bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative floral development inPseudolysimachion (Scrophulariaceae): intraspecific variation and comparison withVeronicaandVeronicastrum
Authors: Kampny Christine M. , Dickinson Timothy A. , Dengler Nancy G.
Published: January 2018

Intraspecific variation in floral development was studied in four morphologically distinct strains of Pseudolysimachion longifolium and two of P. spicatum. Size increase of whole buds from living plants of P. longifolium was followed in absolute time. Growth rates were homogeneous within inflorescences and within individual plants, and significantly different between individual plants. Organ growth trajectories (plotted as organ size over gynoecium size) differed little among individuals of Pseudolysimachion belonging to morphologically distinct strains; variation was most pronounced in the calyx. Corolla tube as well as calyx and corolla lobe measurements varied more during the early stages of development than near maturity, suggesting constraints on mature flower form. In addition to intraspecific variation, floral development in Pseudolysimachion was compared with that in related Veronica chamaedrys and Veronicastrum virginicum, using data from a previous study. Mature flowers of Pseudolysimachion have long corolla tubes similar to those of Veronicastrum and long corolla lobes similar to those of Veronica. The trajectories of most organs of Pseudolysimachion were intermediate between those of Veronica and Veronicastrum in position as well as in type of curve, i.e., different trajectories lead to similar end products; thus, the shapes of the mature organs are not strictly homologous and not indicative of close relationship.
The relationship between the number ofexpanded and developing leaves in shoot apices of palms
Authors: Dalrymple Nancy K. , Fisher Jack B.
Published: January 2018

The number of developing leaves was compared to the number of mature expanded leaves in the crowns of 42 species of palms representing 28 genera. One species had fewer developing vs. mature leaves. Ten species had approximately the same number of developing and mature leaves. Eighteen species had approximately 1.5 times the number of developing leaves vs. mature leaves. Eleven species had approximately twice as many developing leaves vs. mature leaves. Two species (Copernicia gigasandGastrococos crispa) had approximately three times the number of developing vs. mature leaves. Additional data from the literature and previously unpublished observations for 19 species are also presented. The 1:1 ratio between the number of developing leaves vs. mature leaves, as hypothesized by earlier authors, was not found in most species of palms.
Plasmodial tapetum and pollen wall development inButomus umbellatus (Butomaceae)
Authors: Fernando Danilo D. , Cass David D.
Published: January 2018

This report describes the ultrastructural development of plasmodial tapetum and pollen wall of Butomus umbellatus. The tapetum contains extensive arrays of rough endoplasmic reticulum, vesicles from which are responsible for the formation of sporopollenin‐like bodies. The tapetum is also involved in the formation of other forms of sporopollenin precursors. Development of pollen wall continues after microspores are released from their callosic walls; they are then enclosed by plasmodial tapetum. The activity and products of the plasmodial tapetum show substantial correlation with pollen wall development, particularly ektexine formation. In B. umbellatus, the tapetum intrudes into the anther locule at early microspore stage. This timing of plasmodial intrusion occurs at a later stage of pollen development as compared to those in the advanced monocotyledons. We report the rough endoplasmic reticulum origin of sporopollenin‐like bodies and their occurrence in the plasmodial tapeta of B. umbellatus.
Pollen‐ovule ratio, pollen size, and breeding system inAstragalus (Fabaceae) subgenusEpiglottis:a pollen and seed allocation approach
Authors: Gallardo Rafael , Dominguez Eugenio , Muñoz Jesus M.
Published: January 2018

The correlation between pollen/ovule (P/O) ratio and breeding system has generally been accounted for either on the basis that P/O reflects pollination efficiency, or in terms of the sex allocation theory. The following were assessed for taxa belonging to genus Astragalus subgenus Epiglottis: 1) Degree of correlation between P/O and the breeding system, measured by means of autofertility; 2) The absence or existence of correlation between P/O and pollen grain size; and 3) The ability of various theories to account for the results obtained. Results showed a minimal correlation between P/O and autofertility, and between P/O and pollen grain size in the taxa studied. Analysis of these results in terms of the sex allocation theory enabled this correlation to be explained as a function of the variation existing between taxa with respect to the resources invested in each pollen grain and in each ovule. The predictive capacity of this theory, which has moreover proven valuable in explaining the structural peculiarities of the androecium in these taxa, was also highlighted. The type of self‐pollination applicable was also discussed, as was the phenotypic model of selection of self‐fertilization considered most plausible for these taxa.
Inheritance of plastid DNA in theTurnera ulmifoliacomplex (Turneraceae)
Authors: Shore Joel S. , McQueen Karina L. , Little Stephen H.
Published: January 2018

We used PCR to amplify most of the rbcL gene and identified restriction fragment length polymorphisms to study the inheritance of chloroplast DNA (cpDNA) in the cross between two taxonomic varieties of the Turnera ulmifolia L. complex, vars. angustifolia and velutina. We identified an Alu I restriction site polymorphism that distinguished the parental plants. All 23 progeny from the cross var. angustifolia × var. velutina, where var. angustifolia was the maternal parent, possessed the paternal cpDNA. Results for the reciprocal cross were more varied, and the 16 progeny showed maternal, paternal, or biparental inheritance. We believe this represents the first study of plastid inheritance for any species in the Tumeraceae. The results are unusual and warrant further investigation using other species in this family.
Male sterility in flowering plants: are plant growth substances involved?
Authors: Sawhney Vipen K. , Shukla Amit
Published: January 2018

Male sterility in flowering plants is of tremendous importance not only in molecular and developmental studies of stamen and pollen grains and evolutionary studies on the origin of dioecy, but also in its commercial application in hybrid seed production. This paper reviews the literature on the possible involvement of plant growth substances (PGSs) in male sterility, and in normal stamen and pollen development. Different experimental approaches on a number of male sterile systems and normal plants have shown that nearly all PGSs, i.e., gibberellins, cytokinins, auxin, abscisic acid, and ethylene, directly or indirectly influence the expression of male sterility. Analyses of endogenous PGSs have revealed that in male sterile plants the level and/or metabolism of more than one PGS is affected. These studies support the suggestion that it is the relative ratio of various PGSs, rather than any one substance, that is critical for normal stamen and pollen development. It is also proposed that gene‐regulated male sterility is likely mediated through an altered balance of endogenous PGSs in developing flowers and stamens.
Spatial and genetic structure of two sandhills oaks:Quercus laevisandQuercus margaretta(Fagaceae)
Authors: Berg Edward E. , Hamrick J. L.
Published: January 2018

Quercus laevisWalt, (turkey oak) andQ. margarettaAshe (scrubby post oak) are important scrub oaks in the sandhills forest communities of the Coastal Plain of the southeastern United States. We used allozyme loci and Ripley's L‐statistics to examine clonal structure and spatial dispersion in these species.Q. laevisgreater than 1.5 m in height were randomly dispersed on a scale of 0–40 m; smaller individuals (< 1.5 m) were slightly clustered on a scale of 0–12 m. Larger individuals separated by ≤1 m had 15% probability of being ramets of the same clone.Q. margarettashowed strong clustering on a scale of 0–20 m. Stems separated by ≤ 1 m had a 71% probability of being ramets of the same clone. Clonal offspring were strongly clustered about the presumed clonal parent: 50% fell within 0.50 m of this individual. Simulation modeling and direct comparison of adult and juvenile genotypes indicated that acorns are dispersed on a scale of tens of meters for both species, suggesting animal vectors such as squirrels or blue jays.
Mating system, life‐history, and reproduction in Canada thistle (Cirsium arvense; Asteraceae)
Authors: Lalonde R. G. , Roitberg B. D.
Published: January 2018

Canada thistle (Cirsium arvense) (L.) Scop, is an almost perfectly dioecious, perennial plant that can express strong vegetative reproduction by means of its extensive root system. We explore some of the consequences of this type of reproductive strategy on the plant's pollination success, its ability to allocate resources to individual achenes, its ability to abort excess achenes, and on how pollen limitation affects the primary sex ratio of its offspring. Seed set in females is constrained by the availability of pollen. Clumps of female thistle isolated from males by at least 50 m set far fewer achenes per head than females that are interspersed with males. Even when such interspersion occurs, distance to nearest effective pollen donor correlates negatively with fertilization. Achene mass is significantly higher in plants that set fewer seed due to pollen limitation; however, the proportion of achenes that abort is not affected by the availability of pollen. Plants partially compensate for pollen limitation by maintaining stigmas in a receptive stage longer when pollination is sparse. Primary sex ratio is not affected by the availability of pollen; both high‐ and low‐pollen availability treatments produced highly female‐biased sex ratios.
Fungi from the Lower Devonian Rhynie chert: My Coparasitism
Authors: Hass Hagen , Taylor Thomas N. , Remy Winfried
Published: January 2018

Several examples of mycoparasitism are described from the Lower Devonian (Siegenian) Rhynie chert. These fungal interactions include thick‐walled chlamydospores and vesicles in which epibiotic fungi are attached to the outer surface of the spore. Other fossil spores are characterized by mycoparasites developing between the layers of the spore wall or within the lumen. The presence of callosities extending from the inner surface of some fossil spores demonstrates that the hosts were alive when parasitized. This response by the mycohost is identical to that found in certain modem mycoparasitic symbioses involving vesicular arbuscular mycorrhizae that are parasitized by various aquatic fungi. The presence of mycoparasitism in a 400‐million‐year‐old ecosystem underscores the potential significance of the fungal genome early in the evolution of other organisms.
Spectrophotometric analysis of nectar production in Silene vulgaris (Caryophyllaceae)
Authors: Jolls Claudia L. , Chenier Thomas C. , Hatley Cynthia L.
Published: January 2018

Significant differences in nectar content were observed between hermaphrodite and female plants of the gynomonoecious‐gynodioecious taxon, Silene vulgaris, from populations in northern lower Michigan. These differences in nectar sugar content were observable with a carbohydrate digestion technique involving sulfuric acid, phenol, and measurement of the color change with a spectrophotometer. A hand‐held refractometer did not provide sufficient resolution to discern differences between the genders. Both genders were similar in the pattern of sugar content of nectar during floral development. A splitplot factorial design revealed significant differences both among individual plants and stages of floral phenology within each gender. The spectrophotometric technique and statistical analysis provided the needed resolution to discern differences between the genders that we relate to pollinator activity, levels of inbreeding depression, and the maintenance of gynodioecy in this taxon.
Nonrandom mating in Clarkia gracilis (Onagraceae): a case of cryptic self‐incompatibility
Authors: Jones Kristina Niovi
Published: January 2018

In plants capable of both self‐fertilization and outcrossing, the selfing rate depends on the proportion of self pollen in pollen loads and on the relative postpollination success of self pollen in siring offspring. While the composition of pollen loads is subject to unpredictable variation, paternity success of self vs. outcross pollen following pollen deposition may be controlled by maternal plants. This study examined postpollination paternity success in Clarkia gracilis ssp. sonomensis, in which deposition of self pollen is common. Pure loads of self and outcross pollen produced similar numbers of mature seeds, but equal mixtures of self and outcross pollen yielded more than three times as many outcrossed offspring as selfed offspring. The finding that the paternity success of self pollen depends on whether it is in competition with outcross pollen helps to explain an earlier finding that the selfing rate in experimental populations was highest when pollinator activity was lowest. Cryptic self‐incompatibility allows paternity by self pollen when outcross pollen is unavailable.
A study of two fungal epibionts of grasses: structural features, host relationships, and classification in the genus Myriogenospora (Clavicipitales)
Authors: White James F. , Glenn Anthony E.
Published: January 2018

Morphological studies are made on specimens referred to Myriogenospora atramentosa and Balansia linearis. Stromata of both are epibiotic, linear, and have immersed perithecia. In addition, development of ascospores proceeds in a similar fashion. Linear filamentous ascospores disarticulate to form short segments that reinitiate bipolar growth at opposite ends to form fusoid‐shaped part‐spores. This method of part‐spore development is unknown to occur in other Clavicipitaceae. As a result of the common features of these species, it is proposed that B. linearis be classified in the genus Myriogenospora. Aspects of the biology and taxonomy of these species are discussed.
Genetic differentiation between Carex lasiocarpa and C. Pellita (Cyperaceae) in north america
Authors: McClintock Katherine A. , Waterway Marcia J.
Published: January 2018

Carex lasiocarpa and C. pellita (sect. Carex) share a very similar morphology and have overlapping ranges in North America, but are found in different habitats characterized by contrasting soil types and pH. We studied allozyme variation and chromosome numbers to assess genetic differentiation between the two taxa. Both principal components analysis on the allele frequencies from 12 putative enzyme‐coding loci and cluster analysis of genetic identities separated 51 sampled populations into two groups that were consistent with recognized structural differences between C. lasiocarpa and C. pellita. Mean within‐group genetic identities were 0.95 for C. lasiocarpa and 0.93 for C. pellita; mean between‐group genetic identity was 0.81. With the exception of two rare alleles, the alleles of C. pellita were a subset of those found in C. lasiocarpa. Principal components analysis of measurements of structural characters from voucher specimens representing 46 populations also separated the two species with minimal overlap. Meiotic squashes of microsporocytes revealed haploid chromosome numbers of 38 and 38 + 1 for C. lasiocarpa and 41 and 40 + 1 for C. pellita. These data support the continued recognition of the two taxa as distinct species, and suggest that C. pellita may be a daughter species still in the process of divergence from C. lasiocarpa.
Interspecific compatibility among 15 Leucaena species (Leguminosae: Mimosoideae) via artificial hybridizations
Authors: Sorensson Charles T. , Brewbaker James L.
Published: January 2018

Leucaenas are fast‐growing neotropical trees and shrubs used as forage and fuelwood. This study tested the seed crosscompatibilities among 15 of the 16 well‐defined species of the paleopolyploid genus Leucaena Bentham (Leguminosae: Mimosoideae) to determine if genes of interest could be transferred between species. Twelve diploid and four tetraploid taxa were artificially hybridized in 118 of all 120 possible two‐way combinations and 31 of 32 possible self‐ and intraspecific matings, with 58,218 floret pollinations. Ninety‐one combinations (77%) produced well‐filled seed, and 73 of these combinations were grown and validated in the field. The qualitative crossability within ploidy levels (diploid, triploid, tetraploid) was 78%, 75%, and 100%, respectively, whereas quantitative crossability (relative to intraspecific matings) of successful matings within identical ploidy levels was 32%, 11%, and 73%, respectively. One‐third (34%) of the 114 interspecific combinations tested in both directions exhibited weak unilateral incompatibility (UI), due, in part, to reciprocal differences in stylar length. Other mechanisms for UI (embryo‐endosperm imbalance, sex‐specific use of self‐compatible parents) were ruled out. Wide hybridization appears to be “buffered” by polyploidy in the genus.
Carbon integration in Plantago aristata (Plantaginaceae): the reproductive effects of defoliation
Authors: Horton Margaret , Lacey Elizabeth P.
Published: January 2018

Patterns of carbon integration in aclonal species are poorly understood in spite of their potential to influence individual fitness. To provide more information about these patterns, we performed a defoliation experiment with P. aristata. We examined, at the metameric level, the reproductive responses to the removal of the major carbon sources within metamers. Bracts on marked reproductive spikes and leaves subtending these spikes were removed at three stages of reproductive maturity: spike elongation, flowering, and fruiting. Spike dry weight and length, capsule number, seeds per capsule, and seed weight were measured. We tested the hypothesis that seed weight would respond least to defoliation. We also performed a complementary 14C translocation experiment to measure the amount of radioactive carbon moving into the marked spikes from outside the metamer. Defoliation depressed all components of reproduction within marked spikes, and little 14C was translocated from outside the metamer into the reproductive spikes, even those that were defoliated. Both results support the view that reproductive metamers in this species are largely autonomous with respect to their carbon budget. Defoliation during spike elongation most depressed reproduction, and bract removal depressed reproduction more than did leaf removal. The data suggest that bracts compensate for leaf removal by increasing their photosynthetic rate; however, the ability to compensate differs among plant populations. Of all the reproductive components, seed weight was least affected by defoliation. The data show, however, that the time of defoliation relative to reproductive development influences which reproductive components are affected.
Factors associated with a rust infection (Sphenosphora saphena) in an epiphytic orchid (Tolumnia variegata)
Authors: Meléndez Elvia Janet , Ackerman James D.
Published: January 2018

The interaction of a rust infection (Sphenosphora saphena) with the orchid Tolumnia (Oncidium) variegata was studied in northern Puerto Rico to determine which intrinsic and extrinsic factors are associated with the development of the infection. The relationship between anatomical and morphological characters, life‐history stage, density, herbivory, horizontal and vertical location, and frequencies of allo‐ and autoinfection were investigated. Stomatal densities and plant age were not associated with the incidence of disease. However, larger plants were more frequently infected than small ones. Censuses showed that seedlings were affected less frequently than adults, but inoculations demonstrated that both stages were equally susceptible to infection. Infection frequencies varied considerably over time and space. Population density was positively correlated with incidence of infection in two out of five censuses within a 3‐year period. Vertical distribution of the orchid was not related to the incidence of infection. Infection frequencies were related to site location, but this varied with time. Infections were highly localized, and new shoots were more likely to become infected if the previous shoot was diseased. Herbivory was more frequent among noninfected plants and may impart some degree of resistance. Our results suggest that the infection frequencies are associated more strongly with infection histories, plant size, and ecological conditions rather than with age, life histories, or anatomical traits of the orchid.
Neotropical Eocene coastal floras and 18O/16O‐estimated warmer vs. cooler equatorial waters
Authors: Graham Alan
Published: January 2018

The history of the earth's sea‐surface temperature (SST) in equatorial regions during the Tertiary is unsettled because of uncertainty as to the presence and extent of glaciers during the Paleogene. The 16O trapped in glaciers and subsequently released back to the ocean basins as meltwater during interglacials aifects the 18O/16O ratio of sea water, one of the variables that must be known for oxygen isotope paleotemperature analyses of calcareous fossils. Estimates of SST range from ~ 18 to 20 C, assuming an ice‐free earth, to ~ 28 C assuming glaciers were present in the Paleogene. Low latitude SST presently averages 28 C, so the former estimate gives a value 8 to 10 C cooler than present, while the latter gives a value as warm or slightly warmer than present. The figures are important for interpreting terrestrial vegetational history because the temperature differential between low and high latitudes is a major factor in determining global climates through the control of poleward transfer of heat. The middle(?) to late Eocene Gatuncillo Formation palynoflora of Panama was deposited at the ocean‐continental interface at ~9° N latitude. The individual components and paleocommunities are distinctly tropical and similar to the present vegetation along the Atlantic coast of southern Central America. This is consistent with data emerging from other recently studied tropical coastal biotas and represents a contribution from paleobiology toward eventually resolving the problem of Eocene equatorial marine environments. Collectively, the evidence is beginning to favor a model of Eocene SST near present values.
The allometry of safety‐factors for plant height
Authors: Niklas Karl J.
Published: January 2018

Regression curves for the relation between the critical buckling height Hcrit, and the diameter D of columnar support members composed exclusively of different tissues were established based on Greenhill's formula and previously reported mean values for the density‐specific stiffness and density‐specific strength of parenchyma, primary xylem, sclerenchyma, and wood. These regression curves were used to determine the extent to which the actual heights H of 249 plant species approach or transgress the Hcrit for stems relying principally upon different tissue‐types for stiffness. Based on empirically determined H and estimated Hcrit, the safety‐factor Hcrit/H (computed on the basis of E/p) against elastic instability resulting from self‐loading imposed on stems was determined for dicot and gymnosperm tree species (N = 56), mosses (N = 40), pteridophytes (N = 16), dicot herbs (N = 120), and palms (N = 17). With the exception of tree species, Hcrit/H was size‐dependent, decreasing with increasing D. This was a consequence of the scaling exponents (i.e., the slopes of the regression curves) for tree Hcrit, vs. D and H vs. D which were nearly identical, whereas the scaling exponents for H vs. D for “nonwoody” species were in excess of those for Hcrit, vs. D. With the exception of a few very tall specimens of palm species, however, the majority of nonwoody and woody species did not exceed their estimated Hcrit. The upper size‐range obtained by the procession of taller plant grades and clades was bounded by the regression curves of Hcrit, vs. D established for progressively stiffer plant tissues: parenchyma Å primary xylem Å sclerenchyma Å wood. This appears to be a consequence of the incorporation of progressively stiffer tissues within the stems of taller nonwoody species and the adjustment in the girth of stems, which developmentally occurs for trees.
The determination of pea leaves, leaflets, and tendrils
Authors: Gould Kevin S. , Cutter Elizabeth G. , Young J. Peter W.
Published: January 2018

Pea leaf determination was examined by culturing excised leaf, leaflet, and tendril primordia of different ages on a nutrient medium. Pinna primordia were designated as 1) determined, if they grew normally in culture; 2) undetermined, if they grew into differentiated structures that were morphologically and anatomically different from either leaflet or tendril; or 3) partially determined, if the two pinnae of an opposite pair developed unequally in isolation, or for leaflet pinnae only, if laminae were initiated but did not develop completely. The compound pea leaf as a whole is determined over four plastochrons of development. Proximal pinnae are determined during the second leaf plastochron, approximately 0.8 plastochron after their initiation. The second most proximal pair of pinnae is determined during the third plastochron, and the terminal portion of the rachis is determined last, during the fourth plastochron. Determination of leaflet dorsiventrality is gradual, requiring a critical minimum period with the leaf in physiological contact with the shoot system. The rachis primordium, when isolated from the shoot, does not affect determination of its pinnae as leaflets or tendrils. Afila and tendril‐less homeotic mutations do not alter the timing of pinna determination.
Ovular development and morphology of the outer integument of Magnolia grandiflora (Magnoliaceae)
Authors: Umeda Azusa , Imaichi Ryoko , Kato Masahiro
Published: January 2018

Ovular development of Magnolia grandiflora was examined to determine the morphology of the outer integument. At the time the ovular primordium begins incurving, the outer integument is initiated subdermally, and later the inner integument arises from the dermal layer. Whereas the inner integument is annular, the outer integument is formed as a semiannular rim interrupted on the concave side of the funiculus. Later the outer integument becomes a hood‐shaped envelope. The obturator is formed as a transversely elongate outgrowth on the concave side of the funiculus and intervenes in the gap of the outer integument. During further development the inner integument produces several distal lobes, and the outer integument becomes bilobed. The exostome is a transverse slit with a middle notch, formed by the outer integument and the obturator. Presumed wide occurrence of the hood‐shaped outer integument in primitive families suggests that it is a primitive state. The outer integument is compared with the ovuliferous sporophylls of the glossopterid and caytonialean seed ferns.
Potential for seed bank formation in seven Great Lakes sand dune species
Authors: Zhang Jianhua , Maun M. Anwar
Published: January 2018

Seeds of seven dune species were collected from sand dunes of Lakes Erie and Huron and buried to various depths in a natural sand dune habitat along Lake Huron. The seed samples were then retrieved after varying lengths of time and examined for their germinability and dormancy. Results showed that buried seeds remained viable for at least 2.5 years and had the potential to form a persistent seed bank. Seed banks were larger and longer lasting at greater depths of burial than those at shallow burial depths. The results suggested that failure to verify the existence of effective seed banks in previous studies may be due to insufficient number of samples, shallow sample depth, local population variations, and fruiting events. Several species also possessed a temporary, aboveground seed reserve formed by retention of a small proportion of viable seeds on the previous year's inflorescences. In some species, seeds retained aboveground were dormant and thus capable of forming a persistent seed bank when they entered the soil.
Plastic allometry in young sugar maple (Acer saccharum): adaptive responses to light availability
Authors: Bonser Stephen P. , Aarssen Lonnie W.
Published: January 2018

Age, height, number of shoot endings, neighbor density, and overhead cover from local neighbors were recorded for over 1, 400 young sugar maple trees under 200 cm tall and growing in open vs. closed (shaded) habitats from two sites. Up to about age 5 yr, seedlings increase in height but rarely branch. Once branching starts, there begins a general decrease with age in the number of centimeters of height added for every new shoot ending that is produced. The pattern of this allometric relationship, however, is plastic—in the closed habitats, this switch to increased branching relative to height growth is delayed compared with trees from the open habitats. Within the closed habitats, branching is also delayed for trees having dense cover from local neighboring understory vegetation compared with trees that are not overtopped by understory vegetation. The oldest and tallest unbranched seedlings were recorded from the closed habitats. Seedlings displaying the first branch, however, were younger in the open habitats than in the closed habitats, and at one site they were shorter in the open habitat than in the closed habitat. These results suggest that the allometric relationship between height and degree of branching can display adaptive plasticity depending on light availability: As competition for light decreases (with greater light availability), there is an increasing premium on lateral growth (branching) to maximize light interception. Conversely, as competition for light increases (under decreasing light availability), there is an increasing premium on vertical growth (through strong and persistent apical dominance) to minimize the chances of being overtopped by neighbors.
The secotioid form of Lentinus tigrinus: genetics and development of a fungal morphological innovation
Authors: Hibbett David S. , Tsuneda Akihiko , Murakami Shigeyuki
Published: January 2018

Secotioid fungi resemble gasteromycetes, but are presumably closely related to agaricoid fungi. Lentinus tigrinus is a wood‐decaying mushroom that has both a secotioid and an agaricoid form. We examined ontogeny and heritability of the secotioid phenotype in L. tigrinus with a combination of formal genetic crosses, scanning electron microscopy, and macroscopic observation of cultured sporocarps. For F1 analysis, we crossed single‐spore isolates (SSIs) representing four mating types derived from a secotioid dikaryon and four mating types from an agaricoid dikaryon. All F1 sporocarps had typical agaricoid morphology. For F2 analysis, 200 SSIs from one F1 sporocarp and 100 SSIs from another F1 sporocarp were backcrossed to tester SSIs from sporocarps produced by the parental secotioid dikaryon. Ratios of secotioid to agaricoid dikaryons thus produced were 47:49 and 84:109, which confirms previous reports that the secotioid phenotype is conferred by a recessive allele at a single locus (χ2 = 0.0417, P > 0.05, χ2 = 3.2383, P > 0.05, respectively). Early ontogeny of the secotioid form is indistinguishable from that of the agaricoid form. Later, the hymenophore is obscured by a weft of hyphae that proliferates from the margins of the developing lamellae. Longevity of the sporocarps and rate and duration of sporocarp growth are approximately equal in the secotioid and agaricoid forms. Developmental evolution of the secotioid form is interpreted as an example of von Baerian differentiation, rather than paedomorphosis, which has been implicated in evolution of other secotioid taxa.
The role of Hydropteris pinnata gen. et sp. nov. in reconstructing the cladistics of heterosporous ferns
Authors: Rothwell Gar W. , Stockey Ruth A.
Published: January 2018

Large segments of intact plants that represent a heterosporous fern have been discovered within an aquatic plant community from the Late Cretaceous St. Mary River Formation near Cardston in southern Alberta, Canada. Branching rhizomes of Hydropteris pinnata gen. et sp. nov. are 1–2 mm wide. They produce fronds at intervals of 2–12 mm and bear numerous elongated roots. Fronds, up to approximately 6 cm long, are pinnate with subopposite to alternate pinnae that exhibit anastomosing venation. Large, multisoral sporocarps occur at the junctures of the rhizome and frond rachides. Both microsporangiate massulae and megaspore complexes occur within each sporocarp. Megaspore complexes are assignable to the sporae dispersae genus Parazolla Hall. Microspores are trilete, smooth‐walled, and are embedded in episporal material of the massulae. A numerical cladistic analysis indicates that the heterosporous aquatic ferns are monophyletic, and not as closely related to either schizaeaceous or hymenophyllaceous ferns as they are to some other filicaleans. Systematic revisions are proposed to reflect newly recognized cladistic relationships within the heterosporous clade, and character originations in the evolution of heterosporous aquatic ferns are evaluated. Hydropteridaceae fam. nov. is proposed, and included with Salviniaceae and Azollaceae in the Hydropteridineae subord. nov., and the Hydropteridales Willdenow.
Effects of ovular secretions on pollen in Pseudotsuga menziesii (Pinaceae)
Authors: Takaso Tokushiro , Owens John N.
Published: January 2018

Effects of ovular secretions on pollen grains were examined in Pseudotsuga menziesii. The exine is cast off in the micropylar canal. A membranelike structure covers parts of pollen grains and appears to protect them. The outer intine consists of fibrous materials, but it also shows a thicker filamentous appearance in some ovules during pollen elongation. The inner intine is electron‐dense. Its fibrous nature is occasionally visible. Dissolution of the outer intine varies in amount and manner in ovules from different trees. The plasma membrane near the pollen wall alternatively appears normal and distorted. These different morphologies of the outer intine and of the plasma membrane are considered to result from secretions from the ovule. The outer intine may contain electron‐dense globules that are formed in the tube cell and traverse the inner intine. Pollen tube formation appears to be triggered by a secretion from the ovule. Cross‐pollinated grains are less distorted compared with self‐pollinated grains.
Life history variation in blue flax (Linum perenne: Linaceae): seed germination phenology
Authors: Meyer Susan E. , Kitchen Stanley G.
Published: January 2018

Linum perenne L. is a nonclonal perennial herb widely distributed across a range of habitats. Variation in seed germination patterns was examined for 21 Intermountain collections and for the commercial cultivar ‘Appar’. Collections from sites with long, snowy winters were largely dormant at harvest and responded positively to chilling. Collections from middle elevation sagebrush‐grassland sites were generally nondormant and contained a fraction induced into secondary dormancy by chilling. Collections from palouse prairie and pinyon‐juniper sites were generally nondormant and unaffected by chilling, as was ‘Appar’. When seeds of contrasting populations were planted in seed retrieval experiments at low, middle, and high elevation sites, their field germination phenology was predictable from laboratory experiments. In common garden experiments, there were significant among‐sibship differences in germination for each garden‐grown wild accession but not for ‘Appar’, suggesting that differences both among and within populations may be genetically based. Garden‐grown seeds were generally less dormant than wild‐collected seeds, possibly because of selection during propagation. Results demonstrated the existence of ecologically relevant among‐population and within‐population variation in germination phenology for blue flax. Seeds of high‐montane populations are spring‐emerging and have little provision for between‐year carryover. Populations from lower elevation habitats with less predictable weather have seeds with contrasting germination patterns, allowing for emergence in both fall and spring as well as for seed bank carryover. ‘Appar’ seeds lack these predictive and carryover mechanisms.
Pollinator response to male floral display size in two Sagittaria (Alismataceae) species
Authors: Muenchow Gayle , Delesalle Veronique
Published: January 2018

One hypothesis for the evolution of maleness in plants postulates the following: male plants appear that have re‐allocated resources from female parts into a larger number of male flowers, creating a larger floral display. Pollinators respond “dramatically” to the increased display, driving the spread of males in the population (Bawa, K. S., 1980, Annual Review of Ecology and Systematics 11:15–40). To test this, we measured the total number of flowers and the size of male displays in dioecious Sagittaria latifolia and monoecious S. australis. We also measured how fast visitors arrived at “target” flowers in the displays. Then we used the Cox Model, a failure time analysis procedure, to analyze the relationship between visitor arrival and display size. We found that male display sizes were somewhat larger in the dioecious than the monoecious plants, but this was due to more compressed blooming rather than to a larger total number of flowers. The visitors to both plants were similar arrays of generalist bees. Visitors did not show the predicted “dramatic” response, however, but rather a plateauing response to larger display sizes, so our results do not support the hypothesis. Reviewing the literature, we found no reports of the “dramatic” response the hypothesis asserts. Instead, relative insensitivity to display size is the rule.
Puzzle box, a tobacco line with flowers that mix floral and inflorescence characteristics
Authors: Trull Melanie C. , Malmberg Russell L.
Published: January 2018

We characterized the development of a tobacco morphological mutant, puzzle box, previously obtained by selection for resistance to an inhibitor of an enzyme in the polyamine biosynthetic pathway. Puzzle box plants are shorter than wild type with smaller leaves and an irregular leaf plastochron. The diameter and shape of the puzzle box shoot apex are similar to wild type. In puzzle box plants, the terminal flower develops but not the cymose inflorescence. This flower has a variable phenotype with more than five sepals, five petals, and five stamens. The organs in the fourth whorl are produced by carpellike primordia and contain tissue biochemically similar to wild type transmitting tissue. These organs form a cylinder within which additional floral organs are produced. Some cultures of puzzle box buds and excised cylinders produce additional floral organs. The inflorescence and floral programs may be expressed together in puzzle box.
Palisade mesophyll cell expansion during leaf development in Zinnia elegans (Asteraceae)
Authors: Knight Benjamin W. , Roberts Alison W.
Published: January 2018

Temporal and spatial patterns of palisade mesophyll cell expansion in Zinnia elegans were characterized as a basis for developing a suspension culture model for mesophyll cell expansion. Our objectives were to 1) identify the leaf regions from which cells in various stages of expansion could be selectively isolated for culture, and 2) develop a basis for comparison of rate and extent of mesophyll cell expansion in culture with that in the leaf. Palisade mesophyll cells were isolated from expanding leaves by gentle physical maceration without the use of enzymes. Isolated cells from leaves in different stages of expansion were then measured by computer image analysis. Analysis of size frequency distributions showed that unexpanded cells can be isolated from the entire blade of small leaves or the basal regions of partially expanded leaves. Fully expanded cells can be obtained from the apical and middle regions of partially expanded leaves. Within the leaf, Zinnia mesophyll cells expanded from about 400 μm2 to about 2.300 μm2 at an estimated rate of 160 μm2 d‐1. The percent increase in cell length exceeded the percent increase in cell width. Expansion of mesophyll cells continued for 6–8 d after epidermal expansion ceased. This difference in the timing of cell expansion in epidermal and mesophyll cells indicates that different regulatory factors may be operating in these adjacent tissues and underscores the importance of investigating the regulation of mesophyll cell expansion at the cellular level.
Effects of Petunia cytoplasmic male sterile (CMS) cytoplasm on the development of sterile and fertility‐restored P.parodii anthers
Authors: Conley Catharine A. , Parthasarathy Mandayam V. , Hanson Maureen R.
Published: January 2018

The developmental defects causing cytoplasmic male sterility in Petunia parodii are described in isonuclear fertile, sterile, and fertility‐restored plants using both light‐ and scanning electron microscopy. The aberrant development of the sporogenous tissue and tapetal layer caused by the cytoplasmic male sterile cytoplasm in both Petunia hybrida and P. parodii nuclear backgrounds is similar in onset and progression. The degeneration of the sporogenous tissue and tapetal layer of sterile anthers is first apparent late in meiosis and results in highly abnormal sterile sporogenous tissue by tetrad stage of fertile anthers. The stomium and endothecium do not show major developmental differences between fertile and sterile anthers, but the inner connective tissue of sterile anthers contained calcium crystals not found at high abundance in fertile anthers. Ovoid bodies containing magnesium and phosphorus were seen only in the vascular bundles of fertile anthers. Material prepared for the scanning electron microscope by freeze drying showed better retention of fragile morphological features, while critical‐point drying permitted examination of nonvolatile structures, such as cell walls.
Evolution of microsporangium numbers in Microseris (Asteraceae: Lactuceae)
Authors: Battjes Johannes , Chambers Kenton L. , Bachmann Konrad
Published: January 2018

The genus Microseris contains species with disporangiate stamens and species with tetrasporangiate stamens. We determined the number of microsporangia per stamen in serial sections of heads from all 13 species of Microseris, its close relative Uropappus lindleyi, and the two allopolyploid species of Slebbinsoseris. Four Microseris species, three diploid and one tetraploid, have two microsporangia per stamen; all other species investigated have four. The most parsimonious assumption is that the disporangiate condition is derived and arose once in the evolution of Microseris. The inheritance of the number of microsporangia per stamen in crosses between M. bigelovii (disporangiate) and M. douglasii (tetrasporangiate) was determined. Segregation of microsporangium number per stamen in F2s derived from these crosses is quantitative rather than Mendelian. The average number of microsporangia per stamen in the F2 plants ranges from 2.0 to 4.0. There is a predominance of tetrasporangiate stamens in the F1 and in most F2 plants. The observed pattern of inheritance suggests a major gene with dominance and quantitative modifiers.
Permineralized seed fern cupules from the Triassic of Antarctica: implications for cupule and carpel evolution
Authors: Taylor Thomas N. , Fueyo Georgina M. Del , Taylor Edith L.
Published: January 2018

In this paper we describe the first anatomically preserved Mesozoic seed fern cupule–Petriellaea. The multiovulate cupules were produced singly at the end of a short dichotomizing axis. Cupules are bilateral with a dorsal groove and transverse narrow ventral opening. The vascular system of the cupule consists of a series of traces that extend up the dorsal surface of the cupule and down the ventral face. Ovules are orthotropus, sessile, and borne on the adaxial surface of the leaflike cupule either singly or in multiple rows. They are up to 1.5 mm long, triangular in transverse section, and characterized by a multilayered integument. Nucellus and integument are fused throughout their length, but no pollen chamber is present. In the chalaza is a small vascular disc of transfusion tracheids that represents the extent of the ovule vascular system. Ovules are interpreted as being fossilized at a prepollination stage, although a few possess some evidence of a cellularized megagametophyte. These permineralized cupules indicate that in at least one Mesozoic seed fern group, ovule enclosure resulted from the transverse folding (tip to petiole) of a megasporophyll bearing adaxial ovules. Cupule morphology and ovule enclosure in other Late Paleozoic and Mesozoic seed ferns is discussed.
Early Devonian fungi: a blastocladalean fungus with sexual reproduction
Authors: Remy Winfried , Taylor Thomas N. , Hass Hagen
Published: January 2018

In this paper we describe a fossil fungus–Paleoblastocladia milleri gen. et sp. nov.–from the 400 million‐year‐old Early Devonian Rhynie chert that shares numerous features with modern zoosporic fungi placed in the order Blastocladiales. The fungus occurs in tufts that arise from stomata or between the cuticle and epidermis of Aglaophyton major axes. Thallus development begins from an irregular bipolar basal cell that produces a system of intramatrical rhizoids and clavate‐shaped extramatrical, nonseptate hyphae. These hyphae develop into two types of mature thalli. Sporothalli are characterized by several orders of dichotomous branching and the production of terminal, globose zoosporangia, as well as thick‐walled, pitted resting sporangia. On separate dichotomously branched thalli (gametothalli) are terminal chains of two or three gametangia, in which the terminal one is slightly larger. Despite the fact that all of the reproductive organs contain either zoospores or gametes, none show evidence of discharge papillae. The fossil fungus is compared with extant members of the Blastocladiales, and the presence of sexual reproduction is discussed.
Adaptation to metal‐contaminated soils in populations of the moss, Ceratodon purpureus: vegetative growth and reproductive expression
Authors: Jules Erik S. , Shaw A. Jonathan
Published: January 2018

Many observations suggest that morphological evolution occurs slowly in bryophytes, and this has been suggested to reflect low genetic diversity within species. Isozyme studies, however, stand in apparent contrast and have shown that bryophytes can contain high levels of genetic variability within and among populations. In light of this conflict, we tested the potential of the moss, Ceratodon purpureus, to undergo adaptive change (i.e., ecotypic differentiation) in response to soils that have been contaminated with high levels of metals for 90 years by measuring gametophytic growth and reproductive expression under experimental conditions. Variation in protonemal growth in sterile culture indicates that plants from one population growing on contaminated soil near a smelter are significantly more tolerant of zinc, cadmium, and lead than plants from uncontaminated sites. Results from a common garden experiment, in which plants were grown on soil from the smelter site, indicate that plants from near the smelter are significantly more tolerant of contaminated soils than plants from uncontaminated sites for vegetative growth. The same experiment suggests that plants from the smelter site are also more tolerant in terms of gametangial production (although we could not test this statistically). Our results demonstrate that C. purpureus has been able to undergo relatively rapid evolution in response to strong selective pressures.