bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROOT APICAL MERISTEM OF EQUISETUM DIFFUSUM: STRUCTURE AND DEVELOPMENT
Authors: Gifford Ernest M.
Published: January 2018

The root apical meristem of Equisetum diffusum Don has a prominent four‐sided pyramidal apical cell with its base (distal face) in contact with the root cap. Derivatives (merophytes) that contribute to the main body of the root are produced from the three proximal faces of the apical cell. The first division of a proximal merophyte is periclinal to the root surface separating a small inner cell from a larger outer cell. The inner cell is the precursor of the vascular cylinder. The larger outer cell is the precursor of the epidermis, cortex, endodermis, and pericycle. Radial sectors, established early in the development of the cortex, alternate with sectors in the vascular cylinder. These developmental steps show quite clearly that early root development in Equisetum is markedly different from that of most ferns.
ANATOMICALLY PRESERVED GLOSSOPTERIS STEMS WITH ATTACHED LEAVES FROM THE CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA
Authors: Pigg Kathleen B. , Taylor Thomas N.
Published: January 2018

Stems and buds of Glossopteris skaarensis Pigg and buds of G. schopfii Pigg from the Permian Skaar Ridge locality in the central Transantarctic Mountains, Antarctica demonstrate the first anatomically preserved glossopterids known with stem/leaf attachment. Stems of G. skaarensis are 1–12 mm in diameter ( = 3.1 mm) with a broad pith, poorly defined primary xylem, and a zone of secondary xylem up to 6 mm thick. Pycnoxylic wood conforming to Araucarioxylon Kraus is composed of tracheids with uni‐ to biseriate oval to hexagonal bordered pits on radial walls, uniseriate rays one to a few cells high, and cupressoid to taxodioid cross‐field pitting. Stems have a narrow zone of secondary phloem, aerenchymatous cortex with scattered sclereids, and sometimes a narrow periderm. Two wedge‐shaped leaf traces each bifurcate to form four strands in the base of each petiole. Small axillary branches are vascularized by double branch traces that fuse at the margin of the main axis. Buds of G. skaarensis have leaves with narrow lateral laminae and a thickened midrib containing a wide lacuna, delicate vascular strands, and a prominent hypodermis. In contrast, buds of G. schopfii have uniformly thick leaves with prominent, circular vascular bundle sheaths. These anatomical details are used to reconstruct individual types of glossopterid plants, providing new information toward understanding the ecology and evolution of this important group of Permian seed plants.
A CYTOLOGICAL ANALYSIS OF MICROSPORES OF TRITICUM AESTIVUM (POACEAE) DURING NORMAL ONTOGENY AND INDUCED EMBRYOGENIC DEVELOPMENT
Authors: Reynolds Thomas L.
Published: January 2018

Uninucleate microspores of Triticum aestivum cv. Pavon can be induced in vitro to alter their development to produce embryoids rather than pollen. Microspores expressed their embryogenic capacity through one of two division pathways. In the more common route, the first sporophytic division was asymmetric and produced what appeared to be a typical bicellular pollen grain. Here the generative cell detached from the intine, migrated to a central position in the pollen grain, and underwent a second haploid mitosis as the vegetative cell divided to give rise to the embryoid. In the second pathway, the first division was symmetric and both nuclei divided repeatedly to form the embryoid. This comparative analysis of normal pollen ontogeny and induced embryogenesis provided no evidence for the existence of predetermined embryogenic microspores in vitro or in vivo. Instead, microspores are induced at the time of culture, and embryogenesis involves continued metabolic activity associated with the gradual cessation of the gametophytic pathway and a redifferentiation into the sporophytic pathway. In conjunction with a previous study, it appears that embryogenic induction of wheat microspores involves switching off gametophytic genes and derepressing sporophytic genes.
OUTCROSSING AND FECUNDITY ADVANTAGE OF FEMALES IN GYNODIOECIOUS CHIONOGRAPHIS JAPONICA VAR. KUROHIMENSIS (LILIACEAE)
Authors: Maki Masayuki
Published: January 2018

The selling rate of hermaphrodites, inbreeding depression, and relative fecundity of females compared to hermaphrodites were estimated for a gynodioecious population of Chionographis japonica var. kurohimensis to test the models for the evolution of gynodioecy. In spite of the high level of selling of hermaphrodites, significant amounts of inbreeding depression were found in seed germination and seedling growth. In addition, females produced more fertilized ovules than hermaphrodites. Nevertheless, the conditions theoretically required for maintaining gynodioecy were not satisfied even if the combined effect of these two factors was considered. Additional causes for the evolution of gynodioecy, including biparental inbreeding, are discussed.
HEAT‐PRODUCTION AND CROSS‐POLLINATION OF THE ASIAN SKUNK CABBAGE SYMPLOCARPUS RENIFOLIUS (ARACEAE)
Authors: Uemura S. , Ohkawara K. , Kudo G. , Wada N. , Higashi S.
Published: January 2018

The Asian skunk cabbage Symplocarpus renifolius has an exothermic spadix on which about 100 flowers bloom in very early spring when effective pollinators such as bees and drone flies are inactive. This species is protogynous; female phase and male phase took 6.8 ± SD 5.8 days and 16.7 ± 5.7 days, respectively, with a short transitional phase of bisexuality (2.1 ± 0.9 days). The spadices produced heat 24 hours/day throughout female and bisexual phases, but temperature dropped quickly after the beginning of male phase. Although self‐compatibility was expected from the flower structure, the basipetal flowering, and the absence of effective pollinators, bagging tests demonstrated that they rarely produce seeds without crossing. The spadices were visited by small numbers of invertebrates throughout the flowering season. Of these invertebrates, house flies, rove beetles, and mosquitos were the likeliest pollinators, since they are probably attracted both to the pollen produced in male phase and to the stench or carbon dioxide in female phase. On two female spadices with immature male flowers, we fortuitously collected a rove beetle and a mosquito that carried some pollen grains; these had to have been transported from other S. renifolius spadices. This infrequent and ineffective pollination appears to explain why as low as 13% of spadices set seeds in a natural population. We examine alternative hypotheses to explain production of heat in spadices of skunk cabbage.
GENDER‐RELATED DIFFERENCES IN GAS EXCHANGE ARE NOT RELATED TO HOST QUALITY IN THE XYLEM‐TAPPING MISTLETOE, PHORADENDRON JUNIPERINUM (VISCACEAE)
Authors: Marshall John D. , Dawson Todd E. , Ehleringer James R.
Published: January 2018

Male and female individuals of dioecious species often differ in morphology, physiology, growth, and habitat distribution. Where habitat distribution differences have been demonstrated, female plants generally occupy those habitats with greater resource availability (“rich” habitats). Gender‐specific habitat preferences are often presumed to be a consequence of greater resource requirements, per gamete, of female reproduction. Previous work has shown that Phoradendron juniperinum, a xylem‐tapping dioecious mistletoe that parasitizes Juniperus species in western North America, displays the opposite pattern: males are relatively more numerous than females in richer sites (i.e., branches with relatively high light and low evaporative demand within the host tree). We report here differences in host (“site”) quality and gas‐exchange properties between the sexes. To minimize environmental variation, all measurements were made on sunlit foliage between 9:00 a.m. and 2:00 p.m. Males had significantly higher photosynthetic rates (4.0 [SE = 0.2] μmol m‐2 sec‐1) than either females (2.9 [0.3] μmol m‐2 sec‐1) or nonreproductive individuals (3.0 [0.2] μmol m‐2 sec‐1). Female photosynthetic rates were not statistically different from those of nonreproductive individuals. No concomitant differences in stomatal conductance were observed. Gas exchange data were independently confirmed by significant differences in carbon isotope ratio (δ13C). Gender‐related differences were not related to host quality as measured by foliar N, foliar δ13C, or water potential of the host tree. The fate of the additional photosynthate in males is unknown, but we discuss the possibility that carbon costs of reproduction in males have been underestimated in past work.
EFFECTS OF PHOTOPERIOD AND VERNALIZATION ON THE NUMBER OF LEAVES AT FLOWERING IN 32 ARABIDOPSIS THALIANA (BRASSICACEAE) ECOTYPES
Authors: Karlsson Björn H. , Sills Gavin R. , Nienhuis James
Published: January 2018

The extent of natural variation among wild type Arabidopsis thaliana L. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32 Arabidopsis ecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and nonvernalized plants were transplanted into 8‐ (short‐day) and 20‐hour (long‐day) photoperiods in controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.
MONOPHYLY OF ANEUPLOID ASTRAGALUS (FABACEAE): EVIDENCE FROM NUCLEAR RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACER SEQUENCES
Authors: Wojciechowski Martin F. , Sanderson Michael J. , Baldwin Bruce G. , Donoghue Michael J.
Published: January 2018

Evolutionary relationships within Astragalus L. (Fabaceae) were inferred from nucleotide sequence variation in nuclear ribosomal DNA of both New World and Old World species. The internal transcribed spacer regions (ITS) of 18S–26S nuclear ribosomal DNA from representatives of 26 species of Astragalus, three species of Oxytropis DC., and two outgroup taxa were analyzed by polymerase chain reaction amplification and direct DNA sequencing. The length of the ITS 1 region within these taxa varied from 221 to 231 bp, while ITS 2 varied in length from 207 to 217 bp. Of the aligned, unambiguous positions, approximately 34% were variable in each spacer region. In pairwise comparisons among Astragalus species and outgroup taxa, sequence divergence at these sites ranged from 0 to 18.8% in ITS 1 and from 0 to 21.7% in ITS 2. Parsimony analyses of these sequences resulted in a well‐resolved phylogeny that is highly concordant with previous cytogenetic and chloroplast DNA evidence for a major phylogenetic division in the genus. These data suggest that the New World aneuploid species of Astragalus form a monophyletic but morphologically cryptic group derived from euploid species of Old World (Eurasian) origin, which are consequently paraphyletic.
EFFECTS OF SOIL NITROGEN ON POLLEN PRODUCTION, POLLEN GRAIN SIZE, AND POLLEN PERFORMANCE IN CUCURBITA PEPO (CUCURBITACEAE)
Authors: Lau Tak‐Cheung , Stephenson Andrew G.
Published: January 2018

To determine the effects of soil nitrogen on pollen production, pollen size, and pollen performance, two cultivars of zucchini (Cucurbita pepo) were grown under two nitrogen regimes in an experimental garden. The two cultivars were true breeding for alternative alleles for a one gene trait, ovary color. The soil nitrogen treatment had a significant effect on most measures of reproductive output through the female function. The nitrogen treatment did not affect the number of staminate flowers per plant but did have an effect on the number of pollen grains per staminate flower and the mean pollen grain size. A pollen mixture experiment revealed that pollen produced by plants in the high nitrogen treatment sired significantly more seeds than pollen from low nitrogen plants. Moreover, we found that the high nitrogen pollen sired even a greater percentage of seeds in the region of the fruit (ovary) previously shown to be fertilized by the fastest growing pollen tubes. Thus, the difference in the number of seeds sired by pollen from the two nitrogen treatments is due to differences in pollen performance. We conclude that spatial heterogeneity in soil nitrogen can influence the paternity of seeds in a plant population.
PATTERNS OF EMBRYO AND ENDOSPERM FORMATION IN MONOTROPA HYPOPITYS (MONOTROPACEAE) FROM NORTH AMERICA AND WESTERN SWEDEN
Authors: Olson A. Randall
Published: January 2018

Within the Monotropaceae. Monotropa hypopitys L. has the widest geographical distribution with sporophytes characterized as achlorophyllous, mycotrophic, and morphologically reduced. General and histochemical observations at the light microscope level concerning the postpollination changes in the numerous anatropous, unitegmic ovules reveal a precise embryogeny and endosperm development. Following double fertilization, the primary endosperm cell produces a lipid‐rich cellular endosperm situated between a micropylar and a chalazal haustorium. A cytoplasmically unequal division of the elongated zygote initiates proembryo formation. The degeneration of the basal cell of the proembryo results in an isolated terminal cell that undergoes a cytoplasmically equal, transverse division establishing a two‐celled embryo embedded in endosperm. Prior to final seed maturation, proteins replace the lipids as the dominant cytoplasmic reserve material. In contrast with earlier studies that depicted the mature embryo as variable in structure, here the embryo is shown to be consistently uniform within and between those populations sampled from North America and Europe.
CHLORANTHUS‐LIKE STAMENS FROM THE UPPER CRETACEOUS OF NEW JERSEY
Authors: Herendeen Patrick S. , Crepet William L. , Nixon Kevin C.
Published: January 2018

Fossil angiospermous stamens with in situ pollen from the Turonian (ca. 90 million years before present, Late Cretaceous) of New Jersey are described and assigned to the Chloranthaceae. The fossil stamens, which are three‐parted and bear two bisporangiate thecae on the central lobe and one bisporangiate theca on each lateral lobe, are indistinguishable from stamens of several extant species of Chloranthus. The pollen is spheroidal, 13–18 μm in diameter, with a reticulate exine and apparently elongate/elliptical apertures. The pollen is similar to that in extant Chloranthus in grain size, shape, exine sculpture, and aperture structure. Like pollen of some extant species of Chloranthus, aperture number in the fossil pollen appears to be variable. Because fossil pistillate chloranthoid reproductive structures have not been found at this locality it is unknown whether the fossil stamens described here were borne on the side of the ovary, as in extant Chloranthus, or in another arrangement. The three‐parted stamen of Chloranthus is unique in angiosperms and there has been considerable debate concerning the origin and evolutionary significance of the structure. Uncertainty as to whether the three‐parted stamen represents a synapomorphy for the genus or a retained plesiomorphy in angiosperms is the primary reason why these fossil stamens are not assigned to the extant genus Chloranthus.
NUTRIENT AND WATER RELATIONS OF THE MISTLETOE PHORADENDRON LEUCARPUM (VISCACEAE): HOW TIGHTLY ARE THEY INTEGRATED?
Authors: Panvini A. Darlene , Eickmeier William G.
Published: January 2018

Tissue mineral concentrations of calcium, copper, iron, magnesium, manganese, nitrogen, phosphorus, potassium, sodium, and zinc, and long‐term water‐use efficiency (as estimated by δ13C±) were measured in the mistletoePhoradendron leucarpumand its hosts to investigate the relationship between nutrient concentrations and water economies of the parasite and hosts. The mistletoe had mineral concentrations 0.97 to 2.88 times greater than the hosts. Mean long‐term mistletoe water‐use efficiency (‐27.89±) was comparable to mean long‐term host water‐use efficiency (‐27.69±) and generally greater than the water‐use efficiency reported for most mistletoe species. Differences between mistletoe and host water‐use efficiency ranged from +0.65 to ‐0.75± and were more similar to mistletoes found growing on nitrogen‐fixing host species as reported in other studies. Mistletoe nutrient concentrations, in particular nitrogen, were not related to changes in mistletoe water‐use efficiencies. Nutrient: calcium ratios indicated that mistletoes acquire nutrients in excess of that which can be delivered by the host xylem. These data are discussed relative to the passive vs. active theories of nutrient uptake.
RESPONSE OF TROPIC LEAF MOVEMENTS AND PHOTOSYNTHETIC GAS EXCHANGE TO WATER AVAILABILITY IN N2‐FIXING AND NO3‐FED SOYBEAN
Authors: Kao Wen‐Yuan , Forseth Irwin N.
Published: January 2018

Leaf movements, water status, and gas exchange were measured in soybean inoculated with Bradyrhizobium and grown under high and low soil water and nitrate availabilities. We hypothesized that paraheliotropism in low NO3‐grown plants (which have greater N2 fixation rates) would differ from that of high NO3‐grown plants (which have lower N2 fixation rates), such that carbon return on nitrogen investment into photosynthesis would be enhanced. Low NO3‐low water plants had more vertical leaf angles and received lower solar irradiances at midday than high NO3‐low water plants. Under constant, vertical illumination, low NO3‐low water plants had steeper leaf angles, increased rates of leaf movement, lower photosaturated photosynthetic rates, and lower stomatal conductances for a given leaf water potential than high NO3‐low water plants. Leaves of high NO3 plants had lower photosynthetic nitrogen use efficiencies than did low NO3 plants. Low water plants had lower leaf osmotic potentials and ratios of intercellular/ambient CO2 concentration than high water plants, but NO3 treatment did not affect these parameters. Results provided support for our initial hypothesis, and demonstrated a high degree of correspondence between gas exchange and heliotropic response to soil nitrogen and water availabilities in soybean.
MEDULLARY BUNDLES AND THE EVOLUTION OF CACTI
Authors: Mauseth James D.
Published: January 2018

Medullary bundles are absent from the pith of the leafy, relictual cacti (genus Pereskia) but are present in most members of subfamily Cactoideae. They are absent only from tribes Hylocereeae, Rhipsalideae, and some members of Cacteae and Notocacteae. Presence of medullary bundles tends to be correlated with presence of a broad pith, but exceptions occur. Most medullary bundles are collateral, and in all genera phloem is produced and accumulates throughout the lifetime of the bundle. Xylem definitely accumulates as medullary bundles age in some groups, but it definitely does not accumulate in others, being produced only while the bundle is young. Pith can be broad (up to 75 mm in diameter), can constitute half the shoot volume, and is long‐lived, remaining alive as long as the shoot is alive. Medullary bundles appear to be adaptive in allowing this large pith to be used for storage of water and starch. Medullary bundles have fewer, narrower tracheary elements than does the stele xylem in the same region; medullary bundles probably could not carry out significant longdistance transport if a major part of the stele becomes damaged.
VARIATION IN A POLYPLOID, DIOICOUS LIVERWORT, MARCHANTIA GLOBOSA
Authors: Bischler H. , Boisselier‐Dubayle M. C.
Published: January 2018

This study was undertaken in order to determine the population structure in a tropical, geographically isolated liverwort, Marchantia globosa Brid. ex Web., a thallose species endemic to the Mascarenes and Comoro Islands. A survey of numerous populations on Réunion showed M. globosa to be ecologically tolerant and morphologically quite variable. The morphological differences between populations could only be explained by a size effect, due principally to altitude. Neither cytological nor electrophoretic analyses revealed any genetic basis for distinguishing subpopulations. In spite of an apparently high reproductive effort, sexual structures being produced abundantly, few spores reach maturity. No electrophoretically detectable genetic polymorphism was found. Morphological variation appears to result from phenotypic plasticity.
Plant‐animal‐fungal interactions in Early Devonian Trimerophytes From Gaspé, Canadal
Authors: Banks Harlan P. , Colthart Brenda J.
Published: January 2018

Permineralized branchlets of Early Devonian Psilophyton and related trimerophytes sustained wounds that suggest the activity of animals, perhaps arthropods, with chewing and sucking mouthparts. Plant responses to injury were multiplication of cells beneath the wound, enlargement and lysing of those cells in some cases, and/or the formation of a protective tissue, a periderm. These reactions demonstrate that the plants were alive when injured. Presumed coprolites provide indirect evidence of the coexistence of plants and animals although the latter are lacking in the material. Spores, but no hyphae, assignable to Zygomycota demonstrate the presence of fungi in the community. Vascular plants, animals (? arthropods), and fungi apparently interacted freely in early terrestrial ecosystems.
Population biology of the rare copper moss, Scopelophila cataractae
Authors: Shaw A. Jonathan
Published: January 2018

The so‐called copper mosses include a number of rare species that exhibit very broad intercontinental geographic distributions comprised of highly disjunct occurrences. In one species, Scopelophila cataractae, only the haploid gametophyte generation exists in the United States, although sporophytes occur in tropical America and in Asia. Gametophytic plants were sampled from all U.S. populations to determine what factors limit sexual reproduction. More than 50% of the plants in every population were devoid of gametangia, and no population contained plants with both male and female gametangia. Morphological differences between plants from putative male and female populations (when each was interpreted to be unisexual) suggested gametophytic sexual dimorphism, but generalized sexual differences were not maintained under common garden conditions. Experimental growth of plants on soils with low, moderate, or high concentrations of metals demonstrated extensive morphological variability, and thus genetic polymorphism, among five asexual populations. Morphological traits were also significantly plastic in response to differing soil types, but there was no evidence of differences in patterns of plasticity between sexes or populations. All populations produced higher cover area and individual plants formed larger leaves on the most highly metal‐contaminated soil. Populations varied significantly in growth on less contaminated soil, again suggesting genetic variability.
Diploid hybrid speciation in Penstemon (Scrophulariaceae) revisited
Authors: Wolfe Andrea D. , Elisens Wayne J.
Published: January 2018

Diploid hybrid speciation remains a central issue in plant evolutionary biology. Here we test hypotheses of diploid hybrid speciation and introgressive hybridization in Penstemon section Peltanthera where P. spectabilis is a purported hybrid derivative species of the progenitors P. centranthifolius and P. grinnellii, and P. clevelandii is regarded as a hybrid derivative of P. centranthifolius and P. spectabilis. Forty‐five populations representing P. centranthifolius (subsection Centranthifolii); P. spectabilis, P. clevelandii, P. grinnellii, P. palmeri in subsection Spectabiles; and P. × parishii (a purported hybrid between P. centranthifolius and P. spectabilis) were examined for allozyme differentiation. Penstemon centranthifolius has high‐frequency allozymes at seven isozyme loci that differentiate it from species in subsection Spectabiles, whereas no genetic markers are detected that reliably differentiate species within Spectabiles. Because our data reveal that P. centranthifolius is genetically distinct compared to species in Spectabiles, we conclude that a recent hybrid origin of P. spectabilis and P. clevelandii with P. centranthifolius as a progenitor is not supported. Bidirectional gene flow and introgression between P. centranthifolius and species of subsection Spectabiles is indicated, however, based on the low‐frequency occurrence of P. centranthifolius marker alleles in species of Spectabiles and of Spectabiles marker alleles in P. centranthifolius in areas of sympatry.
Patterns of stem photosynthesis in two invasive legumes (Spartium junceum, Cytisus scoparius) of the California coastal region
Authors: Nilsen Erik T. , Karpa D. , Mooney H. A. , Field C.
Published: January 2018

Stem assimilation of Spartium junceum and Cytisus scoparius was measured over diurnal cycles during four time periods of 1992 in California. Spartium junceum plants were growing at an inland, coastal mountain site while the C. scoparius plants were growing at a coastal bluff habitat. Both species had positive stem assimilation that resulted in approximately 200 mmol m 2 day‐1 carbon dioxide accumulation. Daily carbon gain decreased from spring to fall for S. junceum due to a decrease in shoot water potential. Although C. scoparius had the same relationship between assimilation and shoot water potential as that of S. junceum, carbon gain and water potential did not decrease during the year for C. scoparius. The major limitation for carbon gain of C. scoparius was light intensity because the coastal site was characterized by lower temperature, higher humidity, and more fog than the inland site. Although these species grew in habitats that had a different vapor pressure and temperature, the assimilation response to vapor pressure was similar between the species. Water use efficiency was higher and intercellular carbon dioxide was lower for S. junceum compared to C. scoparius. Although the leaves of both species are ephemeral, the canopy has a constant positive carbon balance because of stem assimilation. The constant carbon gain throughout the year, from stem assimilation, may enhance the growth capacity of these invasive species in disturbed habitats.
Characterization of an anther‐specific glycoprotein in Lilium longiflorum
Authors: Wang Co‐Shine , Walling Linda L. , Eckard Kathleen J. , Lord Elizabeth M.
Published: January 2018

Antiserum was raised in rabbits against a lily (Lilium longiflorum) anther‐specific glycoprotein (LLA‐75). LLA‐75 protein bound to concanavalin A, suggesting that it was a glycoprotein. Monospecific anti‐LLA‐75 antibodies were prepared to investigate its distribution during anther development. Immunoblot analyses of total protein from floral and vegetative organs show that LLA‐75 glycoproteins accumulated to detectable levels primarily in one discrete stage of anther development, during the microspore and early pollen phase when the tapetum is actively secreting. A cross‐reactive protein with molecular mass of 43.0 kD was also observed. Immunoblots of two‐dimensional polyacrylamide gels of lily anther proteins indicated that the four isoforms of LLA‐75 glycoprotein ranged from isoelectric point 5.6 to 6.1. These affinity purified antibodies to LLA‐75 cross‐reacted with anther proteins in two dicot species of the Bignoniaceae. In situ localization data using antirabbit immunoglobulin G (IgG) conjugated with gold particles was not definitive but demonstrated that LLA‐75 glycoprotein in lily anthers occurred prominently in tapetal tissue and all other tissues to a lesser degree.
Nucleolar activity in the fusiform cambial cells of Abies balsamea (Pinaceae): effect of season and age
Authors: Mellerowicz E. J. , Riding R. T. , Little C. H. A.
Published: January 2018

Nucleolar involvement in the regulation of the activity‐rest‐quiescence cycle of the vascular cambium was assessed by determining the seasonal variation in number, diameter, and volume of nucleoli in fusiform cells of Abies balsamea (L.) Mill. The cells were isolated from 1‐ and 19‐yr‐old cambia and stained with either silver nitrate or Feulgen + naphthol yellow‐S. The ability of fusiform cells to incorporate [5‐3H]‐uridine into nuclei and nucleoli was also determined. In the 1‐yr‐old cambium, the activity of the nucleoli, as evidenced by their diameter, total volume per cell, and intensity of staining with silver nitrate, exhibited two maxima during the year—a large one during cambial reactivation in April‐May and a small one during the rest‐quiescence transition in October. Incorporation of radiolabeled uridine at 20 C was low at the end of the active period and increased during the rest–quiescence transition, suggesting that the quiescent, but not the resting, cambium can rapidly resume nucleolar activity when the temperature is permissive. The number of nucleoli per cell varied between two and eight, and was higher during the dormant than the active period. The increase in number took place during the autumnal activity–rest–quiescence transition, when cambial cells were arrested in the G1 phase of the cell cycle. Similar seasonal changes in nucleolar morphology were observed in the 19‐yr‐old cambium. Nucleolar diameter and total nucleolar volume were larger in the 19‐yr‐old cambium than in the 1‐yr‐old cambium, whereas nucleolar number was lower. Th results suggest that repression of rRNA genes underlies the development of rest when the cambium will not produce new cells.
Clonal reproduction and patterns of genotypic diversity in Decodon verticillatus (Lythraceae)
Authors: Eckert Christopher G. , Barrett Spencer C. H.
Published: January 2018

Most perennial plants combine sexual reproduction with some form of clonal propagation. These mixed strategies may produce considerable variation among populations in levels of clonal diversity in response to ecological factors limiting one or other reproductive mode. Surveys of style morph frequencies in 163 populations of the eastern North American, clonal, tristylous aquatic, Decodon verticillatus (L.) Ell. (Lythraceae) suggested a wide range of clonal diversity among populations. Populations consisting of a single style morph were most common at the northern margin of the species' range and could have arisen through severe founder events followed by exclusive clonal propagation. Here, we test this hypothesis by comparing allozyme variation in populations monomorphic and polymorphic for style length located in Ontario and Michigan. Each of the four populations monomorphic for style length were fixed for a single three‐locus allozyme genotype while the seven trimorphic and five dimorphic populations contained an average of 26 multilocus genotypes each. Measures of genotypic diversity were high in polymorphic populations (average D = 0.93 ± 0.02 standard error; D = 0.00 for all populations monomorphic for style length). Three of the populations monomorphic for style length were fixed for a heterozygous genotype at one of the loci surveyed, suggesting that each consists of a single clone. In contrast, genotype frequencies in polymorphic populations conformed to Hardy‐Weinberg proportions indicative of sexual reproduction. The range of clonal diversity found in D. verticillatus is the largest reported for a clonal plant species, although the literature is too limited to determine whether this is truly unusual. Clonal diversity in D. verticillatus is likely to be regulated largely by ecological factors affecting seed production and establishment. However, genetically based sexual sterility also occurs in some populations.
Interannual variations in the seed production ofPinus Banksianaat the limit of the species distribution in northern Québec, Canada
Authors: Houle Gilles , Filion Louise
Published: January 2018

Interannual variations in cone and seed production ofPinus banksianaLamb, were studied at the species northern limit of distribution in Québec (Canada). Cone number per cone‐bearing branch, potential number of seeds per cone, number of formed, filled, and viable seeds per cone, and seed viability, germination rate, and mass were determined for two populations of the species, over a 9‐year series. There were significant differences among years, but not between populations, in all the variables considered. The populations were well synchronized with each other, suggesting that climatic influence on the variables considered might be significant. Apparent periodicity in reproductive output also suggests the existence of some internal cycle, possibly in relation to tree reserves. Annual viable seed production is the result of a combination of events in the reproductive cycle of an individual (i.e., cone initiation, pollination, fertilization, and embryo maturation), each one specifically affected by climate. There are no apparent trade‐offs between seed mass and number of filled seeds per cone over time; moreover, there seems to be a positive relationship between seed mass and number of viable seeds per cone. Climate conditions during fertilization and embryo maturation (both of which occur during the same season) appear to significantly influence the species reproductive output. We present regression models based on meteorological variables to estimate cone and viable seed production, and seed mass.
Rhizome gravitropism precedes gravimorphogenesis after inversion of the green algal coenocyte Caulerpa prolifera (Caulerpales)
Authors: Jacobs William P.
Published: January 2018

Previous investigations reported that the marine alga Caulerpa prolifera, a giant coenocyte, had a fast morphogenetic response to a change in position with regard to gravity: the next rhizoid formed approximately 1 day later on the new underside of the inverted rhizome (Jacobs and Olson, 1980, American Journal of Botany 67: 141–146). Preceding the change in site of rhizoid development was a striking accumulation of amyloplasts at the new prospective rhizoid‐initiation site in the rhizome tip. Detailed monitoring with video equipment of inverted Caulerpa plants, growing under controlled conditions, now reveals that after the amyloplast accumulation, but before the gravimorphogenetic effect on rhizoid development, the inverted rhizome tip shows a negative gravitropism that restores it to its normally upturned position. Because the experiments were performed with two‐sided illumination, this was clearly not a phototropic response.
Why Prunus mahaleb (Rosaceae) produces more flowers than fruits
Authors: Guitian Javier
Published: January 2018

Various mutually compatible hypotheses have been proposed to explain the low levels of fruit set observed in many hermaphrodite plants. I carried out trials to determine which of these hypotheses best explains the low fruit set occurring in Prunus mahaleb L. (Rosaceae). The results of insect exclusion, supplementary pollination, and flower removal experiments indicate that the ovary reserve hypothesis and the selective abortion hypothesis seem to be the most likely explanations for the production of excess flowers in P. mahaleb.
Sporocarp ontogeny in Panus (Basidiomycotina): evolution and classification
Authors: Hibbett David S. , Murakami Shigeyuki , Tsuneda Akihiko
Published: January 2018

Ontogenies of cultured Panus conchatus, P. rudis, and P. fulvus sporocarps were observed macroscopically and with scanning electron microscopy. Hymenophore differentiation in Panus involves periclinal growth of context hyphae below a closed surface palisade of hymenial elements, resulting in a cantharelloid appearance and radiate trama. This pattern is qualitatively different from that in Lentinus s. str., which suggests that lamellae of Panus and Lentinus are not homologous. Panus conchatus and P. rudis sporocarps have short stipes, develop directly from the mycelium, and mature in 5–10 d. Panus fulvus sporocarps have an elongate stipe, develop from a pseudosclerotium, and mature in about 3 wk, the first approximately 15 d of which involve apical elongation of a stipelike primordium that is able to dedifferentiate and regenerate cut apices. Panus conchatus and P. rudis sporocarps lacked regeneration ability. Panus conchatus sporocarps developed an ephemeral partial veil that was obliterated during sporocarp expansion. Outgroup comparison suggests that evolutionary changes in developmental programs in Panus have included: 1) delay in offset of primordium growth, with a corresponding increase in primordium size and time to maturation (hypermorphosis); 2) insertion of the pseudosclerotial stage in ontogeny; 3) gain of ability for dedifferentiation and regeneration; and 4) nonterminal gain or loss of veil tissue.
Effects of light and nutrient availability on chasmogamy and cleistogamy in an understory tropical herb, Calathea micans (Marantaceae)
Authors: Le Corff Josiane
Published: January 2018

The effects of light and nutrient availability on chasmogamous and cleistogamous flower and fruit production were investigated in an understory tropical herb, Calathea micans (Marantaceae). I censused chasmogamous and cleistogamous flower and fruit production at five permanently marked demographic study sites in Costa Rica, characterized by different successional stages. Using a transplant experiment, I examined whether an increase in light and/or nutrients would increase chasmogamous and/or cleistogamous flower production. In natural populations as well as in the experiment, chasmogamous reproduction increased with light; nutrient availability significantly increased chasmogamous reproduction in the transplant experiment. Field observations indicated that very few plants reproduced and low investment in reproduction might have been due to poor environmental conditions. Larger plants had a higher probability of reproducing, but plant size did not have an effect on the mode of reproduction, chasmogamy vs. cleistogamy. However, the production of new vegetative shoots increased the probability of producing chasmogamous inflorescences. Cleistogamy may allow the plant to reproduce even in conditions of poor habitat quality and assures some seed set even in conditions unfavorable to plant growth.
Population variation of leaflet sleep movements in Oxalis grandis (Oxalidaceae)
Authors: Levy Foster , Moore Darrell
Published: January 2018

To identify intraspecific variation in the expression of circadian leaflet movements, we observed changes in leaflet elevation angle in a controlled environment and in the field. Two morphologically and ecologically distinct populations of Oxalis grandis were compared: a typical mesic forest ecotype and an atypical, densely hirsute ecotype found on partially exposed shale outcroppings. Significant genotypic variation was detected within both populations. The controlled environment experiment revealed significant differences in the intrinsic rhythm between the two populations, primarily at the beginning and end of the photophase. We observed leaflet ascent and descent prior to lights‐on and lights‐off, respectively, processes we define as anticipatory. Hirsute ecotype plants showed a greater anticipation of lights‐on, whereas the mesic ecotype plants showed a greater anticipation of lights‐off. In the field, significant differences in leaflet elevation between the populations occurred in early morning and late afternoon, but not immediately preceding dusk. Contrary to the controlled environment experiment, mesic ecotype plants showed greater anticipation of dawn; plants from both populations showed similar anticipation of dusk. Plants of the hirsute ecotype exhibited higher sensitivity to sudden fluctuations in light level. We hypothesize that differences in light sensitivity partially explain the differences in the leaflet angle patterns between the field and controlled environments.
Translocation, remineralization, and turnover of nitrogen in the roots and rhizomes ofSpartina alterniflora (Gramineae)
Authors: White David S. , Howes Brian L.
Published: January 2018

We used 15N to quantify rates of N translocation from aerial to belowground tissues, foliar leaching, and turnover and production of root and rhizome biomass in the plant‐sediment system of short Spartina alterniflora areas of Great Sippewissett Marsh, Massachusetts. Decay of belowground tissues in litterbag incubations at 1‐ and 10‐cm depths resulted in 80% remineralization of the original plant (15N‐labeled) N and 20% burial after 3 years. Translocation of 15N from plant shoots in hydrologically controlled laboratory lysimeters maintained under field conditions was 38% of the aboveground pool while leaching of N was 10% from June to October. Most of the translocated N was not retranslocated to new aboveground growth in December but appeared to be either remineralized or buried in the sediment. Injection of 15N into field stands of grass showed initially high incorporation into plants followed by a continuous decline over the next 7 years yielding a gross tumover time of 1.5–1.6yr. Correcting the gross N turnover for recycling of label via translocation and uptake of remineralized label during this period, a net root and rhizome turnover time of 1.0–1.1 yr was obtained. Combining the turnover time with independent estimates of seasonal belowground biomass yielded an estimate of belowground production of 929–1,022 g C m−2 yr−1, similar to measurements by traditional biomass harvest, CO2 based budgets and models for comparable areas of this marsh. Integration of the production and nitrogen balance estimates for short Spartina marsh yielded translocation, 1.4 g N m−2 yr−1, leaching, 0.4 g N m−2 yr−1, remineralization, 14.9–16.3 g N m−2 yr−1, and burial, 3.7–4.1 g N m−2 yr−1.
Predicting the height of fossil plant remains: an allometric approach to an old problem
Authors: Niklas Karl J.
Published: January 2018

Interspecific correlations between plant height and basal stem diameter (the allometry of height) and between stem length distal to where diameter is measured (the allometry of stem taper) were determined for a total of 265 species with self‐supporting stems and for the shoots of five conifers and 15 angiosperm vine species. The allometric equations obtained for these data are proposed as a method to predict the heights of fossil plants for which basal stem diameters are either known or inferred, and to predict the missing lengths of fragmented stems based on the most proximal stem diameters observed.
Pollen viability, vigor, and competitive ability inErythronium grandiflorum (Liliaceae)
Authors: Thomson James D. , Rigney Lisa P. , Karoly Keith M. , Thomson Barbara A.
Published: January 2018

To determine how the capability of pollen is affected by lengthy exposure to field conditions, we obtained pollen samples (from Erythronium grandiflorum) that were fresh (from newly dehisced anthers) or aged, from 6 to 24 hr. Without pretreating the collected grains, we compared their abilities 1) to retain viability, as indicated by the Heslop‐Harrison fluorochromatic reaction (FCR) test; 2) to retain germinability, as indicated by pollen‐tube growth in vitro on Brewbaker‐Kwack medium; 3) to sire seeds when used as a pollen donor on recipient flowers in the field; and 4) to sire seeds competitively when mixed with another donor pollen in competitive pollinations. FCR scores declined drastically with pollen age. Germinability typically declined with age, but less drastically; the correlation between FCR and germinability ranged from strong to nil in different trials. The sharp decline in FCR was probably due to nonlethal, reversible desiccation. Seed‐siring success, both in competitive and noncompetitive trials, bore no relation to pollen age or to germinability. Any loss in seed‐siring ability in E. grandiflorum pollen over 24 hr is apparently overwhelmed by other sources of variation. The lack of correlation between seed‐siring ability and FCR or germinability scores means that those tests should not be used to estimate overall pollen competence in this species. They should be so used in other species only if experiments have demonstrated their greater reliability.
Allozyme variability within and among populations of the epiphytic mossLeucodon (Leucodontaceae: Musci)
Authors: Akiyama Hiroyuki
Published: January 2018

Enzyme electrophoresis was used to estimate genetic variability within and among populations of five species of the genus Leucodon (L. atrovirens, L. luteus, L. nipponicus, L. sapporensis, and L. temperatus). All of these perennial, dioecious plants are epiphytic on tree trunks and produce numerous spores that are released in winter. Gene diversity within populations (HS) was low (0.070) in L. nipponicus, which grows in disturbed habitats, and high (0.169–0.202) in the other four species, which inhabit stable environments. Gene diversity between populations relative to total diversity (GST) was low in L. temperatus (0.042) and L. luteus (0.043), suggesting that extensive gene flow occurs among populations. GST was moderate in L. sapporensis (0.104) and L. atrovirens (0.114); these values are still less than those previously reported for terrestrial mosses. Since epiphytes could disperse their spores effectively by the wind, low genetic divergence among populations may be related to the epiphytic habit of the species. On the other hand, high GST value (0.208) was found in L. nipponicus. It is probably explained by the genetic differentiation of populations by genetic drift, for the species forms geographically and ecologically isolated populations with small number of individuals. We also observed incongruity between morphological and genetic similarity among species.
Genome origins ofTriticum cylindricum, Triticum triunciale,andTriticum ventricosum (Poaceae) inferred from variation in restriction patterns of repeated nucleotide sequences: a methodological study
Authors: Dubcovsky Jorge , Dvorak Jan
Published: January 2018

Three methods of phylogenetic inferences on polyploid plants employing variation in restriction sites in repeated nucleotide sequences were compared. Allotetraploid Triticum species of well‐established origin were used as a model. Methods based on determination of the proportion of restriction fragments shared between a polyploid and its diploid relatives generated biased results because of uneven numbers of restriction fragments among diploid species and presence of common bands in phylogenetically related diploid species. A method employing restriction fragments unique to a diploid species (marker bands) was not affected by either factor and generated results consistent with cytogenetic inferences. It is shown that the latter method can be used to investigate the origin of a polyploid species even when one of its progenitors is extinct or when the polyploid and its diploid progenitors have diverged.
Correlation between time of flowering and phenotypic plasticity inArabidopsis thaliana (Brassicaceae)
Authors: Zhang Jianhua , Lechowicz Martin J.
Published: January 2018

We observed substantial variation in the time of flowering among 13 populations of Arabidopsis thaliana (Brassicaceae) from an extensive latitudinal range when grown under uniform experimental conditions. The later the onset of flowering, the greater was potential reproduction. Later flowering plants also had greater plasticity in a host of morphological and physiological traits measured in nutrient‐rich vs. nutrient‐poor test environments. This relationship between flowering time and overall plasticity was only apparent for traits measured at the time of seed production, not at the time of flowering or earlier. At the time of seed production in this short‐lived annual, the regression of a multivariate measure of overall plasticity on the time of flowering was linear and highly significant (r2 = 0.90, P < 0.0001). These correlations among time of flowering, reproductive fitness, and plasticity support the idea that selection for late‐flowering genotypes would select concomitantly for greater plasticity.