摘要:

A new fossil walnut,Juglans eocinereasp. nov, very similar to the fossilJuglans tephrodesUnger and the extant butternutJuglans cinereaL., is described and illustrated based on nut specimens from the Beaufort Formation (Miocene?) on southwestern Banks Island. Extremely good preservation permitted the following external measurements: length, maximum width, maximum width to base, maximum thickness, maximum thickness to the base, and the internal measurements: seed length, seed width, maximum seed depth, divided width, length and width of the major septum, and wall thickness.In addition, ratios such as length to width, length to maximum width to base, length to height, length to distance from maximum height to base, length to seed length, seed length to width, length to length of major septum, and seed depth to height are calculated.These measurements were also made on the fossilJ. tephrodesUng., and the extant speciesJ. nigraL. andJ. cinereaL.Comparisons with modern and fossil forms indicate that the fossil is most closely related to the fossilJuglans tephrodes, but is also very similar toJuglans cinerea. It is suggested that the fossil is ancestral to bothJ. tephrodesandJ. cinereaand that it explains the anomalous occurrence of the latter species in North America.

ISSN:0008-4026    

DOI:10.1139/b74-011

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Three different cytotypes, diploid, triploid, and tetraploid, occur within the fern speciesPolypodium virginianumor rock polypody. Previous studies have shown morphological differences in the sporophyte and this study was undertaken to determine the distinctiveness of the gametophyte of these cytotypes. The cytotypes differ in several developmental features: percentage of viable spores produced, time required for germination to take place, and time required for the gametophytes to reach sexual maturity. Of the three cytotypes, the tetraploid had a higher germination rate and considerably faster rate of development than either the diploid or triploid. The triploid showed a high percentage of aborted spores and a slow and irregular development of the gametophyte.

ISSN:0008-4026    

DOI:10.1139/b74-012

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The discovery of several distinctive root fragments in carbonate petrifaction material from Illinois provides the basis for the investigation of a Middle Pennsylvanian medullosan rooting system. Specimens range from minute rootlets with incomplete primary development, to large axes over 2 cm in diameter with extensive secondary development. The axes are characterized by an exarch actinostele with up to five protoxylem points. The pericycle of small rootlets is surrounded by endodermis, parenchymatous cortex, and epidermis. More mature specimens exhibit periderm at the outer margin of the pericycle, and in the largest specimens the periderm forms the outermost tissue zone. Secondary xylem is extensively developed in large specimens, and completely surrounds the primary wood. The newly discovered specimens are compared with previously described medullosan roots, and possible affinities with the Middle Pennsylvanian species ofMedullosaandSutcliffiaare discussed.

ISSN:0008-4026    

DOI:10.1139/b74-013

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Nitrogen and phosphorus nutrition were investigated as limiting factors to primary production in a lowland wet sedge meadow and an upland birch–willow–heath community.Response to nitrogen fertilization in both communities, including increased protein content and dry weight production, indicates that nitrogen supply limits production in both soils. In the upland community, phosphorus supply does not limit production, but in the lowland sedge meadow, dilution of the soil solution may decrease phosphorus availability and render this element limiting to production.Nitrogen, if available, can be taken up and metabolized into organic compounds despite low soil temperatures. Phosphorus metabolism may be directly limited by low soil temperatures and low available nitrogen levels.Low soil temperature exerts an indirect limitation on plant production through limitation of organic matter decomposition and microbial nitrification, thus limiting the rate of nitrogen cycling.The importance of a low nutrient regime in the Arctic may be seen in the widespread occurrence of xeromorphic characters in many taxa, which thus require minimal mineral nutrition to best use their photosynthetic capacity. The low nutrient regime may partially explain the high proportion of perennial plants in the Arctic, since these species can accumulate a nutrient pool over time from a deficient environment.

ISSN:0008-4026    

DOI:10.1139/b74-014

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Seasonal changes in aboveground and belowground standing crop and primary production in aCarex lacustriswetland were determined and related to the basic life history of this species. There was a seasonal minimum of 180 g/m2green material aboveground frozen in the ice in winter and a maximum of 1037 g/m2in summer (early August). Seasonal aboveground production based on quadrat data and based on the difference between maximum and minimum standing crop is estimated to be 857 g/m2per year, maximum daily production 15 g/m2per day. A second estimate, also based on quadrat data but taking into account the very high shoot mortality during the growing season, was determined. Seasonal aboveground production then is 1580 g/m2per year, maximum daily production is 20.3 g/m2per day. Belowground standing crop was 387 g/m2in winter but then declined to an average summer low of 226 g/m2. Belowground standing crop increased during autumn and, by October 7, a value equal to the previous winter's value was reached. Shoots of this species live for 1 year or less, emerging in autumn, overwintering, and then dying sometime during the next summer.

ISSN:0008-4026    

DOI:10.1139/b74-015

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Development of the floret ofOryzopsis virescensandO. hymenoideswas studied. Evidence from this study and from other studies on grass floret development has brought the following interpretations. Histogenesis of the lemma, palea, posterior lodicule, and gynoecial wall is similar, and indicates their foliar nature. They are determinate organs, have a shallow site of initiation, and exhibit marginal growth. The anterior lodicules differ from them in having a deeper initiation site. The interpretation of the anterior and posterior lodicules as reduced perianth structures of one whorl rather than as structuresde novois preferred. The callus is formed by the downward projection of the base of the lemma. Developmentally, the stamens are stem-like. The gynoecium consists of a unit ascidiform gynoecial wall surrounding a terminal ovule. There are two styles, each of which develops from a lateral portion of the gynoecial wall. The floret apex is not used up in the formation of the gynoecial wall. The residual floret apex develops into the ovule. The grass gynoecium may be considered acarpellate.

ISSN:0008-4026    

DOI:10.1139/b74-016

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

An examination was made of the ability of the previously defined growth parameters to distinguish between Marquis and several other cultivars of wheat under controlled non-hardening (25 °C) and hardening (2–4 °C) temperature conditions. The spring wheats Marquis and Pitic were compared with the winter wheats Cappelle, Talbot, Rideau, and Kharkov. The maximum growth coefficient,kmL, for cv. Pitic significantly exceeded all others, those for Cappelle and Rideau were intermediate, and that for Talbot was lowest, but the range for winter wheats was not different from that for spring wheats at either temperature. Considerably reduced growth occurred under the lower temperature but neither the inverse relationship that is generally recognized to exist between plant growth and hardiness nor the recent evidence for growth in hardening tissues themselves were supported by any quantitative match between the growth parameters and freeze tolerance. It was concluded that the intrinsic growth coefficient, rather than the gross growth coefficient with its storage component, must be determined for correlation with hardening.

ISSN:0008-4026    

DOI:10.1139/b74-017

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Echinate bodies most commonly 20–40 micrometers (μm) in diameter are conspicuous inclusions carried with the cyclosis in the internode cells of some charophytes. Those inNitella flexiliswere investigated with light and electron microscopes. The chemical nature of the inclusion identified through various cytochemical techniques in the present study disagrees with the generally held belief that the echinate body is almost entirely composed of proteins. Microchemical tests have convincingly revealed the presence of tannin. The inclusion's close spatial association to endoplasmic reticula and to vesicles apparently derived from the Golgi apparatus and the cytochemical demonstration of acid phosphatase and thiamine pyrophosphatase activities in the matrix of the inclusion suggest that both cell organelles are actively involved in the development of this bizarre body with unknown function.

ISSN:0008-4026    

DOI:10.1139/b74-018

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Numbers of airborneMonilinia laxaconidia were related to the maturity of the sporodochia, the nature of the host structure bearing them, and the presence or absence of rain or fog. Hirst spore traps collected more airborne conidia during rains and on rainy days than on dry days among prunaceous hosts during the spring of 1966 and 1967. Numbers of conidia were greatest (6440 m−3 h−1) in the first 3–4 h of rain, while in dry periods, numbers were greatest (1200 m−3 h−1) when ambient humidity was lowest and temperature and wind speeds were highest. Fruit mummies, twig cankers, limb cankers, pedicels, and peduncles all bore sporodochia. Rains washed off successive crops of conidia, and with 52 800 conidia cm−2were collected directly below a sporulating peach fruit mummy. The significance of these dispersal periods in disease development and control is discussed.

ISSN:0008-4026    

DOI:10.1139/b74-019

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

An efficient, reliable, and economical technique is described which eliminates the problems associated with liquid scintillation counting of35SO42−. Acid digests of plant tissue are prepared for application to either filter paper or glass fiber, which acts as a carrier in the scintillator solution. The digests are also suitable for the assay of a number of other radioactive and stable isotopes.

ISSN:0008-4026    

DOI:10.1139/b74-020

出版商:NRC Research Press    

年代:1974

数据来源: NRC