摘要:

TheMinuartia rossiicomplex, which consists ofM. austromontana, M. elegans, andM. rossii s. str., is confined primarily to Arctic–Alpine North America. Previously, the three taxa have been recognized at various taxonomic levels. However morphological, cytological, and phytogeographical data support the recognition of the taxa at the specific level. The basic chromosome number of the complex isx = 15, withM. rossiihaving 2n = 58 and 60,M. austromontana2n = 30, andM. elegansboth 2n = 30 and 2n = 60. With respect to reproductive biology, the complex as a whole exhibits pronounced protandry and is gynodioecious; however,M. rossii s. str. rarely flowers and relies almost exclusively on vegetative reproduction via bulbils. The three taxa have distinct geographical distributions:M. rossii. Wrangel Island, high Arctic North America, Greenland, and Spitzbergen;M. elegans. Eastern Siberia, Alaska, the Yukon, and south to Alberta; andM. austromontana, confined primarily to the front ranges of the northern and central Rocky Mountains. This distribution pattern is probably the result of Pleistocene survival of the taxa in three different areas: the Canadian Arctic Archipelago, Beringia, and south of the ice. The epithetcolumbianafrequently applied to the Rocky Mountain taxon is invalid. The nameMinuartia austromontanaS. J. WolfetPacker is proposed for this taxon and it is herein described, having never previously been given formal taxonomic recognition.

ISSN:0008-4026    

DOI:10.1139/b79-205

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Pea plants (Pisum sativumL. cv. Trapper) were inoculated and grown in controlled-environment chambers at two irradiance levels. Shoot and root dry weights and nitrogen contents, total leaf and stipule areas, and rates of C2H2reduction were determined during growth in different treatments of NH4NO3addition. Although overall growth increased with irradiance, the growth responses to combined nitrogen addition were similar at both light levels. Two phases of early vegetative growth were identified by their different responses to combined nitrogen. During the first phase, low levels of NH4NO3greatly increased the relative growth rate, the growth per unit leaf area, and the percentage of nitrogen in the tissues. This indicated a period of nitrogen stress which lasted only until the 3rd week. Over the next 2 weeks, combined nitrogen increased the relative growth rates to a lesser extent, primarily through an increased partitioning of assimilates to shoot development. This distribution effect was rapidly reversible on changing nutrient conditions. The early stimulation of leaf area development by addition of combined nitrogen during these two growth phases resulted in greater capacity for symbiotic fixation after NH4NO3was removed.

ISSN:0008-4026    

DOI:10.1139/b79-206

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A cytological study of meiotic pairing behavior in intraspecific hybrids was undertaken utilizing seven different collections ofCeratopteris thalictroides. Two mutant gametophyte stocks with nonfunctional spermatozoids were utilized to facilitate the synthesis of intraspecific hybrids. Low levels of univalent and quadrivalent formation were found in most of the hybrids, indicating that some structural differences existed, but major pairing homologies were still evident. The fertility of hybrids ranged from 10 to 75% spore germination. One collection, from Hawaii, showed high levels of univalent formation and very low spore viability. In that this stock is both biologically and morphologically distinct, it should be given taxonomic recognition. The study, in general, is in agreement with the most recent taxonomic treatment ofCeratopterisin that it shows a significant amount of cytological variation within the polymorphic speciesC. thalictroides.

ISSN:0008-4026    

DOI:10.1139/b79-207

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Cultures ofLeptosphaeria typhaesubmitted to nycthemeral photoperiods produced perithecia on the 7th day of growth. Control developed in darkness remained sterile. At the beginning of growth, fertile cultures had more lipids which contained more palmitic acid and less linoleic and linolenic acids than vegetative mycelia. After the first perithecia appeared, the evolution of lipid content was entirely reversed.

ISSN:0008-4026    

DOI:10.1139/b79-208

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The competitive and synergistic interactions ofDrechslera sorokinianaandCurvularia geniculataon pathogenesis of leaf spot was evaluated on sequentially senescent leaves ofPoa pratensis. Leaf age had no effect on the mean number of lesions produced from inoculations withD. sorokinianaorC. geniculataalone. The combination ofD. sorokinianaandC. geniculataproduced a significant increase in the mean number of lesions between the youngest and oldest leaves at 20, 25, and 30 °C. Disease severity on leaves of all ages resulting from inoculations at 20 and 25 °C was greatest in response toD. sorokinianaalone, followed by the combination of organisms, and byC. geniculataalone, in descending order. No difference in disease severity occurred on leaves of different ages in reponse to the inoculations at 20 °C, but a significant increase in disease occurred on the two oldest leaves at 25 °C in response to inoculations withD. sorokinianaand to the combination of organisms. At 30 and 35 °C, disease severity on leaves of all ages was greatest in response to inoculations with the combination of organisms,D. sorokinianaalone, andC. geniculataalone, in descending order. Disease severity increased from the youngest to the oldest leaves at 30 °C in response to inoculations with the combination of organisms or withD. sorokinianaalone. Reisolations established that inoculations withD. sorokinianaalone resulted in successful establishment of the pathogen in the tissue of leaves of all ages at 20, 25, and 30 °C. At these temperatures, inoculations withC. geniculataalone produced a significantly higher level of reisolation from the youngest to the oldest leaves of the shoot. Reisolation of the individual organisms from leaves inoculated with both organisms showed thatC. geniculataestablished more successfully thanD. sorokinianain leaves of all ages as temperatures were increased. It was concluded that the synergistic increase in disease produced by the combination ofD. sorokinianaandC. geniculataat high temperatures is the result of increased high-temperature growth of C.geniculatawhich is probably more saprophytic than parasitic on senescing, heat-stressed leaves and does not reflect a high-temperature increase in virulence of this organism.

ISSN:0008-4026    

DOI:10.1139/b79-209

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Measurements of pollen tetrad diameters of eight ericad species from Burns Bog, Delta, B.C., showed that although diameters range continuously from 22 to 53 μm, groups of species can be recognized. These groups are ecologically significant with (i) small tetrads indicating dry habitats, (ii) intermediate tetrads indicating intermediate to dry sites, and (iii) large tetrads characteristic of wet habitat species. Pollen productivity of six of the above species varies, with those in dry sites producing much more pollen than species of wet habitats. Tetrad diameter spectra obtained from bog sediments under various ericad associations are dominated by tetrads of a diameter characteristically produced by the species growing at the site. Therefore fossil ericad assemblages can be interpreted on the basis of tetrad diameters.

ISSN:0008-4026    

DOI:10.1139/b79-210

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

LeucophlepsandLeucogasterare not related to the other genera traditionally placed in the Melanogastrales and have been placed in a new orderLeucogastrales, with a single family, Leucogastraceae. The genusLeucophlepsis described on a worldwide basis. Four species are included:L. magnataHarkness.L. aculeatisporasp.nov.,L. levispora(Mattirolo) comb, nov., andL. spinisporanom.nov.Leucophleps clelandii, L. foveolala, L. Candida, L. citrina, andL. odorataare excluded.

ISSN:0008-4026    

DOI:10.1139/b79-211

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The seed coverings, including the pericarp and testa of the caryopsis and the hull, arc the main barriers to the exchange of gases and the penetration of exogenous gibberellic acid (GA3) for germination of wild oats (Avena fatuaL.). Dormancy was induced in seeds by immersing them in water for 15 minor longer. Dormancy induction was greater in those seeds immersed for up to 1 h in 6% sodium hypochlorite (NaOCl) and then 1 h in water than in those seeds immersed only in water for 1 h. The addition of GA3, to seeds subjected to NaOCl treatment for 15 min or less did not break dormancy, indicating a slow rate of entry, or the exclusion, of GA3, by the seeds. In the presence of GA3, germination increased with increasing exposure to NaOCl. Maximum germination was obtained by immersing dry seeds in NaOCl for 2 h, in water for 1 h, and then incubating the seeds in GA3. Gibberellic acid was not required for complete germination of imbibed, dehulled seeds immersed in NaOCl for 1 h then in water for 1 h, but it was necessary to use 10−4 MGA3for complete germination of intact seeds that were treated with NaOCl or 2 h then with water for 1 h. Imbibed, dormant seeds that were dehulled and pierced required 10−7 MGA3, to give complete germination in this study. Piercing of the seed coverings enhances GA3, penetration and thus increases the availability of GA3, for germination. NaOCl treatment to the seeds mimics the effects of piercing. NaOCl may also have caused loss of germination inhibitors or rendered these inhibitors susceptible to oxidation. However, prolonged NaOCl treatment resulted in either poor germination or seed disintegration.

ISSN:0008-4026    

DOI:10.1139/b79-212

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Seed germination of wild buckwheat (Polygonum convolvulusL.) and cow cockle (Saponaria vaccariaL.) increased with increasing time of immersion in 6% sodium hypochlorite (NaOCl). Maximum germination was obtained at 6 to 8 h for wild buckwheat and at 2 h for cow cockle. The effect of NaOCl treatment of wild buckwheat seeds mimics the effect of acid scarification. Wild buckwheat germination was not influenced by light and (or) gibberellic acid (GA3). To induce 50% germination (t½) of cow cockle NaOCl treatments of 0.5 and 1 h were required for seeds incubating in the dark and light, respectively. Once the seed coat was made more permeable by NaOCl, both the promoting effect of GA3and the inhibitory effect of light were increased. When the optimum effect of NaOCl occurred, all the seeds germinated. However, prolonged NaOCl treatment resulted in either poor germination or seed disintegration.The hard coat seems to be the main factor in regulating wild buckwheat seed germination. Cow cockle, however, is regulated by at least two other factors, light and hormones, in addition to seed coat.

ISSN:0008-4026    

DOI:10.1139/b79-213

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Permineralized specimens ofPolysporiaare described from coal balls of three Middle Pennsylvanian age coals of the Illinois Basin. Identification is based on the presence ofEndosporitesmicrospores andValvisporitesmegaspores along with sporangial fragments in the axils of leaves interpreted as sporophylls. The shoots exhibit alternating fertile and vegetative zones. Vegetative leaves are larger than sporophylls which are often desiccated and folded back against the stem surface; a short zone of transitional sterile leaves is found between vegetative and spore-bearing zones. Ligule pits are present on the adaxial surface of vegetative leaves. The stems are essentially herbaceous but robust and 4–6 cm in diameter. Small amounts of periderm and wood were produced but primary tissues were not disrupted.Polysporiais the first herbaceous lycopod with an alternation of fertile and vegetative areas found in Pennsylvanian peats and is compared withSpencerites, Sporangiostrobus, andLepidodendron dacrydioides(proposed vegetative stem ofSporangiostrobus) which are suspected to have similar structure. The rarity ofPolysporiain coal balls and its frequent associations withSphenophyllum, combined with low numbers of arborescent lycopods,PsaroniusorMedullosa, suggest an environment of growth not frequently encountered in coal-ball studies of the swamps.Polysporiamay have grown in marginal wetland environments where herbaceous and low shrubby plants predominated; this suggests that someEndosporites—rich coals of the Upper Pennsylvanian are derived in large part from marshland peats.

ISSN:0008-4026    

DOI:10.1139/b79-214

出版商:NRC Research Press    

年代:1979

数据来源: NRC