摘要:

Vegetative multiplication of 'Passe Crassane' pear seedlings was obtained by micropropagationin vitro. Two clones (6 and 14) were selected on the basis of their rooting ability. This article describes optimal culture conditions to obtain a rate of multiplication greater than 6 shoots per month, together with good elongation, no morphological abnormalities, and a high degree of rooting, stable in time and of good quality.

ISSN:0008-4026    

DOI:10.1139/b87-108

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The stamens of theoguCMS line ofB.napusL. exhibited different patterns of differentiation in response to temperature but were not fertile under any conditions. Three types of CMS stamens were recognized. Type 1 stamens had a distinct anther and filament and, in some cases, microspores were observed. These stamens were found most frequently under a high temperature regime (28:23 °C, light:dark). Type 2 stamens bore features of both stamens and carpels and were most common under intermediate temperature conditions (23:18 °C, light:dark). Type 3 stamens were carpelloid bearing a stigmatic surface and external ovules, lacked a filament, and were predominant under low temperature conditions (18:15 °C, light:dark). Normal stamens retained the same morphology under all temperature conditions. The sizes of the floral organs of normal and CMS flowers were also influenced by temperatures. Sepals, petals, and stamens were longer under low temperature conditions than intermediate and under intermediate temperature conditions than high temperature conditions. The floral organs of normal plants were generally larger than those of the CMS line.

ISSN:0008-4026    

DOI:10.1139/b87-109

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The effect of Congo red, a dye which inhibits crystallization of cell wall polysaccharides, on hyphal differentiation and sporulation ofBotryodiplodia theobromaePat. was studied. The fungus has an obligate requirement for light to fruit in culture. The dye replaced the light requirement for formation of pycnidia. It also affected the structural integrity of the hyphal wall and the branching frequency of the hypha.

ISSN:0008-4026    

DOI:10.1139/b87-110

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Rooting ofPicea marianaMill. BSP. andLarix laricina(Du Roi) K. Koch trees was examined in four peatlands with different depth of water table. Peat blocks, 60 cm deep, 1.0 m from the base of each tree, were excavated and sectioned into 10-cm horizontal strata and the roots extracted. The presence of and depth to frost and the depth of water table were determined on each peat block. The periodic annual increment in basal area of each tree was determined. Rooting depth was strongly correlated with depth to water table. On wet sites, roots of both black spruce and tamarack were confined to hummocks, while on dry sites, roots penetrated to 60 cm. The deep roots were generally <2 mm in diameter and held in frozen peat layers until late June. There was a strong positive correlation between fine root biomass and depth of water table; however, total root biomass was not correlated with depth to water table. In general, growth rates of both black spruce and tamarack were positively correlated with water table.

ISSN:0008-4026    

DOI:10.1139/b87-111

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The objective of this study is to describe the structure, composition, and ecological relationships of old-growth forests of west central Vancouver Island. Data were obtained by sampling 172 plots, at elevations up to 1000 m, located within 13 drainage areas. Relationships between vegetation and environmental variation were examined using indirect and direct gradient analysis. Successive reciprocal averaging ordinations using data from the tree, sapling, seedling, shrub, herb, and bryophyte – lichen strata led to the recognition of six vegetation groups (floodplain, subalpine,Pinus contorta,Pseudotsuga,Thuja,Abies) and 23 community types. Vegetation groups are differentiated along climatic and soil parent material gradients. The floodplain group occurs on alluvial terraces and thePinus contortagroup on rock outcrops. The vegetation of thePseudotsugagroup, dominant inland and influenced by fire disturbance, appears to respond to gradients of elevation and soil moisture. TheThujagroup is found only near the coast, and its vegetation varies along gradients of soil nutrients and elevation, soil moisture having little effect. Wind is the strongest disturbance factor in this group. The vegetation patterns of theAbiesgroup are correlated with elevation and soil moisture. Most community types of this group are associated with cool microclimates.

ISSN:0008-4026    

DOI:10.1139/b87-112

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A flow cytometric method to identifyBrassicasomatic hybrids has been developed. The procedure is based on the use of fluorescein isothiocyanate stained hypocotyl protoplasts and unstained mesophyll protoplasts as partners for polyethylene glycol induced protoplast fusion. The fluorescein isothiocyanate stained hypocotyl protoplasts and unstained mesophyll protoplasts were passed through the flow cytometer – cell sorter separately to maximize the sensitivity of the red and green detectors to chlorophyll and fluorescein isothiocyanate fluorescence, respectively, and to ensure that there was no spillover of chlorophyll fluorescence into the green detector or fluorescein isothiocyanate fluorescence into the red detector. When adjusted properly, suspensions of a single protoplast type gave populations that fell on either the green or red axis of a two-dimensional green versus red fluorescence plot. With the same machine settings three populations of protoplasts could be identified in fusion mixtures of the two types of protoplasts: namely, the parental protoplasts that fell on the green or red axis as well as a third that had significant green and red fluorescence.

ISSN:0008-4026    

DOI:10.1139/b87-113

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The natural age and stand structure of Scots pine (Pinus sylvestrisL.), Norway spruce (Picea abies(L.) Karst.), and birch (Betula pubescensEhrh.) was studied in a virgin forest stand in northern Sweden. The stand has been unaffected by fire during the past 500 years. It is suggested that the variations in age structure and invasion pattern are the result of low-frequency climatic fluctuations influencing seed production, germination, and early survival of seedlings. The periods of climatic amelioration that occurred during the 1870s and during this century have been especially favourable to pine, resulting in a pine-dominated regeneration underneath a tree layer where spruce and birch are the most abundant species. This is contrary to generally accepted theories concerning postfire successional trends in this part of the boreal zone. It is concluded that small gap-phase replacement of trees by climatically induced regeneration and mortality events probably is the reason for the general weak correlation between age and size of trees. It is also concluded that this postfire succession will not lead to a total spruce dominance during a continuous succession under prevailing climate regimes.

ISSN:0008-4026    

DOI:10.1139/b87-114

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The regulatory actions of light, temperature, and various nitrogenous compounds on germination of dormantSinapis arvensisL. seeds were examined to evaluate possible strategies for manipulating germination of soil-bome weed seeds. These treatments, when given singly, had little or no promotive effect on germination. However, KNO3plus NH4Cl combined with irradiation and a change in temperature to 20 °C after 2 days of incubation at 5 °C induced over 90% germination. The effects of NH2OH∙HCl, KNO2, CS(NH2)2, KCN, and NaN3were also significantly enhanced when given in combination with a brief exposure to red light and a temperature shift. However, these sources of nitrogen were less effective than KNO3or NH4Cl in stimulating germination. The promotive effect of light, a temperature shift, and KNO3and NH4Cl declined when the period of incubation at 5 °C was less than 2 days. This combined treatment was also less effective when the treatment with nitrogen or light was delayed beyond the first 48 h of incubation. Our results indicate that applications of nitrogen fertilizers in combination with surface tillage to expose the seed to light could promote germination of dormantS.arvensisseeds in the fiel

ISSN:0008-4026    

DOI:10.1139/b87-115

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This study compares the vegetation composition in the Kananaskis Valley from a forest survey in 1883 to another survey in 1972 and reconstructs the fire frequency for the period 1783 – 1882 and the period 1883 – 1972. A comparison of the 1883 to 1972 forest surveys using transition probabilities revealed that sites populated mostly by lodgepole pine (Pinus contorta) or Englemann spruce (Picea Englemannii) tended to remain the same in both surveys. The fire reconstructions for the period 1730 – 1972 showed no change in fire frequency after the beginning of European activity in 1883. Further, for the periods both before and after 1883, the valley burned, on average, once every 150 years. The distribution of the fire sizes for the 100-year period before 1883 was slightly larger than the period after 1883. It appears that in 1972 natural processes (site differences and fire occurrence) still dominated the changes in the vegetation composition and age.

ISSN:0008-4026    

DOI:10.1139/b87-116

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Rhacomitrium pacificum, from western British Columbia, Washington, Oregon, and California, is described as new. The species is apparently related toR.heterostichum(Hedw.) Brid.

ISSN:0008-4026    

DOI:10.1139/b87-117

出版商:NRC Research Press    

年代:1987

数据来源: NRC