摘要:

The presence and magnitude of photorespiration in the submersed freshwater angiospermScirpus subterminalisTorr. was investigated by gas-exchange characteristics in an open water-flow system. The minimal rates of photorespiration during active photosynthesis were measured by following the time course of differential14CO2and12CO2uptake. At 8 mg O2L−1(equal to oxygen saturation at 20 °C), the rate was 0.4 μg C (mg organic dry weight)−1h−1, which was about 10% of net photosynthesis under the experimental conditions. Increasing the oxygen concentration to 30 mg O2 L−1, enhanced photorespiration to 30% of net photosynthesis. It was shown that the concentration of oxygen affected net photosynthesis, CO2evolution into CO2-free water in the light, the post-illumination CO2burst, and the CO2compensation point.The effect of the internal gas space on recycling of CO2was investigated by comparing gas-exchange by intact and sectioned leaves. About 30% of the CO2of photorespiratory origin was recycled internally within the lacunal system. The gas-exchange characteristics ofScirpuswere similar to those observed in terrestrial C3species although of a minor magnitude and a different time course. The ecological implications of these finds are discussed.

ISSN:0008-4026    

DOI:10.1139/b80-075

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Examination of the Chrysophyceae flora in Otter Lake, British Columbia, by electron microscopy verified the occurrence of eight scale-bearing species belonging to the generaEpipyxis, Spiniferomonas, Chrysosphaerella, Mallomonas, andMallomonopsis. Two of the species,Epipyxis kenaiensisandMallomonopsis paxillata, are reported from Canada for the first time. This report also includes notes on the taxonomy and distribution of the eight species of Chrysophyceae and basic limnological data for Otter Lake.

ISSN:0008-4026    

DOI:10.1139/b80-076

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Scoring for morphometric characters was conducted on both herbarium material (including artificially produced hybrids) and specimens collected across Canada and Alaska and studiedin situ. The data from herbarium material were analysed by means of various principal component analyses and by a series of discriminant analyses. The morphometric data from field material were obtained by repeated observations of every spikelet along the one side of each spike selected for analysis. A representative sample of spikes was collected from every population visited, with emphasis on hybrid populations. These repeated observations within spikes were also made in order to evaluate the reliability, representability, and taxonomic value of every spikelet and the degree of homologization within a spike. The field data were analysed by means of discriminant analyses and various cluster analyses.The conclusion reached is the recognition of three species for Canada and Alaska,H. jubatumL.,H. caespitosumScribn.,H. brachyantherumNevski, and a hybridH. jubatum×brachyantherumrepresenting F1and F1-like phenotypes. Classification function coefficients were computed and are provided in this paper in order to effect both the identification of the three taxa and the hybrid and their circumscription.All the herbarium specimens were identified by means of these coefficients and, as a result, previously unsuspected hybrids were revealed. This study indicated that an analysis of herbarium specimens alone can be misleading and, consequently, that field data are necessary. It is also demonstrated that the spikelets within a spike are not uniform enough for taxonomic reliance to be placed on observations made on one spikelet alone.

ISSN:0008-4026    

DOI:10.1139/b80-077

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Total cell volume estimates and species composition for twig microepiphytes are presented for four species of coniferous trees common in the Pacific Northwest. Fungal cell volumes per square centimetre were much greater onPseudotsuga menziesiithan on the other conifers sampled; population densities of algal cells were similar on all hosts. OnP. menziesii, microbial populations build up as the twigs age, with total cell volumes at a maximum on 6- and 7-year-old twigs; thereafter total cell volumes decline as twig surface areas decline, although population densities remain high. When fungal cell volumes are expanded to tree and stand levels, estimates of 372 cm3/tree and 15 kg/ha are generated. These values are significant in comparison with estimated standing crops of epiphytic fungi on needles (30 kg/ha) and suggest that twig microepiphytes must be considered in any investigation on the role of epiphytes in nutrient cycling in coniferous forests.

ISSN:0008-4026    

DOI:10.1139/b80-078

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The ontogeny of the sclerotia ofColletotrichum coccodeswas investigated by scanning electron microscopy. The sclerotium originated as an acervulus differentiated from a stroma, a mass of tightly interwoven thick-walled hyphal cells. Initially, hyphae at the surface of the stroma differentiated into conidiophores and conidia which resulted in a typical acervulus. Following sporulation, the stroma beneath the acervulus assumed the form of a sclerotium. This sclerotium expanded laterally by repeating the processes of acervulus development. As a result, a large aggregate composed of several small sclerotia was formed.Structurally, a mature sclerotium, regardless of its size and shape, consisted of three zones: the outermost, sclerotized, brown spongy layer; the middle, plectenchymatous layer; and the innermost, prosenchymatous core (medulla). The majority of cells in the spongy layer were empty. The plectenchyma consisted of living, tightly packed, thick-walled cells with little or no intercellular spaces. The prosenchyma consisted of loosely packed, living hyphal cells.

ISSN:0008-4026    

DOI:10.1139/b80-079

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The study of the expression of morphogenetic potential in stem segments of flax (Linum usitatissimumL.) was undertaken as a function of donor plant age and level (basal, median, or apical) on the stem axis and in the absence of growth regulatory substances. Neoformation of normal buds (resembling seedlings) gave rise to shoots with no visible axillary buds, and a few roots were obtained from explants taken from young, vegetative plants; these organs were more numerous on basal than on apical explants. If the donor plant was in a prefloral or floral state, thus older and at a different physiological stage, a "modified" bud was formed, characterized by its slow growth, short thick stem and leaves, and sometimes with visible axillary buds. This type of bud was more numerous in apical than in basal segments. Callus was also formed and was reduced in size and limited to the cut extremities of explants when the donor plant was young, but was large and covered almost all the explant when the plant was older.

ISSN:0008-4026    

DOI:10.1139/b80-080

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Eocronartiumhas long been considered a parasitic Auriculariales, perhaps representing an ancestral form of our modern-day rusts of higher plants. Septal ultrastructure of two collections ofE. muscicolareveals a pore structure essentially identical to those of the Uredinales and Septobasidiales and different from those of other Auriculariales studied thus far.

ISSN:0008-4026    

DOI:10.1139/b80-081

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Suspension cultures ofDaucus carotaCa68,Cannabis sativa95C, andIpomoeasp. were screened for their ability to utilize an alternate to sucrose as a carbon source for growth. Of the substrates tested glycerol was chosen for further study and all three cultures were adapted to growth on this carbon source addedin lieuof sucrose to 71V medium. Growth ofC. sativa95C proceeded only after a long lag phase. The latter could be reduced by replacing the ammonia nitrogen with nitrate nitrogen or almost eliminated by controlling the pH of the medium at either pH 5.1 or pH 6.3. In contrast, cultures ofD. carotaCa68 andIpomoeasp. grew on glycerol after a short lag of 1–2 days.The utilization of glycerol as a carbon source by plant cell cultures is discussed with respect to other reports using this and other substrates as alternatives to sucrose. The influence of ammonia on the initiation of growth, nitrate utilization, and the initial pH of the medium is discussed in view of our findings.

ISSN:0008-4026    

DOI:10.1139/b80-082

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Forty-seven isolates ofCeratocystis ulmicollected from Canada, the United States, the United Kingdom, France, the Netherlands, and Iran were classified with respect to their ability to produce cerato-ulmin (CU) and synnemata, their radial growth, mycelial habit, and pathogenicity.Twenty-nine isolates clearly produced CU in a measurable quantity while 18 isolates produced it only in trace quantities. In general, the former produced fluffy mycelium and were active in synnemata formation. They were aggressive in pathogenicity with one exception. The latter group of isolates generally produced waxy, yeastlike mycelium and formed very few synnemata. They were all nonaggressive in pathogenicity. Radial growth was generally higher among the isolates that produced CU in larger quantities than among those producing CU in trace quantities. The relationship between CU production and pathogenicity affords a method for estimating isolate pathogenicity without the need for host inoculation.

ISSN:0008-4026    

DOI:10.1139/b80-083

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Recovery of cerato-ulmin (CU) in the water extract from intact hyphae ofCeratocystis ulmiproved that it is present on the hyphal surface. Degrees of the accumulation of unidentified material on the cell surface of hyphae, together with CU recovery, varied from high, among isolates classified as distinct in CU production, to unmeasurable, among isolates classified as negligible in CU production. There was a correlation between the accumulation of unidentified material on the hyphal surface as observed under the scanning electron microscope (SEM) and recovery of CU from hyphal colonies. Most of the accumulated material was water-extractable, as is CU, and it is therefore concluded that the material accumulated on the hyphae of isolates classified as distinct in CU production does, indeed, contain CU.

ISSN:0008-4026    

DOI:10.1139/b80-084

出版商:NRC Research Press    

年代:1980

数据来源: NRC