摘要:

Trees are among the most variable of organisms, the result, it would seem, of fusion between gametes from genetically different individuals. Genetically different individuals may result from selection, causing population differentiation over small geographic areas or selecting for different individuals in different climatic regimes that prevailed during different years. However, selection is not necessary to explain the existence of genetically different individuals. The evolutionary theory of Wiley and Brooks predicts an increase in variation as a consequence of natural laws pertaining to increasing disorder. The effect of habitat differences, trees, age, size of trees, and past climate, as evidenced by tree ring site summaries, on pattern of variation in needle variables was estimated by calculating the percentage of variation in principal components analysis axis scores for which each factor accounts. In all comparisons made, the greatest percentage of variation was accounted for by trees and an error term, indicating selection has little impact on patterns of variation. While it may be argued that relevant selective factors were missed, it should be pointed out that such arguments can lead to the unacceptable stance of explaining away unpopular results by asserting that the important elements were not measured. A large percentage of variation that is apparently unaccounted for by selection is a prediction that would follow from the theory of Wiley and Brooks.

ISSN:0008-4026    

DOI:10.1139/b84-061

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Results show the feasibility of regenerating rootingBidens albaplants from nopaline-type crown galls incited byAgrobacterium tumefacienscontaining pTi-T37. Transmission of the tumour marker nopaline synthesis is demonstrated into the fourth generation but decreases in level of expression or loss of the trait occurs. Nopaline synthesis and auxin autotrophy, as markers, can also be differentially lost, making it difficult to demonstrate Mendelian inheritance. Formation of octopine-type tumours on nopaline positive plants occurs in a high percentage of inoculations. Transformed plants show several morphological traits which distinguish them from normal plants: they are smaller, have decreased apical dominance, show hypertrophy of the hypocotyl region, lower nodes, and petiole bases, and frequently form an extra spur of tissue in ray flowers.

ISSN:0008-4026    

DOI:10.1139/b84-062

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Clonal material of one genotype ofStellaria longipesGoldie s.l. was used to study the effects of photoperiod and temperature on stem elongation. Temperature is the more important influence for induction of stem elongation. Photoperiod exerts a lesser effect. A combined synergistic effect of temperature and photoperiod is in operation. A minimum number of heat degree-days, equivalent to about 3 days at 22:18 °C (day: night) temperature, is required to induce elongation. A minimum period of "winter cold," equal to 50 short, cold days is required for maximum elongation in subsequent warm, long days. Some elongation will occur in continuous long, warm days, but a short cold period is essential for flowering. After 8 months in short, cold days flowering will occur without elongation.

ISSN:0008-4026    

DOI:10.1139/b84-063

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

When seedlings ofHelianthus annuusL. were grown in the dark with their roots in vermiculite saturated with distilled water the rate of elongation of the hypocotyl was significantly increased by increasing the relative humidity around the shoot from approximately 25 to 100%. This response was correlated with a reduction in transpiration rate of approximately 95% and with increases in the water potential and cell turgor in the growing region. Measurements with a transducer revealed very rapid growth responses to changes in humidity, usually preceded by a variable period of growth oscillations. Excision of the roots, either in water or in air, induced an immediate increase in rate of elongation at low humidity, but at high humidity this response was delayed and markedly reduced. The growth rate was significantly increased by supplying 10 mMKCl to the roots at both high and low humidity. The response to K was slower than the response to humidity and was correlated with a significant reduction in the osmotic potential of the growing region. A growth response was first detected approximately 45 min after the application of K to the roots and 10 min after application to the shoot. These results arc consistent with the hypothesis that, in the intact plant, stem elongation is largely controlled by the interacting effects on cell turgor of transpiration-induced negative pressure potential in the apoplast and the osmotic potential of the growing cells.

ISSN:0008-4026    

DOI:10.1139/b84-064

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Giant cells associated with egg-laying females ofMeloidogyne javanicain lima bean,Phaseolus lunatuscv. L-136, were examined by light and electron microscopy. These giant cells have characteristics that are typical of nematode-induced giant cells in a wide range of hosts, but they differ in that they (i) are less closely associated with xylem vessels, (ii) contain a very large number of plastids which are devoid of starch grains, and (iii) contain several different forms of cytoplasmic crystals. One form of the crystal is associated with a large number of "spiny" vesicles. The possible role of these features, especially the crystals, in the giant cell response of lima bean is discussed.

ISSN:0008-4026    

DOI:10.1139/b84-065

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Buds and developing branches ofBetula papyriferawere collected weekly from mature trees during three successive growing seasons. Material was prepared to show stages of bud inception, development, flushing, shoot expansion, and male inflorescence inception and early development. Stages of bud development were correlated with axillant leaf and subjacent internodal extension. Long-shoot buds develop in the axils of distal late leaves of the previous season's long shoot. The bud contains one rudimentary leaf with prominent stipules, two or three embryonic foliage leaves which flush as early leaves, and about five smaller primordia which expand in the spring as late leaves. Preformed primordia are produced in mid-May through to early August. A pause in the inception sequence occurs in June, corresponding to the period of rapid late-leaf and internodal expansion of axillant leaves and subjacent internodes. Long-shoot bud determination occurs in mid-July. True late leaves may form during shoot extension. Male inflorescence induction, which occurs before bud break, restricts late leaf production and results in the last-formed leaf primordia maturing as transitional leaves instead of foliage leaves. Male induction limits crown expansion by reducing sites for axillary bud formation. This reduces the photosynthetic potential of the shoot.

ISSN:0008-4026    

DOI:10.1139/b84-066

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Postflush observations on shoots ofBetula papyriferaMarsh. indicated that long and short shoots differ in a range of morphological characteristics. Long shoots developed from distal axillary buds and short shoots developed from proximal axillary buds on the previous year's long shoots. Consequently, the potential of a bud to develop into a long shoot decreased basipetally. Potential long-shoot buds had higher bud-relative growth rates, stem-relative growth rates, leaf-relative growth rates, and stem dry weights during the course of postflush growth. Changes in leaf thickness, expressed in terms of specific leaf area and specific leaf weight, indicated that long shoots temporarily had thinner leaves than did short shoots a few weeks after flushing. Net assimilate requirements in long shoots for late leaf and internodal expansion may explain these observations. Nearing maturity, long-shoot early leaves became thicker, possibly owing to greater shoot vigour and (or) higher photosynthetic efficiency. Consequently, mature long-shoot early leaves possessed larger and thicker laminae, longer petioles, more side nerve pairs, and tended to grow more in length than width than short-shoot leaves on shoots of comparable age. Leaves of older short shoots, 2–10 years old, attained a greater size and had longer petioles than those of 1-year-old short shoots. Stem elongation and the development and expression of leaves in long shoots seemed to have a correlative influence on the overall vigour of long shoots.

ISSN:0008-4026    

DOI:10.1139/b84-067

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Chromosome counts are provided for 25 populations representing 18 species ofAgalinisRaf. Chromosome numbers are reported for the first time forA.pinetorum,A.laxa,A.acuta,A.gattingeri, andA.skinneriana. The base chromosome number for sectionLinifoliae, sectionHeterophyllae, sectionPurpureaesubsectionsPurpureaeandSetaceae, and sectionTenuifoliaeis established atx = 14. SectionErectaeand sectionPurpureaesubsectionPedunculareshave a base number ofx = 13.

ISSN:0008-4026    

DOI:10.1139/b84-068

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

In vitrodisassembly of tobacco mosaic virus (TMV) strains U1, U2, U4, U6, and U7with alkali and urea was studied by sucrose or sucrose–dimethylsulfoxide (DMSO) density gradient centrifugation and by agarose gel electrophoresis. All strains gave similar decapsidation patterns with both agents when partially stripped virus particles (PSVs) were analyzed by sedimentation and electrophoresis. However, U6was more sensitive to decapsidation than the other strains and U2exhibited resistance to decapsidation. Agarose gel electrophoresis of TMV decapsidation products allowed the detection of several classes of PSVs in addition to aggregation products involving PSVs and monomer particles. Agarose gel electrophoresis is thus very rapid and useful for analysis of TMV disassembly products especially when aggregation phenomena and kinetic studies with numerous samples are considered.

ISSN:0008-4026    

DOI:10.1139/b84-069

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The present study describes the effects of simulated acid rain (pH 2.5–5.6) on foliar histology of an arctic herb,Artemisia tilesiiLedeb., which is remarkably tolerant to naturally occurring atmospheric acidity at Smoking Hills, N.W.T. Plants were exposed to simulated acid rain twice weekly for 4 weeks in exposure chambers in the greenhouse. Droplets as acidic as pH 2.5 caused limited macroscopic foliar damage. However, much greater damage was observed when sectioned leaf tissue was examined microscopically. On leaves having no injury visible to the unaided eye, small lesions consisting of one to three collapsed epidermal cells were observed in scanning electron micrographs and in cleared leaves after exposure to rain of pH 3.0 and 3.5. Stomata remained open in damaged areas of acid-sprayed leaves. Lesions most commonly developed from an initial collapse of a few adaxial epidermal cells, followed by progressive injury of underlying tissues. Palisade and spongy mesophyll cells underwent hypertrophic (abnormal cell enlargement) and hyperplastic (abnormal cell division) responses in the region adjacent to severely collapsed tissue, causing reduced intercellular spaces. These effects isolated the injured areas from adjacent healthy tissues, and resembled wound periderm responses to fungal pathogens and to mechanical irritation. This response may be one mechanism of limiting acid rain damage.

ISSN:0008-4026    

DOI:10.1139/b84-070

出版商:NRC Research Press    

年代:1984

数据来源: NRC