bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual polymorphism, growth, and reproductive effort in Egyptian Thymelaea hirsuta (Thymelaeaceae)
Authors: Ramadan A. A. , El‐Keblawy A. , Shaltout K. H. , Lovett‐Doust J.
Published: January 2018

Gender phenotypes of Thymelaea hirsuta (L.) Endl. were surveyed in six major habitats in the western Mediterranean region of Egypt. Five gender phenotypes were observed at all sites: subandroecious (male), subgynoecious (female), protogynous, protandrous, and gender‐labile individuals. Patterns of vegetative growth, reproductive effort, and sex‐size relationships were also determined. Females and males were comparable in overall abundance (35.5% and 30.2%, respectively). However, the frequency of sex forms varied significantly among habitats. Plant size (canopy volume) was used as a measure of environmental quality for the species: the coastal dunes were by far the most favorable habitat, followed by the nonsaline depressions, inland plateau, and inland siliceous deposits. The smallest plants were associated with the inland ridges and saline depressions. Protandrous individuals, and female shrubs at the more favorable habitats (e.g., the coastal dunes and nonsaline depressions), had greater canopy volume than males. In contrast, males were larger than females at the less favorable habitats (e.g., the inland plateau and saline depressions). Advantageous growth conditions at the coastal dunes are demonstrated by the greater rate of increase in crown diameter and crown volume noted there, for each size class and sex form. The greatest rates of increase were present in smaller‐sized individuals. Size differences between the sex forms were considered in terms of trade‐offs between individual growth rate (GR) and reproductive effort (RE); evidence of a trade‐off was mixed. Indeed, in a comparison of GR and RE at two extremes of habitat (coastal dune vs. inland plateau), females had greater GR and greater RE at the relatively benign coastal dunes, while at the more harsh, inland plateau site males showed greater GR and RE than females. Peak reproductive effort varied significantly with gender phenotype and habitat type.
A survey of autofluorescent patterns in the staminal connective base epidermis in 60 species of Asteraceae
Authors: Sullivan Victoria I. , Pesacreta Thomas C. , Durand John , Hasenstein Karl H.
Published: January 2018

All 60 Asteraceae species sampled, i.e., two species of Bamadesioideae, 21 species in six tribes in Cichorioideae, and 37 species in nine tribes of Asteroideae, show specific patterns of autofluorescence in abaxial connective base epidermal cells. Two species of Cichorioideae and 15 species of Asteroideae have autofluorescence in adaxial epidermal cells of the connective base. Several taxonomically useful features of the connective base are identified; they include shapes of autofluorescent cells, patterns of distribution of cells with autofluorescent walls, and patterns of distribution of autofluorescence in walls. Cellular features of many species coincide with recognized generic, tribal, and subtribal classifications. The results extend Cassini's characterization of the article anthérifere and indicate that the variable features of the connective bases of stamens of Asteraceae could contribute to phylogenetic understanding.
Developmental evidence for the derivation of syncephalia in Lagascea (Heliantheae; Asteraceae)
Authors: Harris Elizabeth M.
Published: January 2018

The theme of condensation of inflorescences, often accompanied by reduction, is widespread throughout the Asteraceae. Many examples of condensation of the primary Asteraceae inflorescence into secondary aggregations have long been noted. Descriptions of tertiary condensation of inflorescences (i.e., condensation of secondary aggregations) are rarer; partially due to the difficulty of unequivocal documentation. Comparative investigations with the scanning electron microscope yield clear evidence of inflorescence condensation. Developmental stages demonstrating tertiary condensation heads characterize Lagascea helianthifolia, L. aurea, L. palmeri, and L. rigida. Dissections of L. decipiens and L. heteropappus also suggested tertiary condensation. Added to a previous account of the tertiary condensation of L. mollis, seven of the eight species of the genus have been examined and have been found to display tertiary condensation, accompanied by a reduction of the primary inflorescence to single flowers. The most parsimonious explanation would suggest that the tertiarily aggregated inflorescences found in the genus Lagascea evolved only once in that lineage.
Isozymes of Eleusine (Gramineae) and the origin of finger millet
Authors: Werth Charles R. , Hilu Khidir W. , Langner Clara A.
Published: January 2018

The predominantly African grass genus Eleusine comprises nine species, including diploids and tetraploids based on n = 8, 9, and 10. Among the polyploids are the important crop finger millet, Eleusine coracana subsp. coracana, and its putative wild ancestor, E. coracana subsp. africana. Eleusine coracana is believed to be an allotetraploid derived by hybridization between E. indica and an unknown diploid. To evaluate this hypothesis, 16 isozyme loci coding nine enzymes were compared among seven of the nine Eleusine species (E. intermedia and E. semisterilis were unavailable). Genetic variability differed substantially among diploid species, ranging from P = 0.563, A = 1.6, H = 0.208 in E. indica to P = 0.188, A = 1.2, H = 0.042 in E. jaegeri. The diploids tended to be genetically distinct, with values of Rogers' Similarity ranging from S = 0.294 (E. jaegeri/floccifolia) to S = 0.794 (E. indica/tristachya). Both subspecies of the tetraploid E. coracana exhibited fixed heterozygosity at several loci, verifying their hypothesized allotetraploid status. Both tetraploids also possessed E. indica marker alleles at all loci, corroborating ancestry by this taxon. Genotypes of the non‐indica ancestor, inferred separately for each tetraploid, differed substantially from all candidate diploids and also from each other. These data indicate that 1) none of the candidate diploids investigated is likely to have been the non‐indica ancestor of E. coracana, and 2) the non‐indica ancestor of the wild tetraploid may differ from that of the crop. The latter conclusion is inconsistent with the complete chromosomal homology exhibited between the two tetraploid subspecies, indicating the need for additional evidence bearing on their relationships.
Monoclonal antibodies against phloem P‐protein from plant tissue cultures. II. Taxonomic distribution of cross‐reactivity
Authors: Tóth Karen F. , Sjölund Richard D.
Published: January 2018

P‐protein, a filamentous protein found in the sieve elements of most angiosperms, is believed to function in the sealing of phloem wound sites. We report here on the use of a highly sensitive immunomicroscopy assay to study the ability of P‐protein specific monoclonal antibodies RS21, RS22, and RS23, made against the P‐protein from Streptanthus tortuosus (Brassicaceae), to recognize the native P‐protein in a number of different plant genera. RS21, RS22, and RS23 all recognized the P‐protein in other genera within the Brassicaceae including Arabidopsis and in the closely related family, Capparaceae. RS21 and RS22 also were able to bind to the P‐protein in plants more distantly related to S. tortuosus. The labeling of P‐protein was also observed in the monocots Iris and Narcissus probed with RS21. No label was seen with members of the Poaceae that are reported to lack P‐protein. None of the monoclonal antibodies was able to bind to the P‐protein in members of the Cucurbitaceae.
Pollen tube penetration and fertilization inLilium longiflorum (Liliaceae)
Authors: Janson Juliette , Willemse Michiel T. M.
Published: January 2018

The ultrastructure of the embryo sac, nucellus, and parts of the micropyle of Lilium longiflorum were studied both before and after pollen tube penetration to examine the interactions between ovule and pollen tube, using transmission electron microscopy and light microscopy. Before pollen tube penetration the egg cell and two synergids are similar. No filiform apparatus was detected and no synergid degeneration occurs prior to pollen tube penetration. The polar nuclei do not fuse until fertilization. No differences in embryo sac ultrastructure were detected between pollinated ovules unpenetrated by pollen tubes and unpollinated flowers of a comparable age. Shortly after the discharge of the pollen tube two enucleated cytoplasmic bodies with different ribosome densities were observed in the degenerated cytoplasm. These structures border both on the central cell and the egg cell as well as each other and are interpreted as remains of sperm cytoplasm after transmission of sperm nuclei. In the central cell both the sperm nucleus and the polar nuclei are associated with endoplasmic reticulum (ER). ER is thought to be a transport mechanism to achieve contact between the haploid polar nuclei and the sperm nucleus. In the egg cell sperm nucleus alignment is not visibly achieved by ER. The persistent cells of the egg apparatus and the central cell appear to become more metabolically active after pollen tube penetration. Pollen tube penetration already occurs despite the absence of a filiform apparatus and a low level of differences between the cells of the egg apparatus.
The ultrastructure of zygotic embryo development in pearl millet (Pennisetum glaucum; Poaceae)
Authors: Taylor Mark G. , Vasil Indra K.
Published: January 2018

The ultrastructure, morphology, and histology of zygotic embryogenesis in pearl millet (Pennisetum glaucum) were examined using light and electron microscopic techniques. Embryogenesis was initially characterized by the presence of a vacuolated egg cell and zygote. The increased presence of Golgi bodies in the zygote suggested it was metabolically more active than the egg cell. The first zygotic division resulted in a densely cytoplasmic apical cell and a highly vacuolated basal cell. The club‐shaped proembryo displayed a large amount of endoplasmic reticulum (ER) and ribosomes, very few lipids, and a continuous gradient of vacuoles from the highly vacuolated basal suspensor cells to the densely cytoplasmic apical cells. The embryo had well‐defined parts by 8 days after pollination, including shoot and root meristems, coleoptile, scutellum, provascular system, and the first leaf primordium. Large increases in ER, lipids, starch, and vacuoles occurred in the scutellum during the maturation of the embryo, except in the provascular cells. Throughout zygotic embryogenesis, embryo cells were connected by plasmodesmata except where intercellular spaces occurred. Ultrastructural, morphological, and histological observations of zygotic embryogenesis in pearl millet are in agreement with previous reports for other grass species.
Chloroplast‐DNA restriction site analysis in the genusBromus (Poaceae)
Authors: Pillay Michael , Hilu Khidir W.
Published: January 2018

Chloroplast DNA (cpDNA) restriction site variation was examined in 32 species, representing five subgenera, of Bromus (Poaceae). Thirty‐seven phylogenetically informative restriction sites were detected. Cladistic analysis of the restriction site data produced a single most‐parsimonious tree of 50 steps. The cladogram indicated two major clades within the genus. One clade included B. trinii of subgenus Neobromus and species of subgenus Ceratochloa. The other was composed of subgenera Festucaria, Stenobromus, and Bromus. Within the second clade, species of subgenus Festucaria appeared in three lineages. The second clade also contained an assemblage of species belonging to subgenera Stenobromus and Bromus in a separate lineage. There was very little resolution of relationships in this assemblage since several species appeared individually in separate lineages. The cpDNA phylogenetic hypothesis did not separate species of subgenera Stenobromus and Bromus into well‐defined clades as circumscribed by morphology and cytogenetics. The cpDNA tree is in agreement with the phylogenetic scheme based on traditional data in that: 1) subgenera Neobromus and Ceratochloa were the first to diverge, while Bromus and Stenobromus diverged later; 2) within the genus Bromus species with small chromosomes are ancestral; and 3) subgenera Bromus and Stenobromus probably originated from similar ancestors as Festucaria. The tree based on cpDNA data does not support that: 1) subgenera Neobromus and Ceratochloa did not have a common origin; 2) subgenus Festucaria is monophyletic; and 3) subgenera Stenobromus and Bromus are distinct entities. The mean nucleotide sequence divergence values between pairs of subgenera ranged from p = 0.0 to 0.9. These values suggest that cpDNA evolution in Bromus is slow.
Analysis of active nucleolus organizing regions inCapsicum (Solanaceae) by silver staining
Authors: Moscone Eduardo A. , Loidl Josef , Ehrendorfer Friedrich , Hunziker Armando T.
Published: January 2018

Nucleolar activity of 22 samples belonging to nine diploid species of Capsicum was analyzed in somatic metaphases and interphase nuclei. They are: C, chacoënse, C. parvifolium, C. frutescens, C. chinense, C. annuum var. annuum, C. baccatum var. pendulum, C. pubescens, all with 2n = 24, and C. mirabile var. mirabile and C. campylopodium with 2n = 26. Silver staining was applied for the first time in Capsicum, providing useful markers for chromosome identification in combination with other banding techniques already employed in the genus. From two to eight AgNORs (silver‐stained nucleolus organizing regions) were found in the diploid complement of the taxa studied. Nucleolar organizers are located at secondary constrictions of chromosomes which are conventionally stained or banded (C‐banding or fluorochrome banding). Polymorphism of AgNORs and attached satellites often occurs. Nucleoli are usually fused to a variable extent. Number and position of active rDNA loci are variable not only between but also within species and populations. Homologies in position of NORs between species were established. The data obtained are related to previous conclusions on phylogenetic relationships in Capsicum. Possible trends of karyotype evolution concerning nucleolar organizers are discussed, and four NORs in the diploid complement (on chromosome pairs #1 [m] and #12 [st]) are regarded as the plesiomorphic condition.
Effect of canopy gap light environment on evaporative load and stomatal conductance in the temperate forest understory herbAster macrophyllus (Asteraceae)
Authors: Schulz Kurt E. , Adams Michael S.
Published: January 2018

Aster macrophyllus, a temperate forest understory species of the northeastern United States, inhabits a broad range of light habitats. Plants receiving several minutes of direct sun in canopy gap and forest edge habitats occasionally wilt, a response indicative of water stress. We compared two alterative scenarios for patterns of evaporative load and stomatal conductance for plants in large (0.15 ha) tree canopy gaps and small (3 m2) herbaceous subcanopy gaps: 1) evaporative loads are typically moderate and stomatal conductance is largely governed by light intensity; or 2) evaporative loads are often substantial, mandating stomatal closure to prevent excessive transpiration. In all cases evaporative loads were elevated by light intensity above 25% of full sun. This was accompanied by substantial stomatal closure. Transitions from low to moderate light intensity (<13% full sun) caused little increase in leaf evaporative load, and stimulated increases in stomatal conductance. Very brief periods of high light also stimulated stomatal opening. Light environments in the small herbaceous subcanopy gaps differ greatly in their patterns of evaporative load from day to day.
A model for coding pollen size in reference to phylogeny using examples from the Ebenaceae
Authors: Morton Cynthia M. , Kincaid Dwight T.
Published: January 2018

Most genetically based features should be available for use in cladistic analysis. Palynologists routinely measure polar (P) and equatorial (E) axes and place pollen into size classes defined by earlier pollen workers. Grouping of pollen into globally arbitrary classes may not correspond to statistically significant differences among the taxa of a study. We propose a model using conventional statistical procedures coupled with data visualization and Monte Carlo simulation. This approach is not a final solution to the general problem of coding continuous characters into discrete states; it is an attempt to address the problems of character state delimitation in pollen morphology. We suggest that the coding of continuous measurement variables (e.g., P, E) into character states should be done following a logical sequence of interactive visualization (2D and 3D) of bivariate frequency distributions including the inspection of prediction and confidence ellipses (e.g., 99%), and use of ANOVA. We illustrate our approach using realistic pollen data sets generated by a computer program (POLSIM) written to perform Monte Carlo sampling from normally distributed statistical populations of polar and equatorial axes. Our model is then applied to an original data set of 4,134 pollen grains from the Ebenaceae, resulting in the coding of the four genera into three character states for pollen size.
LEAF CROSS SECTIONS AND PHYTOGEOGRAPHY: A POTENT COMBINATION FOR IDENTIFYING MEMBERS OF FESTUCA SUBGG. FESTUCA AND LEUCOPOA (POACEAE), OCCURRING IN NORTH AMERICA
Authors: Aiken Susan G. , Consaul Laurie L.
Published: January 2018

Icon‐like diagrams are used to summarize the anatomical patterns observed in leaf cross sections of 30 taxa of Festuca subgg. Festuca and Leucopoa occurring in western North America. Measurements of four variables, notes on the degree of development and the position of sclerenchyma, along with distribution maps of 24 native taxa, are presented. Twenty‐nine diagrams were created from the synthesis of at least ten leaf‐section drawings based on five plants chosen from across the geographic range of each taxon (fewer suitable specimens were obtained for two taxa). A key based on data collected in this study allows identification of species in subg. Festuca. Geographic distribution is more reliable than leaf anatomy for separating taxa in subg. Leucopoa.
The origin of Dendrosenecio within the Senecioneae (Asteraceae) based on chloroplastDNA EVIDENCE
Authors: Knox Eric B. , Palmer Jeffrey D.
Published: January 2018

Chloroplast DNA restriction‐site variation was surveyed using 15 enzymes for 37 accessions from the tribe Senecioneae (Asteraceae), plus two outgroup species, in order to determine the placement within the tribe of the giant senecios (Den‐drosenecio). The survey revealed 176 phylogenetically informative mutations and 121 autapomorphic mutations. Dendro‐senecio is diagnosed by a minimum of 15 mutations, which suggests that the giant senecios evolved from a relatively isolated lineage within the Senecioneae, and this conclusion is supported by earlier evidence from chromosome counts and phytochemistry. Among the taxa sampled, the closest relatives of Dendrosenecio are Cineraria deltoidea and two species of Euryops. Support was not found for suggestions in the literature that the closest relatives of Dendrosenecio are species in Solanecio or Senecio subgen. 'Crociseris.' The position of the Dendrosenecio/Cineraria/Euryops clade is weakly supported as basal to the majority of other senecionoid genera. The tussilaginoid genera sampled (Ligularia, Petasites, Roldana, and Tussilago) are monophyletic in our analysis, with the surprising inclusion of Pericallis hybrida as the sister‐taxon to Roldana suffulta. The sister‐group to the Dendrosenecio/Cineraria/Euryops clade includes all species of Delairea, Gynura, Kleinia, Packera, Senecio, and Solanecio sampled. Within Senecio, subgenera Senecio and ‘Crociseris’ form a monophyletic core, with subgenus ‘Kleinioidei’ being broadly paraphyletic or possibly polyphyletic.
Estimates of nuclear DNA content in bryophyte sperm cells: phylogenetic considerations
Authors: Renzaglia Karen S. , Rasch Ellen M. , Pike Lee M.
Published: January 2018

Nuclear DNA contents of developing sperm were estimated for 17 species of bryophytes by cytophotometry in squash preparations of antheridia after Feulgen staining. Genome sizes are in the lower end of the range for land plants. Two homwort C‐values have the lowest recorded for bryophytes at 0.17 and 0.26 pg DNA per nucleus. In liverworts, C‐values range from 0.49 pg in Blasia pusilla to 4.05 pg in Pellia epiphylla, while moss genome sizes are less variable, ranging from 0.38 pg in Takakia ceratophylla to 0.92 pg in Atrichum oerstedianum. DNA content is not correlated with chromosome number in these bryophytes, but sperm cell size and cellular complexity are directly related to C‐value. Structural variations in the locomotory apparatus are viewed as evolutionary modifications associated with changes in genomic complexity, with a generalized increase in complexity of the motile assemblage accompanying increases in DNA content. Nuclear DNA values are not as variable in bryophytes as they are in pteridophytes and seed plants. We suggest that in plants producing biflagellated gametes, lower DNA contents afford a selective advantage. Comparisons with plants that produce multiflagellated or pollen‐dispersed sperm indicate operation of a nucleotypic effect in archegoniates with biflagellated sperm. This effect may be on sperm cell functioning, which in turn influences reproductive success.
In vitro allelopathic effects of pollen from three Hieracium species (Asteraceae) and pollen transfer to sympatric Fabaceae
Authors: Murphy Stephen D. , Aarssen Lonnie W.
Published: January 2018

Pollen allelopathy occurs when pollen toxins inhibit sexual reproduction in heterospecifics. To quantify pollen allelopathic effects in vitro, pollen of Hieracium aurantiacum, H. floribundum, and H. pratense was extracted with double distilled water into concentrations of 0 (control), 0.1, 1, 3, 5, 10, and 25 pollen grains/μl. A subset of these extracts was partitioned by ion‐exchange chromatography into acidic, basic, and neutral fractions. Pollen from six sympatric species of Fabaceae (Lotus corniculatus, Medicago sativa, Trifolium hybridum, T. pratense, T. repens, Vicia cracca) and the species of Hieracium was germinated on agar media containing different extract concentrations. As extract concentrations from intact pollen or from acidic fractions increased, mean percent germination of pollen of all Fabaceae decreased nonlinearly. Extract concentrations of 0.1 grains/μl and above inhibited pollen germination in the Fabaceae. In no case was any Hieracium species affected, i.e., there was no autotoxicity. Similar results were obtained using plants from nine populations of H. floribundum and H. pratense across eastern Canada. Observation of floral visitors indicated that there were relatively few movements between Hieracium and the Fabaceae (about 15% of total visits). Hence there is limited opportunity for heterospecific pollen transfer. This was consistent with censuses of stigma, i.e., few pollen grains of Hieracium were found on stigma of the Fabaceae. Thus, pollen allelopathy in Hieracium is unlikely to affect reproductive success in these six species of Fabaceae.
Arrangement of microtubules during spore formation inEquisetum arvense(Equisetaceae)
Authors: Uehara Koichi , Murakami Satoru
Published: January 2018

The arrangement of cortical microtubules (MTs) during spore formation inEquisetum arvensewas examined by immunofluorescence microscopy. The arrangement of MTs was observed to change during sporoderm formation. During exospore formation, the cortical MTs of the tapetum appeared along the tapetal plasma membrane that enclosed each developing spore cell. After exospore formation, the arrangement of the cortical MTs changed into one of separate bands of MTs arranged spirally (spiral bands of MTs). The spiral bands of MTs were superimposed on the developing elaters. This new pattern corresponded to the pattern of cellulose microfibrils deposited in the inner layer of the elater, suggesting that these spiral bands are involved in the deposition of the cellulose microfibrils in the elater. We conclude that the spiral bands of MTs are functionally equivalent to cortical MTs in secondary wall formation.
Genome identification of the Triticum crassum complex (Poaceae) with the restriction patterns of repeated nucleotide sequences
Authors: Dubcovsky Jorge , Dvorak Jan
Published: January 2018

Species of the Triticum crassum complex, tetraploid and hexaploid T. crassum, hexaploid T. juvenale, and hexaploid T. syriacum, share a similar morphology. Variation in the restriction profiles of nuclear repeated nucleotide sequences is employed in identification of genomes of these species. The data show that hexaploid T. crassum originated from hybridization of the tetraploid cytotype of T. crassum with T. tauschii. Triticum juvenale and T. syriacum originated from hybridization of tetraploid T. crassum with T. umbellulatum and T. searsii, respectively. Tetraploid T. crassum appears to be an ancient allotetraploid that originated from hybridization of primitive T. tauschii with an ancient species in the evolutionary lineage leading to the section Sitopsis of the genus Triticum.
Salt effects on membranes of the hypodermis and mesophyll cells ofAvicennia germinans(Avicenniaceae): a freeze‐fracture study
Authors: Balsamo Ronald A. , Thomson William W.
Published: January 2018

Freeze‐fracture electron microscopy was used to investigate intramembranous particle (IMP) densities and particle distributions in the plasma membrane and tonoplast of the cells of secreting and nonsecreting leaves ofAvicennia germinans(L.) Steam. Intramembranous particle densities of the protoplasmic (P) and exoplasmic (E) face of the plasma membrane and tonoplast were significantly higher in hypodermal cells of secreting leaves than of nonsecreting leaves. In contrast, no significant differences in the frequency of intramembranous particles were found in any membrane faces of secreting or nonsecreting mesophyll cells. However, particle densities were higher in the plasma membrane and tonoplast of the mesophyll cells, compared to the hypodermal cells, with the exception of the P‐face of hypodermal plasma membranes of secreting tissue, which had the highest particle density measured. Particle distributions were dispersed and no discernible patterns such as paracrystalline arrays or other multi‐IMP structures were observed. Results support the hypothesis that secretion is coupled to changes in membrane ultrastructure, and the possibility that salt secretion is an active process driven by integral membrane proteins such as the H+/ATPase. Additionally, the hypodermal cells of the leaf may function as storage reservoirs for salt as well as water, suggesting a regulatory role in salt secretion.
Population genetics of Cordia alliodora (Boraginaceae), a neotropical tree. 3. Gene flow, neighborhood, and population substructure
Authors: Boshier David H. , Chase Michael R. , Bawa Kamaljit S.
Published: January 2018

The utility of a) rare allozyme markers and b) paternity exclusion in estimating gene dispersal in tropical forest trees was demonstrated for a population of Cordia alliodora (R. & P.) Oken in Costa Rica. Based on the number of alleles in common, near neighbors were more highly related genetically than were more distant trees. The spatial clustering of relatives was within 50 m, coinciding to a large extent with the seed dispersal curve. Most pollen originated from within 75 m of the mother tree, although a low but substantial proportion of pollen movement was from as far as 280 m. Overall gene flow was extensive, with neighborhood areas as large as 7 ha. Neighborhood sizes at any moment in time and space were, however, relatively small, such that overall variation is maintained by continuous gene flow between neighborhoods. The results indicate that deforestation and fragmentation could curtail such gene flow leading to an erosion of genetic variation within fragments.
Effects of Benlate 50 DF on microtubules of cucumber root tip cells and on growth of cucumber seedlings
Authors: Woo Young M. , Wick Susan M.
Published: January 2018

The aim of this study was to determine whether the fungicide Benlate 50 DF has adverse effects on the microtubules of cucumber root tip cells and on growth of the young seedlings. Germinating cucumber seeds and young seedlings were exposed to six concentrations of Benlate ranging from 1 mg/liter to 10 g/liter. Although seed germination was not affected by Benlate, seedling growth, especially number and length of branch roots, was reduced in proportion to the concentration of Benlate and length of treatment. Significantly lower mitotic indices were obtained from root tips exposed to 0.1, 0.6, 1, or 10 g/liter of Benlate. By means of immunofluorescence microscopy, the major microtubule arrays of root tip cells exposed to Benlate were compared and contrasted to those of controls. A few abnormalities in microtubule arrays were found at or after cytokinesis, and were of two types: 1) persistence of phragmoplast microtubules; and 2) presence of an array of microtubules between two recently divided daughter nuclei in the plane that would normally be occupied by the new cell wall. These abnormalities are somewhat similar to those induced by caffeine, and, as with caffeine treatment, possibly reflect impaired or/and incomplete cytokinesis that results in production of binucleate cells. A few binucleate cells were observed in root tips exposed to 10 g/liter of Benlate.
Relationships and evolution of Hydrangeaceae based on RBCl sequence data
Authors: Soltis Douglas E. , Xiang Qiu‐Yun , Hufford Larry
Published: January 2018

Phylogenetic analyses of rbcL sequences were used to address both systematic and evolutionary questions posed by the angiosperm family Hydrangeaceae. Our analyses suggest the presence of a monophyletic Hydrangeaceae most closely allied with Loasaceae, a finding in agreement with other molecular as well as morphological analyses. Molecular data indicate that Hydrangeaceae comprise Decumaria, Pileostegia, Schizophragma, Hydrangea, Dichroa, Broussaisia, Platycrater, Cardiandra, Deinanthe, Carpenteria, Philadelphus, Deutzia, Fendlerella, Whipplea, Fendlera, Jamesia, and the enigmatic Kirengeshoma. A particularly close relationship of Kirengeshoma and Deutzia is indicated. Analysis of rbcL sequences suggests that Fendlera and Jamesia are sister to the remainder of the family, lending support to the hypothesis that at least some Carpenterieae are basal in the family and that Hydrangeaceae may have originated in xeric habitats. If this phylogenetic placement of Jamesia and Fendlera is correct, the rbcL trees also suggest that the level of epigyny has decreased in these genera, as well as in the Fendlerella‐ Whipplea clade and Carpenteria when compared to the outgroup taxa, which are wholly epigynous. Furthermore, the rbcL trees support proposed evolutionary trends in wood anatomy, suggesting, for example, that upland tropical taxa have evolved longer vessel elements with more numerous bars on scalariform perforation plates. The xerophytic basal members of Hydrangeaceae, like the closely related Loasaceae, have short, narrow vessel elements with scalariform perforation plates bearing few bars. Following Jamesia and Fendlera, the remaining hydrangeoids are divided into two large subclades that closely parallel the traditional division of the family into Philadelpheae and Hydrangeae. Both rbcL sequences and morphological data suggest close relationships between: 1) Fendlerella and Whipplea; 2) Decumaria, Pileostegia, and Schizophragma; 3) Carpenteria and Philadelphus; 4) Deinanthe and Cardiandra; 5) Dichroa, Broussaisia, and Hydrangea macrophylla. Molecular and morphological data also concur in demonstrating that the large genus Hydrangea is not a monophyletic assemblage.
Phylogenetic relationships between Juncaceae and Cyperaceae: insights from rbcL sequence data
Authors: Plunkett Gregory M. , Soltis Douglas E. , Soltis Pamela S. , Brooks Ralph E.
Published: January 2018

Among the commelinid monocots, phylogenetic relationships involving Juncaceae and Cyperaceae have been difficult to resolve because of parallel and convergent evolution of morphological features. Using comparative sequencing of the chloroplast gene rbcL, hypotheses of relationships between these two families were tested. Sequences from 13 taxa were obtained for this study and analyzed using parsimony with 15 previously published sequences. Results of this analysis suggest that two genera of Juncaceae, Oxychloë and Prionium, are not closely related to the other genera of this family. Further, Cyperaceae appear to be more closely related to Juncaceae than to Poaceae, with which Cyperaceae are sometimes classified. In fact, Cyperaceae appear to be derived from within Juncaceae. The progenitor‐derivative relationship of Juncaceae and Cyperaceae suggested by this study reveals an additional example of paraphyletic families which presents a series of taxonomic dilemmas.
Pollen competition in Turnera ulmifolia (Turneraceae)
Authors: Baker Angela M. , Shore Joel S.
Published: January 2018

We performed mixed pollinations, involving self vs. within‐ or between‐population pollen, and used starch gel electrophoresis to assay 2,210 progeny to detect pollen competition in Turnera ulmifolia. Within populations there was no evidence for a competitive advantage to outcross pollen. Between populations a marked advantage to self pollen occurred for most populations, and the extent of this competitive advantage was correlated with increasing morphological divergence of the outcross pollen donor population. A comparison of rates of ovule abortion revealed that the biased paternity ratios cannot be the result of ovule abortion alone, and that pollen competition must be the major contributing factor. We suggest that reproductive divergence among the populations, perhaps through adaptation to different pollinators or through the evolution of increased selling, has resulted in the evolution of reproductive isolation through pollen competition.
The predominant role of the pith in the Growth and development of internodes in Liquidambar styraciflua (Hamamelidaceae). I. Histological basis of compressive and tensile stresses in developing primary tissues
Authors: Brown Claud L. , Sommer Harry E. , Pienaar Leon V.
Published: January 2018

Quantitative changes in cell pattern in the pith, cortex, cortical collenchyma, and epidermis were followed in developing internodes of Liquidambar to examine the cellular basis of compressive and tensile stresses in organized shoot growth. Initially, the highest rates of cell multiplication occur in the pith, followed successively by the epidermis, cortex, and cortical collenchyma. As internodes enter the phase of maximum elongation growth, mitotic activity begins to shift acropetally, accompanied by pronounced changes in cell pattern. The highest rates of cell multiplication now occur in the pith and cortex and continue until the cessation of internode growth. Concomitantly, reduced rates of cell division in peripheral tissues result in rapid increases in rates of cell elongation in the cortical collenchyma and epidermis. Attention is focused on the role of continued cell division in developing internodes with emphasis on differences in rates of cell multiplication between inner and outer tissues affecting patterns of tissue stress. For example, rapid and sustained increases in cell number in the pith, accompanied by growth of readily extensible pith cells, result in the development of compressive forces driving the growth of internodes. Conversely, continuing divisions in less extensible collenchyma and epidermal cells can relieve threshold tensile stresses resulting from the continuous stretching of these tissues by the developing pith. The concept that the passive extension of peripheral tissues, especially the epidermis, control the rate of internode elongation is viewed as an oversimplification of the interacting role of compressive and tensile forces in organized growth and development.
Natural selection of UDP genotypes in an experimental population of Lolium perenne (Poaceae)
Authors: Rainey‐Foreman Daphne , Mitton Jeffry B.
Published: January 2018

The mating system determines the range of genotypes on which selection will act. Ultimately, the population will contain only those genotypes that can survive in the current environment. This study was conducted to determine the extent to which selection affects genotype at four enzyme loci in Lolium perenne. Starch gel electrophoresis was used to determine genotype at the phosphoglucomutase, 6‐phosphogluconate dehydrogenase, phosphoglucose isomerase, and UDP‐glucose pyrophosphorylase loci. Genotypes of progeny arrays were used to infer maternal genotype in a field‐grown population of plants. A mating system analysis was performed on maternal and progeny plants of the field population and also on a population of plants, from the same seed stock, grown in a greenhouse environment. Allelic frequencies differed among populations at the Udp locus. Results indicate that high mortality in the field strongly favored one allele. Assumptions of the mating system model are examined and used to interpret the observed differentiation among populations.
Appomattoxia ancistrophora gen. et sp. nov., a new Early Cretaceous plant with similarities to Circaeaster and extant Magnoliidae
Authors: Friis Else Marie , Pedersen Kaj Raunsgaard , Crane Peter R.
Published: January 2018

A new genus and species of fossil angiosperm (Appomattoxia ancistrophora) is established based on well‐preserved fruiting units and associated pollen from the Early Cretaceous (Early or Middle Albian) Puddledock locality in the Potomac Group sequence of Virginia, eastern North America. Fruiting units are small, unilocular, and with a single, pendulous, orthotropous seed. The fruit surface is characterized by densely spaced unicellular spines with hooklike tips, which probably functioned in biotic dispersal. Pollen grains adhering to the stigmatic area of many specimens are monocolpate and tectate with granular to columellate infratectal structure, and are similar to dispersed grains assigned to Tucanopollis and Transitoripollis. Comparison of fossil Appomattoxia ancistrophora with extant plants reveals an unusual combination of characters that includes similarities with some magnoliid taxa, particularly Piperales (Piperaceae, Saururaceae) and Laurales (Chloranthaceae), as well as the monotypic ranunculid family Circaeasteraceae. Appomattoxia ancistrophora differs from extant Piperales in having a pendulous rather than erect ovule, and differs from extant Circaeaster in details of the fruit wall, as well as the presence of monosulcate rather than tricolpate pollen.
Establishment of chasmogamous and cleistogamous seedlings of an ant‐dispersed UNDERSTORY HERB, CALATHEA MICANS (Marantaceae)
Authors: Corff Josiane Le
Published: January 2018

This study compares the establishment success of cleistogamous (CL, obligately selfed) and chasmogamous (CH, potentially outcrossed) seeds of the neotropical understory herb, Calathea micans (Marantaceae). In this species, CH and CL seeds are morphologically identical and are both dispersed by ants. I measured dispersal distances and analyzed seedling recruitment and seedling size for ant‐planted CH and CL seeds, a protocol made possible by the fact that the seed coat of C. micans can be indelibly marked and remains attached to the base of the seedling for a few months. Seeds were taken by ants from experimental depots placed in natural conditions. In a second experiment, I planted CH and CL seeds in gap and understory sites to determine the effects of seed type and light on germination percentage, date of emergence, and seed and seedling survivorship. Ant‐planted CH and CL seedlings did not differ in dispersal distance. CH and CL seeds did not differ significantly in recruitment probability and seedling size in either experiment. However, for the ant‐planted seedlings, CH recruitment was higher in the understory than in the gap, while CL recruitment was uniform across light environments. In conclusion, I found a difference in the establishment success of CH and CL seeds in this understory herb, only after dispersal by ants in field conditions.
Microhabitat and time‐since‐fire: effects on demography oFEryngium cuneifolium(Apiaceae), a Florida scrub endemic plant
Authors: Menges Eric S. , Kimmich Jennifer
Published: January 2018

Eryngium cuneifoliumSmall. (Apiaceae) is a narrowly distributed endemic found only inCeratiola ericoides(Florida rosemary)‐dominated Florida scrub, a periodically burned, shrub‐dominated habitat. Multivariate analyses using 22 ∗∗∗microhabitat characteristics indicated significant microhabitat and time‐since‐fire effects on survival, growth, and fecundity of 1287 individuals over a 4‐yr period. Survival increased with distance to the nearest shrub, and plants in larger open patches had greater survival rates. Neighboring shrubs ofCeratiola ericoidesandCalamintha asheiwere associated with a higher mortality ofE. cuneifoliumthan other neighboring shrub species. Survival was reduced by two‐thirds over 4 yr (14% vs. 42%) forE. cuneifoliumnearC. ericoides.Sand accretion increased growth and fecundity. With greater time since fire, woody shrubs increasingly dominate and open patches shrink, significantly reducing survival, growth, and fecundity ofE. cuneifolium.Effects were particularly dramatic between 2 and 7 yr postfire, when annual mortality increased from <10% to >30% (r =0.74). This herbaceous species is dependent on an open habitat maintained by periodic fire. Belowground competition or allelopathy from shrubs probably restrictsE. cuneifoliumto recently burned, open patches within the most xeric parts of Florida scrub.
INVITED SPECIAL PAPER: The hows and whys of cytoplasmic inheritance in seed plants
Authors: Mogensen H. Lloyd
Published: January 2018

Cytoplasmic organelles are inherited in a nonMendelian fashion in all eukaryotic organisms investigated. Among the seed plants, plastids can be inherited strictly from the female parent, strictly from the male parent, or biparentally. Most flowering plants studied to date exhibit maternal plastid inheritance, but approximately one‐third of the genera investigated display biparental plastid inheritance to some degree. Among the gymnosperms, paternal plastid inheritance is the rule in the conifers, whereas the other groups appear to have maternal plastid inheritance, although they have been less well studied. Mitochondrial inheritance is predominantly maternal in the seed plants, except for a few coniferous families where it is predominantly paternal. The advent of recombinant DNA technology has allowed restriction fragment length polymorphisms to be used as molecular markers, and has stimulated much research in organelle inheritance and its application to studies of population genetics and phylogenetic biology. This report emphasizes the various mechanisms by which organelles are, or are not, transmitted among the seed plants in order that researchers directly or indirectly involved with organelle inheritance may better understand the potential and the limitations of their investigations. A summary and discussion of the possible evolutionary significance of the various patterns of cytoplasmic inheritance among the seed plants are also included.
The influence of vegetation, salinity, and inundation on seed banks of oligohaline coastal marshes
Authors: Baldwin Andrew H. , McKee Karen L. , Mendelssohn Irving A.
Published: January 2018

Sea level rise may alter salinity and inundation regimes and create patches of open water in oligohaline coastal marshes, potentially affecting the composition and germination of seed bank species. We conducted seedling emergence experiments to: (1) examine the effects of standing vegetation on the seed banks of three oligohaline marsh communities in coastal Louisiana (dominated by Paspalum vaginatum Sw., Sagittaria lancifolia L., or Spartina patens (Ait.) Muhl., respectively); and (2) investigate the effects of salinity and inundation regime on germination of seed bank species. We also studied the effect of a temporary increase in salinity (to simulate a salt water intrusion event) on the viability of buried seeds. We found that the presence or absence of vegetation within a community affected the abundance of some species in the seed bank but had little effect on species composition. Also, the seed banks of the three communities exhibited considerable overlap in species composition and had similar species richness (10–11) and diversity (antilog Shannon‐Weaver diversity index = 6.5–7.1), despite differences in vegetation type. Higher salinities and flooding reduced seedling emergence for most species; few species emerged at salinities above four parts per thousand (ppt), and only Sagittaria lancifolia and Eleocharis parvula germinated well under flooded conditions. A temporary increase in salinity did not affect species richness or seedling emergence of most species. Our results suggest that differences in vegetation may have little effect on the composition of seed banks of oligohaline marshes. However, higher salinities and greater depth and duration of inundation (anticipated as global sea level continues to rise) may decrease recruitment of seed bank species, reducing their abundance in oligohaline marsh communities.
No differential consequences of reproduction according to sex in Juniperus communis var. depressa (Cupressaceae)
Authors: Marion Christine , Houle Gilles
Published: January 2018

In dioecious plant species, males and females are thought to have dissimilar allocation patterns. Females are believed to invest more in reproduction and less in growth and maintenance than males. This differential investment between sexes could result in distinct growth patterns and contrasting survival rates, thereby affecting the sex ratio of a population and the age and size distribution of males and females, possibly leading to habitat segregation according to sex. These effects might become more apparent under particularly limiting conditions, such as in nutrient‐deficient soils or in climatically stressed environments. To verify these predictions, growth patterns, microsite characteristics, and age and size distribution of male and female individuals were compared, and population sex ratio was determined in three populations of the dioecious shrub Juniperus communis var. depressa (Cupressaceae, Pinophyta) along a short latitudinal gradient on the eastern coast of Hudson Bay (Northern Québec, Canada). We found that the northernmost population had a male‐biased sex ratio, but that the southernmost one had a higher proportion of females. Our results failed to reveal any significant differences in radial growth patterns, mean sensitivity, annual elongation of the main axis, and size and age frequency distribution between males and females in any population. Furthermore, there was no evidence of microhabitat segregation according to sex as indicated by the lack of differences in the physicochemical characteristics of the substrate under males and females. Clearly, the expected ecological consequences of a presumed greater investment of females in reproduction were not apparent even under the very stressful conditions prevailing on subarctic dunes. Many factors could reduce differences in the cost of reproduction between males and females, such as the number and quality of reproductive structures produced annually by individuals of each sex, the possible photosynthetic activity of the immature female cones, and the complexity of the source/sink relationship within individuals. Alternatively, there may be no differences between sexes in their reproductive investment.