摘要:

Turnera ulmifolia(Turneraceae) is a polymorphic complex native to the New World tropics which is composed of heterostylous and homostylous forms. The distylous varietieselegans, intermedia, andsurinamensisexhibit the typical expression of heterostyly. Floral dimorphism is associated with a strong self-incompatibility system and size dimorphism of pollen. Approximately equal representation of floral morphs occurred in 24 out of 28 New World populations surveyed. In 9 out of 10 populations studied, there were no significant differences between the seed fecundity of floral forms. Populations of the homostylous varietyangustifoliaare self-compatible and produce monomorphic pollen.In contrast to the majority of heterostylous species, some varieties ofT. ulmifoliaare ruderal weeds. Varietiesangustifolia, elegans, andintermediaare also used as garden ornamentals, and man has played a major role in the expansion of their ranges. Weediness inT. ulmifoliais not associated with features commonly found in other weed species, such as self-compatibility, vigorous clonal propagation, and long-distance seed dispersal. However, the continuous year-round flowering ofT. ulmifoliaplants gives populations a high reproductive capacity. Seed dispersal is by ants which transport seeds relatively short distances. Local seed dispersal favors the establishment of dense populations and increases the likelihood of seed set. Hence the dispersal system ofT. ulmifoliaappears to be coadapted with the population requirements of the breeding system.

ISSN:0008-4026    

DOI:10.1139/b78-203

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A new variety of the maidenhair fern,Adiantum pedatumvar.subpumilumW. H. Wagner, is described. Known previously only as a garden plant, a natural population has been discovered on coastal rock cliffs on the Brooks Peninsula of NW Vancouver Island. The basic frond structure is like the typical variety, but the plant is extremely dwarfed, the fronds are only 6–12 cm tall with imbricated pinnules. The venation pattern is much simplified. Horticultural plants of var.subpumilumyieldn = 29 pairs of chromosomes, like the typical variety. The diminutive stature of var.subpumilumis genetically fixed.

ISSN:0008-4026    

DOI:10.1139/b78-204

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Eighty cacao isolates ofPhytophthorafrom Africa, the Americas, the Pacific, and Southeast Asia, originally designated asPhytophthora palmivora, were studied. The sporangial stalk or pedicel length of various isolates was significantly different. These isolates were separated into four groups on the basis of the stalk or pedicel length. The differences in characteristics among the four groups and their relationships to the morphological forms (MF) ofP. palmivoraare described.One group of isolates, designated as MF 1, had short and thick sporangial stalks averaging less than 5 μm in length. Isolates in a second group corresponded to MF 3, with rather thin sporangial stalks, intermediate in length, averaging 5–15 μm. Sporangial stalks of a third group of isolates, designated as MF 4, had unusual and characteristically long stalks with an average length of more than 15 μm. A fourth group of isolates had noncaducous sporangia. Similarities between MF 4 isolates and the type culture ofP. capsiciare noted.The stability of sporangial stalk length under several different environmental conditions makes this character very useful as a taxonomic criterion for identifying isolates in theP. palmivoracomplex.

ISSN:0008-4026    

DOI:10.1139/b78-205

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Rates of net photosynthesis, transpiration, and dark respiration of seven populations representing the diversity of theDaucus carotacomplex were measured. The two taxonomic groups of this complex proved physiologically distinguishable, with subspecies aggregategingidiumpossessing lower capacities for photosynthesis and transpiration and a lower frequency of stomata than subspecies aggregatecarota. In comparison with wild populations of the complex, cultivars manifested greater efficiency of photosynthesis with respect to water use, possibly the result of an increased demand for photosynthate in domesticated populations. The highest rate of photosynthesis was exhibited by a vigorous, primitive, Asian cultivar, which also possessed the highest stomatal frequency.

ISSN:0008-4026    

DOI:10.1139/b78-206

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The effectiveness of excess cadmium, cobalt, nickel, and zinc in eliciting similar early responses was studied in white beans. Each metal caused the appearance of a red–brown discoloration first in the veins of unifoliate leaves and later in petioles and stems. Cadmium, nickel, and zinc did so within 1 day, cobalt within 4 days. The effectiveness of the metals in inducing visual symptoms and in decreasing dry matter production were in the order. Within 1 day of adding excess metal, each caused the unifoliate leaves to orient themselves towards the vertical from the normal horizontal. Each metal caused premature leaf closure within the normal nyctinastic cycle.Excess cobalt, nickel, and zinc all caused abnormal starch accumulations in unifoliate leaves within 2–3 days. These metals also caused a major shift towards relatively apolar soluble phenolic components in leaves but not in roots. Cadmium, besides being most toxic, did not cause starch accumulation or a shift in the complement of soluble phenolics.

ISSN:0008-4026    

DOI:10.1139/b78-207

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The relative abundance of native species in both the Cactaceae and Crassulaceae in different regions of North America is highly negatively correlated with the coefficient of humidity, an estimate of soil moisture content. The species of both families are relatively more abundant in dry habitats as estimated by this coefficient and other moisture variables. The two families exhibit different patterns of seasonal correlation with the monthly values of the coefficient of humidity. The Cactaceae are most strongly correlated with winter values and the Crassulaceae with summer values. The preferred habitats of the Cactaceae are characterized by high rates of evaporation, while the preferred habitats of the Crassulaceae are characterized by low amounts of precipitation. The species of the Cactaceae are much more highly correlated (multipleR = 0.977) with the combination of moisture and temperature variables that best predict their relative geographic abundance than are those of the Crassulaceae (multipleR = 0.888) with the combination of variables yielding the best prediction of their abundance. It is suggested that the expression of the crassulacean acid metabolism (CAM) phenotype may be of less overall importance to the members of the Crassulaceae of North America than it is to the members of the Cactaceae.

ISSN:0008-4026    

DOI:10.1139/b78-208

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Isotherms were obtained for the influx of K+into roots of intact barley (Hordeum vulgare(L.) cv. Conquest) plants which had previously been grown in either 0.5 mMCaSO4solution or 0.5 mMCaSO4plus 5 mMKGl solution.KmandVmaxvalues obtained from these influx data were 0.03 ± 0.003 mMand 10.8 μmol g−1 h−1respectively for the low-K+plants and 0.1 ± 0.01 mMand 1.74 ± 0.08 μmol g−1 h−1for the high-K+plants.When the K+content of low-K+plants was increased, by pretreating the roots of intact plants in 10 mMKCl plus 0.5 mMCaSO4solution, K+influx values, as determined from 0.1 mMKCl plus 0.5 mMCaCl2solutions, declined continuously during the 12 h of pretreatment. Hill plots of this data revealed a consistent biphasic response to internal K+. Below 50 μmol K+ g−1the Hill coefficient was close to unity. Above 50 μmol g−1the Hill coefficient increased to values close to 3. The time, or root K+concentration, at which this change in Hill coefficient occurred corresponded to the first indications of net transfer of K+to the shoot.

ISSN:0008-4026    

DOI:10.1139/b78-209

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A survey of phytoplankton in lakes, rivers, and temporary pools in the Northwest Territories was conducted during 1975, 1976, and 1977.Dinobryon bavaricumwas the most abundant and widespread species, occurring in almost all collections. It was followed in order of decreasing importance byD. cylindricum, D. sociale, andD. divergens. The predominant diatoms wereCyclotella glomerataandC. ocellata. Both species reached greatest abundance in lakes and rivers in the high arctic and were completely absent from temporary pools. AlthoughAsterionella formosa, Diatoma tenuevar.elongatum, andMelosira islandicawere common in Great Slave Lake and other southern lakes, they were either rare or absent north of latitude 65°. The Chlorophyta, particularlyAnkistrodesmus falcatusandScenedesmusspp., occurred in almost all collections but always in low numbers. Planktonic Cyanophyta (primarilyOscillatoria limnetica) were normally rare.

ISSN:0008-4026    

DOI:10.1139/b78-210

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Poronia pileiformisis described and illustrated. Cultures were obtained from germinated ascospores. On SME agar, stromatal stipes developed but did not produce heads or perithecia. Conidia were produced at the apices of the young stipes only. The conidia were holoblastic, borne on sympodial conidiogenous cells.

ISSN:0008-4026    

DOI:10.1139/b78-211

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Fifty-seven species of Corticiaceae collected in Venezuela are reported. The genusRogersellaand the speciesR. asperulaare described as new and one new combination is made:Rogersella sambuci.

ISSN:0008-4026    

DOI:10.1139/b78-212

出版商:NRC Research Press    

年代:1978

数据来源: NRC