摘要:

Pollen of the American myristicaceous generaOtoba, Iryanthera, andOsteophloeumwas studied with light, scanning electron, and transmission electron microscopy. Formal generic pollen descriptions are provided for each genus, all three of which possess distinctive pollen that is most readily distinguished by characters of exine structure and sculpturing. Pollen ofOtobahas a basically granular interstitium with pendent granules attached to the inner face of the basically imperforate tectum and an unique patch of well‐developed columellae and a semitectate reticulum on its presumed proximal face. The somewhat similar, distinctly columellate, tectate‐perforate to semitectate pollen ofIryantheraandOsteophloeummay be distinguished by a reticulum that is beadlike in the former and psilate in the latter. Pollen ofIryantherais more or less indistinguishable from that of the previously studied African myristicaceous genusCoelocaryon.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06398.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

A comparison of the epidermal leaf cell ultrastructure of three seagrasses,Thalassia testudinum(tropical, high salinity),Zostera marina(North temperate, moderate salinity), andRuppia maritima(North temperate, brackish) provides confirmation for the theory that an invaginated plasmalemma‐mitochondrial transport system is developed at least in part as a response to salt concentration. Cytochemical localization of presumed Cl−ion provides further evidence for the presence of a salt secretion or exclusion mechanism.Immature epidermal leaf cells communicate with each other and with mesophyll cells through numerous plasmodesmata, but during cell maturation these cytoplasmic connections are lost and the apoplastic transport system develops to replace the symplastic one. The two North temperate region seagrasses contain cytoplasmic lipids which are absent in the tropical species.ThalassiaandZosterahave chloroplasts which lack starch, but stain densely for polysaccharides with thiocarbohydrazide. The polysaccharide staining is essentially negative in the chloroplasts ofRuppia, but mesophyll chloroplasts of this brackish water species contain starch. These and other cytological findings are compared with other seagrasses.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06399.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The genusGlycineis composed of two subgenera,GlycineandSoja. Sojaincludes the cultivated soybean,G. max, and its wild annual counterpartG. soja, whileGlycineincludes seven wild perennial species. Hybridization was carried out within and between wild perennial species of the subgenusGlycine. The success rate (pods set/flowers crossed) was 11% for intraspecific and 8% for interspecific crosses. A total of 220 F1hybrids was examined morphologically and cytologically where possible. Hybrids withinG. canescens(2n= 40) andG. latifolia(2n =40) were fertile as expected.Glycine clandestina(2n =40) was morphologically separable into at least three groups, which produced fertile hybrids within each group. One cross between two groups gave vegetatively vigorous but sterile hybrids. The majority of crosses withinG. tabacina(2n =80) were fertile, except that extremely narrow‐leaved forms gave sterile hybrids in combination with more usual forms. Sterility was also encountered inG. tomentellawhen aneuploids (2n= 78) from New South Wales, Australia, were crossed with tetraploids(2n =80) from either Queensland, Australia, or Taiwan; crosses between the latter two populations resulted in seedling lethality. Cytological behavior of sterile hybrids followed a similar pattern, whether at the diploid or tetraploid level. The frequency of chromosome pairing was approximately half that expected if genomes showed full pairing homology. Bivalent disjunction at anaphase I was usually followed by precocious division of the majority of univalents. Telophase I and II were characterized by lagging chromosomes and micronuclei, so that resulting pollen was misshapen and sterile. Chromosome pairing data from sterile intraspecific hybrids at the tetraploid level may indicate a polyphyletic origin of tetraploids, whereby different diploid populations were involved in their formation. Similarly, chromosome pairing in sterile intraspecific diploid hybrids may indicate that the various diploid groups arose independently of one another. Both 40‐ and 80‐chromosome forms are fully diploidized, however, and if they are of ancient origin, divergence since that time could have resulted in the chromosomal differentiation which becomes apparent when intraspecific hybridization is effected.Diploid (2n =40) interspecific hybridsG. falcata × G. canescens, andG. falcata × G. tomentellagrew poorly and did not reach flowering stage. Diploid (2n= 40) crosses betweenG. latifoliaandG. tomentellaproduced inviable seedlings. Tetraploid (2n =80) hybrids betweenG. tomentellaandG. tabacinawere vegetatively vigorous but sterile owing to low chromosome pairing at meiosis, indicating little pairing homology between the two species. Diploid hybrids betweenG. canescensandG. clandestina, however, showed almost complete chromosome pairing at diakinesis and partial fertility. Although morphologically distinct, these two species have not diverged sufficiently to prevent hybridization and possible gene exchange through recombination.Self compatibility, perennial growth habit, and geographic isolation have favored divergence amongGlycinepopulations to the point that gene exchange appears no longer possible in many cases. Internal isolating mechanisms have been shown to operate at various levels of plant development from hybrid lethality at seedling stage, to failure of seed‐set in sterile but vegetatively vigorous hybrids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06400.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Our current understanding of the photosynthetic process in species utilizing the C4photosynthetic pathway suggests that photosynthetic efficiency should be enhanced by: 1) maximizing the conductance of the gas phase transport pathway from the leaf exterior to the mesophyll cell surfaces; 2) maximizing cytoplasmic connections and metabolite transport between bundle sheath and mesophyll parenchyma cells; and 3) minimizing the conductance of the gas phase transport pathway from the bundle sheath cells to the leaf exterior. In this study we have examined several species in the Poaceae with C4photosynthesis to determine if there is any evidence for anatomical specialization which would lead to enhanced photosynthetic efficiency by these processes. Observations with light and scanning electron microscopes revealed specializations in mesophyll cell morphology and arrangement which include branched cells forming intercellular channels. These specializations are hypothesized to contribute to photosynthetic efficiency through its influence on the above transport processes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06401.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Anthochlors (chalcones and aurones) occur in floral tissues of all members of North AmericanCoreopsis. The genus in North America consists of 46 species distributed in 11 sections, and a total of five chalcone aglycones are found in it. The chalcone butein occurs in all sections, and is the only anthochlor constituent in the closely related woody Mexican sectionsElectraandAnathysana. These two sections are viewed as primitive. The morphologically distinct but putatively unspecialized woody Mexican sectionPseudo‐Agaristasequesters both okanin and butein; the same two anthochlors also characterize two additional sections of herbaceous perennials,SilphidiumandTuckermannia. SectionsEuleptosyneandPugiopappus, comprised of annuals restricted primarily to California, exhibit the rare chalcone stillopsidin in addition to butein and okanin. The remaining four sections,Palmatae, Coreopsis, CalliopsisandEublepharisare among the more specialized in North America, and are sometimes considered to represent a distinct phyletic line or two related lines. All or some of the members of these sections sequester the very rare chalcone lanceolatin in floral tissues in addition to okanin.Butein is also present in some or all species in each section, and isoliquiritigenin occurs rarely in two sections. Those sections considered more specialized have additional anthochlors relative to primitive sections, and any compound found in a more primitive section also occurs in a more advanced one. Thus, the trend in floral anthochlors in North AmericanCoreopsisis toward increased number of compounds rather than reduction.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06402.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The effects of increasing salt stress on leaf senescence and salt regulation were investigated in the halophyteJaumea carnosain hydroponic culture experiments. The plants were grown in Hoagland's nutrient solution plus additional NaCl salt (0, 300, 400, 500 mmNaCl). Decreases in nucleic acids, protein, and chlorophyll were used as indicators of leaf senescence. The results indicated no definitive pattern of acceleration in leaf senescence with increasing salt stress. Salt regulation was also unaffected as leaves aged under increasing NaCl concentrations. The results are consistent with those of previous studies of the halophyte which indicated that the species was very tolerant of high NaCl concentrations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06403.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

An inexpensive photographic technique for visualizing the ultraviolet and visible wavelengths perceived by honeybees is described. Using a standard daylight‐balanced color slide film and illumination from blacklight and filtered daylight fluorescent lamps, a recording balance was achieved which approximates the spectral sensitivity of the honeybee eye.The technique was used to illustrate floral features amongRudbeckiaspecies and among color morphs ofPhlox. TheRudbeckiahave inflorescences that are similar in visible coloration but distinctive in ultraviolet patterning andPhloxcolor morphs are distinctive in visible coloration but similar in ultraviolet patterning. The efficacy of the technique was judged from comparison with in vivo reflectance spectra of the floral subjects. Generally, photographic visualizations of entomophilous flowering plants portray only the ultraviolet or the visible components of floral coloration. This technique emphasizes the importance of considering the entire spectrum of floral colors relevant to most insect pollinators.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06404.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Floral tissue of dormant sour cherry (Prunus cerasusL.) flower buds was examined by light and electron microscopy during field development and laboratory chilling. Differentiation of flower parts ceased by early November and there was no further morphological development until visible signs of budbreak occurred after the end of rest. Pollen meiosis occurred at the half green budbreak stage. No ultrastructural changes accompanied chilling accumulation except development of numerous starch grains in plastids. Buds on cut shoots held at the non‐chilling temperature of 15 C developed more mitochondria but acquired no starch when compared with buds on cut shoots held at a 5 C chilling temperature. Nuclei and nucleoli enlarged with chilling in ovules and sporogenous cells but not in ovary parenchyma. Accumulation of starch with chilling in most bud tissues was demonstrated histochemically.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06405.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Traquairiais one of the several unusual fungal structures occurring in Pennsylvanian coal balls. Specimens were initially described from European sediments and are now known from the Pennsylvanian of North America. AlthoughTraquairiawas originally believed to be a protozoan closely related to the radiolarians, its structure and organization suggest affinities with members of the fungal group, Ascomycota. Specimens are irregularly shaped and up to 1.0 mm in diameter. Each cleistothecium bears prominent radiating spines that are continuous with a peripheral mat of extensively branched, delicate hyphal filaments. A complex wall encloses a central cavity which may contain a number of asci with ascospores. Among extant fungi,Traquairiais most similar in form to members of the Eurotiales and Erysiphales.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06406.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Coenogonium interplexumNyl. is a green to yellow‐orange filamentous lichen commonly found on tree bark, rocks, and soil. The mycobiont is the ascomycetous fungusCoenogonium. The ultrastructure of the lichenized phycobiont,Trentepohlia, closely resembles that of the non‐lichenized form, a filamentous subaerial green alga. The mycobiont has a typical fungal ultrastructure, and the cell wall sometimes appears thinner at points of contact with the phycobiont wall. Several branched fungal hyphae are usually randomly arranged around aTrentepohliafilament, and may in some cases completely ensheath the alga. Although no haustoria were observed, this relationship may still be termed a lichen since there is some modification of the alga and the lichen is structurally distinct from the two symbionts.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb06407.x

出版商:Wiley    

年代:1983

数据来源: WILEY