Abstract：
:We launched imbibed seeds and seedlings of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on 1) root-cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth-grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth-grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and ellipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar of Z. mays.
journal_name
Am J Botjournal_title
American journal of botanyauthors
Moore R,McClelen CE,Fondren WM,Wang CLsubject
Has Abstractpub_date
1987-01-01 00:00:00pages
218-23issue
2eissn
0002-9122issn
1537-2197journal_volume
74pub_type
杂志文章abstract：PREMISE OF THE STUDY:The fossil record of Agathis historically has been restricted to Australasia. Recently described fossils from the Eocene of Patagonian Argentina showed a broader distribution than found previously, which is reinforced here with a new early Paleocene Agathis species from Patagonia. No previous phylo...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.1002/ajb2.1127
更新日期：2018-08-01 00:00:00
abstract：:The response of axillary buds to floral stimulus activity in stem pieces was examined in two near-isogenic cultivars of tobacco that differ in the recessive maryland mammoth (mm) allele, which confers short-day behavior. All axillary buds from day-neutral plants assayed on six-internode stem pieces made few nodes (les...
journal_title：American journal of botany
pub_type： 杂志文章
doi：
更新日期：1997-07-01 00:00:00
abstract：:In rainforests, trunk size, strength, crown position, and geometry of a tree affect light interception and the likelihood of mechanical failure. Allometric relationships of tree diameter, wood density, and crown architecture vs. height are described for a diverse range of rainforest trees in Brunei, northern Borneo. T...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.94.12.1951
更新日期：2007-12-01 00:00:00
abstract：:Bamboo is considered useful for controlling landslides, but we observed numerous shallow-slope failures in forests of big node bamboo (Phyllostachys nidularia) in Sichuan, China. Therefore, we inventoried landslide occurrence and vegetation type along one valley. To quantify bamboo root anchorage, we performed uprooti...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.94.7.1129
更新日期：2007-07-01 00:00:00
abstract：:Cladistic parsimony analyses of rbcL nucleotide sequence data from 171 taxa representing nearly all tribes and subtribes of Orchidaceae are presented here. These analyses divide the family into five primary monophyletic clades: apostasioid, cypripedioid, vanilloid, orchidoid, and epidendroid orchids, arranged in that ...
journal_title：American journal of botany
pub_type： 杂志文章
doi：
更新日期：1999-02-01 00:00:00
abstract：:The micromorphology of pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm pits are largely invariant. In most Rosaceae, pit membranes between fibers and tracheids frequently appear to have amorphous thickenings with a...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.94.4.503
更新日期：2007-04-01 00:00:00
abstract：:The pathways of micro- and megagametophyte development in Agave fourcroydes (henequén) and A. angustifolia were studied. We used histology and light microscopy to observe anther ontogeny and ovary differentiation in relation to flower bud size. Both species have the same sexual reproductive strategies and gametophyte ...
journal_title：American journal of botany
pub_type： 杂志文章
doi：
更新日期：2001-11-01 00:00:00
abstract：:The cacti are well-known desert plants, widely recognized by their specialized growth form and essentially leafless condition. Pereskia, a group of 17 species with regular leaf development and function, is generally viewed as representing the "ancestral cactus," although its placement within Cactaceae has remained unc...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.92.7.1177
更新日期：2005-07-01 00:00:00
abstract：:In a detailed analysis of how limited seed dispersal can create spatial structuring of genetic variation, several nuclear microsatellites were assayed in seedlings from two forests of Pinus strobus, one old growth (OG) and the other (second site, SS) logged in ca. 1900. By using loci with a large number of alleles and...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.91.4.549
更新日期：2004-04-01 00:00:00
abstract：:Oxalate crystals are very common in angiosperms, but few descriptions of their macropattern (crystal types, their tissue distribution, and development) exist. Because unusually large prismatic crystals and druses, are known from pomegranate, we traced the development of crystal macropattern in various-aged leaf sample...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.92.12.1935
更新日期：2005-12-01 00:00:00
abstract：:A conspicuous feature of Vochysiaceae flowers is their single fertile stamen. In some genera, the stamen is in front of a petal, whereas in others it is in front of a sepal. This difference has been attributed to two independent reductions, which implies the stamen is not homologous across the family. The observation ...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.90.11.1548
更新日期：2003-11-01 00:00:00
abstract：:We used the chloroplast gene ndhF to reconstruct the phylogeny of the moonseed family (Menispermaceae), a morphologically diverse and poorly known cosmopolitan family of dioecious, primarily climbing plants. This study includes a worldwide sample of DNA sequences for 88 species representing 49 of the 70 genera of all ...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.94.8.1425
更新日期：2007-08-01 00:00:00
abstract：:Sphenobaiera huangii (Sze) Hsü is typical Early Mesozoic fossil foliage of Ginkgoales in China. It has been recorded from the Upper Triassic to the Lower Jurassic. The cuticular anatomy is investigated based on material from the type locality, Lower Jurassic Hsiangchi Formation, Zigui County, Hubei Province. The speci...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.92.4.709
更新日期：2005-04-01 00:00:00
abstract：:In a 3-yr study, we examined the pollinator guild and intersexual floral characteristics of the dioecious, perennial cloudberry (Rubus chamaemorus), which flowers in early spring. The findings contribute to our general understanding of pollination ecology at high latitudes and provide important information for the com...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.0800102
更新日期：2009-06-01 00:00:00
abstract：PREMISE OF THE STUDY:Gravity has been a major force throughout the evolution of terrestrial organisms, and plants have developed exquisitely sensitive, regulated tropisms and growth patterns that are based on the gravity vector. The nullified gravity during spaceflight allows direct assessment of gravity roles. The mic...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.1200343
更新日期：2013-01-01 00:00:00
abstract：:Clarkia (Onagraceae) is a genus of 42 annual species, mostly native to California, that has served as a model for many studies of plant evolutionary biology, particularly morphological, cytological, and genetic divergence; reproductive isolation; and speciation. Section Sympherica is the largest section with eight dip...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.90.2.284
更新日期：2003-02-01 00:00:00
abstract：PREMISE OF THE STUDY:A total of 38 polymorphic microsatellite loci of the Indian jujube (Ziziphus mauritiana), an economically important fruit tree, were developed to evaluate genetic diversity and aid in the identification of cultivars. METHODS AND RESULTS:The 38 microsatellite markers were isolated from the Indian j...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.1100500
更新日期：2012-05-01 00:00:00
abstract：:Terrestrial plant leaves are complex structures of composite materials. Resistance to fracture is achieved by a number of mechanisms, which operate at the molecular, cell, tissue, and structural levels. Leaves of dicots have different venation patterns and cell wall volume fractions from those of grasses, and conseque...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.93.10.1531
更新日期：2006-10-01 00:00:00
abstract：PREMISE:Despite the fast pace of exploration of the patterns and processes influencing Neotropical plant hyperdiversity, the taxa explored are mostly from large groups that are widely distributed, morphologically diverse, or economically important. Vochysiaceae is an example of an undersampled taxon, providing an excel...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.1002/ajb2.1502
更新日期：2020-07-01 00:00:00
abstract：:Competition and herbivory are ubiquitous environmental challenges that affect most plants. We examined the influence of phenotypic responses to either competition or herbivory on the subsequent response of the plants to the other factor. The stem-elongation response of Chenopodium album to light competition attenuated...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.92.1.21
更新日期：2005-01-01 00:00:00
abstract：:After 120 yr of burial in moist, well-aerated sand, 23 seeds of Verbascum blattaria and two seeds of a Verbascum sp. germinated and produced normal plants (50% germination for Verbascum). After a 6-wk cold treatment, a single seed of Malva rotundifolia germinated also, producing a normal plant (2% germination). Plants...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.89.8.1285
更新日期：2002-08-01 00:00:00
abstract：:Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain. Genet sex ratio was significantly male biased in one locality but not in the other. However, ramet and flowering ramet sex ratios were male biased at both study sites. Males ...
journal_title：American journal of botany
pub_type： 杂志文章
doi：
更新日期：1998-11-01 00:00:00
abstract：:Cladistic analyses of plastid DNA sequences rbcL and trnL-F are presented separately and combined for 48 genera of Amaryllidaceae and 29 genera of related asparagalean families. The combined analysis is the most highly resolved of the three and provides good support for the monophyly of Amaryllidaceae and indicates Ag...
journal_title：American journal of botany
pub_type： 杂志文章
doi：
更新日期：1999-09-01 00:00:00
abstract：PREMISE OF THE STUDY:The evolutionary shift from radial to bilateral symmetry in flowers is generally associated with the evolution of low flower-size variation. This phenomenon supports the hypothesis that the lower size variation in bilateral flowers can be attributed to low pollinator diversity. In this study, we pr...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.1500371
更新日期：2015-12-01 00:00:00
abstract：:Phylogenetic relationships and biogeography of the genus Cerastium were studied using sequences of three noncoding plastid DNA regions (trnL intron, trnL-trnF spacer, and psbA-trnH spacer). A total of 57 Cerastium taxa was analyzed using two species of the putative sister genus Stellaria as outgroups. Maximum parsimon...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.91.6.943
更新日期：2004-06-01 00:00:00
abstract：:Multicellularity has evolved at least once in every major eukaryotic clade (in all ploidy levels) and numerous times among the prokaryotes. According to a standard multilevel selection (MLS) model, in each case, the evolution of multicellularity required the acquisition of cell-cell adhesion, communication, cooperatio...
journal_title：American journal of botany
pub_type： 杂志文章,评审
doi：10.3732/ajb.1300314
更新日期：2014-01-01 00:00:00
abstract：PREMISE OF THE STUDY:The life histories of lichen fungi are not well known and cannot be readily studied in laboratory culture. This work documents in situ the complete life cycle of the widespread crustose lichen Calopadia puiggarii, which reproduces sexually and asexually on the surfaces of leaves. METHODS:Plastic c...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.1400272
更新日期：2014-11-01 00:00:00
abstract：:Scaling relationships among photosynthetic rate, foliar nutrient concentration, and leaf mass per unit area (LMA) have been observed for a broad range of plants. Leaf traits of the carnivorous pitcher plant Darlingtonia californica, endemic to southern Oregon and northern California, USA, differ substantially from the...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.92.7.1085
更新日期：2005-07-01 00:00:00
abstract：:New individuals in clonal populations arise through the recruitment of sexual or clonal offspring. The predominance of one type of regeneration over the other has been correlated with different selective environmental pressures. We compared the reproductive mode (sexual through seeds and vegetative through plantlets o...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.93.4.505
更新日期：2006-04-01 00:00:00
abstract：PREMISE OF THE STUDY:One explanation for the evolution of selfing, the drought escape hypothesis, proposes that self-fertilization may evolve under conditions of intensifying seasonal drought as part of a suite of traits that enable plants to accelerate the completion of their life cycle, thereby escaping late-season d...
journal_title：American journal of botany
pub_type： 杂志文章
doi：10.3732/ajb.1400557
更新日期：2015-06-01 00:00:00
