摘要:

The changes in vesicular‐arbuscular (VA) mycorrhiza inoculum potential (MIP) in soil profiles from a mid‐elevation sage community were measured using a corn bioassay. The MIP was significantly reduced below 30 cm depth and approached zero at less than 1 m depth. The decrease in inoculum potential with depth in diluted soils did not always parallel changes in the nondiluted soil, indicating factors other than numbers of inoculum units also may be important in determining the extent of mycorrhiza formation. The relationship of these results to land disturbance and associated dilution of populations of VA mycorrhizal fungi and to defining topsoil is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07839.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The pollination and fruit production ofGaultheria procumbensL. (Ericaceae), an evergreen sub‐shrub, were studied in five woodland sites in New Jersey and one in northeastern Pennsylvania. Pollinator exclusion methods at three of the sites produced no consistent differences in fruit and seed set between enclosed plants and controls. Insect pollinators, almost exclusively bumblebees, were sparse at all sites; visitation rates were about 0.01 bee visits/flower/hr. All fruits examined contained at least 35 seeds, but about half of the pistils examined, from open‐pollinated plants, did not contain enough pollen tetrads on their stigmatic surfaces to fertilize this number of ovules. However, the low average fruit set of 8.2% on open‐pollinated plants was due more to the high mortality of buds prior to anthesis than to inadequate pollination. Bud mortality was high and fruit set low in 3 years of observations at various study sites, indicating that this may be a general pattern for the species in northeastern United States and adjacent Canada. The amount of sexual reproduction showed no consistent relationship to stem density.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07840.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Palaeostachya dircein. sp. is described from an authigenically cemented specimen collected from the Anna Shale Member occurring above the Herrin (No. 6) Coal Member and below the Brereton Limestone in the Carbondale Formation, Kewanee Group (Middle Pennsylvanian). The strobilus is three‐dimensionally disposed within the matrix, allowing the preparation of ground thin sections, as well as selected maceration of the specimen. The imbricate strobilus is preserved for at least 7 cm of its original length and is composed of alternating whorls of sterile bracts and fertile sporangiophores. An articulated axis extends the length of the strobilus and attains a maximum width of 3 mm at the nodal areas. A whorl of 24 sterile bracts arises at each node, with each bract emerging at a 90° angle from the axis. Bracts are free except for a slight adaxial fusion at their point of origin. A slight downward‐projecting keel develops at the point where the bract begins ascending at least past the second supra‐adjacent node, where it is appressed into an abaxial furrow of the superposed bract. A whorl of sporangiophores originates above the bracts and is equal in number to the bracts. The sporangiophores are obliquely inserted on the axis and possess four superposed and thin‐walled sporangia inserted upon a (?) cruciate head. Spores assigned toCalamosporahave been recovered and range in diameter from 68–115μm (x̄ =89μm). The cone appears to be homosporous.Palaeostachya dircein. sp. is compared to the reported permineralized and coalified compression species and appears similar toP. veraSeward andP. gracilisRenault.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07841.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Equisetalean strobili normally are encountered as disarticulated organs. This condition has necessitated the creation of 12 form genera to accommodate the various morphological architectures and anatomical configurations. Taxonomically useful characteristics, which are discernable in permineralized specimens, are rarely distinguishable in coalified compressions due to their destruction during diagenesis and coalification. Therefore, genera established on the position of sporangiophore‐trace origin, such asSchimperiaRemy and Remy, are untenable when dealing with coalified compressions. Although the two largest genera of strobili,CalamostachysSchimper andPalaeostachyaWeiss, may be synonymous, it is proposed that these form genera be retained when dealing with coalified compression specimens. Each genus provides a particular architectural concept for specimens which may not be assignable to the species level.CalamostachysandPalaeostachyaare highly overspeciated genera. It is suggested that characteristics necessary to delimit new species include bract height, degree of bract fusion, disposition of bracts, bract: sporangiophore ratio, number of sporangia per sporangiophore, and sexual status.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07842.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Zenobiais a shrub endemic to the coastal plain of the Carolinas and southeastern Virginia. The sole species,Zenobia pulverulenta, appears to be weakly self‐compatible and partially self‐pollinating. Fruit set was reduced, but not eliminated by excluding insect floral visitors. Insect visitors were collected and their pollen loads examined forZenobiaand foreign pollen. Analysis of these pollen loads and observations of insect‐foraging behavior indicate that workers of three species of bumblebee (Bombus bimaculatus, B. griseocollisandB. impatiens) are. the principal pollinators ofZenobia. However, pollinator density and composition appear to be strongly influenced by the habitats in whichZenobiagrows. Pollen and nectar serve as the primary rewards for pollinators.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07843.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Papaver nudicauleplacentae with attached ovules were dissected out of unpollinated gynoecia 1–3 days after anthesis, dusted with pollen, and cultured on modified Nitsch's growth medium at 23 C. Ovules were removed from expiants at 15, 24, 31, and 48 hr postpollination, fixed in GA‐OsO4, embedded in Spurr's resin and sectioned (1.0μm) for light microscopy. Placentae, 15 hr after pollination, were fixed and processed for scanning electron microscopy. Pollen germinates within 1 hr. Although most pollen tube growth appears random, there is directional growth toward the micropyle. The crassinucellate ovule contains an embryo sac consisting of three antipodals, two polar nuclei, and an egg apparatus composed of two synergids and a polarized egg having a large chalazal vacuole and micropylar nucleus. Pollen tube access into the megagametophyte is through a degenerate synergid, with fertilization occurring between 24 and 31 hr after pollination. Zygote establishment is accompanied by polarity reversal in which the nucleus assumes the chalazal position subtended by a large micropylar vacuole. Fertilized ovules normally develop into germinable seeds.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07844.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Chromosome numbers are presented for 99 populations of 13 species ofAntennaria, includingA. plantaginifolia, A. neglecta, A. virginica, A. solitaria, A. racemosa, A. corymbosa. A. rosea, A. media, A. Parlinii, A. fallax, A. neodioica, A. canadensis, andA. petaloidea. Four species from the eastern United States (A. plantaginifolia, A. neglecta, A. solitaria, andA. virginica) were determined as diploid (n =14), and these are all sexual. Diploid counts were also obtained for two sexual species (A.racemosaandA. corymbosa) from the western United States. Chromosome counts are presented for two heteroploid agamic complexes occurring in the eastern United States; these include what have traditionally been referred to as A.Parlinii, A. fallax, A. neodioica, A. canadensis, andA. petaloidea. Determinations of 2n =56, 70, 84, and 112 were obtained for theA. Parliniiand A.fallaxgroups, where 2n =84 had been the only number previously reported. Numbers of 2n =84 were confirmed forA. petaloideaandA. canadensisand 2n= 56 forA. neodioica. The western United States polyploid species (A. roseaandA. media) are reported as 2n= 56. The presence of apomixis is correlated with polyploidy. The distribution of chromosome numbers in eastern United StatesAntennariademonstrates that two diploids and many polyploids occur above the glacial margin, and thus there is an increase in the frequency of polyploidy with latitude. Colonization of the glaciated region byAntennariafollowing the recession of the Wisconsin ice sheet is also discussed. Many of the polyploids occur only in the glaciated region, thus suggesting a recent origin for these cytotypes. There is evidence indicating that the original base number inAntennariamay be x = 7.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07845.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

The flowers ofCassia didymobotryaand C.auriculatahave three types of fertile anthers that differ in orientation, size, shape, and pollen production. Flowers with right‐handed or left‐handed style deflections, i.e., enantiostylous flowers, occur in the same raceme. In Israel, both species are pollinated by pollen collecting buzzing females ofXylocopa pubescens. Vibrations of the carpenter bee are necessary for release of pollen from poricidal anthers and, inC.didymobotrya, also for absorption of pollen through the stigmatic opening into a cavity of the style tip. The largest anthers supply pollen for pollination. Pollen for consumption by the bee, on the other hand, appears to be supplied by all fertile anthers. This is in contrast to the accepted view of a complete separation of functions in the heteromorphic anthers inCassia. The pollen/ovule ratio inC. didymobotryawas 55,200, and that inC. auriculata32,000. Only 0.01% of the pollen produced by a flower was found in the stigmatic pollen load, and this fraction allows for high seed sets. From a comparison of the pollen production and utilization in theCassiaspecies and in certain distylous plants, it is concluded that heteranthery inCassiadoes not confer an advantage in pollen economy. The high pollen/ovule ratios are explained by lack of nectar as well as by the large area on which pollen is deposited on the bee's body relative to the small size of the stigma. Enantiostyly inCassiais considered as part of a pollination syndrome whose characteristics are outlined. The function of enantiostyly as an outbreeding strategy is discussed. In the twoCassiaspecies, opportunities for self‐ and geitonogamous pollinations and self‐compatibility minimize an effect of enantiostyly in promotion of outcrossing. Instead, it is proposed that style deflections may clear access of the pollinator to the anthers and protect female parts from injury by a vibrating heavy‐bodied visitor.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07846.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Olmeca, a new bamboo genus of two species is described from southern Mexico. It is unique among New World bamboos in its production of fruits that are large and fleshy, in contrast to the smaller, dry type—caryopsis or achene—that characterizes the other genera. The fleshy fruit is found in few other bamboos, among themDinochloa, Melocanna, andOchlandra. These Asiatic genera are not all closely related to each other nor to the new American genus, but do share a similar type of habitat: the tropical lowland rain forest, where ample water is available throughout the year. Besides the rare type of fruit found inOlmeca, the rhizomes of this genus develop necks up to 8 m or more long, an uncommon feature among any world bamboo of the sympodial type. The solitary culms ofOlmecagrow widely spaced from one another because of these elongated, intervening necks. One species.O. recta, is known only from the mountain range of Los Tuxtlas, in Veracruz, where it grows on acidic soils derived from basalt; the other,O. reflexa, occurs on calcareous soils and has a wider range that encompasses parts of Veracruz, Oaxaca, and Chiapas.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07847.x

出版商:Wiley    

年代:1981

数据来源: WILEY

摘要:

Nephrostrobus cliffwoodensisgen. et sp. nov.,Nephrostrobus bifurcatussp. nov., andRhombostrobus cliffwoodensisgen. et sp. nov. are described based on anatomical studies of seed cone fragments from the Upper Cretaceous Magothy Formation of New Jersey. These species belong to the Taxodiaceae. As inSequoia, Sequoiadendron. andMetasequoia, the vascular strands supplying the scale and bract inNephrostrobusare about equal. These vascular strands are arranged in a reniform pattern resembling that found inMetasequoia, but the orientation differs by 180 degress.Nephrostrobus cliffwoodensisandNephrostrobus bifurcatusdiffer from each other in the branching of the complex trace and associated resin canals.Rhombostrobus cliffwoodensisresemblesCunninghamiain the arrangement of vascular strands and associated resin canals in its bract‐scale complexes. However, the relative amount of bract and ovuliferous scale making up the complex is more like that inSequoia. This combination of cone features does not occur in any of the extant genera.NephrostrobusandRhombostrobusare not considered to be ancestral to any of the extant taxodiaceous genera, but are extinct members of an ancestral complex from which the extant genera were derived.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1981.tb07848.x

出版商:Wiley    

年代:1981

数据来源: WILEY