摘要:

The gross photosynthetic response ofCladonia stellaris(Opiz.) Pouz. & Vezda.,Cladonia rangiferina(L.) Wigg., andCetraria cucullata(Bell.) Ach. to a continuous, long-term,in situSO2fumigation was monitored during the growing season at Anaktuvuk Pass, Alaska. The photo-synthetic capabilities of the test species were either destroyed or significantly reduced depending upon the SO2stress gradient over the fumigation plot. Additional sampling of the plot 1 year after termination of the fumigation revealed no significant recovery in photosynthesis, and chlorophyll contents of the test species were significantly less than the controls.

ISSN:0008-4026    

DOI:10.1139/b80-258

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A new spiny trimerophyte is described from early to middle Emsian (Lower Devonian) strata of Atholville, New Brunswick, Canada, where the specimens occur in a secondarily silicified tuff.Psilophyton crenulatumsp.nov. is characterized by vegetative branches which are 2 mm to 8.3 cm long, twice to seven times dichotomous and terminated by slender recurved tips. Some vegetative divisions are two closely spaced dichotomies (double dichotomies) which appear as trifurcations. The central axis of the trifurcation varies from about 1 mm to 2.5 cm in length. Fertile units terminate a dichotomous axis, and are alternate and distichous or are helically arranged. They are five to seven times dichotomous in three dimensions and consistently pendulous after the second or third dichotomy. These units are covered with crenulations on the first few orders of branching and terminate in sporangia 3–5 mm long by 1–2 mm wide. Sporangia are consistently twisted around each other.In situspores are 48–102 μm in diameter and are compared with the dispersed spore genusApiculiretusispora. Stomata are reported but an epidermis is usually lacking in most specimens. Spines are terete in cross section, multicellular, up to 6 mm long, and undivided, bifurcate, or trifurcate. Crenulations are semicircular to oval and 100–200 μm in diameter. Vascular strands up to 1 mm in diameter are centrarch with metaxylem tracheids that have scalariform- to circular-bordered pits.Psilophyton crenulatumrepresents the oldest known bonafide species ofPsilophyton. A reconstruction is included along with a discussion on the evolution of megaphyllous leaves, the origin of adventitious roots, and branching similarities betweenP. crenulatumand younger ferns.

ISSN:0008-4026    

DOI:10.1139/b80-259

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The lipids in teliospores ofTilletia carieswere analyzed at 12 different sample periods during the germination process. The lipid analysis included the separation and identification of hydrocarbons, natural methyl esters of fatty acids, and free fatty acids. Dormant spores contained more free fatty acids than natural methyl esters of fatty acids. However, 12 h after imbibition of water, the free fatty acid content was a small percentage of the total fatty acid content and the natural methyl esters were then the major lipid fraction, and they remained the major lipid fraction throughout germination. Stable isotope [2H] exchange experiments indicated that the methylation of the fatty acids was not an artifact of the extraction process. The role of natural methyl esters of fatty acid in the germination process is not clear.

ISSN:0008-4026    

DOI:10.1139/b80-260

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The anatomical development of the abscission zone in grains ofZizania aquaticaL. was correlated with development of the embryo. The abscission zone is well developed when the embryo sac is mature. Soon after pollination, the first anatomical evidence of abscission appears as plasmolysis of the separation layer parenchyma cells. This is followed by separation of the layers by dissolution of the middle lamella and fragmentation of cell walls. Persistence of intact vascular tissue and presence of a surrounding cone-shaped mass of lignified cells may be involved in abscission of wild rice grains.

ISSN:0008-4026    

DOI:10.1139/b80-261

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Four hundred and eighty plants in northern California from 27 taxa in the Ericaceae and 5 in the Pyrolaceae were surveyed for presence of ectomycorrhizae, arbutoid, or ericoid mycorrhizae between September 1977 and April 1978. Of these, 337 in the Ericaceae and 8 in the Pyrolaceae had one or more types of mycorrhizae.At least 88% of the plants of larger shrubs or trees (Arbutus menziesiiorArctostaphylosspp.) were mycorrhizal in various locations in northern California. Of the plants in the remaining twenty-two taxa that were mycorrhizal, 67–100% had ectomycorrhizae or arbutoid mycorrhizae. Twenty-three taxa of ericaceous or pyrolaceous plants in the generaCassiope, Gaultheria, Kalmia, Ledum, Leucothoe, Phyllodoce, Rhododendron, Vaccinium, Pyrola, andChimaphilawere also mycorrhizal. The type and abundance of mycorrhizae appear to depend on as yet undefined ecological factors.Ectomycorrhizae (including theCenococcumtype) or ericoid mycorrhizae are reported for the first time inArbutus, mostArctostaphylosspp.,Gaultheria shallon, Kalmia polifolia, Ledum glandulosumvar.columbianum, Leucothoe davisiae, Rhododendron macrophyllum, Vaccinium arbuscula, V. ovatum, V. scoparium, Chimaphila menziesii, andPyrola pictaf.picta.

ISSN:0008-4026    

DOI:10.1139/b80-262

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Medium that had supported the growth of a peanut cell suspension culture was found to be a rich source of peroxidase. Precipitation with acetone and ammonium sulfate, followed by a pH shift and ion exchange chromatography, led to the isolation of a single cationic peroxidase isozyme of high specific activity and high RZ of 2.91. The isolated peroxidase was shown to be a single peptide chain.

ISSN:0008-4026    

DOI:10.1139/b80-263

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Callus of the tumor hybrid ofNicotiana glauca×N. langsdorffiigrew better on agar in flasks than on liquid medium in flasks or on agar medium in Petri dishes. Asymmetric callus without roots produced small leaves and parenchyma cells were the most common type of cell. Few meristematic clusters were present, but these were very active during exponential and deceleration growth phases. The volume of their nucleoli, which were large and stained intensely, was used as a marker of the cell cycle. Shortly after transplantation the tissue divided synchronously, but thereafter it became asynchronous. An investigation of nucleic acids and polyamines showed that subcultures initiated a rapid synthesis and accumulation of DNA; thereafter the levels of tRNA and rRNA increased, especially in the deceleration phase, the amount of tRNA always being higher than rRNA. The polyamines putrescine and spermidine are always in larger amounts than in the normal tissue, and spermine could be detected in trace amounts. Their metabolism is correlated with arginine levels, the most important precursor of putrescine. Polyamine levels increased several fold during the deceleration phase, their increase being positively correlated with increased levels of nucleic acids, mainly during the very beginning of the subculture and, then during the deceleration phase.

ISSN:0008-4026    

DOI:10.1139/b80-264

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The species composition and standing crop of epilithic, epipelic, and planktonic algae were determined in three widely separated inshore areas of Great Bear Lake during the summers of 1976, 1977, and 1978. The most frequently encountered diatoms in the epilithon wereTabellaria ftocculosaandAchnanthes minutissimaregardless of location, whereas the predominant chlorophyte wasUlothrix zonata. These species were generally rare in the epipelon and were replaced in importance byGyrosigma spenceri, Nitzschia obtusa, Cocconeis placentula, Amphora ovalis, andAchnanthes lanceolata, depending on sampling site. The densities of the epilithon and epipelon were low in June but increased gradually during the summer, reaching maxima of 78 × 107and 120 × 107 μm3 cm−2, respectively (19.5 × 105and 40 × 105 cells cm−2), in either August or September. These values are among the lowest recorded for fresh waters and are probably due to continually low water temperatures and wave action rather than nutrient limitation. The most important species in the plankton in all three sampling areas wereDinobryon bavaricum, Dinobryon sociale, Rhodomonas minuta, Cyclotellaspecies,Synedra acusvar.radians, andAnkistrodesmus falcatus. Plankton standing crops of up to 62 mg fresh weight m−3were recorded in June at a temperature of 0 °C, and they increased to 70–91 mg m−3(23.3 × 107−30.1 × 107 cells m−3) by September. These values are again among the lowest on record, a reflection of low water temperatures. The similarity in the species composition and standing crop of the plankton, epilithon, and epipelon in all collection areas was due to the similarity in water chemistry and temperature throughout Great Bear Lake.

ISSN:0008-4026    

DOI:10.1139/b80-265

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The effects of fall clipping or burning on the subsequent morphology of bluebunch wheatgrass were studied in both the big sagebrush – bluebunch wheatgrass and Douglas fir – bluebunch wheatgrass communities. Observations were made to the 2nd year after treatment. Burning, in the big sagebrush community, resulted in a larger ratio of plant weight to volume. Burning also increased tiller density by the 2nd year in the big sagebrush community. Plants that were burned had lighter tillers in the 1st year after treatment. They also had a greater proportion of weight distributed near their base. The morphological characteristics of clipped plants were generally intermediate between those of burned and control plants. In general, the treatment effect was less in the Douglas fir community than in the big sagebrush community.

ISSN:0008-4026    

DOI:10.1139/b80-266

出版商:NRC Research Press    

年代:1980

数据来源: NRC