bluuebunny/crossref_metadata_2025 huggingface dataset:
REPRODUCTIVE OUTPUT AND BIOMASS ALLOCATION IN SESBANIA EMERUS IN A TROPICAL SWAMP
Authors: Augspurger Carol K. , Geber Monica A. , Evans Jonathan P.
Published: January 2018

This study examined the correlation of moisture, reproductive phenology, density of mature plants, and herbivory of apical meristems with the morphology and reproductive output of Sesbania emerus, an annual legume growing along a moisture gradient in a swamp in Guanacaste Province, Costa Rica. It also determined how biomass allocation varied and how it was related to reproductive output of plants growing along the moisture gradient within the swamp. Morphological changes included production of more stems and branches in response to herbivory, more and higher prop roots and more aerenchyma as water depth increased, and greater stem diameter in lower densities. Plant height varied greatly within a site, but not among habitats. Plants began to produce flowers and fruits later in wet sites than in dry sites. Reproductive output was generally more sensitive to environmental variables than was plant size. Fruit number and plant height were positively correlated for almost every treatment. Greater fruit and seed production were correlated with drier sites, earlier phenology, and lower density, but not with herbivory. Total biomass accumulation did not vary among moisture sites, but root production appeared to occur at the expense of reproductive output in the wetter sites. Plants in the wetter sites had both a greater percent and a greater absolute amount of biomass in roots, and a lower percent and a lower absolute amount of biomass in fruits and seeds than plants in drier sites. The root: shoot ratio was nearly five times higher in the wet than the dry site. Seed number per plant ranged from a mean of 6,800 at the wet site to a mean of 16,878 at the dry site. If this striking phenotypic variation in reproductive output and biomass accumulation has a genetic basis, the possibility of ecotypic differentiation exists in S. emerus.
VASCULAR CAMBIUM AND WOOD DEVELOPMENT IN CARBONIFEROUS PLANTS. I. LEPIDODENDRALES
Authors: Cichan Michael A.
Published: January 2018

Patterns of activity in the vascular cambium of Carboniferous arborescent lycopods (Paralycopodites and Stigmaria) were studied by analysis of serial tangential sections of the secondary xylem. The analysis assumes that cell patterns in the wood accurately reflect those of the corresponding cambium. An evaluation using indirect evidence indicates that the assumption is valid as far as can be determined from comparison with living plants. The tracheids of the secondary xylem enlarge in a centrifugal pattern, suggesting a progressive enlargement of the fusiform initials. There is no evidence of periodic anticlinal division of these initials, and it is proposed that the increase in cambial circumference was accommodated primarily by an increase in fusiform initial size. In some axes with abundant secondary xylem there is evidence that isolated initials or groups of initials sporadically subdivided to form numerous, spindle‐shaped meristematic cells. Some of these cells subsequently developed into typical cambial initials. Tissues presumably formed during the cessation of cambial growth in Lepidodendron and Stigmaria are described; the structure of the tissues is suggestive of a postmeristematic parenchymatous sheath. It is concluded that cambial activity in these arborescent cryptogams was clearly different from that of modern seed plants, further attesting to the distinctive nature of this ancient group.
ALLOZYME VARIATION WITHIN AND BETWEEN LASTHENIA MINOR AND ITS DERIVATIVE SPECIES, L. MARITIMA (ASTERACEAE)
Authors: Crawford Daniel J. , Ornduff Robert , Vasey MichaelC.
Published: January 2018

Enzyme electrophoresis was employed to examine genetic variation at 20 loci in 16 populations of Lasthenia minor and 18 populations of its presumed derivative species L. maritima. The purposes of the study were to ascertain levels of genetic variation in each species, to assess how the variation at enzyme‐coding genes is apportioned within and among populations of each species, and to determine the level of divergence between the two species. The two species are both diploid annuals, similar morphologically, and produce fertile F1 hybrids when crossed. Lasthenia minor is self‐incompatible and restricted to mainland California, whereas L. maritima is self‐compatible and probably largely autogamous; it occurs on seabird rocks from central California to British Columbia. Mean genetic identities for pair‐wise comparisons of populations of the two species are similar to values for populations of the same species, indicating they have not diverged at the 20 genes coding for soluble enzymes. Despite its more extensive geographical range, L. maritima exhibits only 50% of the genetic diversity of L. minor. The latter species apportions a greater amount of its diversity within populations, whereas the former harbors more diversity among populations than within them. This is probably a reflection of the different breeding systems of the two species. Six unique alleles were detected in L. minor, whereas only one novel allele was found in a single individual of L. maritima. The electrophoretic data are concordant with the suggestion that L. maritima is relatively recently derived from L. minor. The switch from outcrossing to selfing and selection of genotypes adapted to the chemically and physically unusual substrate on the seabird rocks are considered the critical steps in the evolution of L. maritima.
LOSS AND UPTAKE OF15N‐AMMONIUM IN SUBMERGED SOILS OF A CATTAIL MARSH
Authors: Dean John V. , Biesboer David D.
Published: January 2018

The uptake, distribution, and recovery of nitrogen by field populations of T. latifolia L. (cattails) were determined using (15NH4)2SO4. The results show that 75.3% (53.6% in the plant and 21.7% in the soil) of the isotopically labeled nitrogen added to sampling cylinders containing a single cattail plant could be recovered at the end of one growing season, whereas only 34.6% could be recovered from control cylinders. The increased recovery of 15NH4+‐nitrogen in cylinders containing actively growing T. latifolia compared to cylinders not containing plants suggests that T. latifolia rapidly assimilates labeled nitrogen before it is lost via denitrification or uptake by free‐living soil microorganisms.

Measurements of redox potentials in a 60‐cm‐deep field core planted or not planted with T. latifolia showed that only the top 2 and 5 cm of the water column was oxidized (greater than 200 mv at pH 7), respectively. The remaining 58 and 55 cm of the column, including the soil‐water interface, was reduced (less than 200 mv at pH 7). The presence or absence of actively growing T. latifolia plants in the soil cores did not appear to alter significantly the redox profile. The presence of an oxidized zone overlying a reduced zone in cores collected from the field indicates that a portion of the 15NH4+‐nitrogen added to cylinders during the field experiment may have been lost through nitrification‐denitrification reactions.
STUDIES ON THE LEAF OF POPULUS DELTOIDES (SALICACEAE): ULTRASTRUCTURE, PLASMODESMATAL FREQUENCY, AND SOLUTE CONCENTRATIONS
Authors: Russin William A. , Evert Ray F.
Published: January 2018

The minor veins and contiguous tissues of mature leaves of Populus deltoides Bartr. ex Marsh. were examined with the electron microscope to determine the ultrastructural characteristics of the component cells and to determine the structure, distribution, and frequency of plasmodesmata between the various cell types. In addition, plasmolytic studies were carried out to determine the solute concentrations of the various cell types of the minor veins and contiguous tissues. The cells comprising the mesophyll and bundle sheath contain all the components typical of photosynthetic cells. Paraveinal mesophyll cells and bundle‐sheath cells have fewer microbodies and smaller chloroplasts than do palisade parenchyma cells. Vascular parenchyma and companion cells tend to intergrade with one another structurally but can be distinguished from one another by their characteristic plastids. The mature, enucleate sieve‐tube member is lined by a parietal layer of cytoplasm consisting of plasmalemma, endoplasmic reticulum, mitochondria, plastids, and P‐protein. Plasmodesmata occur along all possible routes from the palisade parenchyma cells to the sieve tubes of the minor veins, and their frequency increases with increasing proximity to the sieve‐tube members. Plasmolytic studies revealed that the paraveinal mesophyll cells had a higher C50 (estimated mannitol concentration plasmolyzing, on the average, 50% of a given cell type) than any other cell type of the leaf. Concentration gradients existed along the palisade cell/bundle‐sheath cell/companion cell (or vascular parenchyma cell) route as well as along the paraveinal mesophyll cell/bundle‐sheath cell/companion cell (or vascular parenchyma cell) route. Considering the frequency of plasmodesmata along these routes, it is conceivable that photosynthate diffuses from palisade cells to the companion cells along concentration gradients. Within the minor veins, the C50 was higher for sieve‐tube members than for either companion cells or vascular parenchyma cells, indicating that loading of the sieve tubes is an active, energy‐dependent process.
POLLEN EXINE SUBSTRUCTURE. I. LILIUM LONGIFLORUM
Authors: Southworth Darlene
Published: January 2018

Acetolyzed exines ofLilium longiflorumpartially extracted with hot 2‐aminoethanol decrease in size and change from a homogeneous substructure to one with discrete interconnected granules. At first, the granules are arranged in irregular pentagons. As attachments between them are broken, compound polygons result, and with further extraction, the polygons become open at the surface. Granules are angular or ellipsoidal with a diameter of 10 nm or with major and minor axes of 7 and 15 nm. Higher order patterns include clumps of densely packed granules and ladderlike arrangements of adjacent polygons. The size and arrangement of granules and polygons is similar to the structures observed in developing exines of numerous genera.
MORPHOLOGICAL, ANATOMICAL, AND MOLECULAR CONSEQUENCES OF GROWTH AND DEVELOPMENT AT LOW TEMPERATURE IN SECALE CEREALE
Authors: Puma L. CV. , Huner N. P. A.
Published: January 2018

Growth of winter cereals at low, nonfreezing temperatures is essential for the establishment of a cold‐hardy state and subsequent survival of the overwintering plant. In this paper, I describe the consequences of growth and development of Secale cereale L. cv. Puma at cold‐hardening temperatures with respect to leaf morphology, anatomy, and biochemistry, and with particular emphasis on their relationship to photosynthetic acclimation. Low temperature‐induced structural and functional alterations at the level of ribulose bisphosphate carboxylase‐oxygenase and the chloroplast thylakoid membrane are described and related to overall photosynthetic efficiency and capacity for CO2 utilization. Growth and development at cold‐hardening temperatures appear to result in changes in protein conformation and membrane organization, but not in basic composition. It is proposed that developmental temperature imparts a significant effect on the assembly of these multimeric, photosynthetic components, which leads to distinct structural and functional changes.
RATE OF INDUCED CELLULAR DEDIFFERENTIATION IN CATHARANTHUS ROSEUS
Authors: Verbeke Judith A. , Walker Dan B.
Published: January 2018

During floral ontogeny in Catharanlhus roseus, approximately 400 epidermal cells are induced to rapidly dedifferentiate during postgenital fusion, an unequivocal case of intercellular communication between somatic plant cells. Some fusing cells completely dedifferentiate within 4.3 hr of cell contact, and by 8.9 hr virtually all the cells undergo the dramatic change in cell shape and cytological features. To our knowledge, this is the fastest case of induced cell differentiation reported to date in any eukaryotic system.
ACTIN NETWORK AS A NORMAL COMPONENT OF THE CYTOSKELETON IN MANY VASCULAR PLANT CELLS
Authors: Parthasarathy M. V. , Perdue Tony D. , Witztum Allan , Alvernaz Jennie
Published: January 2018

F‐actin was localized in cells of 17 species of vascular plants, using the F‐actin‐specific probe Rhodamine‐phalloidin. F‐actin strands formed a three‐dimensional network in these cells, and orientation of the strands varied to some extent depending on the cell shape. The strands often appeared to terminate near or at the plasma membrane. The observations presented, taken together with those from relevant literature, suggest that actin is a normal component of most, if not all, plant cells.
INCOMPLETE CYTOKINESIS IN FUNARIA STOMATA
Authors: Sack Fred D. , Paolillo D. J.
Published: January 2018

The development of the one‐celled condition in Funaria (Musci) stomata was investigated using light and electron microscopy. The guard cell parent cell is unusual in that it undergoes karyokinesis but incomplete cytokinesis. The septal wall, and the cell plate from which it forms, have incurved edges in contact with the polar cytoplasm. No evidence was found to support Haberlandt's claim that the stomate is initially two celled but undergoes wall resorption. Preprophase microtubule bands appear to be present in nonstomatal epidermal cells with normal cytokinesis, but the possibility is raised that they are absent in guard cell parent cells.
EVOLUTIONARY TRENDS IN DION (ZAMIACEAE)
Authors: Sabato Sergio , De Luca Paolo
Published: January 2018

Distribution, ecology, and morphology of the species of Dion are presented. The genus Dion is distributed in Mexico and in Honduras, where it is generally scattered and restricted to rocky, steep habitats.

On the basis mainly of the morphology of the seeds, of the seedlings, and of the female cones, three natural groups were recognized. The first group, which is the most distinct morphologically, is made up of D. mejiae endemic to Honduras. The second group is made up of D. spinulosum and D. rzedowskii, whose distribution is restricted to a very small area in Mexico. They appear to be the only Dion spp. to be adapted to moist and shaded habitats. The third group is made up of the remaining spp. of Dion, all Mexican in distribution. They appear to be well adapted to open and dry habitats generally. Stems, female cones, and seeds show the trends to decreasing size from south to north in this group.

A key of the genus is given.
CHANGES IN THE ULTRASTRUCTURE OF XYLEM PARENCHYMA CELLS OF PEACH (PRUNUS PERSICA) AND RED OAK (QUERCUS RUBRA) IN RESPONSE TO A FREEZING STRESS
Authors: Wisniewski Michael E. , Ashworth Edward N.
Published: January 2018

An ultrastructural investigation was conducted of xylem parenchyma cells of peach (Prunus persica [L.] Batsch.) cv. Harbrite and red oak (Quercus rubra L.) in response to a freezing stress. Freezing curves of xylem tissues, as determined by differential thermal analysis, were used to predict temperatures at which both living and dead cells would be observed. Tissues were exposed to low temperatures (‐15 to ‐35 C) and fixed in a frozen state at ‐10C and at thawing. Current models of the freezing behavior of supercooled plant cells suggest that xylem parenchyma cells behave as individual water droplets. This implies that cells are unresponsive to the presence of low temperature and extracellular ice until internal nucleation triggers lethal, intracellular freezing. For these reasons, deep supercooling has been described as an avoidance mechanism. Results of this study confirmed earlier reports that xylem parenchyma cells freeze as individuals or in small groups. Individual cells, however, did not exhibit a neutral response. Instead, a range of responses was observed that included internal and external vesiculation, deep invaginations of the plasma membrane, and the formation of electron‐dense deposits external to the plasmalemma. In general, our observations suggested that the cells responded to a dehydrative stress. Results are discussed in context of the biophysical data associated with deep supercooling phenomena and compared to responses of cells that exhibit extracellular freezing.
STOMATAL STRUCTURE OF ALETHOPTERIS SULLIVANTII AND NEUROPTERIS SCHEUCHZERI, PENNSYLVANIAN PTERIDOSPERM FOLIAGE
Authors: Reihman M. A. , Schabilion J. T.
Published: January 2018

The stomatal apparati of the pteridosperm foliage taxa Alethopteris sullivantii (Lesquereux) Schimper and Neuropteris scheuchzeri (Hoffman) forma decipiens (Lesquereux) Gastaldo were examined from Middle Pennsylvanian coal balls collected from central Iowa. Standard light optics, Nomarski, and SEM were utilized to study cellulose acetate peels and macerated cuticle material. The stomatal apparati of both taxa are actinocytic‐haplocheilic and are similar to those found in various modern cycads and conifers. The previous report by Stidd and Stidd of paracytic‐syndetocheilic stomata in A. sullivantii resulted from misinterpretation of the guard cell's configuration and differentially thickened walls.
DETERMINATE BRANCH DEVELOPMENT IN ALSTONIA SCHOLARIS (APOCYNACEAE): THE PLAGIOTROPIC MODULE
Authors: Mueller Richard J.
Published: January 2018

The development of the vegetative lateral branches in Alstonia scholaris (L.) R. Br. was examined. The overall architecture conforms to Prévost's model and the branches are sympodial complexes of plagiotropic modules. Each module consists of two whorls of 6–11 foliage leaves and a whorl of four scale leaves. The apex is parenchymatized just distal to the scale leaves. Renewal branches grow from buds in the axils of the scale leaves. These large buds are initiated simultaneously with the scale leaves and “use up” a large portion of the original apex. Parenchymatization of the central region of the apex occurs after a period of lateral growth and development that separates and vascularizes the renewal branches. Branch extension occurs sympodially by substitution. More typical buds develop in the axils of the foliage leaves but grow out only in response to injury or pruning. They are smaller than the renewal buds and, unlike them, are delimited by a shell zone during early development.
ISOLATION AND PURIFICATION OF GLANDULAR SECRETORY CELLS FROM ARTEMISIA TRIDENTATA (SSP. VASEYANA) BY PERCOLL DENSITY GRADIENT CENTRIFUGATION
Authors: Slone J. Henry , Kelsey Rick G.
Published: January 2018

Glandular trichome heads (the secretory cells), obtained by mechanical homogenization of young floral buds and subtending leaves of Artemisia, were isolated and partially purified in discontinuous and continuous Percoll density gradients. With discontinuous gradients, the mixed‐cell suspension was fractionated on four layers of Percoll with increasing densities: 0, 1.048, 1.068, and 1.084 g/ml. Gland heads banded primarily at the 0/1.048 interface, mesophyll cells at the 1.068/1.084 interface, and the hairs and hair fragments pelleted at the bottom of the tube. Twenty to thirty percent of the cells in the 0/1.048 band were intact gland heads, which represented about half of those recovered from the gradient. Hairs were the major contaminant. Over 90% of the gland heads excluded Evan's blue dye and were apparently viable. Similar results were obtained from preliminary experiments using continuous density gradients. The whole procedure for either method requires 3–6 hr, depending on the amount of starting material.
INTERCELLULAR ADHESIONS IN THE POLLEN‐STIGMA SYSTEM: POLLEN CAPTURE, GRAIN BINDING, AND TUBE ATTACHMENTS
Authors: Ferrari T. E. , Best V. , More T. A. , Comstock P. , Muhammad A. , Wallace D. H.
Published: January 2018

Four independent pollen‐stigma binding forces are differentiated after pollen contacts stigmas of Brassica oleracea var. capitata. Identification is based on their different rates and sequence of appearance during gametophyte development; on their differential occurrence after compatible and incompatible pollinations; and on their different stabilities to NaOH and hexane. The first binding force develops most rapidly, begins seconds after pollen‐stigma contact, is complete within minutes, occurs on compatible or incompatible papillae, and dissociates in methanol. A second slower binding reaction begins about 15 min after contact, continues for at least 90 min (when pollen tubes emerge), results in a binding structure termed the ocreatine, develops only on compatible papillae, and is dissociated by NaOH. A third attractive mechanism binds the tip of the emerging tube to a cuticle, is detected only on incompatible papillae, and is not dissociated by NaOH or methanol. Ocreatine formation and tube development beyond the emergence stage are prevented by the incompatibility response. A fourth attraction mechanism occurs between the surfaces of papilla and elongating tubes. Reviews of physical and biochemical evidence indicate that van der Waals forces and enzymatically mediated lipid polymerization are alternatives to agglutination as mechanisms for binding male gametophyte to papilla.
VASCULAR CONNECTION BETWEEN LATERAL ROOTS AND STEM IN THE OPHIOGLOSSACEAE
Authors: Chau Robert I.
Published: January 2018

The vascular connection between lateral roots and stem in the Ophioglossaceae and in two leptosporangiate fern species was examined. Two types of connections were found: “gradual” connections, which resemble leaf traces in ontogeny and morphology, and “abrupt” connections, which resemble the connections between lateral roots and their parent roots.

Gradual root‐stem connections occur in the genera Ophioglossum and Helminthostachys and in Woodwardia virginica. They are initiated in shoot apices distal to the level where cauline xylem elements mature. They resemble leaf traces in being provascular (procambial) strands that connect the cauline stele with the future vasculature of lateral appendages. As with leaf traces, gradual connections are part of the provascular and, later, protoxylem continuity between stems and lateral appendages. Gradual connections have many features in common with leaf traces, and the term root trace is applicable to them.

The order of radial maturation of the primary xylem in gradual connections varies in different parts of the connections. It is endarch near the intersection with the cauline stele and exarch where the connections intersect root steles. Gradual connections resemble the transition regions of certain seed plants where protoxylem is also continuous from stem to root and the order of maturation is found to change continuously from stem to root.

Abrupt connections occur in Botrychium and Osmunda cinnamomea. They develop in shoot apices at levels where cauline xylem is mature or maturing. The mature xylem does not dedifferentiate, so provascular and protoxylem continuity of the kind found in root traces does not occur. Also, reorientation of the order of maturation does not occur in abrupt connections. Xylem connectors are found in the region where radially oriented elements of the connections abut the longitudinally oriented cauline elements. Abrupt connections resemble the connection of secondary roots with their parent root systems since xylem connectors and the lack of continuity are also features found in these vascular systems.

The resemblance of the vascular pattern of the fern root trace to the transition region of seed plants suggests that the radicle is more closely comparable to the cladogenous roots of pteridophytes than hitherto supposed.
THE OCCURRENCE OF WALL PAPILLAE IN ROOT EPIDERMAL CELLS OF AXENICALLY GROWN SEEDLINGS OF ZEA MAYS
Authors: Clarke K. J. , McCully M. E.
Published: January 2018

Lens‐shaped wall papillae, resembling those known to form in response to fungi or mechanical damage, occur in root epidermal cells of axenically grown seedlings of Zea mays. Papillae are most common in the tabular epidermal cells but also occur in younger cells. Not all tabular cells have papillae, and they are more frequent in some seedlings. Where present, there is usually only one papilla per cell and it lies against the outer periclinal wall just proximal to an emerged root hair or near the position where a hair would be expected to form. Electron micrographs show that a papilla is structurally heterogeneous. Papillae fluoresce strongly in the presence of aniline blue even in freeze‐substituted material.
FUNCTIONAL DIOECISM IN THE MALPIGHIACEAE: THE BREEDING SYSTEM OF SPACHEA MEMBRANACEA CUATR
Authors: Steiner Kim E.
Published: January 2018

The breeding system of Spachea membranacea (Malpighiaceae), an understory tropical rain forest tree, was studied on Barro Colorado Island in central Panama. Two types of trees were found, those with hermaphroditic flowers and those with female flowers. Crossing experiments indicated that morphological hermaphrodites normally function as males but may be induced to set fruit if emasculated prior to cross‐pollination. Thus, although morphologically gynodioecious, S. membranacea is functionally dioecious. This is the first experimental evidence for functional dioecism in the Malpighiaceae. The proportions of hermaphrodites (functional males) in the three populations examined were 44.7% (N = 47), 60.0% (N = 10), and 87.5% (N = 17). The distribution of hermaphrodites and females in size classes was quite similar, suggesting that sexual expression is not influenced by the age of the individual. Flowers are visited and presumably pollinated primarily by bees of the genera Paratetrapedia (Anthophoridae) and Trigona (Apidae).
FLORAL BIOLOGY AND REGULATION OF SEED SET AND SEED SIZE IN THE LILY, CLINTONIA BOREALIS
Authors: Galen Candace , Plowright R. C. , Thomson James D.
Published: January 2018

We studied the reproductive ecology of Clintonia borealis, a clonal understory species, in eastern Ontario. Flowers are protogynous and require insect pollination for outcrossing and maximum seed set. Most pollination is done by nectar‐gathering bumble bees. We recorded pollen deposition and flowering patterns in 1983. Flowering lasted for about 10 days in mid‐June. Stigmatic pollen loads were lowest at the onset of blooming, reflecting the scarcity of male‐phase flowers. Pollination increased significantly by peak bloom and subsequently remained high. However, since bees fly mostly between neighboring stems, much of the pollen transferred may have been geitonogamous. In 1983, seed set per flower was not increased by supplementing pollination or by reducing the number of fruits competing for resources per stem. Rather, flowers set more seeds (14%) only if both treatments were performed simultaneously. Seed size was increased by 25% when competitive fruits were removed and by 5% more when pollen was added under the removal treatment. Further work in 1984 showed that pollination effects may be related to changes in pollen source. Selfed flowers set fewer and smaller seeds than outcrossed ones when screened from insects and hand pollinated. Outcrossing distance had little effect on seed set or seed size. Thus, in C. borealis seed number and seed size are limited by a balance between maternal resource availability and the amount of outcrossing provided by pollinators.
EVOLUTIONARY AND ECOLOGICAL SIGNIFICANCE OF STARCH STORAGE IN POLLEN OF THE ARACEAE
Authors: Grayum Michael H.
Published: January 2018

Starch content was qualitatively assessed for pollen of 79 of the 111 currently recognized genera of the family Araceae—one of three monocot families known to exhibit both starchy and starchless pollen. Although 73% of the genera investigated had exclusively starchy pollen, character correlation suggests that starchless pollen is the primitive type for the family Araceae, as well as for monocots in general. Pollen starch content is a highly conservative character at the generic level in Araceae; only a single genus (Schismatoglottis) clearly exhibits both character states. The distribution of starchy pollen among aroid genera is consistent with what have here been termed Bakers' Starch Laws. Aroid pollen below a certain critical diameter—17‐25 μm—is almost invariably starchless. Larger pollen is nearly always starchy, except where insect pollinators may use pollen nutritionally. There is strong evidence that the trend from starchless to starchy pollen in Araceae is reversible, according to the constraints imposed by the aforementioned factors.
ELECTROPHORETIC STUDY OF THE ALLOPOLYPLOIDAL ORIGIN OF TALINUM TERETIFOLIUM AND THE SPECIFIC STATUS OF T. APPALACHIANUM (PORTULACACEAE)
Authors: Murdy William H. , Carter M. Eloise Brown
Published: January 2018

Electrophoretic evidence supported the hypothesis that Talinum teretifolium is an allopolyploid derivative of T. mengesii and T. parviflorum. Electrophoretic variation was examined for 384 individuals from 21 populations of four Talinum species. Plants were scored for isozymes of nine enzyme systems specified by 23 gene loci of which 4 were monomorphic and 19 polymorphic. Talinum teretifolium populations were electrophoretically uniform, and all alleles of this species were accounted for by combining alleles present in its presumed parents. Genetic identity values between T. teretifolium and each of its presumed parents (I ≥ 0.817) were higher than between any other pair of the four Talinum species examined. The electrophoretic evidence did not support an alternative hypothesis that T. calycinum is a progenitor of T. teretifolium. Electrophoretic data also showed that T. appalachianum is a disjunct population of T. parviflorum. The average genetic identity between T. appalachianum and T. parviflorum (I = 0.884) was higher than the average genetic identity for conspecific populations of both T. mengesii and T. calycinum.
REINITIATION OF VEGETATIVE GROWTH FROM ASEPTICALLY CULTURED TERMINAL FLORAL APEX OF BANANA
Authors: Cronauer Sandra S. , Krikorian A. D.
Published: January 2018

Terminal floral apices of Musa acuminata cv. Dwarf Cavendish were isolated and cultured in a modified Murashige and Skoog (1962) medium supplemented with N6‐benzylamino purine (5 mg/L) and 10% (v/v) coconut water. Under these conditions, the determinate floral buds are transformed into a multiplying vegetative shoot system. Rooted plantlets were obtained by treating shoots with the auxin, naphthaleneacetic acid (1 mg/L), and activated charcoal (0.025%). Practical benefits resulting from these observations, such as the production of virus‐free plants and the rapid multiplication of stock material, are discussed.
COLONIZATION AND ESTABLISHMENT OF MISSOURI PRAIRIE PLANTS ON ARTIFICIAL SOIL DISTURBANCES. I. DYNAMICS OF FORB AND GRAMINOID SEEDLINGS AND SHOOTS
Authors: Rapp Jody K. , Rabinowitz Deborah
Published: January 2018

We observed colonization and mortality of plants in small (26 m2) artificial soil disturbances and undisturbed controls in a tall‐grass prairie from 1977–1980. This paper examines the dynamics of colonists based on mode of origin (seedlings and shoots) and broad taxonomic affinity (forbs and graminoids). Few seedlings colonized either disturbances or controls the first year, probably due to a severe drought in 1976 when few seeds were produced. Graminoid shoots were more abundant in disturbed sites than in controls the first year, probably due to the “edge effect” of cutting roots and rhizomes and stimulating new growth. For each year following the first, the number of current residents peaked early in the season and then declined, with the decline more precipitous for seedlings than for shoots. The population fluctuations of seedlings were very predictable, and separate years resembled each other. In contrast to seedling populations, graminoid shoot populations generally were accumulating throughout the study. Populations of forb shoots rose and fell, but the years did not resemble each other. Neither seedlings nor forb shoots showed a response to the new uncolonized soil resource of the artificial disturbances compared to controls, but graminoid shoots were more common on disturbed sites. These results suggest a nonequilibrium dynamic among colonizers of small‐scale microsites.
COLONIZATION AND ESTABLISHMENT OF MISSOURI PRAIRIE PLANTS ON ARTIFICIAL SOIL DISTURBANCES. II. DETECTING SMALL‐SCALE PLANT‐TO‐PLANT INTERACTIONS AND SEPARATING DISTURBANCE FROM RESOURCE PROVISION
Authors: Rabinowitz Deborah , Rapp Jody K.
Published: January 2018

We investigated whether seedlings and shoots interacted with one another while colonizing small soil disturbances in a tall‐grass prairie in Missouri. Specifically, we tested for density dependence of longevity and whether seedlings responded to the creation of a disturbance and/or the provision of an uncolonized resource. There was little evidence of density‐dependent mortality among either seedlings or vegetative shoots. There were essentially no differences in either colonization or mortality of seedlings between disturbances with a new, competition‐free resource and disturbances without a new resource. Excluding vegetative invaders from a site by means of a polyvinylchloride pipe did not prompt a greater number of seedlings to arise or survive. These results substantiated a noninteractive portrayal of colonization. Individuals of seedlings and shoots appeared and disappeared in a fashion largely independent of one another.
SIEVE PLATE PORES AND PLASMODESMATA, THE COMMUNICATION CHANNELS OF THE SYMPLAST: ULTRASTRUCTURAL ASPECTS AND DEVELOPMENTAL RELATIONS
Authors: Esau Katherine , Thorsch Jennifer
Published: January 2018

This paper is based on the lecture entitled “Communication Channels Between Cells and Their Origin in Higher Plants” presented by K. E. on 14 May 1984 at the University of California‐Davis as part of the Department of Botany Symposium “Integrating Plant Structure and Function.” This symposium was arranged in connection with the UCD 75th Anniversary Celebration. The main theme of the paper is the developmental relation between the plasmodesmata and the sieve plate pores in the phloem conduits of several dicotyledons. New observations and a review of some pertinent data from the literature are combined.
A MICROSCOPIC TECHNIQUE TO MEASURE MESOPHYLL SUCCULENCE
Authors: Sundberg Marshall D. , Zahn Scott G.
Published: January 2018

Mesophyll succulence (Sm), the ratio of water content to chlorophyll content of a cell or tissue, has been proposed as an index of CAM potential. In plant tissues where all cells contain chloroplasts, Sm may be measured easily. If water tissue (water‐storing parenchyma lacking chloroplasts) is present, however, severe technical difficulties arise. We have developed a comparable index, morphological mesophyll succulence (Smm), which allows rapid determination of vacuole to chloroplast volumes in cells. There is a high correlation between the results obtained by these two techniques. Advantages of the microscopic technique include: more rapid determinations, fewer equipment needs, ability to be applied in the field, and no need to physically separate water tissues from photosynthetic tissues.
ELEMENTAL DISTRIBUTION IN SEEDS OF THE HALOPHYTES SALICORNIA PACIFICA VAR. UTAHENSIS AND ATRIPLEX CANESCENS
Authors: Khan M. A. , Weber D. J. , Hess W. M.
Published: January 2018

Little information is available on the distribution of ions in seeds of halophytes. Seeds of two halophytes, Salicornia pacifica var. utahensis (Tidestrom) Munz, a desert salt playa type, and Atriplex canescens (Pursh) Nutt., a desert shrub, were analyzed by energy dispersive X‐ray microanalysis. The relative ion concentration in three regions, the seed coat, endosperm, and embryo, were determined. The total relative concentration of elements was higher in seeds of S. pacifica var. utahensis as compared to A. canescens. The seed coats of S. pacifica var. utahensis contained the highest counts of sodium, chlorine, potassium, and calcium, whereas the embryo and endorsperm were both high in phosophorus. In A. canescens, sodium and chlorine were very low in all three tissues. The embryo contained the major amount of phosphorus, although potassium was high in both the seed coat and the embryo. These results support the concept of ion compartmentalization in the seeds of these two halophytes.
HEAVY METAL ACCUMULATION AND THE NATURE OF EDAPHIC ENDEMISM IN THE GENUS CALOCHORTUS (LILIACEAE)
Authors: Lee Fiedler Peggy
Published: January 2018

Bulb and leaf tissues from five species in the genus Calochortus and the soils from collection sites were analyzed for cation and trace element concentrations. All five species, only three of which are considered ultramafic endemics, possessed high concentrations of nickel and copper in both the bulbs and leaves, but not at levels high enough (> 1% dry wt) to be considered hyperaccumulators. Only moderate to trace amounts of cobalt and chromium were detected in both plant tissues. Calcium‐magnesium ratios, typically low in ultramafic soils and plants, were low in bulb tissue, but two to 10 times higher in leaf tissue.

The ability to tolerate excessively high levels of nickel and other heavy metals may be a physiological exaptation of the genus Calochortus and not necessarily an evolutionary response by several species to life on an ultramafic substrate. The nature of “serpentine” endemism is discussed in the context of heavy metal accumulation by various plant species.
EFFECTS OF CONE COLOR DIMORPHISM ON REPRODUCTIVE OUTPUT OF WHITE FIR GROWING ALONG ELEVATIONAL GRADIENTS
Authors: Farris Michael A. , Mitton Jeffry B.
Published: January 2018

White fir can produce cones that are either green or purple, and the color is genetically determined. The purpose of this study was to determine the effects of elevation and cone color on the cone and seed characters of this species. We collected cones from trees along two elevational gradients, Red Mountain Pass (1981 and 1983) and Cucharas Pass (1983). Over 600 cones were measured for length, diameter, number of viable seeds, mass of five viable seeds, and percent successful seed set. There was a strong overall effect due to elevation, although the Cucharas and Red Mtn. locations showed somewhat different effects on the reproductive characters. Seed mass decreased with elevation in all three samples. There was significant interaction between cone color and elevation for both 1983 samples, suggesting the presence of genotype‐environment interaction. A large difference was seen between the Red Mtn. and Cucharas locations, and the cone colors behaved differently at the two locations. The consistently large differences between the seed characters of green and purple cones suggested that cone color, which is presumably determined by a single gene, may profoundly affect the reproductive potential of individual trees. This appears to be an example of influential coloration in plants which is not associated with pollination or dispersal.
MALE STERILITY IN SOYBEAN (GLYCINE MAX). I. PHENOTYPIC EXPRESSION OF THE ms2 MUTANT
Authors: Graybosch Robert A. , Palmer Reid G.
Published: January 2018

The effects of a nuclear male‐sterile mutant (ms2) of soybean, Glycine max (L.) Merr., on anther development were analyzed by means of light‐ and electron‐microscopy. The structure of microspore mother cells (MMCs) in male‐sterile plants was identical to that of male‐fertile plants. Meiosis was completed, and tetrads of microspores formed. Microspores degenerated after the deposition of primexine and probacullae. The sheath of callose surrounding microspores did not dissolve. No structural abnormalities of the microspores were detected before the onset of degeneration. The tapetal and anther wall layers were characterized by aberrant development. Tapetal abnormalities included premature vacuolation, a persistent inner tangential cell wall, failure to differentiate normal concentrations of endoplasmic reticulum and dictyosomes, disruption of plastids, and premature degeneration. Malfunction of the tapetal layer preceded, and may have induced, microspore degeneration. Gross anther morphology was not influenced until advanced stages of development.
STUDIES OF PALEOZOIC FUNGI. IV. WOOD‐DECAYING FUNGI IN CALLIXYLON NEWBERRYI FROM THE UPPER DEVONIAN
Authors: Stubblefield Sara P. , Taylor Thomas N. , Beck Charles B.
Published: January 2018

An extensive fungal infection is present in silicified specimens of Callixylon newberryi (Dawson) Elkins and Wieland from the Upper Devonian of Indiana. Fungi are represented by branched, septate filaments with both terminal and intercalary chlamydospores. Clamp connections were not observed. Tracheids of the secondary xylem, decayed in varying degrees, show erosion troughs, cavities, and extensive lysis of tracheid walls. The pattern of decay is most similar to modern‐day white rots, which are typically caused by basidiomycetes, while hyphal features are characteristic of either ascomycetes or basidiomycetes. The presence of wood decay coupled with a septate mycelium suggests the presence of higher fungi in the Devonian and indicates a more diverse Devonian mycoflora than has previously been recognized.
SHOOT APICAL MERISTEMS AND MUTATION: STRATIFIED MERISTEMS AND ANGIOSPERM EVOLUTION
Authors: Klekowski Edward J. , Kazarinova‐Fukshansky Nina , Mohr Hans
Published: January 2018

Although apical meristems with a tunica‐corpus organization occur in some gymnosperms and in practically all angiosperms, the adaptive significance of such meristems is unknown. Mathematical modeling and computer simulation studies have shown that such stratified meristems promote the long‐term retention of many categories of somatic mutation (selectively advantageous, neutral, and disadvantageous). These mutations are maintained primarily as periclinal chimeras. The individual component meristems of a stratified apex have relatively small populations of apical initials. Thus, in long‐lived genets, the individual component meristems of the stratified meristems of the ramets would be expected to accumulate mutations due to the operation of Muller's Ratchet. In angiosperms the accumulation of mutants and the associated loss in reproductive capacity (sexual) is compensated for by developmental selection that promotes the loss of defective genotypes without proportionate losses in reproductive capacity.
DEMOGRAPHIC ASPECTS OF COEXISTENCE IN ENGELMANN SPRUCE AND SUBALPINE FIR
Authors: Shea Kathleen L.
Published: January 2018

The mechanisms for the maintenance of coexistence of Engelmann spruce and subalpine fir in subalpine forests of the Colorado Front Range were examined by comparing age, size, and spatial distributions of spruce and fir in two adjacent, previously logged sites of differing moisture availability. Adult tree ages were calculated from stem cores, while seedling ages were calculated from a multiple regression equation based on diameter, height, and number of branch whorls. Tree size was measured by height and diameter; spatial distributions were described by Morisita's index of dispersion.

Cumulative age and size distributions were significantly different in the two species, with greater longevity and a larger overall size in spruce than fir. Both species showed a significant linear relationship between size and age, while fir showed a faster height growth rate than spruce. The linear relationship beween age and size was much closer in seedlings than in adults. Seedling spatial distribution was highly clumped in both species, but mature trees showed little or no clumping. Because both species are mainly wind dispersed, the greater clumping in spruce than in fir seedlings suggests that spruce have more specific establishment requirements than fir. Colonization patterns indicated that spruce seedlings were primarily found in forest gaps or associated with fir canopy trees, while fir seedlings were more commonly found in the forest, associated with either spruce or fir canopy trees. Tree density, growth rates, and mortality rates were higher in the wet site, with spruce showing the largest between site differences. These data suggest a new hypothesis for coexistence stating that Engelmann spruce and subalpine fir are maintained as codominants because the greater longevity and size of spruce is balanced by the faster height growth and more flexible seedling establishment requirements of fir.
SYSTEMATIC SIGNIFICANCE OF CHROMOSOME NUMBERS IN ACMELLA (ASTERACEAE)
Authors: Jansen Robert K.
Published: January 2018

Chromosome counts are reported for 372 individuals from 202 populations in 26 taxa of Acmella (Asteraceae: Heliantheae). Chromosome numbers for 15 taxa are first reports. A review of previous counts and the new reports supports a basic chromosome number of 13 for the genus. The results show that polyploidy, sometimes accompanied by hybridization and asexual reproduction, is widespread in Acmella and has contributed to the taxonomic difficulties in the genus. These factors have produced a variable polyploid pillar complex in sect. Acmella. In one taxon in this complex, A. oppositifolia var. oppositifolia, intrataxon and even intrapopulational chromosomal variation has been detected. Morphological studies in conjunction with observations of meiotic pairing suggest that most polyploids are alloploid in origin. The occurrence of polyploidy in 16 of the 27 taxa known chromosomally emphasizes the important role this process has had in speciation within Acmella. Although intrataxon chromosomal variation has limited the taxonomic utility of chromosome numbers, a few examples are presented in which these data have been valuable for separating some pairs of closely related taxa (A. decumbens var. affinis from var. decumbens and A. poliolepidica from A. oppositifolia).
ULTRASTRUCTURE OF PARKIA POLYADS (MIMOSOIDEAE: LEGUMINOSAE)
Authors: Feuer Sylvia , Niezgoda Christine J. , Nevling Lorin I.
Published: January 2018

Pollen of 16 species of Parkia (ca. 30 spp.) was examined in the light, scanning and transmission electron microscopes (LM, SEM and TEM). Pollen is shed as large (61‐236 μm), globose, 16–32‐grained polyads that remain united following acetolysis. Thin sections reveal that polyad cohesion is maintained through fusion and/or adhesion and/or appression of adjacent ektexines in lateral and/or proximal and/or distal regions. In lateral and proximal regions the ektexine is often embedded in a dense granular endexinous matrix. Individual grains of the polyad are clearly outlined in most species but are completely obscured in several New World species. Sculpturing varies both in pattern and type of element. Nonuniformly sculptured polyads, in which the sculpturing of individual grains differs between the peripheral and central portions of the distal face, occur only among Old World species. Uniformly sculptured polyads occur among both New and Old World taxa. Two main sculpturing types are present among Parkia species: verrucate and tectate‐perforate, the latter particularly well developed in the reticulate polyads of the neotropical P. ulei and P. multijuga p.p. Ultrastructurally, all Parkia polyads exhibit ektexine and endexine continuous around the individual grain. Distal ektexine is prominent and clearly stratified, usually exhibiting a thick, perforate tectum, columellate interstitium, and a thin, locally discontinuous foot layer. Lateral and proximal ektexine is significantly thinner and less structured. Individual grains within the polyad possess three to four peripheral‐distal apertures usually at the points of contact between adjacent grains. Proximal and central grain apertures occur in most, but not all, species. Polyad characters suggest a particularly close relationship among the New World species P. decussata, P. discolor, P. gigantocarpa, P. igneiflora, and P. nitida. Parkia ulei, though sculpturally closest to P. multijuga p.p., is ultrastructurally most similar to the African P. biglobosa. The large tectate‐perforate‐fossulate polyads of P. pendula and P. platyparkia are unique in the New World.