bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecophysiology of seed germination in Erythronium japonicum (Liliaceae) with underdeveloped embryos
Authors: Kondo Tetsuya , Okubo Nori , Miura Taku , Honda Kazushige , Ishikawa Yukio
Published: February 2008

Erythronium japonicum (Liliaceae) (Japanese name, katakuri) is indigenous to Japan and adjacent Far East regions. We examined their embryo elongation, germination, and seedling emergence in relationship to the temperature. In incubators, seeds did not germinate at 20°/10° (light 12 h/dark 12 h alternating temperature), 20°, 15°, 5°, or 0°C with a 12‐h light photoperiod for 200 d. They germinated at 15°/5° or 10°C, starting on day 135. If seeds were kept at 20° or at 25°/15°C before being exposed to 5°C, the seeds germinated, but if kept at 25° or 30°C they did not. Embryos at 25°/15°C grew to half the seed length without germinating; at 0° or 5°C, embryos elongated little. Embryos grew and seeds germinated when kept at 25°/15°C for 90 d and then at 5°C. In the field, seeds are dispersed in mid‐June in Hokkaido and in Honshu, mid‐May to mid‐June. Seeds do not germinate immediately after dispersal because the embryo is underdeveloped. Embryos elongated at medium temperatures in autumn after summer heat, and germination ends in November at 8°/0°C. After germination, seedling emergence was delayed, and most seedlings were observed in early April around the snowmelt when soil cover was 2–3 mm.
Limited hybridization between Quercus lobata and Quercus douglasii (Fagaceae) in a mixed stand in central coastal California
Authors: Craft Kathleen J. , Ashley Mary V. , Koenig Walter D.
Published: February 2008

Many oak species are interfertile, and morphological and genetic evidence for hybridization is widespread. Here we use DNA microsatellite markers to characterize hybridization between two closely related oak species in a mixed stand in central coastal California, Quercus lobata (valley oak) and Q. douglasii (blue oak) (Fagaceae). Genotypes from four microsatellite loci indicate that many alleles are shared between the two species. However, each species harbors unique alleles, and allele frequencies differ significantly. A Bayesian analysis of genetic structure in the stand identified two highly differentiated genetic clusters, essentially corresponding to species assignment based on morphology. Data from the four loci were sufficient to assign all 135 trees to one of the two species. In addition, five putative hybrid individuals having intermediate morphologies could be assigned genetically to one or the other species, and all but one had low probability of hybrid ancestry. Overally, only six (4.6%) trees showed >0.05 probability of hybrid ancestry, in all cases their probabilities for nonhybrid ancestry were substantially higher. We conclude that adult hybrids of Q. douglasii × Q. lobata are rare at this site and plasticity in morphological characters may lead to overestimates of hybridization among Quercus species.
A comparison of the taxonomic richness of temperate plants in East Asia and North America
Authors: Qian Hong
Published: February 2008

The taxonomic richness of seed plants at different taxonomic levels was compared between temperate East Asia and North America at both continental and semi‐continental scales. In each comparison, land area and latitude range were adjusted to a comparable level between the two continental regions. East Asia is significantly more diverse than North America. In general, differences in taxonomic diversity arise at and below the genus level. At the continental scale, East Asia has 1.3 and 1.5 times as many genera and species, respectively, as North America. The northern part of East Asia has 1.1 times as many species as the northern part of North America. At the genus level, the northern part of East Asia is less diverse than the northern part of North America by a factor of 0.94. This pattern indicates that the diversity bias between the two continental regions results from the flora of southern East Asia. The diversity differences between East Asia and North America are not homogenously distributed across different plant groups. At the species level, East Asia had significantly more species than expected in magnoliids, alismatids, Liliidae, ranunculids, and rosids and had significantly less species in the Commelinidae, Caryophyllidae, and euasterids than North America.
Diversity and host specificity of endophytic Rhizoctonia‐like fungi from tropical orchids
Authors: Otero J. Tupac , Ackerman James D. , Bayman Paul
Published: February 2008

All orchids have an obligate relationship with mycorrhizal symbionts. Most orchid mycorrhizal fungi are classified in the form‐genus Rhizoctonia. This group includes anamorphs of Tulasnella, Ceratobasidium, and Thanatephorus. Rhizoctonia can be classified according to the number of nuclei in young cells (multi‐, bi‐, and uninucleate). From nine Puerto Rican orchids we isolated 108 Rhizoctonia‐like fungi. Our isolates were either bi‐ or uninucleate, the first report of uninucleate Rhizoctonia‐like fungi as orchid endophytes. We sequenced the internal transcribed spacer (ITS) region of nuclear ribosomal DNA from 26 isolates and identified four fungal lineages, all related to Ceratobasidium spp. from temperate regions. Most orchid species hosted more than one lineage, demonstrating considerable variation in mycorrhizal associations even among related orchid species. The uninucleate condition was not a good phylogenetic character in mycorrhizal fungi from Puerto Rico. All four lineages were represented by fungi from Tolumnia variegata, but only one lineage included fungi from Ionopsis utricularioides. Tropical epiphytic orchids appear to vary in degree of specificity in their mycorrhizal interactions more than previously thought.
Decline of photosynthetic capacity with leaf age and position in two tropical pioneer tree species
Authors: Kitajima Kaoru , Mulkey Stephen S. , Samaniego Mirna , Joseph Wright S.
Published: February 2008

The effect of leaf age on photosynthetic capacity, a critical parameter in the theory of optimal leaf longevity, was studied for two tropical pioneer tree species, Cecropia longipes and Urera caracasana, in a seasonally dry forest in Panama. These species continuously produce short‐lived leaves (74 and 93 d, respectively) during the rainy season (May–December) on orthotropic branches. However, they differ in leaf production rate, maximum number of leaves per branch, light environment experienced by the leaves, leaf mass per unit area, and nitrogen content. Light‐saturated photosynthetic rates for marked leaves of known ages (±1 wk) were measured with two contrasting schemes (repeated measurements vs. chronosequence within branch), which overall produced similar results. In both species, photosynthetic rates and nitrogen use efficiency were negatively correlated with leaf age and positively correlated with light availability. Photosynthetic rates declined faster with leaf age in Cecropia than in Urera as predicted by the theory. The rate of decline was faster for leaves on branches with faster leaf turnover rates. Nitrogen per unit leaf area decreased with leaf age only for Urera. Leaf mass per unit area increased with leaf age, either partly (in Cecropia) or entirely (in Urera) due to ash accumulation.
Experimental hybridizations of Eriophyllum annuals (Asteraceae, Helenieae)
Authors: Mooring John S.
Published: February 2008

Seven of the eight annual species of Eriophyllum, a western North American genus, were studied in greenhouse and garden. Eriophyllum congdonii and E. nubigenum proved to be self‐compatible; E. ambiguum, E. multicaule, E. pringlei, and E. wallacei were self‐incompatible; E. lanosum was not studied. All combinations of artificial hybridizations were attempted except E. congdonii × E. lanosum. Among the species with n = 7, fertile hybrids came from E. congdonii × E. nubigenum and sterile hybrids from E. ambiguum var. ambiguum × E. pringlei, E. ambiguum var. paleaceum × E. congdonii, E. multicaule, E. nubigenum, and E. pringlei, as well as E. multicaule × E. congdonii and E. multicaule × E. pringlei. The other homoploid combinations failed, as did heteroploid combinations involving the annual species with n = 7 and either E. wallacei (n = 5) or E. lanosum (n = 4). Sterile hybrids were generated in crosses of E. congdonii to the perennial E. lanatum (x = 8).
Relationships among seed plants inferred from highly conserved genes: sorting conflicting phylogenetic signals among ancient lineages
Authors: Magallón Susana , Sanderson Michael J.
Published: February 2008

Phylogenetic studies based on different types and treatment of data provide substantially conflicting hypotheses of relationships among seed plants. We conducted phylogenetic analyses of sequences of two highly conserved chloroplast genes, psaA and psbB, for a comprehensive taxonomic sample of seed plants and land plants. Parsimony analyses of two different codon position partitions resulted in well‐supported, but significantly conflicting, phylogenetic trees. First and second codon positions place angiosperms and gymnosperms as sister clades and Gnetales as sister to Pinaceae. Third positions place Gnetales as sister to all other seed plants. Maximum likelihood trees for the two partitions are also in conflict. Relationships among the main seed plant clades according to first and second positions are similar to those found in parsimony analysis for the same data, but the third position maximum likelihood tree is substantially different from the corresponding parsimony tree, although it agrees partially with the first and second position trees in placing Gnetales as the sister group of Pinaceae. Our results document high rate heterogeneity among lineages, which, together with the greater average rate of substitution for third positions, may reduce phylogenetic signal due to long‐branch attraction in parsimony reconstructions. Whereas resolution of relationships among major seed plant clades remains pending, this study provides increased support for relationships within major seed plant clades.
Hybridization in the section Mentha (Lamiaceae) inferred from AFLP markers
Authors: Gobert V. , Moja S. , Colson M. , Taberlet P.
Published: February 2008

The amplified fragment length polymorphism (AFLP) method was used to evaluate genetic diversity and to assess genetic relationships within the section Mentha in order to clarify the taxonomy of several interspecific mint hybrids with molecular markers. To this end, genetic diversity of 62 Mentha accessions from different geographic origins, representing five species and three hybrids, was assessed. Three EcoRI/MseI AFLP primer combinations generated an average of 40 AFLP markers per primer combination, ranging in size from 50 to 500 base pairs (bp). The percentage of markers polymorphic ranged from 50% to 60% across all accessions studied. According to phenetic and cladistic analysis, the 62 mint accessions were grouped into two major clusters. Principal coordinates analysis separated species into well‐defined groups, and clear relationships between species and hybrids could be described. Our AFLP analysis supports taxonomic classification established among Mentha species by conventional (morphological, cytological, and chemical) methods. It allows the assessment of phenetic relationships between species and the hybrids M. spicata and M. × piperita, largely cultivated all over the world for their menthol source, and provides new insights into the subdivision of M. spicata, based for the first time on molecular markers.
Saponaria Pumila (Caryophyllaceae) and the Ice Age in the European Alps
Authors: Tribsch Andreas , Schönswetter Peter , Stuessy Tod F.
Published: February 2008

The polymerase chain reaction (PCR)‐based amplified fragment length polymorphism (AFLP) technique was applied to elucidate the glacial history of the alpine cushion plant Saponaria pumila in the European Alps. Special emphasis was given to a dense sampling of populations. Our data support a survival of S. pumila during the last ice age in at least three refugia, which are characterized by unique marker sets. Patterns of genetic diversity and divergence can be explained by survival in peripheral refugia and additional in situ survival within the ice sheet on peripheral nunataks. A nunatak survival in interior parts of the Alps needs not be postulated to explain our results. The level of genetic diversity is dramatically different between populations (Shannon's diversity index: 0.87–19.86). Some peripheral populations are characterized by a high number of rare fragments indicating long isolation, but not necessarily by a high level of genetic diversity. Parts of the present distributional area were recolonized via recent long‐distance dispersal, leading to severely bottlenecked populations lacking private or rare fragments. The combination of our data with palaeogeological and palaeoclimatological evidence allows us to confine Pleistocene refugia to certain regions and to draw a detailed scenario of the glacial and postglacial history of S. pumila.
The tracheid–vessel element transition in angiosperms involves multiple independent features: cladistic consequences
Authors: Carlquist Sherwin , Schneider Edward L.
Published: February 2008

Current definitions of tracheids and vessel elements are overly simple. These definitions are based on light microscope studies and have not incorporated information gained with scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Current definitions are based primarily on angiosperms, especially eudicots, and were devised before many basal angiosperms were carefully studied. When all sources of information are taken into account, one can recognize changes in six characters in the evolution of tracheids into vessel elements in angiosperms (or vice versa) as well as in other groups of vascular plants. There is an appreciable number of taxa in which all criteria for vessel origin are not met, and thus incipient vessels are present. At the very least, vessel presence or absence should not be treated as a single binary character state change in construction of cladistic matrices. Increase in conductive area of an end wall by means of lysis of progressively greater areas of pit membrane and increase in pit area on the end wall (as compared to pit area on equivalent portions of lateral walls) are considered the most important usable criteria for recognizing intermediacy between tracheids and vessel elements. Primitive character states in vessel elements are briefly discussed to differentiate them from changes in character states that can be regarded as intermediate between tracheids and vessel elements.
The maize mutant barren stalk1 is defective in axillary meristem development
Authors: Ritter Matthew K. , Padilla Christopher M. , Schmidt Robert J.
Published: February 2008

barren stalk1 is a recessive mutant of maize that has no tassel branches, spikelets, tillers, or ears. Here we present a detailed characterization of the ba1 mutant phenotype, including scanning electron microscopy of developing inflorescences, in situ hybridization analysis using a meristem marker, molecular mapping, and genetic analysis demonstrating an epistatic relationship between ba1 and teosinte branched1 (tb1). These data show that the primary defect in the ba1 mutant is a failure in axillary meristem development.
Morphology and development of the female flowers in Geonoma interrupta (Arecaceae)
Authors: Stauffer Fred W. , Rutishauser Rolf , Endress Peter K.
Published: February 2008

Morphology and development of the female flowers in Geonoma interrupta are described and compared with other taxa within Arecaceae. Inflorescences are pleiothyrses. Cincinni are immersed in pits and arranged according to the Fibonacci pattern along the rachillae. The gynoecium is composed of three free carpels in early stages and later becomes pseudomonomerous. Two carpels are sterile; they develop to different degrees and are commonly unequal in size. The fertile carpel contains a single, crassinucellate, anatropous ovule. Styles are formed in each carpel. The style of the fertile carpel becomes basifixed as the ovary enlarges. The stigmas remain free and plicate during development and expose unicellular papillae at anthesis. Pollen tube transmitting tracts and a compitum are present in the ventral slits of the stigmas and the postgenitally united styles during anthesis. A septal nectary is formed by incomplete union of the flanks of the carpels at the base of the gynoecium, and nectar is secreted from an epithelium. It is suggested that in Geonoma as a whole, the attraction of pollinators to female flowers is due to a combination of nectar reward and partial mimicry of male flowers.
Phytochrome photoreceptors mediate plasticity to light quality in flowers of the Brassicaceae
Authors: Weinig Cynthia
Published: February 2008

The family of phytochrome photoreceptors mediates stem‐elongation responses to ambient ratios of red : far‐red light (R : FR). Although phytochrome genes are expressed in flowers in addition to vegetative parts, nothing is known about floral plasticity to R : FR or the pleiotropic effects of phytochrome genes on flowers. Here, the following floral morphologies were compared: (1) wild‐type Arabidopsis thaliana and Brassica rapa plants experiencing high R : FR characteristic of sunlight vs. low R : FR typical of foliar shade and (2) wild‐type and phytochrome‐deficient A. thaliana plants. Wild‐type A. thaliana exposed to low R : FR had diminished petal and pistil lengths but longer filaments for a given petal size than plants experiencing high R : FR. Brassica rapa plants had qualitatively similar responses. In comparison to wild‐type A. thaliana, mutants lacking phytochrome A had smaller flowers (smaller petals, pistils, and filaments), whereas phytochrome B‐deficient mutants exhibited longer filament lengths. These results provide the first evidence that R : FR and phytochromes affect floral phenotypes in addition to vegetative ones. Although the ecological relevance remains to be established, the observed plasticity of flowers to R : FR may be relevant to individual fitness in some species because stigma and filament positions can affect pollen removal and levels of self‐pollination.
Long‐living lotus: germination and soil γ‐irradiation of centuries‐old fruits, and cultivation, growth, and phenotypic abnormalities of offspring
Authors: Shen‐Miller J. , Schopf J. William , Harbottle Garman , Cao Rui‐ji , Ouyang Shu , Zhou Kun‐shu , Southon John R. , Liu Guo‐hai
Published: February 2008

Sacred lotus (Nelumbo nucifera) has been cultivated as a crop in Asia for thousands of years. An ∼1300‐yr‐old lotus fruit, recovered from an originally cultivated but now dry lakebed in northeastern China, is the oldest germinated and directly 14C‐dated fruit known. In 1996, we traveled to the dry lake at Xipaozi Village, China, the source of the old viable fruits. We identified all of the landmarks recorded by botanist Ichiro Ohga some 80 yr ago when he first studied the deposit, but found that the fruits are now rare. We (1) cataloged a total of 60 lotus fruits; (2) germinated four fruits having physical ages of 200–500 yr by 14C dating; (3) measured the rapid germination of the old fruits and the initially fast growth and short dormancy of their seedlings; (4) recorded abnormal phenotypes in their leaves, stalks, roots, and rhizomes; (5) determined γ‐radiation of ∼2.0 mGy/yr in the lotus‐bearing beds; and (6) measured stratigraphic sequences of the lakebed strata. The total γ‐irradiation of the old fruits of 0.1–3 Gy (gray, the unit of absorbed dosage defined as 1 joule/kg; 1 Gy = 100 rad), evidently resulting in certain of the abnormal phenotypes noted in their seedlings, represents the longest natural radiobiology experiment yet recorded. Most of the lotus abnormalities resemble those of chronically irradiated plants exposed to much higher irradiances. Though the chronic exposure of the old fruits to low‐dose γ‐radiation may be responsible in part for the notably weak growth and mutant phenotypes of the seedlings, it has not affected seed viability. All seeds presumably repair cellular damage before germination. Understanding of repair mechanisms in the old lotus seeds may provide insight to the aging process applicable also to other organisms.
Collection and storage of pollen from Salix (Salicaceae)
Authors: Kopp Richard F. , Maynard Charles A. , Rocha de Niella Patricia , Smart Lawrence B. , Abrahamson Lawrence P.
Published: February 2008

Genetic improvement of willows through traditional breeding can be facilitated by pollen collection and storage so that female flower receptivity need not be synchronized with pollen shed for breeding. Two experiments were completed to test the effectiveness of various organic solvents for willow pollen collection. In the first experiment, seven pollen collection treatments and an untreated control were tested with two willow clones. The other experiment tested three treatments that showed promise in the initial experiment and an untreated control with eight willow clones. Toluene and carbon tetrachloride were effective for pollen extraction, with average pollen germination percentages that were >15%, but both chemicals reduced pollen viability by 10–20% compared with an untreated control based on in vitro germination tests. Pollen extracted with carbon tetrachloride or toluene was successfully used in controlled pollination, and >100 new families were produced with this technique. Pollen viability remained high after 18 mo of storage at −20°C. Based on our results, toluene is the preferred solvent for future willow pollen extractions because it is as effective as carbon tetrachloride, is not a known carcinogen, and is less expensive.
The use of dna sequencing (ITS and trnL‐F), AFLP, and fluorescent in situ hybridization to study allopolyploid Miscanthus (Poaceae)
Authors: Hodkinson Trevor R. , Chase Mark W. , Takahashi Chigusa , Leitch Ilia J. , Bennett Michael D. , Renvoize Stephen A.
Published: February 2008

Two clones of Miscanthus, grown under the names M. ×giganteus and M. sacchariflorus, have been used in biomass trials in Europe, but neither the identity of these clones nor their origin has been established. DNA sequencing, amplified fragment length polymorphism (AFLP), and chromosome studies confirm that M. ×giganteus is an allotriploid (2n = 3x = 57) combining genomes from M. sinensis (2n = 2x = 38) and M. sacchariflorus (2n = 38 or 76). Two alleles of the internal transcribed spacer of 18S–25S nuclear ribosomal DNA (ITS) were discovered in polymerase chain reaction products of M. ×giganteus. Cloning of these revealed that one matched M. sinensis and the other M. sacchariflorus. Plastid trnL intron and trnL‐F spacer sequences showed that the maternal lineage of M. ×giganteus was M. sacchariflorus. Fluorescent in situ hybridization, FISH, was used to investigate genome organization in Miscanthus but was unable to differentiate between the different parental genomes present in M. ×giganteus, indicating that two parental genomes are still extremely similar at the repetitive DNA level. This study is an example in which rDNA sequences and AFLP fingerprints permit identification of the parental genomes in a hybrid, but FISH methods, at the repetitive DNA level (including genomic in situ hybridization, GISH), were unable to do so because their sequences remain too similar.
Ashicaulis woolfei n. sp.: additional evidence for the antiquity of osmundaceous ferns from the Triassic of Antarctica
Authors: Rothwell Gar W. , Taylor Edith L. , Taylor Thomas N.
Published: February 2008

Numerous small fern trunks and dispersed osmundaceous frond fragments occur within a Middle Triassic silicified peat near Fremouw Peak in the Transantarctic Mountains of Antarctica. These specimens form the basis of a new species of osmundaceous ferns that further helps to characterize the early Mesozoic vegetation of high latitude Gondwana. Ashicaulis woolfei n. sp. consists of small, upright trunks with a persistent armor of frond bases, adventitious roots, and vegetative frond parts. In cross section the trunks are ∼2.5 cm in diameter and include up to 45 frond bases. Stems range from 5 to 8 mm in diameter with a xylem cylinder of 8–9 xylem segments separated by leaf gaps. Phyllotaxy is variable, approaching 2/5 or 3/8, with 10–12 frond traces in the cortex. Stipes have parenchymatous, stipular wings that are usually devoid of sclerenchyma; fronds are pinnate with alternate‐subopposite pinnatifid pinnules. Although the absence of fertile pinnules and sporangia precludes assigning the fossils to a living genus, this species demonstrates that ferns with stelar architecture and histology similar to Osmunda subgenus Osmundastrum (Osmundaceae) were present in the Southern Hemisphere by the mid‐Triassic.
Slow heating of barley aleurone layers to heat‐shock temperature preserves heat‐shock‐sensitive cellular properties
Authors: Johnston Mark K. , Benson Paul A. S. , Rodgers Tracy M. , Brodl Mark R.
Published: February 2008

In barley (Hordeum vulgare L. cv. Himalaya) aleurone layers, heat shock causes the selective suppression of α‐amylase synthesis by destabilizing this secretory protein's mRNA. The lamellar stacks of the endoplasmic reticulum (ER), which serve as the site of α‐amylase mRNA translation, are dissociated by heat shock, suggesting that heat‐shock‐induced changes in ER may be important in selectively targeting α‐amylase mRNAs for destabilization. We have found that samples maintained at heat‐shock temperature (40°C) for 18 h recover the ability to synthesize α‐amylase and that the ER membranes in these samples contain membrane phospholipids with enhanced levels of fatty acid saturation. This present study investigated whether gradual warming to 40°C over 3–6 h (ramping) would preserve α‐amylase synthesis by permitting ER membrane phospholipid retailoring during the gradual temperature increase. Analyses by sodium dodecyl‐sulfate polyacrylamide gel electrophoresis revealed that α‐amylase synthesis was markedly increased in ramped samples. Furthermore, northern hybridization analyses and transmission electron microscopy showed that these samples had increased α‐amylase mRNA levels and stacks of ER lamellae, respectively. Gas chromatographic analyses of ER membrane phospholipids indicated that the fatty acids of ramped samples were more saturated than their heat‐shocked counterparts. These data indicate that heat‐induced increases in aleurone ER membrane phospholipid fatty acid saturation may be important in maintaining secretory protein expression at normally nonpermissive heat‐shock temperatures.
Diurnal and nocturnal pollination of Silene alba (Caryophyllaceae)
Authors: Young Helen J.
Published: February 2008

Flowers that are open for >12 h may be visited by both diurnal and nocturnal pollinators. I compared the effectiveness (measured as seed production and pollen movement distance) of diurnal and nocturnal pollinators of Silene alba, a species whose flowers open in evening but close by midmorning the following day. By bagging flowers either during evening hours or during daylight hours or both day and night, I compared seed production caused by diurnal and nocturnal pollinators. Flowers exposed only to nocturnal visitors (mostly sphingid and noctuid moths) produced significantly more seeds than flowers exposed only to diurnal visitors (bees, flies, and wasps). Fluorescent dye applied to anthers moved significantly further and to more stigmas at night than during the day. In both measures of pollination effectiveness, nocturnal‐visiting moths are better pollinators of S. alba than are the diurnal‐visiting bees, flies, and wasps. These data support the hypothesis that floral phenology is an adaptation to expose flowers to the most effective pollinators.
Temporal variation in floral display size and individual floral sex allocation in racemes of Narthecium asiaticum (Liliaceae)
Authors: Ishii Hiroshi S. , Sakai Satoki
Published: February 2008

We analyzed the effects of temporal variation in floral display size (number of flowers open at one time on a plant) on the rate of pollen removed and receipt of individual flowers for the sequential blooming plant Narthecium asiaticum (Liliaceae). Because of the acropetal blooming of this species, the display sizes when upper flowers opened was much greater than the display sizes when lower flowers opened. Our experiments revealed that large displays lead to a high rate of pollen removal from individual flowers, though they do not lead to a high rate of ovule fertilization. Consequently, the rate of pollen grains removed per flower by pollinators was greater in upper flowers than in lower flowers. The pattern of sex allocation in individual flowers within a raceme was consistent with such variation. Namely, both maleness [stamen mass/(stamen mass + pistil mass)] and pollen : ovule ratio were larger in upper flowers. We suggest that the temporal variation in display size, in addition to such factors as dichogamy and pollinator directionality, also produces variation in the probability of successful pollen transfer from individual flowers that may cause the variation in the sex allocation of individual flowers.
Does clonal integration improve competitive ability? A test using aspen (Populus tremuloides [Salicaceae]) invasion into prairie
Authors: Peltzer Duane A.
Published: February 2008

Many clonal plants consist of many connected individual ramets, allowing them to share water and nutrients via physiological integration. Integration among ramets may also improve the ability of clonal plants to tolerate abiotic stress or improve the competitive ability of individual ramets. Here I use a field experiment to determine whether clonal integration improves ramet performance for a widespread clonal tree species invading into native prairie. Aspen (Populus tremuloides) dominates the southern treeline in western Canada, has long‐lived belowground connections between mother and daughter ramets, and reproduces vegetatively via resprouting rhizomes after disturbance. I applied two competition treatments (neighbors present or absent) and two clonal integration treatments (belowground rhizomes between mother and daughter ramets either severed or left intact) to 12 replicate Populus daughter ramets at each of three sites. Neighbors improved the survivorship of Populus ramets by 25–35% after 2 yr, but decreased growth by ∼20%. Clonal integration tended to improve ramet survival and growth, but these trends were often not significant. Clonal integration did not alter the effects of competition from neighboring vegetation, suggesting that connections between ramets do not necessarily improve the competitive ability of Populus invading into native prairie.
Genetic diversity in Delphinium variegatum (Ranunculaceae): a comparison of two insular endemic subspecies and their widespread mainland relative
Authors: Dodd Shana C. , Helenurm Kaius
Published: February 2008

Delphinium variegatum is subdivided into three subspecies: D. v. variegatum is widespread in central and northern California, while D. v. kinkiense (an endangered taxon) and D. v. thornei are endemic to San Clemente Island off the coast of southern California. Electrophoretic data for 19 loci were collected from 7 populations of the mainland subspecies and all 24 known populations of the two insular endemic subspecies. Populations of the widespread mainland subspecies have more polymorphic loci (33.6% vs. 24.5%) and more alleles per polymorphic locus (2.61 vs. 2.15) than the insular endemic subspecies. However, observed heterozygosities are lower in the mainland subspecies (0.041 vs. 0.071), presumably due to lower levels of outcrossing (t = 0.464 vs. 0.895). Expected heterozygosities are similar (0.064 vs. 0.074) due to lower alternative allele frequencies in populations of the mainland subspecies (mean q = 0.075 vs. 0.190). Populations of the two insular subspecies are almost equivalent genetically (mean I = 0.997) regardless of taxonomic designation or geographic location. In contrast, one of the mainland populations is genetically well differentiated from the others. If this exceptional population is excluded, the mainland subspecies partitions genetic diversity similarly to the island subspecies, with most variation being found within populations (GST = 0.073 vs. 0.030).
Saltwater spray as an agent of natural selection: no evidence of local adaptation within a coastal population of Triplasis purpurea (Poaceae)
Authors: Cheplick Gregory P. , White Timothy P.
Published: February 2008

An ability to tolerate airborne saltwater spray is critical for plant populations in coastal environments. The opportunity for continued microevolution for improved salt tolerance can exist if there is variation in the response of genetic families to saltwater spray. Our objective was to determine whether or not there was differentiation among subpopulations near (15 m) and far (80 m) from shore and among families within subpopulations in relation to the effects of salt spray on life history traits in a population of the dunegrass Triplasis purpurea. In this annual, most seeds are matured in cleistogamous spikelets on axillary, leaf‐sheath enclosed panicles and show poor dispersal capacity. Plants were reared in the greenhouse from seeds of 13 and 11 families from the near and far subpopulations, respectively. Fifty percent of plants in a family were subjected to 6 seawater sprays/wk, resulting in weekly salt deposition of 213 μg/cm2; the others were sprayed with distilled water. Data were recorded on life span, tiller numbers, root and shoot dry mass, and seed production. There was no effect of subpopulation on any measured trait and, hence, no evidence for local adaptation to salt spray. Final tiller numbers, but not dry mass or seed production, were reduced by salt spray. However, for most traits there were significant family (within subpopulation) effects, indicating genetic substructuring. Life span and mean seed mass showed a significant family by treatment interaction, indicating genetic variation in phenotypic responses to salt spray. Life span and mean seed mass were reduced by salt spray in some, but not all, families. Path analysis revealed that an increase in life span or tiller number indirectly increased seed production via direct effects on vegetative mass. For this relatively salt‐tolerant T. purpurea population on the south shore of Staten Island, New York, USA, salt sprays may not be a significant agent of natural selection. However, there are pronounced phenotypic differences among inbred family groups and opportunity for genetic substructuring within these subpopulations. Variable effects of salt spray among families could result in microevolutionary changes in life span and mean seed mass, both of which impact annual fitness in this dunegrass.
Propagation mechanisms in Agave macroacantha (Agavaceae), a tropical arid‐land succulent rosette
Authors: Arizaga Santiago , Ezcurra Exequiel
Published: February 2008

Agave macroacantha can sexually reproduce by seeds and propagate vegetatively by aerial bulbils and ground‐level basal shoots and rhizomes. It forms compact patches apparently generated by the multiplication of ground‐level offshoots. We experimentally evaluated the establishment and survival of bulbils and seedlings of A. macroacantha in the Tehuacán Valley, Mexico, between 1991 and 1994 and studied comparatively the effectiveness of sexual reproduction against vegetative propagation.

Seedlings showed low survival rates. Cohorts placed outside nurse plants died in less than 1 yr, while 1–10% of cohorts under nurse plants survived for more than 2 yr. Herbivores negatively affected seedling survival in non‐nursed plots. In rainy years, survival rates increased. Bulbils showed higher survival rates than seedlings.

The excavation of rosettes showed that most are derived from vegetative shoots, as indicated by remains of rhizomes in their base. Most rosettes had ground‐level vegetative offspring totaling almost three shoots per rosette.

In A. macroacantha, the establishment of seedlings and bulbils is a rare event that possibly only occurs under nurse plants in rainy years, while ground‐level cloning is highly effective as a propagation mechanism. These results are consistent with the aggregated spatial pattern of the species.
Anatomy of Umkomasia (Corystospermales) from the Triassic of Antarctica
Authors: Klavins Sharon D. , Taylor Thomas N. , Taylor Edith L.
Published: February 2008

The permineralized, corystosperm, cupulate, ovule‐bearing organ Umkomasia resinosa is described from the early Middle Triassic of Antarctica. This is the first description of anatomically preserved Umkomasia, which consists of a determinate cupulate branch with helically arranged, recurved, pedicellate megasporophylls, each of which bears one or two abaxially attached unitegmic ovules. Cupules are ovoid, bilobed with elongate ventral and dorsal openings or unlobed with a single ventral opening, and have a two‐zoned parenchymatous cortex and abundant secretory cavities. Ovules are small, orthotropous, and possess a thin integument that contains numerous secretory cavities. The ovules are broadly attached at the base, with a bifid integumentary apex that extends past the cupule lobes. The cupulate branch displays stem‐like anatomy, producing paired traces into each cupule stalk. These structurally preserved ovulate organs can be related to other corystosperm organs from Antarctica, particularly the pollen‐organ Pteruchus fremouwensis. Both anatomical and morphological features support interpretation of corystosperm reproductive structures as branching systems rather than as compound sporophylls. As a result of an increased understanding of the organization of Umkomasia, it appears doubtful that any direct relationship exists between the corystosperm and angiosperm lineages.
Using RPB1 sequences to improve phylogenetic inference among mushrooms (Inocybe, Agaricales)
Authors: Matheny P. Brandon , Liu Yajuan J. , Ammirati Joseph F. , Hall Benjamin D.
Published: February 2008

An investigation of mushroom phylogeny using the largest subunit of RNA polymerase II gene sequences (RPB1) was conducted in comparison with nuclear ribosomal large subunit RNA gene sequences (nLSU) for the same set of taxa in the genus Inocybe (Agaricales, Basidiomycota). The two data sets, though not significantly incongruent, exhibit conflict among the placement of two taxa that exhibit long branches in the nLSU data set. In contrast, RPB1 terminal branch lengths are rather uniform. Bootstrap support is increased for clades in RPB1. Combined data sets increase the degree of confidence for several relationships. Overall, nLSU data do not yield a robust phylogeny when independently assessed by RPB1 sequences. This multigene study indicates that Inocybe is a monophyletic group composed of at least four distinct lineages—subgenus Mallocybe, section Cervicolores, section Rimosae, and subgenus Inocybe sensu Kühner, Kuyper, non Singer. Within subgenus Inocybe, two additional lineages, one composed of species with smooth basidiospores (clade I) and a second characterized by nodulose‐spored species (clade II), are recovered by RPB1 and combined data. The nLSU data recover only clade I. The genera Astrosporina and Inocybella cannot be recognized phylogenetically. “Supersections” Cortinatae and Marginatae are not monophyletic groups.
Rapid diversification of the cotton genus (Gossypium: Malvaceae) revealed by analysis of sixteen nuclear and chloroplast genes
Authors: Cronn Richard C. , Small Randall L. , Haselkorn Tamara , Wendel Jonathan F.
Published: February 2008

Previous molecular phylogenetic studies have failed to resolve the branching order among the major cotton (Gossypium) lineages, and it has been unclear whether this reflects actual history (rapid radiation) or sampling properties of the genes evaluated. In this paper, we reconsider the phylogenetic relationships of diploid cotton genome groups using DNA sequences from 11 single‐copy nuclear loci (10 293 base pairs [bp]), nuclear ribosomal DNA (695 bp), and four chloroplast loci (7370 bp). Results from individual loci and combined nuclear and chloroplast DNA partitions reveal that the cotton genome groups radiated in rapid succession following the formation of the genus. Maximum likelihood analysis of nuclear synonymous sites shows that this radiation occurred within a time span equivalent to 17% of the time since the separation of Gossypium from its nearest extant relatives in the genera Kokia and Gossypioides. Chloroplast and nuclear phylogenies differ significantly with respect to resolution of the basal divergence in the genus and to interrelationships among African cottons. This incongruence is due to limited character evolution in cpDNA and either previously unsuspected hybridization or unreliable phylogenetic performance of the cpDNA characters. This study highlights the necessity of using multiple, independent data sets for resolving phylogenetic relationships of rapidly diverged lineages.
Discovery of an endophytic alga in Ginkgo biloba
Authors: Trémouillaux‐Guiller Jocelyne , Rohr Thomas , Rohr René , Huss Volker A. R.
Published: February 2008

Although intracellular associations with mycorrhizal fungi are known for Ginkgo biloba, no other endosymbiotic relationships have ever been reported for this “living fossil.” A protoplast culture derived from haploid explants has now revealed the existence of a green alga in vitro, whose eukaryotic status was confirmed by transmission electron microscopic studies. Phylogenetic 18S rDNA sequence analyses showed this alga to be closely related to the lichen photobiont Coccomyxa. Algae, which in host cells exist as more or less undifferentiated “precursor” forms, proliferated within necrosing G. biloba cells of a subculture derived from a zygotic embryo and were finally released into the medium. Light and electron microscopic observations showed that G. biloba cells rapidly filled up with countless green particles whose number increased up to the bursting of the hypertrophic host cells. At the beginning of reproduction no algae were visible in the nutritive medium, demonstrating that the proliferation started inside the G. biloba cells and excluding the possibility of an exogenous contamination. Occasionally, mature algae together with their precursor forms were detected by transmission electron microscopy in intact host cells of a green callus. The algae were easily identified by their similarity to the cultured algae. Eukaryotic algae have never been reported to date to reside inside higher plant cells, whereas several algal associations are well known from the animal kingdom.
Floral ontogeny in Sophoreae(Leguminosae: Papilionoideae). III. Radial symmetry and random petal aestivation in Cadia Purpurea
Authors: Tucker Shirley C.
Published: February 2008

Floral organogeny and development are described in Cadia purpurea, a legume with radial symmetry, unstable petal aestivation, and free organs, all unusual features among papilionoids. Flowers are usually solitary or, rarely, in few‐flowered racemes. No bracteoles are formed. The order of organ initiation is unidirectional in each whorl, and the carpel initiates directly after petal initiation. The petal primordia remain small until all other floral organs have initiated, enlarged, and differentiated. Petal aestivation is variable, unlike the great majority of papilionoid flowers. Petal margins of Cadia grow straight outward rather than some petal margins curving inward inside the adjacent petal as is the case in other papilionoids. When adjacent growing petal margins of Cadia meet, chance determines which petal becomes positioned inside the other. Hence, the pattern of petal aestivation is random.
Regional patterns of genetic diversity in Pinus flexilis (Pinaceae) reveal complex species history
Authors: Jørgensen Stacy , Hamrick J. L. , Wells P. V.
Published: February 2008

Pinus flexilis (limber pine) is patchily distributed within its large geographic range; it is mainly restricted to high elevations in the Rocky Mountains and the Basin and Range region of western North America. We examined patterns of allozyme diversity in 30 populations from throughout the species' range. Overall genetic diversity (He = 0.186) was high compared with that of most other pine species but was similar to that of other pines widespread in western North America. The proportion of genetic diversity occurring among populations (GST = 0.101) was also high relative to that for other pines. Observed heterozygosity was less than expected in 28 of the 30 populations. When populations were grouped by region, there were notable differences. Those in the Basin and Range region had more genetic diversity within populations, a higher proportion of genetic diversity among populations, and higher levels of inbreeding within populations than populations from either the Northern or Utah Rocky Mountain regions. Patterns of genetic diversity in P. flexilis have likely resulted from a complex distribution of Pleistocene populations and subsequent gene flow via pollen and seed dispersal.
Canonical rules for plant organ biomass partitioning and annual allocation
Authors: Niklas Karl J. , Enquist Brian J.
Published: February 2008

Here we review a general allometric model for the allometric relationships among standing leaf, stem, and root biomass (ML,MS, andMR, respectively) and the exponents for the relationships among annual leaf, stem, and root biomass production or “growth rates” (GL,GS, andGR, respectively). This model predicts thatML∝MS3/4∝MR3/4such thatMS∝MRand thatGL∝GS∝GR. A large synoptic data set for standing plant organ biomass and organ biomass production spanning ten orders of magnitude in total plant body mass supports these predictions. Although the numerical values for the allometric “constants” governing these scaling relationships differ between angiosperms and conifers, across all species, standing leaf, stem, and root biomass, respectively, comprise 8%, 67%, and 25% of total plant biomass, whereas annual leaf, stem, and root biomass growth represent 30%, 57%, and 13% of total plant growth. Importantly, our analyses of large data sets confirm the existence of scaling exponents predicted by theory. These scaling “rules” emerge from simple biophysical mechanisms that hold across a remarkably broad spectrum of ecologically and phyletically divergent herbaceous and tree‐sized monocot, dicot, and conifer species. As such, they are likely to extend into evolutionary history when tracheophytes with the stereotypical “leaf,” “stem,” and “root” body plan first appeared.
Seed germination ecophysiology of the Asian species Osmorhiza aristata (Apiaceae): comparison with its North American congeners and implications for evolution of types of dormancy
Authors: Walck Jeffrey L. , Hidayati Siti N. , Okagami Nobuo
Published: February 2008

Osmorhiza aristata is an herbaceous perennial that grows primarily in Japan, through southern China, to the Himalayas. It closely resembles the eastern North American species O. claytonii and O. longistylis, and, together, the three species are an example of the well‐known North American–Asian pattern of disjunction. Requirements for dormancy break and embryo growth were determined for seeds of O. aristata collected in Japan during the summers of 1998–2000. Embryos in fresh seeds were ca. 0.5 mm long, and they had to grow to 9 mm before the radicle emerged from the mericarp. Embryo growth and germination occurred during cold stratification at 5°C, the optimum temperature for germination. Gibberellic acid did not substitute for cold stratification. Thus, O. aristata seeds have deep complex morphophysiological dormancy (MPD). The type of MPD in O. aristata is similar to that in two western North American congeners but different from that in eastern North American congeners (nondeep complex MPD). Mapping the types of MPD onto a phylogeny of the genus suggests that nondeep complex MPD is derived from deep complex MPD. Although eastern North American–Asian disjuncts often exhibit morphological stasis, the taxa may differ greatly in physiological traits, such as seed dormancy.