摘要:

The heritability of the dormancy of primary seeds in four populations of wild oats was estimated by the parent–progeny regression method and found to be approximately 50% under field conditions.

ISSN:0008-4026    

DOI:10.1139/b80-011

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In view of wintertime browning of needles of pines introduced in Alaska, winter desiccation damage was suspected. However, examination of field xylem water potentials and relative water contents indicated little water stress in pine needles but severe stress in sunny native spruce needles and slightly less stress in shaded needles. Spruce were typical of drought tolerant plants, exhibiting field xylem water potentials of –10 to –40 bars and field relative water contents of 88 to 99%, closing stomates at water contents of 71 to 92%, and maintaining cuticular conductances from 0.013 to 0.088 cm s−1. In contrast, pines were drought avoiding, exhibiting field xylem water potentials of 0 bars and field water contents of 100%, keeping stomates closed all winter, and maintaining cuticular conductances from 0 to 0.033 cm s−1and 0 to 0.074 cm s−1in lodgepole pine and yellow pine, respectively. Needles of all species photosynthesized at temperatures from 0 to 10 °C with rates in spruce being 10 times those in yellow pine and 3 times those in lodgepole pine. While spruce needles had significantly more carbohydrate reserves at the end of the winter than did pine needles, the latter were apparently not severely carbohydrate depleted.

ISSN:0008-4026    

DOI:10.1139/b80-012

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A technique has been developed to biosynthesize a water-soluble extract of11C-labelled photosynthate high in [11C]sucrose. The extract can be produced in less than 1 half-life (20 min) and is of high activity. When11C-labelled extract was fed to the individual vascular bundles of other living plants,11C was taken up and translocated, and on the basis of direct and indirect evidence it was largely in the form of [11C]sucrose.11C-labelled extract, if fed to a flap or gentle scraping on the surface of a sunflower stem (or corn, cow-parsnip, pine, or elm) was translocated both apically and basally from the feed point. Incisions into xylem vessels produced very rapid tracer movements which seemed to be associated with xylem vessel liquid cavitation and also transpiration pull. Shallower cuts produced translocation patterns similar to11CO2leaf feedings and are thought to be largely in the phloem. Phloem transport was blocked by ice chilling; xylem transport was only slightly affected by ice, if at all. Phloem translocation profiles often displayed steps at the front of mass flow, and later appeared to have peaks of activity moving along them. The movements were sometimes rapid (>6 cm min−1) and appeared to be complex, as if different channels were conducting at different speeds in parallel.

ISSN:0008-4026    

DOI:10.1139/b80-013

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The inputs of the airborne pollutants nickel, copper, iron, and sulfur were determined in bulk dustfall–rainfall collection and in snow samples taken along transects originating at a large nickel–copper smelter near Sudbury, Ontario. Determinations were made from 1975 to 1978, which was subsequent to the building of a 380-m smokestack at the smelter in 1972. Atmospheric SO2was also monitored, using sulfation plates. Higher levels of all smelter pollutants occurred at sites closer to the smelter, compared with sites as far as 60 km SSE. All bulk rainwater samples collected along a 60-km transect SSE of the smelter were found to be acidic, most with a pH of less than 4.0. Since there was no clear gradient of acidity with distance from the smelter, it appears that the acidic precipitation problem is a severe regional one. Simple deposition budgets based on data collected on six 30-day sampling intervals in 1976 and 1977 indicate that less than 3% of the sulfur emitted from the smelter was deposited within a 60-km radius. In contrast, about 42% of the nickel, 40% of the copper, and 52% of the iron emitted from the smelter were calculated to be deposited within a 60-km radius.The contamination of forest soils, soil litter, and vegetation by copper, nickel, iron, and sulfur at sites closer to the smelter has been caused by past as well as ongoing emissions. In soil profiles, the metals were concentrated in the surface organic horizons, relative to deeper mineral soils. Surface soils up to 70 km from the smelter showed elevated nickel and copper concentrations. Elevated concentrations of these same metals in the foliage of a number of tree species were detectable at least to 12 km from the smelter. The horsetailEquisetum sylvaticumshowed especially high concentrations of sulfur, while the mossPolytrichum communewas an accumulator of nickel, copper, and sulfur at sites up to 6 km. No consistent trends with distance occurred for foliar levels of the bases calcium, magnesium, and potassium. However, higher calcium concentrations occurred in forest litter collected at control sites, compared with sites closer to the smelter.

ISSN:0008-4026    

DOI:10.1139/b80-014

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Inorganic elements in air-dried conidia and conidiophores ofErysiphe graminis hordeiwere analyzed with an energy dispersive X-ray microanalyzer. Prominent peaks of Mg, Si, P, S, K, and Ca were obtained when several points on these fungal structures were analyzed. As peaks of Mg, P, S, and K had not been detected in chemically fixed specimens, these elements were considered to have been leached out during specimen preparation. Area analyses for K and P, and spot analyses for the other elements, led us to conclude that chemical elements were apparently distributed homogeneously in the conidia and conidiophores. This conclusion, however, is persuasive only within the detection capabilities of the present method.

ISSN:0008-4026    

DOI:10.1139/b80-015

出版商:NRC Research Press    

年代:1980

数据来源: NRC