摘要:

Trends in the distribution patterns of 155 species of leafy hepatics over 10 distinct areas in the Luquillo Mountains of Puerto Rico were revealed by factor analysis. The three factors of the Q-mode (area × area) analysis contrasted (1) high-altitude with low-altitude habitats, (2) shaded, moist habitats with open, more exposed habitats of all elevations, and (3) disturbed low-elevation habitats with less disturbed habitats of all elevations. The R-mode (species × species) analysis produced almost identical distribution trends. The coincidence of these two results allowed us to determine which plant species were primarily indicative of habitat differences.

ISSN:0008-4026    

DOI:10.1139/b73-197

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Light and scanning electron microscopic studies and guard cell isolation techniques have confirmed the well-known ridges of theEquisetumstomatal apparatus as belonging to the subsidiary cells. Hitherto unknown features of the subsidiary cells such as the presence of a concentrated H2SO4-resistant region on the ridges and an interlocking mechanism for the closure of the aperture of the subsidiaries are described. These are presented as further evidence for the differences between the two subgenera ofEquisetum. Boiling in dilute NaOH is shown to be a simple but effective means for the isolation of the guard cells inEquisetumas well as in several other plants with sunken stomata. Silicification of the outer layer of the epidermis makes cuticular isolation a difficult process by usual methods (treatments with enzymes or cellulose hydrolyzing reagents). Treatment with concentrated sulfuric acid followed by hydrofluoric acid results in the isolation of the cuticular membranes inEquisetumspp. and in similarly silicified grasses. Involvement of potassium ions in stomatal movements is indicated for two ferns and suggested for two species ofEquisetum.

ISSN:0008-4026    

DOI:10.1139/b73-198

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Ceratocystis ulmi, the Ascomycete responsible for Dutch elm disease, may sporulate by means of a distinctive structure, the synnema, common in nature in the tunnels of elm bark beetles. Developmental stages of this structure and its spores were examined by light microscopy, by conventional transmission electron microscopy of thin sections and freeze-etch replicas, and by scanning electron microscopy of whole spores and fruiting structures. The synnema is a tight bundle of darkly pigmented hyphae growing erect from the substrate and terminated by a mass of colorless, wet spores. A layer of slime covering the hyphal bundle and random cross-connections between parallel hyphae appear to function in stabilization of the structure. Organelles typical of Ascomycetes fill the spores, vegetative hyphae, and young synnemal hyphae. However, in mature synnemal hyphae, the cytoplasmic contents degenerate, leaving only membranous vesicles in the partially collapsed hyphae. The spores contain large lipid droplets not found in either vegetative or synnemal hyphae indicating some differences in metabolism of spores and hyphae. Most synnemal spores form on sympodulae, but some spores form on intrahyphal hyphae.

ISSN:0008-4026    

DOI:10.1139/b73-199

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Seedlings of white pine (Pinus strobusL.) and detached shoots of white and loblolly (P. taedaL.) pines were exposed to various concentrations of ozone either before or during photosynthetic fixation of14CO2. The major changes in distribution of14C as a result of ozone treatment were (1) a reduction of relative activity in soluble sugars; (2) an increase in activity in sugar phosphates; and (3) an increase in activity in free amino acids, especially alanine. Significant differences in14C fixation patterns were observed at ozone concentrations as low as 10 pphm (parts per hundred million), and during14CO2fixation times as short as 10 min. However, other combinations of treatment levels and times did not always result in statistically significant effects.

ISSN:0008-4026    

DOI:10.1139/b73-200

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Three ectomycorrhizal fungi,Cenococcwn graniforme, Suillus luteus, and Thelephora terrestriswere grown in artificial nutrient media. Water potential of the media was varied by the use of the osmoticum polyethylene glycol (PEG) 4000 and measured by thermocouple psychrometry.Cenococcum graniformewas very tolerant of low water potentials and exhibited maximum growth at a potential of −15 bars. Maximum growth ofS. luteusandT. terrestrisoccurred at −5 bars. The water potential of solutions containing PEG 4000 appears to consist of both an osmotic and matric component, making PEG 4000 ideally suited for simulation of soil moisture stress. It was neither metabolized nor readily absorbed byC. graniformeas inorganic salts or sugars might be.

ISSN:0008-4026    

DOI:10.1139/b73-201

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Aegopodium podagraria, widely cultivated in a variegated form, occasionally gives rise to normal (non-variegated) plants which are comparatively vigorous, exhibiting marked weedy tendencies. Net photosynthetic rates and chlorophyll contents were determined for two populations of normal plants and three populations of variegated plants grown separately under full sunlight, and in shade. None of the populations grown in full sunlight differed significantly from each other in rate of photosynthesis on a leaf area basis, despite the mean 83.5% higher chlorophyll content of normal leaves. However, when grown in shade, on a leaf area basis normal plants averaged 50.1% higher rates of photosynthesis, and 73.5% higher content of chlorophyll, and the leaves were 27.4% heavier than the leaves of variegated plants. These differences apparently are responsible for the competitive advantage of normal plants in the usually shady habitat ofA. podagraria.

ISSN:0008-4026    

DOI:10.1139/b73-202

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

In both pasteurized and nonpasteurized soils, higher CO2combined with normal atmospheric O2concentrations were generally favorable for growth and survival in comparison with the effects of lower O2combined with atmospheric CO2concentrations. Different amounts of growth among the various gas treatments and between pasteurized and nonpasteurized soils also occurred in the general populations of soil fungi, actinomycetes, and bacteria. Gas effects on total fungi, actinomycetes, and bacteria may have resulted in indirect effects onPythium.

ISSN:0008-4026    

DOI:10.1139/b73-203

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

An investigation was made of the diatom stratigraphy in a sediment core from Sunfish Lake, a small (8.3 ha), deep (20 m), meromictic lake in southwestern Ontario. About 340 diatom species and varieties distributed among 37 genera were identified from the sediments; however, only 16 taxa had more than 2% representation in any sample. On the whole, the number of individuals and diversity of the samples increase over the postglacial period. Diatoms first appear in pollen zone A and consist mainly of the littoral formsCymbella diluviana, Fragilaria lapponica, andF. construensvar.venter. It is suggested that these taxa are typical of early postglacial lacustrine sediments in northeastern North America.Cyclotella bodanicafirst appears in zone B and is dominant in most samples throughout the core. It is euplanktonic and typical of subalpine, circumneutral, oligotrophic lakes. In C2, when the climate was possibly warmer and drier than present, there is evidence for a lower lake level:C. bodanicais temporarily replaced in importance in the sediments byC. kuetzingianaand the proportion of littoral and epiphytic diatoms increases.Cyclotella bodanicaregains its former importance in C3sediments with the possible return to a cooler, wetter climate. About 850 years before present (B.P.) the lake evidently became eutrophic.Cyclotella bodanicadeclines and there is an increase in the proportion of several species typical of a higher trophic level, e.g.,Stephanodiscus hantzschii, Cyclotella glomerata, and severalSynedraspp. The cause is unknown. The lake probably became meromictic about 140 B.P. at a time when the forest was cleared and agriculture began in the watershed.

ISSN:0008-4026    

DOI:10.1139/b73-204

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Floral buds ofNicotiana tabacumwere fixed, sectioned, and stained by routine procedures, then analyzed microscopically. Initiation and emergence of all four classes of floral organs involved periclinal division in the second tunica layer (T2) and division of corpus cells. The extent of periclinal T2divisions was different in different organs. Plasmolysis of tunica and corpus cells was observed at organ sites. The results generally parallel those of other studies.

ISSN:0008-4026    

DOI:10.1139/b73-205

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Light and electron microscopic studies ofWolffia arrhizaL. frond development during vegetative reproduction showed that the fronds were composed entirely of chlorenchymous cells. Chloroplasts in the epidermal cells other than the guard cells were unique in that they contained no starch. Cell division occurred only at the proximal end of daughter fronds early in their development. Meristematic cells contained chloroplasts with clearly defined grana. Proplastids, commonly observed in meristematic cells of apical regions of other plants, were absent in the cells of these plants.

ISSN:0008-4026    

DOI:10.1139/b73-206

出版商:NRC Research Press    

年代:1973

数据来源: NRC