Cottonwood clone,P.nigraN-80 (sectionAegeiros), which showed low WUE. The reduced transpiration in water-efficient clones per unit of dry matter produced was associated with a higher stomatal resistance on the abaxial leaf surface. However, the physiological and morphological basis of WUE varied in different clones. Water-efficient clones exhibited one or more of the following adaptations restricting water loss: (i) conspicuous cuticular ledges or hairs above the pore openings of stomata, (ii) earlier partial stomatal opening in the morning, and (iii) smaller stomata and a lower stomatal frequency on the adaxial surface of the upper leaves. Poplar clones of low WUE exhibited less stomatal control of transpiration as a result of lower stomatal resistances and they lacked the above adaptations. Relative ranking of genotypes could not be predicted from either dry matter productivity or transpiration rate alone although the most water efficient clones generally exhibited lower transpiration rates compared with less efficient clones.

ISSN:0008-4026    

DOI:10.1139/b84-182

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Decomposition of wild rice (Zizania aquaticaL.) straw was studied by placing 20 g of air-dried straw into 25 × 15 cm size nylon bags. Each set of five straw bags was covered in a fine aluminum screen to avoid damage from aquatic animals. The screens were placed on October 17, 1979, in West Bay representing a river system and in Lulu Lake, a typical shallow wild rice lake. After 350 days the total decomposition by weight of straw was 94 and 72% in West Bay and Lulu Lake, respectively. Release of nutrients from the straw was studied by calculating the percent loss of nutrients in each sampling period. A rapid release of nutrients was observed during the first 3 weeks followed by a slow release of nutrients thereafter. Total amounts of nutrients released after 350 days were about 98% potassium, 82% calcium, 81% phosphorus, 79% sulfur, 72% magnesium, and 57% nitrogen. The amount of nitrogen released and the carbon:nitrogen ratio of straw at the jointing stage of wild rice suggest that a major portion of the total nitrogen remains tied up in straw and may not become available for the next wild rice crop.

ISSN:0008-4026    

DOI:10.1139/b84-183

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The spore mass ofUstilago aegilopsidisis blackish brown; the spores germinate with the production of four primary sporidia on the promycelium, and infection of the host occurs through the coleoptiles of very young seedlings. Two collections of the fungus were pathogenic onAegilops bicornisandAegilops caudata, and one collection was also pathogenic onAegilops cylindrica, but neither collection was pathogenic on 18 otherAegilopsspp., eightTriticumspp., or twoHordeumspp. Experimental hybridization of the fungus with two smuts of barley,Ustilago nigraandUstilago hordei, showed thatU.aegilopsidisis very closely related to these fungi, and possibly conspecific withU.nigra.

ISSN:0008-4026    

DOI:10.1139/b84-184

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The vascular flora of raised bogs in southeastern Labrador is composed of only 26 species, which may be grouped into three different elements: wide-ranging arctic–boreal species, boreal species reaching their northeastern range limits in the forest–tundra transition, and boreal species reaching their range limits along the shores of Lake Melville. The striking impoverishment of the Labrador bog flora relative to those in Newfoundland and other parts of the Gulf of St. Lawrence region is apparently the result of the colder more continental climate of Labrador, which excludes from the regional bog flora the less hardy species of southern affinities.

ISSN:0008-4026    

DOI:10.1139/b84-185

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Internal vascular symptoms induced byCeratocystis ulmiinfection and cerato-ulmin (CU) in white elm (Ulmus americana) were observed under a scanning electron microscope. Symptoms caused by CU were indistinguishable from those caused byC.ulmi. The main symptoms observed were (i) edemalike surface wall alteration, (ii) granular deposit, (iii) pit membrane heaving, (iv) smooth coating, (v) bubble and (or) tylose formation, (vi) rough coating, (vii) droplet formation, and (viii) vessel plugging with calluslike material. Internal symptoms appeared earlier in CU treated elms (as early as 2 h after treatment) than inC.ulmiinfected elms (10 h after infection).

ISSN:0008-4026    

DOI:10.1139/b84-186

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Urophora cardui(L.) induces a large multichambered gall in stem tissues ofCirsium arvense(L.) Scop. Four phases in gall development are identified: initiation, growth, maturation, and dehiscence. Initiation begins when larvae tunnel from a shoot tip into the developing stem and change the polarity of pith and procambial tissues. These cells become gall parenchyma and proliferate during the growth phase. Procambial strands and gall laticifers appear among the gall parenchyma and the cells nearest the larvae differentiate into primary nutritive cells. In the maturation phase, gall tissues cease proliferating, procambial strands near the larvae give rise to secondary nutritive tissue, and all remaining gall parenchyma lignifies. Dehiscence occurs when callus tissues at the top of the gall degrade. Developmental studies utilizing insect-induced galls may increase our understanding of normal plant growth and development.

ISSN:0008-4026    

DOI:10.1139/b84-187

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A 396-cm sediment sequence from SW Lake in the boreal woodland zone near Travaillant Lake, Northwest Territories, Canada, provides a Holocene record of pollen percentages and species interactions. Three local pollen assemblage zones are described: aBetula–Populus–Juniperuszone from 10 500 to 9000 years BP, aPicea–Betulazone from 9000 to 5100 years BP, and aPicea–Betula–Alnuszone from 5100 years BP to the present. The earliest vegetation recorded at this site is a mosaic of poplar groves, juniper andShepherdiashrub, and fragmentary patches of tundra, replaced rapidly by spruce woodland at roughly 8500 years BP, dominated initially byPicea glauca.Picea marianaspread extensively between 8500 and 5000 years BP, probably as a function of increasing paludification. The present spruce-dominated vegetation was in place by 5000 years BP. Some changes in the pollen record can be explained by the Milankovitch early Holocene period of warmer summers followed by a cooling to modern conditions by 5000 years BP. Others require explanations in terms of edaphic factors or biological interactions among the main taxa.

ISSN:0008-4026    

DOI:10.1139/b84-188

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The callus-promoting activity of most commonly known as well as some rarely tested auxins was compared with that of 2,4-dichlorophenoxyacetic acid (2,4-D) forin vitroculture of the excised embryo of spring and winter wheat (Triticum aestivumL.), cv. Chinese Spring and cv. Fredrick. Different auxins in a concentration range from 1 to 50 μMshowed widely different activities. Also the two wheat cultivars responded differently to the auxins. When rapid callus formation with limited root growth was used as the basis for comparison, 2-(2-methyl-4-chlorophenoxy)propionic acid (2-MCPP), α-naphthaleneacetic acid, 3,6-dichloro-2-methoxybenzoic acid (dicamba), 4-amino-3,5,6,trichloropicolinic acid (picloram), γ-(2,4-dichlorophenoxy)butyric acid, 2,4,5-trichlorophenoxyacetic acid, and 2,4,5-trichlorophenoxypropionic acid, in the order of effectiveness, were superior to 2,4,-D for callus induction from the embryo of 'Chinese Spring,' although the concentration required was higher than that of 2,4-D. For the winter wheat 'Fredrick,' however, only picloram, dicamba, and 2-MCPP performed as well as 2,4-D. All auxins tested promoted shoot growth; 2-methyl-4-chlorophenoxypropionic acid was most effective for 'Chinese Spring,' whereas picloram was most effective for 'Fredrick.'

ISSN:0008-4026    

DOI:10.1139/b84-189

出版商:NRC Research Press    

年代:1984

数据来源: NRC