摘要:

Late Cretaceous silicified Cupressaceae remains, recently recovered from the Horseshoe Canyon Formation of Alberta, Canada, include three-dimensional leafy twigs of theCupressinocladus interruptustype with attached seed cones, seeds, pollen cones, pollen, and woody stems. The abundance and excellent preservation of the remains allows detailed description of most aspects of the plant, including foliage, reproductive organs, epidermal features, and wood. Foliage of the fossil is frondlike and flattened, with an opposite, less commonly alternate, branching pattern. Seed cones, borne in decussate pairs, are globose, woody, about 4.0 mm in diameter, and bear four approximately equal-sized cone scales with small umbos near the scale center. Each seed has two broad, semicircular wings. Pollen cones are typical for the Cupressaceae; pollen grains are structurally comparable, but small, for the family. Fertile branches and seed cones are not identical to any extant member of the Cupressaceae, but they are sufficiently similar to those of the Paleocene cedarMesocyparis borealisfrom Western Canada to be referred to that genus. Dissimilarities justify assignment toMesocyparis umbonatasp.nov. Seed cone structure ofMesocyparis umbonataresembles most closely that of the northern hemispheric taxonChamaecyparis nootkatensis; the leaves resemble those ofThujaandChamaecyparis. Other features, including the number of seed cone scales, branching pattern, and wood anatomy, are more comparable to those of taxa of the southern hemispheric Libocedreae. New information, based on these remains, indicates that the relationship between some northern and southern hemispheric taxa is closer than previously proposed, supporting the premise that present systems of classification separating these taxa do not reflect phylogeny.Key words: Cupressaceae,Mesocyparis, Late Cretaceous, fossil, seed cones, evolution, phylogeny.

ISSN:0008-4026    

DOI:10.1139/b94-037

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Asparagus (Asparagus officinalisL.) microspore culture was performed in an array of experiments that assessed the roles of plant growth and culture conditions. The following protocol provided the best results. Flowers with microspores at the late uninucleate stage of development were collected from greenhouse plants grown at 22:18 °C (light:dark) and stored at 5 °C for 3 days. One millilitre of MS medium plus 0.2 g/L yeast extract, 500 mg/L casein hydrolysate, 800 mg/L glutamine, 2.0 mg/L naphthaleneacetic acid, 1.0 mg/L benzyladenine, and 6% sucrose (MSFY) was conditioned with 10 anthers/mL for 1 week, after which it was filtered. One hundred anthers were added to shed their microspores (1.6 × 105 per mL) and were removed after 3 weeks when 0.5 mL of fresh medium was added. Cultures were incubated at 35 °C for 1 week, then 30 °C for 5 weeks. Microcalli were collected subsequently on a 100-μm screen and placed on induction medium (MSFY minus yeast extract, plus 3 g/L gelrite) in darkness at 35 °C for 4 weeks and then in light at 25 °C for 4 weeks. Shoots, roots, and bipolar embryos were produced. The latter were transferred to maturation medium (MS plus 0.1 mg/L naphthaleneacetic acid, 0.5 mg/L kinetin, 3% sucrose, 3 g/L gelrite, and 0.65 mg/L ancymidol) for 4 weeks, then to germination medium (MS plus 1.0 mg/L gibberellic acid, 3% sucrose, 3 mg/L gelrite). Plantlets were grown and maintained on maturation medium. Approximately 0.3% of the cultured microspores produced calli, and 85% of calli produced plantlets. Of 10 plants analyzed, 2 were haploid, 7 were diploid and, 1 was tetraploid.Key words: asparagus, haploid, microspore.

ISSN:0008-4026    

DOI:10.1139/b94-038

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Several hundred vegetative and fertile specimens ofAzollaLam. have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality (Middle Tiffanian (Ti3) age) near Red Deer, Alberta. The spore complexes closely resemble those of the PaleoceneA.stanleyiJain & Hall, and the vegetative material is referred to that species. The specimens are unusually complete in that the remains of the fragile sporophyte are preserved, commonly with reproductive structures in place. Plants reaching up to 2.25 cm in length consist of alternately branched rhizomes bearing alternate, imbricate, sessile leaves. Leaves are ovate with entire margins, papillate surfaces, and a single midvein. Reproductive structures have been examined using light, scanning, and transmission electron microscopy. This new material is compared with the other Paleocene species for which sporophytes are known and discussed in terms of evolutionary trends for the genus. The specimens suggest that most of the vegetative characteristics of modernAzollaspecies were established by the middle Paleocene.Key words:Azolla, Salviniaceae, megaspore, massula, ultrastructure, Paleocene.

ISSN:0008-4026    

DOI:10.1139/b94-039

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Seasonal patterns of frost hardiness and the effects of photoperiod, water stress, and low temperature on hardiness development were examined in shoots of 1st-year seedlings of western red cedar (Thuja plicataDonn), yellow cedar (Chamaecyparis nootkatensis(D. Don) Spach), and white spruce (Picea glauca(Moench) Voss). Under natural conditions, spruce hardened in two stages starting in early August, first at a slow rate in response to shortening photoperiod, then at a faster rate in response to decreasing temperatures. Western red cedar and yellow cedar started hardening in late October to early November when the photoperiod was already less than 11 h and daily maximum temperatures less than 15 °C. Seedlings of these two species attained a greater degree of frost hardiness when exposed to persistent subfreezing temperatures. Under controlled conditions, 4 weeks of short photoperiod at warm temperatures (9 h light:15 h dark, 20:15 °C) had little effect on hardiness of the two cedars but increased hardiness in spruce to about −15 °C. Water stress increased hardiness in spruce under long photoperiod (18 h light: 6 h dark, 20:15 °C) but only marginally in western red and yellow cedar. Low temperatures (7:3 °C, light:dark, 9-h photoperiod) increased hardiness in all species. Exposure to 2 and −3 °C (light:dark, 9-h photoperiod) increased the rate of hardening in western red and yellow cedar but not in white spruce. The ability to deharden in white spruce was related to chilling requirements and not necessarily exposure to warm temperatures. The induction and maintenance of hardiness in the three species appear to be controlled by different environmental signals.Key words: photoperiod, low temperature, water stress, dormancy, dehardening.

ISSN:0008-4026    

DOI:10.1139/b94-040

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A simple technique has been developed to study the absorption capacity of the tufts of mycelial filaments, or hyphae, observed on both black and white trufflesTuber melanosporumandTuber aestivum. These hyphae sprout from the tops of certain scales on the peridium ofTuber. They colonize the surrounding soil and could therefore exploit the nutrients from a large volume of soil. The ability to absorb organic and inorganic nutrients from a source other than the host is a necessary condition for the hypothesis we wished to test, namely that at some stage in its development the truffle ascocarp becomes autonomous. The absorption was demonstrated using autoradiography and liquid scintillation counting. We found that the tufts of hyphae are water permeable (3H2O). In addition, they absorb a sugar ([14C]mannose) and an anion ([32P]phosphate). An analysis of our results shows that the spatial distribution of [32P]phosphate is independent of that of tritiated water; the transport of phosphate is therefore not determined by water flux. The quantity and redistribution of the tracer depended on the application site, directly onto the peridium or on a mycelial tuft. The tufts increase the absorption of the tracer and influence its internal redistribution towards accumulation zones.Key words: ascocarp,Tuber melanosporum,Tuber aestivum, absorption, truffle nutrition.

ISSN:0008-4026    

DOI:10.1139/b94-041

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Biomass and flower production, shoot growth, and shoot N, P, and K concentrations ofChamaedaphne calyculatawere determined in a bog in central Maine. Two separate field experiments were used to compare growth, reproductive output, and shoot nutrient contents ofChamaedaphne: (i) over two seasons under ambient conditions and following addition of N, P, and K individually and in combination; and (ii) during one season using a complete factorial design with three levels of both N and P. Biomass production and shoot length doubled following 1 year of N–P or N–P–K addition, whereas 2 consecutive years of addition tripled these characteristics. Growth responses were accompanied by an increase in tissue N, P, and K concentrations. The most striking response was a fivefold increase in the mass of flower buds produced per plant at the highest levels of N–P and N–P–K addition. The effects of N and P were interactive, and both the absolute quantity and ratio of N:P added were important in terms of the magnitude of the responses. Responses to N were typically curvilinear, whereas responses to P were both curvilinear and linear. AlthoughChamaedaphneis adapted to low levels of nutrient supply, it responds to the addition of nutrients by increasing the production of vegetative and reproductive tissue and by increasing the content of P in shoots. Without additional supplies of N, P, and K, growth byChamaedaphnein bogs may be restricted by competition for nutrients withSphagnum.Key words:Chamaedaphne, bog, nitrogen, phosphorus.

ISSN:0008-4026    

DOI:10.1139/b94-042

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Adaxial epidermises that contained an intact "subepidermal" "T"-shaped sclereid network, were isolated from olive tree leaves using a new method of enzymatic maceration. In the leaf, the sclereid network was anchored on the adaxial epidermis. The basal parts of the T-shaped sclereids penetrate the palisade cell layers into the underlying spongy parenchyma cells. In paradermal sections, the basal parts of the sclereids appeared as light-emitting sources or spots among the dark-green background of the palisade layers. The light spots almost disappeared when the intercellular air spaces were filled with immersion oil that had a similar refractive index to that of cell walls. It is plausible that light is propagated through multiple reflections between the thick cell wall of sclereids and the air filling the intercellular spaces, the former having a significantly higher refractive index. Sclereids act like synthetic optical fibres and, besides other functions, they may contribute to the improvement of the light microenvironment within the mesophyll of the thick and compact sclerophyllous leaves ofOlea.Key words: foliar sclereids, optical fibres, light guiding,Olea europaea.

ISSN:0008-4026    

DOI:10.1139/b94-043

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Lythrumcultivars Morden Pink, Morden Gleam, and Dropmore Purple, and a wild population ofLythrum salicariafrom Lockport, Manitoba were artificially self- and cross-pollinated. Success of pollination and fertilization was measured in terms of the percentage of resulting capsules and the average numbers of viable seeds per capsule. Germination tests were used to measure the viability of seeds produced as a result of successful crosses. Cultivars rarely produced seeds as a result of selfing but many crosses with wild plants or with other cultivars were fertile. As expected, legitimate (i.e., different style morphs) wild crosses were highly fertile, but other crosses gave high fertility, especially those in which 'Morden Gleam' was the provider of pollen or ovules. Although some sterility was indicated in 'Dropmore Purple' and perhaps 'Morden Pink', neither are sufficiently sterile to be considered safe for ornamental flower gardens. Most illegitimate crosses yielded greatly reduced seed outputs in comparison to legitimate crosses, but there were some exceptions. Germinability of ripe seeds from any cross was high and averaged 98%. Cultivars ofLythrumare capable of contributing viable seed and (or) pollen to the spread of purple loosestrife. The sale of cultivars, regardless of parentage, should be prohibited.Key words: purple loosestrife,Lythrumspp., interfertility, hybridization.

ISSN:0008-4026    

DOI:10.1139/b94-044

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Leptosphaeria korrae, the causal agent of necrotic ring spot, is a destructive patch disease of Kentucky bluegrass. To develop a rapid molecular test for the detection of this pathogen, an assay based on the polymerase chain reaction (PCR) was developed utilizing the internal transcribed spacer region 1 (ITS 1) ofL.korraeribosomal DNA. DNA sequence comparison showed 94.8% similarity of the ITS 1 region amongL.korraeisolates and only 45–50% similarity betweenL.korraeand other fungal species. Based on ITS 1 sequence differences, a pair of oligonucleotide primers, LK17S and 5.8SC, were selected. With PCR, the primers specifically amplifiedL.korraeDNA and did not amplify DNA isolated from 15 other fungal species or healthy Kentucky bluegrass. The assay could also specifically detectL.korraein diseased turfgrass samples.Key words: detection, ITS 1,Leptosphaeria korrae, necrotic ring spot, polymerase chain reaction, ribosomal DNA.

ISSN:0008-4026    

DOI:10.1139/b94-045

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Xylem sap of poplar trees was collected by vacuum extraction. Samples were taken year round and concentrations of thiols as well as amino acids were determined. Throughout the season glutathione was the predominant thiol in the xylem sap of poplar trees with concentrations ranging from 0.1 to 13 μM. Cysteine and γ-glutamylcysteine concentrations were 0.1–4 and 0.01–3 μM, respectively. The glutathione content was subject to strong seasonal fluctuations. Highest amounts of glutathione (13 μM) were observed in March, immediately before flowering of the catkins. Like γ-glutamylcysteine and cysteine, glutathione values reached further maxima at the onset of budbreak and leaf expansion in April and May. Also the amino acids investigated (glutamine, asparagine, glutamic acid, methionine, arginine) showed strong seasonal fluctuations in the xylem sap of poplar, with glutamine being the most abundant organic nitrogen compound (max. 13 mM). Highest amounts of amino acids were detected during April and May, the period of budbreak and leaf expansion, presumably owing to an increased degradation of storage protein. The sulfur-containing amino acid methionine was present in high amounts during the early growing season. It appeared to be the dominant reduced sulfur compound translocated in the xylem sap of poplar trees in April and May, whereas glutathione was the predominant organic sulfur compound in the xylem sap in March. The significance of storage and mobilization of reduced sulfur and organic nitrogen compounds for development of reproductive (catkins) and vegetative tissue (leaves and sprouts) in poplar trees is discussed.Key words: xylem sap, amino acid, thiol, transport, storage, mobilization.

ISSN:0008-4026    

DOI:10.1139/b94-046

出版商:NRC Research Press    

年代:1994

数据来源: NRC