bluuebunny/crossref_metadata_2025 huggingface dataset:
Character analysis of the seed coat in Spiranthoideae and Orchidoideae, with special reference to the diurideae (ORCHIDACEAE)
Authors: Molvray Mia , Kores Paul J.
Published: January 2018

Previous work on seed types within Orchidaceae has demonstrated that characters associated with the seed coat may have considerable phylogenetic utility. Application of these characters has been complicated in practice by the absence of quantitative descriptors and in some instances by their apparent lack of congruity with the taxa under consideration. Using quantitative descriptors of size and shape, we have demonstrated that some of the existing seed classes do not represent well delimited, discrete entities, and we have proposed new seed classes to meet these criteria. In the spiranthoid‐orchidoid complex, the characters yielding the most clearly delimited shape classes are cell number and variability and degree and stochasticity of medial cell elongation. Of lesser, but still appreciable, significance are the presence of varying types and degrees of intercellular gaps, and some, but not all, features of cell walls. Four seed classes are evident on the basis of these characters in Spiranthoideae and Orchidoideae. These seed types are briefly described, and their distribution among the taxa examined for this study is reported. It is hoped that these more strictly delimited seed classes will facilitate phylogenetic analysis in the family.
Tests of a mechanistic model of one hormone regulating both sexes in Cucumis sativus (Cucurbitaceae)
Authors: Yin Tongjia , Quinn James A.
Published: January 2018

A mechanistic model of sex determination in flowering plants, which assumes that one hormone has male and female cell receptors to inhibit one sex and induce the other independently, was tested in cucumbers (Cucumis sativus) by applications of hormones and their inhibitors. Applications of gibberellic acid (GA) and an inhibitor of its synthesis (paclobutrazol) showed that GA had dual effects on sex expression of promoting maleness and inhibiting femaleness. Conversely, applications of Ethrel (an ethylene release agent) and AgNO3 (an ethylene action inhibitor) indicated that ethylene induced femaleness and inhibited maleness. Results of various combined applications of the two hormones and their inhibitors suggested that ethylene had overriding effects on GA and acted more directly on sex expression in cucumber. These experiments indicated that there is only one hormone, not two, regulating sex expression in cucumber, and that the sex hormone is likely to be ethylene. Results thus supported the assumption of the model that one hormone can regulate both sexes by inducing one and inhibiting the other independently. Model predictions were confirmed that from a monoecious line, female plants could be induced by increasing the ethylene level, and male plants induced by decreasing the ethylene level. On the other hand, as the model predicts, applications of ethylene or its inhibitor induced gynomonoecious, female, and trimonoecious plants from a hermaphroditic line. In conclusion, all assumptions and predictions of the one‐hormone model were confirmed in the experiments.
Interaction of diffuse competition and insect herbivory in limiting brittle prickly pear cactus, Opuntia fragilis (Cactaceae)
Authors: Burger Jutta C. , Louda Svaa M.
Published: January 2018

We tested the effects of above‐ and belowground competition and evaluated insect herbivory on the growth of a common cactus (Opuntia fragilis) in Sandhills prairie. Our purpose was to determine the independent and joint contribution of these factors to the variation observed in cactus size and local abundance. We manipulated ambient prairie vegetation and surface water availability in a full factorial design. When Opuntia fragilis was released from competition with surrounding vegetation, it grew significantly larger in the second growing season, both in terms of number and size of new cladodes. Ramets grown within live prairie vegetation averaged no net growth. These ramets were also more frequently fed upon by the larvae of two internally feeding cactus insects. As a result, insect herbivory reinforced the competitive suppression of the cactus by grasses. Water supplementation had no significant effect, either on cactus growth or on insect herbivory. We conclude that the mechanism by which dense prairie vegetation influenced net growth of O. fragilis was both direct, through competition for nonwater resources such as light, and indirect, through its mediation of feeding by specialized insect herbivores. Furthermore, since the direct growth response to treatment did not precede the indirect effect of habitat‐mediated variation in feeding by insects, our results contradict the current expectation that indirect effects require more time to be expressed than do direct effects.
Composite bundles, the host/parasite interface in the holoparasitic angiosperms Langsdorffia and Balanophora (Balanophoraceae)
Authors: Hsiao Shu‐Chuan , Mauseth James D. , Peng Ching‐I.
Published: January 2018

Composite bundles are not simply a type of vascular bundles, but an integrated host/parasite interface. We investigated their structure in tubers of Langsdorffia and Balanophora. Composite bundles in both genera have similar components: 1) a central mass of host vascular tissues among which are located large parasite transfer cells; 2) a sheath of parasite parenchyma surrounding the central host vascular tissues; 3) specialized conducting tissues in the sheath; and 4) apical meristems composed of both host and parasite meristematic cells. Sheath parenchyma is recognizable from parasite tuber matrix by having thinner cell walls, and, especially in Langsdorffia, by the presence of collapsed matrix cells between the bundle sheath and tuber matrix. Sheath‐conducting tissues consist of densely cytoplasmic transfer cells and small sieve tube members; in Langsdorffia, tracheary elements are also present. These sheath bundles connect with vascular bundles of the tuber matrix. Direct host/parasite contact only occurs by means of parasite transfer cells in the composite bundles. There is no xylem‐xylem contact at the host/parasite interface. Abundance of parasite transfer cells suggests that they play an important role in nutrient absorption and translocation.
Simaroubaceae, an artificial construct: evidence fromrbcL sequence variation
Authors: Fernando Edwino S. , Gadek Paul A. , Quinn Christopher J.
Published: January 2018

Phylogenetic analyses ofrbcL sequence data of representatives of all subfamilies indicate that Simaroubaceae sensu lato is polyphyletic. It represents at least five separate lineages, only three of which (Simarouboideae,Harrisonia, and Kirkioideae) cluster within a robust sapindalean clade. The family is monophyletic only when comprised of members of the subfamily Simarouboideae plus Leitneriaceae, but excludingHarrisonia. Harrisoniais most closely related toCneorumand Rutaceae. Kirkioideae is distant from Simaroubaceae sensu stricto, although its affinities remain within Sapindales. The other two lineages show an affinity to taxa at some distance from Sapindales:lrvingiawith a group of poorly sampled rosid I taxa comprising in part members of Linales and Malphigiales;PicramniaandAlvaradoacluster together in an isolated position between the broadly comprised groups of rosid I and rosid II. Support for the affinities suggested here is also evident in nonmolecular data sources: wood anatomy, pericarp structure, pollen, and phytochemistry. The elevation of the picramnioid clade, comprisingPicramniaandAlvaradoa, to family rank is signaled, and the recognition of Kirkiaceae and Irvingiaceae is substantiated.
Genetic variability of plant characters in the partial inbreeder Collinsia heterophylla (Scrophulariaceae)
Authors: Charlesworth Deborah , Mayer Stephanie
Published: January 2018

Quantitative genetic variability for six characters was estimated in four populations of the annual plant, Collinsia heterophylla, with estimated selling rates ranging from 0.36 to 0.68. Based on large samples of parental plants, all four populations showed significant genetic variation for two or more characters, and there was no sign that the more selfing populations had lower amounts of genetic variance or lower heritability values. Autogamous fruit set rates in the absence of pollinators also showed significant heritability in one population.
Genetic diversity in the tetraploid sand dune endemicDeschampsia mackenzieanaand its widespread iploid progenitorD. Cespitosa(Poaceae)
Authors: Purdy Brett G. , Bayer Randall J.
Published: January 2018

Electrophoretic variation was examined in 14 populations of tetraploidDeschampsia mackenzieana, an endemic of the Athabasca sand dunes in northern Saskatchewan, Canada, and 20 populations of its geographically widespread diploid progenitor,D. cespitosa.Three of theD. cespitosapopulations were sympatric with the endemic on the Athabasca sand dunes. Populations of the endemic were found to have fewer alleles per locus (1.22 vs. 1.52), fewer alleles per polymorphic locus (2.17 vs. 2.70), lower percent polymorphic loci (18.9 vs. 30.5), and lower heterozygosity (0.062 vs. 0.119) than progenitor populations. Species level genetic diversity parameters also indicated thatD. mackenzieanawas genetically depauperate relative to its progenitorD. cespitosa. Deschampsia mackenzieanahad no novel alleles but did share one allele with sympatric progenitor populations that did not occur in populations ofD. cespitosafrom other habitats. Although both species were found to partition most of their genetic diversity within populations,D. mackenzieanadid have more of its limited genetic diversity partitioned among populations thanD. cespitosa.The close genetic relationship betweenD. mackenzieanaand sympatric populations ofD. cespitosamay suggest the endemic tetraploid evolved from the sympatric diploid gene pool in the Athabasca sand dune region. The low levels of genetic diversity inD. mackenzieanasuggest a restricted origin with limited gene flow from the progenitor since speciation.
Effects of pollination method on paternal success in Lesquerella fendleri (Brassicaceae)
Authors: Mitchell Randall J. , Marshall Diane L.
Published: January 2018

Hand pollinations are frequently used to assess the postpollination success of different donors. We present evidence that the method used for hand pollinations can alter pollen germination rates and paternity of the resulting seeds. Two commonly used methods for hand pollination experiments are mixed pollinations, where pollen from several donors is physically mixed together, and adjacent pollinations, where pollen from one donor is close to, but not in physical contact with, pollen from other donors. These methods offer differing opportunities for pollen interaction, and for females to choose among mates. We found that the success of pollen donors in multidonor pollinations varied with pollination method in unpredictable ways across maternal plants. Pollen germination was significantly lower in adjacent pollinations, perhaps explaining some of the effects of pollination method on paternity. These results may yield insights on the factors influencing pollen success, and indicate that hand pollination experiments should employ pollination methods that mimic as closely as possible the natural arrival of pollen in nature.
Cladistic analysis of chloroplast DNA restriction site characters in Andira (Leguminosae: Dalbergieae)
Authors: Pennington R. Toby
Published: January 2018

Chloroplast DNA (cpDNA) restriction site variation was examined in 29 accessions, representing 29 populations of 17 species of Andira (Leguminosae, Papilionoideae, tribe Dalbergieae). This sample spans the morphological and geographical diversity of this poorly known, woody genus of approximately 30 species, which occurs throughout the neotropics, with one species in Africa. Cladistic analysis of 38 restriction site characters generated 182 equally most‐parsimonious trees. The strict consensus tree preserved four well‐supported clades, which are incongruent with previous infrageneric classifications of Andira. None of these clades has been recognized by previous workers, and three are not marked by any major morphological innovations. There were few restriction site differences between closely related species, but two (possibly three) species showed intraspecific cpDNA polymorphism, which probably reflects processes of hybridization with subsequent introgression, or lineage sorting.
The corystosperm pollen organ Pteruchus from the Triassic of antarctica
Authors: Yao Xuanli , Taylor Thomas N. , Taylor Edith L.
Published: January 2018

The permineralized corystosperm pollen organ Pteruchus is described from the early Middle Triassic of Antarctica. Pteruchus fremouwensis consists of an axis bearing numerous, helically arranged microsporophylls, each of which terminates in a distal flattened head. The axis is 1–2 mm in diameter and eustelic. Spherical to elliptical secretory cavities are present in the ground tissue of the axis, microsporophyll, and pollen sac wall. The basal stalk of the microsporophyll is vascularized by a C‐shaped strand that gives rise to a midvein and numerous lateral veins in the distal head. At least 38 pollen sacs are borne on the abaxial surface of the microsporophyll head. These are arranged in pairs on either side of lateral veins. Each pollen sac is sessile, elongated, and uniloculate. The pollen sac wall is several cell layers thick early in ontogeny, but reduced to a single layer in thickness when mature. Dehiscence is longitudinal along the inner surface. Pollen is monosulcate and bisaccate, and of the Alisporites‐type. The Triassic specimens are the first structurally preserved pollen organs of the Pteruchus‐type and can be related to the associated corystosperm stem and leaf genera based on the presence of unique secretory cavities. The morphology of Pteruchus and the relationship of this pollen organ with other Mesozoic and Paleozoic pollen organs is discussed.
Gas exchange and resource‐use efficiency ofLeymus cinereus(Poaceae): diurnal and seasonal responses to naturally declining soil moisture
Authors: Anderson Jay E. , Nowak Robert S. , Rasmuson Kaylie E. , Toft Nancee L.
Published: January 2018

We examined factors that limit diurnal and seasonal photosynthesis inLeymus cinereus, a robust tussock grass from shrub‐steppes of western North America. Data from plants in a natural stand and in experimental field plots indicate that this bunchgrass has 1) a high photosynthetic capacity, 2) high leaf nitrogen content and high nitrogen‐use efficiency, 3) a steep leaf‐to‐air diffusion gradient for carbon dioxide, which enhances intrinsic water‐use efficiency, and 4) photosynthetic tissues that tolerate severe water stress and recover quickly from moderate water stress. Midday depressions of CO2assimilation (A) and stomatal conductance were slight in plants with plentiful water, but marked in plants subject to moderate water stress. Midday stomatal closure in moderately stressed plants reduced intercellular carbon dioxide concentration (ci) by ≈40μl liter‐1. The maximum rate ofAachieved during the day for severely stressed plants (predawn water potential = ‐4 MPa) was one‐third and daily carbon gain per unit leaf area was about one‐fourth that of well‐watered plants. For plants in the natural stand, CO2‐saturated photosynthesis declined almost linearly with decreasing soil water availability over the growing season, whereas there was little effect onAat CO2ambient levels or on carboxylation efficiency until predawn water potentials reached ‐1.8 MPa. Nitrogen‐use efficiency declined with diminishing soil moisture, but there was no seasonal change in stomatal limitation or instantaneous water‐use efficiency as estimated fromAvs.cicurves at optimal leaf temperature and moderate atmospheric evaporative demand. Thus, reduced stomatal conductance in response to increased evaporative demand may increase stomatal limitation diumally, but over the growing season, stomatal limitation estimated fromAvs.cicurves is relatively constant because maximum stomatal conductance is closely tuned to the CO2assimilatory capacity of the mesophyll.
Nutrients affect allocation to male and female function in Abutilon theophrasti (Malvaceae)
Authors: Havens Kayri , Preston Katherine A. , Richardson Charles , Delph Lynda F.
Published: January 2018

In a pair of similar experiments, we examined the effects of varying substrate nutrient levels on several measures of male and female function in Abutilon theophrasti (Malvaceae). In the first trial, plants adjusted allocation to female function at several levels: number of flowers initiated, locule number, percentage of fruits matured, and percentage of ovules matured. In the second trial, plants were much larger, opened more flowers, and matured more fruit (in total but not on a percentage basis). However, in response to nutrient level, plants adjusted maternal investment at fewer levels than in the first trial. Seed mass varied between, but not within, trials. Little to no adjustment was seen in male characters within either trial, although flower number differed within trials and stamen number differed between trials. The lack of adjustment of paternal investment may be due to the fact that A. theophrasti is primarily an autogamous species. Between the two trials, growing conditions, primarily light intensity, varied and plants adjusted their allocation to reproduction differently, indicating plasticity in this trait.
Protandry, a neuter phase, and unisexual umbels in a hermaphroditic, Neotropical vine (Bomarea acutifolia, Alstroemeriaceae)
Authors: Snow Allison A. , Grove Kathryn F.
Published: January 2018

Protandry is a common form of dichogamy in species with hermaphroditic flowers, yet the temporal separation of male and female organs is rarely synchronized enough to prevent self‐pollination among flowers on the same plant. Here we report an unusual mechanism for synchronized protandry within umbels of Bomarea acutifolia, a hummingbird‐pollinated vine in Costa Rica. Flowers in the same umbel open over a period of several days and spend approximately 9 days in the male phase while the six anthers dehisce one by one. Each flower then enters a week‐long neuter phase during which the spent stamens move away from the elongating style and nectar production continues. This is followed by a short female phase when the stigma finally becomes receptive. The long neuter phase ensures that most umbels are temporally unisexual, thereby limiting opportunities for self‐pollination among flowers in the same umbel. A neuter phase has been reported in a few other dichogamous species, but to our knowledge this is the first description of a phase in which the flowers remain open and continue to provide nectar without dispersing or receiving pollen.
The predominant role of the pith in the growth and development of internodes in Liquidambar styraciflua (Hamamelidaceae). II. Pattern of tissue stress and response of different tissues to specific surgical procedures
Authors: Brown Claud L. , Sommer Harry E. , Pienaar Leon V.
Published: January 2018

Isolated pith segments when freed of the restraint of contiguous vascular tissue during different stages of internode development expand rapidly, whereas, peripheral tissues when separated from each other immediately shrink, confirming the existence of physical stresses first described by 19th century botanists. Evidence is presented that the rapid production and differentiation of vascular tissue in elongating internodes of Liquidambar contribute significantly to the development of compressive forces in the pith by restraining the growth of pith cells. Heretofore, the role of tensile stresses affecting the growth of internodes in herbaceous plants has been ascribed only to the less extensible outer peripheral tissues, especially the epidermis. Different surgical procedures applied to elongating internodes, including disruption of the central core of pith cells without disturbing the vascular and other peripheral tissues, or conversely, injuring or removing portions of the outer tissues leaving the pith intact, confirm the histological observations that the developing pith is the driving force for internodal elongation.
On the ecological and evolutionary significance OF BRANCH AND LEAF MORPHOLOGY IN aquaticSphagnum(Sphagnaceae)
Authors: Rice Steven K. , Schuepp Peter H.
Published: January 2018

In aquatic environments difiusivity is low and CO2availability can limit plant growth. The hypothesis that natural selection has favored morphological features that reduce resistance to diffusion of CO2was tested using three phylogenetically independent species pairs from the genusSphagnum(S. macrophyllumand 5.strictum;S. portoricenseandS. papillosum;andS. trinitenseand S.recurvum). The aquatic (former) and the nonaquatic (latter) species were grown submerged and emerged in a common garden and used for studies of form and function. Aquatic taxa all had similar morphological features that included larger, thinner branch leaves arranged at lower densities and photosynthetic cells more greatly exposed at the leaf surface. The relationship between observed branch and leaf morphology and boundary layer resistance in the S.trinitense–S. recurvumspecies pair was assessed by measuring diffusion and convection of ions onto nickel‐plated models in a variable‐speed electrochemical fluid tunnel. For all flow speeds and orientations, the aquaticS. trinitensemodel had thinner boundary layers than the nonaquaticS. recurvummodel. Analysis of stable isotopes of carbon from the growth experiment corroborated results from the fluid‐tunnel experiments. The aquatic taxa all had lower δ13C values when grown submerged compared to their nonaquatic pair with the exception of the nonaquaticS. strictum, which was removed due to low growth rates. These results indicate that aquatic species did experience lower overall resistance to CO2uptake than nonaquatic taxa. Our observations suggest that aquatic habitats do select for morphological features that lower resistance to gas exchange.
Gender specialization and distyly in hoary puccoon, LITHOSPERMUM CROCEUM (Boraginaceae)
Authors: McCall Claire
Published: January 2018

This 2‐yr study of gender and its relation to the sizes of pin and thrum plants in Lithospermum croceum was performed in central Michigan. The population was composed of 51‐52% thrums, 42‐43% pins, and ≈6% homostyles in 1988 and 1989. Pins produced more flowers and fruits than thrums, and a greater proportion of their ovaries produced more than one nutlet. However, the number of fruits produced by pins and thrums in 1988 did not differ when plant size is a covariate in ANCOVA. The number of seeds produced by plants in 1989 is also unaffected by floral morph when size is a covariate. Instead, plant size is the most important predictor of fecundity in both years. The average percent fruit sets (fruits/ovaries) of the morphs did not differ in either year. Herbivory was more common in 1988 than in 1989, but there was no difference in the frequency with which pins and thrums were attacked. Furthermore, the effect of herbivory on fecundity did not differ for the morphs. The fecundity of neither morph was limited by pollen in 1989. Apparent gender specialization was a consequence of subtle differences in the vegetative sizes of the morphs.
Pleiotropic effects of flowering time genes in the annual crucifer Arabidopsis thaliana (Brassicaceae)
Authors: van Tienderen Peter H. , Hammad Ibtisam , Zwaal Frits C.
Published: January 2018

Variation in flowering time of Arabidopsis thaliana was studied in an experiment with mutant lines. The pleiotropic effects of flowering time genes on morphology and reproductive yield were assessed under three levels of nutrient supply. At all nutrient levels flowering time and number of rosette leaves at flowering varied among mutant lines. The relationship between these two traits depended strongly on nutrient supply. A lower nutrient supply first led to an extension of the vegetative phase, while the mean number of leaves at flowering was hardly affected. A further reduction resulted in no further extension of the vegetative phase and, on average, plants started flowering with a lower leaf number. At low nutrients, early flowering affected the timing of production of siliques rather than the total output, whereas late flowering was favorable at high nutrients. This may explain the fact that many plant species flower at a relatively small size under poor conditions. Flowering time genes had pleiotropic effects on the leaf length, number of rosette and cauline leaves, and number of axillary flowering shoots of the main inflorescence. Silique production was positively correlated with the number of axillary shoots of the main inflorescence; the number of axillary primordia appeared to have a large impact on reproductive yield.
The allopolyploid origin ofSpiranthes hongkongensis(Orchidaceae)
Authors: Sun Mei
Published: January 2018

Morphological and ecological similarities betweenSpiranthes hongkongensisHu et Barretto andS. sinensis(Pers.) Ames suggest a close evolutionary relationship. The hypothesis thatS. hongkongensisevolved through natural hybridization betweenS. sinensisandS.spiraliswas tested using isozyme electrophoresis. A total of 28 isozyme loci were interpreted in the diploid speciesS. sinensisandS. spiralis, and “fixed heterozygosity” owing to gene duplication was observed at ten of these loci inS.hongkongensis.Isozyme phenotypes provided strong evidence for an allotetraploid origin ofS. hongkongensis, withS. sinensisand most likelyS.spiralisas its diploid progenitors. Chromosomal counts ofS. hongkongensisgave a tetraploid number of ≈60. The allotetraploid species is self‐fertile, and completely isolated by sterility barriers fromS. sinensis.Premating isolation also exists betweenS.hongkongensisandS. sinensisdue to earlier flowering and autogamy inS. hongkongensis, which may account for the rarity of natural hybrids in the sites of sympatry. The role of the autogamous breeding system in the establishment and spread ofS. hongkongensisis discussed.
Reclassification of North American Haplopappus (Compositae: Astereae) completed: Rayjacksonia gen. nov.
Authors: Lane Meredith A. , Hartman Ronald L.
Published: January 2018

Rayjacksonia R. L. Hartman & M. A. Lane, gen. nov. (Compositae: Astereae), is named to accommodate the “phyllocephalus complex,” formerly of Haplopappus Cass. sect. Blepharodon DC. The new combinations are R. phyllocephalus (DC.) R. L. Hartman & M. A. Lane, R. annua (Rydb.) R. L. Hartman & M. A. Lane, and R. aurea (A. Gray) R. L. Hartman & M. A. Lane. This transfer completes the reclassification of the North American species of Haplopappus sensu Hall, leaving that genus exclusively South American. Rayjacksonia has a base chromosome number of x = 6. Furthermore, it shares abruptly ampliate disk corollas, deltate disk style‐branch appendages, and corolla epidermal cell type, among other features, with Grindelia, Isocoma, Olivaea, Prionopsis, Stephanodoria, and Xanthocephalum. Phylogenetic analyses of morphological and chloroplast DNA restriction site data, taken together, demonstrate that these genera are closely related but distinct.
matK and rbcL gene sequence data indicate that Saxifraga (Saxifragaceae) is polyphyletic
Authors: Soltis Douglas E. , Kuzoff Robert K. , Conti Elena , Gornall Richard , Ferguson Keith
Published: January 2018

The large genus Saxifraga, which consists of ≈400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK–rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well‐differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species‐rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium‐Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well‐separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.
Reproductive development and nuclear DNA content in angiosperms
Authors: Bharathan Geeta
Published: January 2018

Correlates of nuclear DNA content in angiosperms have been noted previously for a range of features, cellular to geographic. A new hypothesis, the correlation between nuclear DNA content and reproductive developmental features (after Cavalier‐Smith,Journal of Cell Science34, 247–268, 1978) is posed and tested here. Of three features tested (megasporogenesis, microsporogenesis, and endosperm development), megasporogenesis alone was shown to be correlated with nuclear DNA amount. The hypothesis was examined in 107 families of angiosperms using nonparametric statistics, and in 53 families of monocotyledons and outgroups using a phylogenetic test of association. A correlation was found between large genomes and successive microsporogenesis for all angiosperms, but not for monocots and dicots analyzed separately, thus underlining the importance of taking into account phylogenetic relationships in such studies. A correlation between cellular endosperm and large genomes in dicotyledons needs to be confirmed in a phylogenetic context. A tendency for deviations from monosporic megasporogenesis to occur in taxa that have a nuclear DNA content of over 9.0 pg/C was demonstrated using both phylogenetic and nonphylogenetic tests. It is hypothesized that cytoskeleton dynamics are affected in reproductive cells, enabling decoupling between nuclear and cytoplasmic cell cycles and leading to variation in reproductive development.
Floral organ growth and carbohydrate content during pollen development in Lilium
Authors: Clément Christophe , Burrus Monique , Audran Jean‐Claude
Published: January 2018

In order to understand floral sugar physiology, we correlated the growth of the organs with carbohydrate content in the flower of Lilium cv. “enchantment” during pollen development. In a previous work, we distinguished two phases in pollen ontogenesis: the anther growth phase, from the microspore mother cell until the vacuolated microspore, and the anther maturation phase, from the vacuolated microspore until anthesis. In the present work, we showed that during the growth phase, the anther underwent most of its size and dry weight growth, whereas the growth rate of nonanther organs was reduced. Anther and filament possessed the highest amounts of carbohydrates, which decreased progressively until the vacuolated microspore stage. During the maturation phase, sucrose and starch increased in all floral organs. Anther growth was completed at the Mi stage, whereas the nonanther organs began exponential growth. From these observations, we concluded that hierarchic nutritional correlations exist between the flower organs, in which the anther is the main actor: during the anther growth phase, the anther represents the highest sink strength floral organ, and mainly attracts assimilates through the filament. During the anther maturation phase, anther growth is achieved, its needs decrease, and assimilates are thus available for neighboring organs, which undergo intense growth until anthesis.
Higher level relationships of Apiales (Apiaceae and Araliaceae) based on phylogenetic analysis of rbcL sequences
Authors: Plunkett Gregory M. , Soltis Douglas E. , Soltis Pamela S.
Published: January 2018

The two families of the order Apiales (Apiaceae and Araliaceae) represent a classic example of the difficulty in understanding evolutionary relationships between tropical‐temperate family pairs. In Apiales, this problem is further compounded by phylogenetic confusion at almost every taxonomic level, including ordinal, interfamilial, and infrafamilial, due largely to difficulties in understanding trends in morphological evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expanded subclass Asteridae as the sister group to Pittosporaceae, and refute the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, and Toricellia are close relatives of Apiales. Clarification of phylogenetic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxon was probably bicarpellate, simple‐leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subfamily Hydrocotyloideae, often envisioned as an intermediate group between Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the exception of some hydrocotyloids, Apiaceae appear to be monophyletic. The relationship between Apiaceae and Araliaceae remains problematic. Although the shortest rbcL trees suggest that Apiaceae are derived from within a paraphyletic Araliaceae, this result is only weakly supported.
Effect of Salinity on Seed Germination, Growth, and Ion Accumulation of Atriplex patula (Chenopodiaceae)
Authors: Ungar Irwin A.
Published: January 2018

Seeds and seedlings of the halophyte Atriplex patula were exposed to 0–2% NaCl to determine the effect of salt stress on germination and growth. Seeds germinated and plants survived and grew in solutions of up to 2.0% NaCl. Both seed germination and dry mass production were negatively affected by increased salinity. Dry mass production declined to 1% of controls and seed germination to 17% of controls in the 2% NaCl treatments, indicating that seeds were less inhibited than growing plants. Also, recovery treatments indicated that high salinity did not permanently injure seeds. Percent ash, and Na+ and Cl− ions increased in shoots with each salt increment, while the K+ ion content decreased sharply. Atriplex patula is a facultative halophyte, and is limited to low and moderately saline sites because both seed germination and growth are severely reduced at salinities > 1% NaCl.
Gene segregation in autotetraploids: prediction from meiotic configurations
Authors: Jackson R. C. , Jackson Jeff W.
Published: January 2018

Current systems of estimating gene segregation in autotetraploids usually are based on two extreme methods: chromosome segregation with absolute centromere linkage, or maximum equational segregation with crossing over always occurring between the centromeres and marker genes. The hiatus between the two methods is unacceptable quantitatively, and segregation of the d gene in tomato shows that neither method predicts an acceptable fit. We present a new meiotic configuration (MC) method of analyzing tetrasomic inheritance in autotetraploids that allows more accurate estimations of all intermediate types of segregation. The method is based on a maximum of two chiasmata per bivalent and four per quadrivalent. The theoretically expected numbers of bivalents and chain and circle quadrivalents are derived first. Chromosome frequencies from these configurations are then used to determine relative contributions from each configuration to the gamete genotypes by way of newly developed tables for gene segregation in various autotetraploid genotypes. The large sample sizes from classic 4x tomato (Solanum lycopersicum L.) data are used to demonstrate the stepwise method of calculating gamete genotypes, and the method gives acceptable fits for the data tested. The interspecific tetraploid hybrid Solanum lycopersicum × S. pimpinellifolium had good fits to expected autotetraploid segregation, supporting its autoploid nature and the fact that taxonomic rank should not be a consideration in designating categories of polyploids. Autotetraploid allozyme segregation data for several genes in one genus of another family had acceptable and usually better fits to the MC expectations than to the standard methods.
Evolutionary consequences of extensive morph loss in tristylous decodon verticillatus (Lythraceae): a shift from tristyly to distyly?
Authors: Eckert CHRISTOPHER G. , Mavraganis Katherine
Published: January 2018

The evolution of distyly from tristyly has occurred repeatedly, especially in the Lythraceae. However, the evolutionary forces involved remain unclear since species exhibiting transitional stages between tristyly and distyly have rarely been studied. The self‐compatible, wetland perennial Decodon verticillatus (Lythraceae) may provide this transitional variation since populations commonly lack style morphs, particularly the mid‐styled (M) morph. In dimorphic populations lacking the M morph, anthers positioned at the mid level in both the long‐ (L) and short‐styled (S) morphs have lost their target stigma, setting the stage for either evolutionary repositioning of mid‐level anthers to increase pollen export to L and S stigmas, or increased variability in mid‐level anther position resulting from relaxed selection. We examined these two hypotheses by comparing floral morphology in eight dimorphic and ten trimorphic populations from throughout the species’ range. We found no evidence that loss of the M morph has led to evolutionary modification of mid‐level stamens. While mid‐level stamens of the S morph were 11.0 ± 4.0% (mean ± 1 SE) longer than those of the L morph in dimorphic populations, divergence in stamen length between morphs occurred to the same extent (10.4 ± 2.0%) in trimorphic populations and cannot be attributed to the absence of the M morph. Analyses of variability using median ratio tests revealed no difference in the variability of mid‐level stamen length between dimorphic and trimorphic populations. Mid‐level stamens were not more variable than long‐ and short‐level stamens within dimorphic populations. The consistent divergence in mid‐level stamens between the L and S morphs may reflect morph‐specific differences in the optimal position of mid‐level anthers for maximizing cross‐pollination and avoiding self‐fertilization.
Mating system consequences on resistance to herb ivory and life history traits in Datura stramonium
Authors: Núnez‐Farfán Juan , Cabrales‐Vargas Roberto A. , Dirzo Rodolfo
Published: January 2018

The consequences of selfing and outcrossing in Datura stramonium, a colonizing annual species, were experimentally assessed in terms of the fecundity of maternal plants and the performance of their progeny. Selfed and cross‐pollinated plants were produced through controlled crosses and were then planted in their native environment. We recorded size at establishment, final height, number of branches, fruits, total biomass, and resistance to herbivores for each plant. Natural selection was measured for plant size and resistance to herbivores in both types of plants. Seed production (fecundity) was higher for fruits developed from outcrossing than for fruits derived from selfing. Among‐family differences were detected for seed mass, but these were not related to mating system. No differences in germination, plant size, and fruit number were found between the two mating systems. Damage produced by two herbivores, Epitrix parvula and Sphenarium purpurascens, ranged from 0 to 95% of total leaf area; however, there were no differences in resistance to both herbivorous insects either among families or between mating systems. Plant survival through the whole season was similar for plants of both types of crossing. The direction and magnitude of phenotypic selection for each trait were similar for both types of progeny. Directional selection to increase plant size and reduce resistance to E. parvula was detected, while no selection was detected for resistance to 5. purpurascens. Curvilinear (stabilizing/disruptive) and correlational selection modes were not detected for any trait. Inbreeding depression coefficients were all statistically indistinguishable from zero, except for seed number per fruit. The inbreeding depression coefficient for seed number was high and close to 40%, suggesting that evolution toward complete selfing may be prevented in this population of Datura stramonium.
Cytology of 2N pollen formation and pollen morphology in diploid lotus tenuis (fabaceae)
Authors: Rim Yong Woo , Beuselinck Paul R.
Published: January 2018

Two genotypes of Lotus tenuis Waldst & Kit. ex Willd. PI 204882, a diploid (2n = 2x = 12), were identified as producing 2n pollen (maximum = 6%). The objectives of this research were: (1) to determine the mechanism(s) of 2n pollen formation in the L. tenuis genotypes and (2) to morphologically describe n and 2n pollen using light and scanning electron microscopy. Meiotic studies revealed that 2n pollen resulted from tripolar spindles during anaphase II of microsporogenesis. The 2n pollen germinated well, although abnormal pollen tubes were observed. The genetic constitution of 2n pollen resulting from tripolar spindles is equivalent to first division restitution (FDR) of meiosis. Fresh and air‐dried pollen samples exhibited differences in size and shape under light and scanning electron microscopy. The size of diploid (2n) pollen was larger than that of haploid (1n) pollen. Normal haploid (1n) pollen was globose‐prolate in shape, while diploid (2n) pollen was tetrahedral in shape.
Two new species of the pinnate microsporophyll Pramelreuthia from the upper Triassic of the southwestern United States
Authors: Ash Sidney , Litwin Ronald J.
Published: January 2018

Two new species of the enigmatic gymnosperm microsporophyll Pramelreuthia, found in the Upper Triassic Chinle Formation at five localities in the southwestern United States, provide significant new evidence on key morphological characters of the genus and extend its known geographical range. These new fossils also demonstrate that the genus was polytypic and reveal the plant megafossil sources for several common and geographically widespread dispersed Upper Triassic microfossil taxa. The genus Pramelreuthia, which until this study was known only from a single specimen from the Upper Triassic of Austria, is a planar pinnate structure consisting of a slender naked axis bearing stalked synangia in opposite to subopposite pairs. Synangia of all three species of Pramelreuthia are oval to subrectangular in lateral view and are composed of two adpressed flattened valves each of which contains up to 20 or more elongate, subcylindrical, tapered sporangia that bear nonstriate bisaccate pollen. Pramelreuthia yazzi sp. nov. is slightly smaller than the type species P. haberfelneri, and its synangia contain pollen generally similar in morphology and size to several species of the dispersed pollen taxon Pityosporites, including P. chinleana, P. oldhamensis, and P. devolvens. Pramelreuthia dubielii sp. nov. is much larger than the other two species; its synangia contain pollen similar to the dispersed pollen species Protodiploxypinus americus.
Vessels in Nelumbo (Nelumbonaceae)
Authors: Schneider Edward L. , Carlquist Sherwin
Published: January 2018

Vessels have been previously reported in the roots (but not rhizomes) of Nelumbo on the basis of light microscopy. We have reinvestigated vessel occurrence in Nelumbo by means of scanning electron microscopy (SEM). On the basis of these studies, vessels are characteristic of root metaxylem. Pores in primary walls of pits of end walls of these vessels are various in size, but feature incomplete lysis of pit membranes, often with residual webs or threads of primary wall material, much as in vessels of primitive woody dicotyledons. In addition, we newly report occurrence of vessels in metaxylem of rhizomes; pores in these vessels are smaller and more confined than in those of roots. The present study offers not only data of possible use in determining the phylogenetic position of Nelumbonaceae, but also contributes evidence that vessel origin in Nelumbonaceae relates to habit and ecology. We conclude that organographic distribution of vessels in Nelumbo follows the patterns seen in monocotyledons, which, like Nymphaeaceae and other aquatics, have sympodial architecture.
Occurrence of somaclonal variation among somatic embryo‐derived white spruces (Picea glauca, Pinaceae)
Authors: Isabel Nathalie , Boivin Rodolphe , Levasseur Caroline , Charest Pierre‐M. , Bousquet Jean , Tremblay Francine M.
Published: January 2018

Four differentvariegataphenotypes were identified among 2270 white spruce plants [Picea glauca(Moench.) Voss.] produced over a period of 2 yr from the time of induction of embryogenic tissues. The four variegated plants differed from each other in the extent and distribution of chlorophyll‐deficient needles. Light microscopy showed that variegated leaves of a selected variant consisted of a chimeral mixture of green and white cells. Electron microscopy showed that cells in completely white needles had large nuclei with predominant euchromatin, lacked large cytoplasmic vacuoles, and harbored vacuolized plastids with aberrant morphologies. Various observations suggest that the recoveredvariegataphenotypes reflect some kind of genetic instability of either chloroplastic or nuclear genomes. To elucidate the genetic basis of thesevariegataphenotypes in white spruce, three out of the four variants were subjected to randomly amplified polymorphic DNA (RAPD) analysis. Out of more than 250 RAPD markers screened, only one correlated with white needles of variegated plants. The nucleotide sequence of this DNA fragment showed no homology with any known gene, but the amplified sequence appears most likely of nuclear origin.
Ovulate cone, pollination drop, and pollen capture in Sequoiadendron (Taxodiaceae)
Authors: Takaso T. , Owens J. N.
Published: January 2018

In Sequoiadendron ovules are borne inside the ovulate cone, and pollination drops secreted from these ovules collect pollen. We examined: (1) the relation between ovular position and pollen capture; (2) pollen behavior when in contact with a pollination drop; and (3) ultrastructure of ovules during pollination drop secretion. During wet periods a water sheet forms on the surface of the cone due to bract shape and wettability. Pollination drops persist inside the wetted cone, and pollen capture resumes immediately after drying. Pollen landing on a pollination drop is taken inside the drop and carried into the micropyle when the drop contracts. Several notable ultrastructural features appear in the nucellus, integument, chalaza, and bract lamina during pollination‐drop secretion. The abaxial surface of the lamina is covered by a membrane that may contribute to the wettable nature of the surface.