摘要:

Dead fir needles were collected from standing trees ofAbies amabilisin five sites at the margin of the blast zone and located progressively farther from the eruption crater of Mount St. Helens. Scanning electron microscope techniques were used to determine patterns of cuticular melting for these needles and forAbies grandisneedles which were heated at specific temperatures for 2 min. Comparisons between cuticular appearances of oven‐heated needles and needles from Mount St. Helens were made to determine air temperatures at the collection sites at the time of the eruption. Air temperatures at these sites are estimated to have ranged from about 50 C to about 250 C. Analysis of cuticular sulfur content showed these needles adsorbed little or no volcanic S02. Conifer needles provided a record of maximum air temperatures during the eruption, and helped reveal the pattern of heat distribution from the eruption cloud. This technique may prove useful for ecological studies in other heat‐stressed habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12435.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The guard cells ofAnabasis articulatamature and senesce a short distance from the intercalary meristem in which they form. When the guard cells reach final size, their ultrastructure is similar to that of stomata of other plants. At this stage, they contain clearly definable, numerous mitochondrial profiles, chloroplasts with starch grains and plastoglobuli, active Golgi bodies, a large nucleus that stains deeply for chromatin and large vacuoles. During later stages of development the whole protoplasmic content becomes very dense, with myelin‐like figures and crystals appearing in the vacuoles. The cell walls thicken considerably. This is especially true of the tangential walls, where the microfibrils of different lamellae vary in their orientation. It is suggested that as a result of these ultrastructural changes the guard cells lose the ability to move.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12436.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Structural changes during development of the caudicle ofEpidendrum ibaguense(Orchidaceae) were followed using light and electron microscopy. The caudicle begins as a mass of small meristematic cells in the microsporangium. The central cells of the mass enlarge and enter a division cycle. Completion of this cycle produces linear tetrads of cells which remain attached to each other throughout the life of the caudicle. These tetrads then accumulate a thick secondary wall on their outer surfaces. These thick‐walled cells form the main structural element of the caudicle at maturity. The cells on the periphery of the mass differentiate into a gradation of cell types characterized by their very high content of smooth ER. The majority of these thin‐walled cells are located at the junction points between adjacent caudicles and between caudicle and pollinium. The cells in these positions produce large quantities of a lipid polymer. This product is synthesized in association with large tubular ER complexes present in discrete areas in the cytoplasm. Plastids of these cells also produce a lipidic substance. Some thin‐walled cells are located among the thick‐walled structural cells; however, the lipid polymer is not synthesized in these cells. At maturity, all thin‐walled cells undergo breakdown and autolysis resulting in gradual obliteration of cytoplasmic detail and organelles. In the lipid containing thin‐walled cells, lysis of the cells releases the lipidic masses which then form the elastic joining compound between adjacent caudicles and between caudicles and pollinia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12437.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Each sporangium in the Upper Devonian taxonBarinophyton citrulliformecontains both microspores and megaspores. Microspores range up to 50μm in diam and possess a homogeneous sporoderm characterized by an outer separable layer. The sporoderm of the megaspores (up to 900μm) is constructed of sporopollenin units that are loosely arranged in the outer portion of the wall, and that give the megaspore wall a spongy organization. Ultrastructural evidence suggests that the small spores were not abortive megaspores, but that both spore types were functional. The spores of this plant, as well as other Devonian spores that show less dramatic size differences, are suggested as demonstrating a phase in the evolution of heterospory where sex determination was established in spores within the same sporangium prior to the evolution of micro‐ and megasporangia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12438.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Following fertilization, zygotes of the green algaColeochaete orbicularis, which are retained on the haploid thallus, first enlarge, then become covered with a layer of vegetative cells. Light microscopy and high‐voltage electron microscopy revealed the presence of localized wall ingrowths in vegetative cells adjacent to zygotes. These covering cells resemble the gametophytic placental transfer cells of embryophytes in their morphology, location, and time of development. IfColeochaetecells with wall protuberances function as do placental transfer cells of embryophytes, their presence is evidence that photosynthates may be transported between haploid thallus cells and zygotes. Thus, a nutritional relationship between different phases of the life cycle, similar to that which occurs in embryophytes, may also have evolved in green algae. This first report of putative placental transfer cells in a green alga supports Bower's (1908) ideas concerning the origin of land plant sporophytes and alternation of generations. The presence or absence of cells with wall ingrowths in several species ofColeochaetewas correlated with estimates of zygote‐plant area ratios.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12439.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Roots of representative epiphytic orchids were examined for anatomical detail, desiccation resistance and evidence of CAM activity. Those “shootless” taxa examined (Campylocentrum pachyrrhizum(Reichenb. f.) Rolfe,Harrisella porrectaReichenb. f.) Fawc.&Rendle, andPolyradicion lindenii(Lindl.) Cogn. ex Urban) and a semi‐shootless type (Kingidium taeniale(Lindl.) P. F. Hunt) bear thinner or eroded velamina and greater volumes of cortical intercellular space than do those of the leafy forms tested (Campylocentrum sellowii(Reichenb. f.) Rolfe,Encyclia tampensis(Lindl.) Small,Epidendrum radicansPavon ex Lindl.,Phalaenopsis amabilis(L.) Blume,Rangaeris amaniensis(Krzl.) Summerhayes andVanda parishii(Reichenb. f.)). Shootless species also bear a more elaborate aeration apparatus at the velamen‐cortex interface. Structurally distinct cortical cells located in this region may regulate gas exchange across the exodermis. Velamen thickness varies greatly among the ten species, as does the development of outer tangential walls of U cells in the underlying exodermis. Desiccation resistance under laboratory conditions was more closely related to root surface‐to‐volume ratio (S/V) than to any other measured anatomical parameter, including velamen development. Modes of carbon gain and the possible pathway for movement of fungus‐borne carbon into an orchid's pool of assimilates are described, as is the possible significance of these processes to survival in forest canopy habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12440.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The coadaptive, dynamic relationship between the members of a floral community and their respective bumblebee pollinators was studied on the alpine‐tundra of the Beartooth Plateau in southern Montana. A total of ten species ofBombuswas observed foraging for pollen and/or nectar onCastilleja pulchella, Delphinium bicolor, Lupinus monticola, Mertensia ciliata, Oxytropis campestris, Penstemon procerus, andTrifolium dasyphyllum.The number ofBombusspecies per plant species ranged from 1 to 9. Based on relative percentage of pollen types in corbicular loads, monolectic foragers comprised 53.5% and polylectic foragers 46.5% of the bumblebees. Examinations of relative length of nectariferous corolla‐tubes, tongue‐length of pollinators, foraging frequency of pollinators, phenology of floral anthesis, and stature of plants did not indicate specific resource partitioning. Non‐tundra‐nesting bumblebees from lower elevations preferred adventive or typically non‐tundra plants. Examination of perianth colors in visible light by reflectance spectrophotometry and in long‐wave (360 nm) ultraviolet light by photography disclosed well‐defined visible light reflectance spectra in all species but ultraviolet reflectance patterns only inD. bicolor.Insect collections and exclosure studies indicated all plant species exceptD. bicolorandP. procerusare highly reliant on bumblebee pollinators.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12441.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Edgar Nelson Transeau, botanist‐ecologist‐phycologist, accumulated a worldwide collection of algal specimens for the compilation of a monograph on the algal family Zygnemataceae, published in 1951. Following his death on January 26, 1960 this Collection remained at The Ohio State University, Columbus until 1978 when it was transferred to the University of Arizona, Tucson. A set of glycerine‐preserved specimens on microscope slides is the major item of the Collection with the number of species represented as follows:Spirogyra(138),Mougeotia(52),Zygnema(45),Zygnemopsis(16),Sirogonium(9),Debarya(9),Zygogonium(4),Mougeotiopsis(1) andEntransia(1). All specimens ofPleurodiscus, Sirocladium, TemnogametumandTemnogyraare unidentified. With the Transeau Collection it was demonstrated that an old collection need not be an historical relic, but does have continued usefulness. Potential future use is a powerful justification for maintaining seemingly useless collections whose accumulation often represents the expenditure of untold time, effort and money on the part of many persons and institutions worldwide. Further, as man continues to alter his environment and species are destroyed, collections with long histories become increasingly more valuable. Specimens of the Transeau Collection were subjected to modern techniques, not available earlier, resulting in improved characterization of zygospore‐wall structure by scanning electron microscopy and the determination of nuclear DNA by cytofluorometry.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12442.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Spiral tubule structures were observed in sieve elements ofPritchardiaandCocospalms. The spiral tubules were 80–120 nm wide and composed of alternating electron‐lucent and electron‐dense bands 11–16 nm wide which spiraled around a central core.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12443.x

出版商:Wiley    

年代:1983

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb12423.x

出版商:Wiley    

年代:1983

数据来源: WILEY