摘要:

Tolmiea menziesiicomprises diploid (2n= 14) and tetraploid (2n= 28) cytotypes that differ in geographic distribution. Chromosome counts now available indicate that the diploid and tetraploid cytotypes occupy the southern and northern portions, respectively, of the range ofTolmiea.Available data strongly suggest thatTolmiearepresents an example of autopolyploidy. The genus is monotypic and very distinct in both floral and vegetative morphology among genera of tribe Saxifrageae. Infraspecific taxa have not been recognized inT. menziesii,and the two cytotypes appear to be indistinguishable morphologically. Karyotypic, flavonoid chemical, and preliminary allozymic data are all in agreement with the contention that the tetraploid cytotype is of autopolyploidal origin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11971.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Daucus carota,a common herbaceous weed, grows over a wide latitudinal range in eastern North America. Viability and germination tests of mature seeds collected from 36° to 45°N were conducted to measure predispersal seed mortality. Viability and germination declined as latitude of the seed source decreased. Only 30–50% of the seeds from southern populations germinated owing to high embryo inviability and absence of embryos. Sixty to ninety percent of the seeds from northern populations germinated. Reciprocal planting of seeds in outdoor experimental plots at three latitudes and testing of seeds over two generations together showed that the environment in which seeds mature, rather than environmental preconditioning over generations or genetically‐based differences among populations, explain this variation in germination ability. Within‐latitude germination declined in experimental plots as population age of the seed source within latitudes increased. The data indicate that predispersal seed mortality can influence local population persistence and that seed mortality is an increasingly important factor in population regulation at the southern limit of the species’ range.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11972.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

The ability of pollen to effect seed set decreases with age when stored at room temperature or on the plant, but not when stored at 5 C. Seed set declines rapidly with pollen stored 10 days or more at room temperature. Seed set declines rapidly with pollen stored 4 days or more on the plant. The degree of pollen germination on the stigma and the number of pollen tubes in the style correlate positively with seed set. Pollen germination on the stigma and pollen tube growth in the style are strongly correlated with seed set for pollen stored at room temperature, but not, or only weakly, correlated for pollen stored at 5 C. In the latter case, seed sets are lower than expected, indicating a possible viability reduction associated with a post‐pollination function. Inviable pollen grains temporarily interfere with normal pollen germination on the stigma. Essentially no seeds are produced when in viable pollen, immediately followed by viable pollen, is placed on a fresh stigma. However 27 to 65 seeds are produced when in viable pollen, followed in 1 to 6 days by viable pollen, is placed on fresh stigmas. New stigma surface is exposed at the center as expanding stigma surfaces carry the interfering inviable pollen toward the edge of the stigma.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11973.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Thick mats of cellular remains from Eocene brown coal deposits of the Geiseltal near Halle, DDR, were determined to be fossil nonarticulated laticifers. Nuclear magnetic resonance analyses of intact strands showed they consisted of eis‐1,4‐configuration rubber representing the polymerized isoprenoid contents of individual laticifers. Only remains of laticifers are present; other cells are absent as a result of biodegradation. The long laticifers, often with a surrounding cell wall, retained a tubular shape during their preservation. The isoprenoid content, which filled the entire lumen, possessed a cribriform structural character. The interstices within the rubber represent areas of former protoplasm of the cell. Various configurations in the protoplasm molded by the rubber during the initial phase of fossilization appear as negative images of former nuclei, organelles, and possibly membrane surfaces. The laticifer axes possess branches of several configurations comparable in morphology to those in branched, nonarticulated laticifers in extant plants. Acetone extracts of the rubber contents analyzed by gas‐liquid chromatography identified the presence of several hydrocarbons which form a characteristic profile for the laticifer. It is suggested that the distinctive cellular micromorphology, rubber configuration, and hydrocarbon profile of these laticifers can be employed as markers in comparative studies with extant plants to identify the generic or species origin of these laticifers.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11974.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Leaves ofGleditsia triacanthosL. are served by three leaf traces that subdivide in the node to produce subsidiary bundles. The subsidiary bundles differentiate basipetally in the stem and acropetally in the petiole using the original leaf trace bundles (those that developed acropetally) as templates for their development. Within the pulvinus, the acropetal bundle components merge to form the rachis vasculature consisting of a semicircular arc and a ventral chord; several small bundles diverge to form ventral ridge bundles. Mixing of bundles occurs during vascularization of the lateral rachillae axes. Each diverging rachilla axis receives bundles from the semicircular arc, the ventral chord, and a ridge bundle in a relatively reproducible and predictable pattern. During this process the main rachis vasculature is gradually depleted, but the ridge bundles are reconstituted following divergence of each rachilla pair. The distal rachilla pair is vascularized by a bilateral partitioning of the entire rachis vasculature; a remnant of the central leaf trace terminates in a subulate terminal appendage. Vascularization of the bipinnateG. triacanthosleaf is compared to that of the simplePopulus deltoidesleaf.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11975.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Leaflets ofGleditsia triacanthosare vascularized identically, whether they develop from the rachis of a once‐pinnate leaf or the rachilla of a bipinnate leaf. The vascularization process of a leaflet is also similar to that of a rachilla departing the rachis of a bipinnate leaf. Vascularization in all cases involves a rotation and reorientation of the participating bundles to form either a new midvein or a rachilla axis. During this process, the vasculature of the parent axis is progressively depleted. The ventral ridge bundle, however, is partially depleted when each new organ is vascularized and reconstituted after it departs. Observations suggest that the ridge bundles also contribute to formation of the ventral trichome glands that accompany the departure of each new organ. Young, expanding leaflets are vascularized by secondary veins that depart in an acropetal sequence from a consolidated midvein. Major secondary veins that progressively deplete the midvein vasculature are interspersed with minor secondary veins. The lamina expands laterally by anticlinal divisions in the plate meristem between secondary veins. Periclinal divisions that contribute to new cell layers also occur in the plate meristem in association with the secondary veins. No evidence of a recognizable marginal meristem was found. A marginal vein was always present in the leaf margin and cell divisions appeared to occur in association with this vein. Bridge bundles uniting adjacent veins were frequent in the plate meristem. Bridge bundles also occurred between the midvein and the nearest secondary vein and between the marginal veins and leaf margin.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11976.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Ordination and classification techniques were used to analyze patterns of forest vegetation, species diversity, and soil type in the Wichita Mountains Wildlife Refuge of southwestern Oklahoma. Cluster analysis based on tree species produced three general community types: 1)Quercus stellata‐Q. marilandicaforests; 2)Q. stellataforests; and 3) mesophytic forests. A polar ordination produced a gradient of vegetation that corresponded to a moisture gradient. Many high diversity forests were located on loamy drainageway soils or north facing slopes. Tree species diversity (H') was inversely related to the importance ofQuercus stellata.Cluster analysis based on species composition of the tree seedlings produced four general community types: 1)Q. marilandicatype; 2)Q. marilandica‐Q. stellata‐Juniperus virginianatype; 3)Ulmus americana‐Celtis reticulata‐Bumelia lanuginosatype; and 4)Acer saccharumtype. The third seedling type occurred almost exclusively on loamy drainageway soils. There was no relationship between stand location on the first axis of the tree ordination and the first axis of the seedling ordination suggesting that trees and seedlings respond differently along the moisture gradient.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11977.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

The impact of Olympic marmots on subalpine meadow vegetation was examined by descriptive methods. Differential grazing and various earth moving activities of marmots produce marked vegetational contrasts between mound vegetation and the surrounding meadows, between heavily impacted and lightly impacted vegetation immediately surrounding mounds, and between vegetation in the central portion of a colony and that on its periphery. The patterns differed in degree between a dry meadow with lower production and a wet meadow with higher production. In dry meadows, marmots forage over greater distances and their impacts are less concentrated near mounds. In wet meadows, impacts are intense near mounds. Differences were documented in structural features such as species richness, equitability, and percent vegetation cover and in shifts of species composition. As marmot impact increased, graminoid species declined somewhat, palatable species declined markedly, and both ruderal and unpalatable species increased greatly. Moderate marmot activity reduced the dominance of common species and thereby enhanced community diversity. These observations emphasize that much of the natural landscape, seemingly in harmonious equilibrium with its physical environment, is strongly molded by the activities of native animals.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11978.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Flowers ofIpomoea purpureaare larger, more colorful, more numerous per plant, and more conspicuous than those ofI. hederacea.Because the nectar supply per flower is less variable i:I. purpureaand because the flowers of this species are visually more attractive,Bombus pennsylvanicusdemonstrated a foraging preference and greater constancy forI. purpureathan forI. hederaceain experimental and natural sympatric populations in accordance with expectations derived from optimal foraging theory.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11979.x

出版商:Wiley    

年代:1984

数据来源: WILEY

摘要:

Carpospore differentiation inFaucheocolax attenuataSetch. can be separated into three developmental stages. Immediately after cleaving from the multinucleate gonimoblast cell, young carpospores are embedded within confluent mucilage produced by gonimoblast cells. These carpospores contain a large nucleus, few starch grains, concentric lamellae, as well as proplastids with a peripheral thylakoid and occasionally some internal (photosynthetic) thylakoids. Proplastids also contain concentric lamellar bodies. Mucilage with a reticulate fibrous substructure is formed within cytoplasmic concentric membranes, thus giving rise to mucilage sacs. Subsequently, these mucilage sacs release their contents, forming an initial reticulate deposition of carpospore wall material. Dictyosome vesicles with large, single dark‐staining granules also contribute to wall formation and may create a separating layer between the mucilage and carpospore wall. During the latter stages of young carpospores, starch is polymerized in the perinuclear cytoplasmic area and is in close contact with endoplasmic reticulum. Intermediate‐aged carpospores continue their starch polymerization. Dictyosomes deposit more wall material, in addition to forming fibrous vacuoles. Proplastids form thylakoids from concentric lamellar bodies. Mature carpospores are surrounded by a two‐layered carpospore wall. Cytoplasmic constituents include large floridean starch granules, peripheral fibrous vacuoles, mature chloroplasts and curved dictyosomes that produce cored vesicles which in turn are transformed into adhesive vesicles. Pit connections remain intact between carpospores but begin to degenerate. This degeneration appears to be mediated by microtubules.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1984.tb11980.x

出版商:Wiley    

年代:1984

数据来源: WILEY