bluuebunny/crossref_metadata_2025 huggingface dataset:
POLLEN MORPHOLOGY OF THE EUCHARIDEAE (AMARYLLIDACEAE)
Authors: Meerow Alan W. , Dehgan Bijan
Published: January 2018

Eucharis, Caliphruria, andUrceolinaform a monophyletic group of petiolate‐leaved, Neotropical Amaryllidaceae ecologically specialized to the understory of primary tropical rain forest below 2,000 m elevation. Pollen morphology of the three genera is surveyed. Pollen grains of all species ofEucharis, Caliphruria, andUrceolinaare boat‐shaped elliptic, monosulcate, heteropolar, and bilateral in symmetry. Exine sculpturing is semitectate‐columellate and reticulate in all species examined. A transformation series in reticulum coarseness and pollen grain size is described. The large pollen grain with coarse reticulum of mostEucharisspecies is considered ancestral. The fine reticulation ofCaliphruriais considered derived and the exine morphology ofUrceolinais intermediate. Both of these genera have medium‐sized pollen grains. Exine dimorphism common to allUrceolina, but rare inEucharisandCaliphruria, may be symplesiomorphous among those taxa exhibiting this morphology. The three genera are largely uniform in pollen grain ultrastructure, with completely ektexinous exines. Pollen grain size inEucharisis not closely correlated with style length. Several wide‐ranging species show considerable intraspecific variation in pollen size. Parallelisms in pollen grain evolution among related tribes of Neotropical Amaryllidaceae are discussed.
EFFECT OF CROSSING DISTANCE AND MALE PARENT ON IN VIVO POLLEN TUBE GROWTH IN CHAMAECRISTA FASCICULATA
Authors: Fenster Charles B. , Sork Victoria L.
Published: January 2018

Gametophytic competition among pollen grains has been proposed as an important mechanism of sexual selection in plants. The purpose of this paper is to examine the contribution of pollen source on in vivo pollen tube growth in Chamaecrista fasciculata. We addressed two questions: 1) Is pollen tube growth affected by the genetic relatedness between the pollen source and the pollen recipient? 2) Is there significant phenotypic variation among pollen donors for pollen tube growth? We compared pollen tube growth by measuring the number of pollen tubes which germinated, reached quarter length of style, and reached the ovary resulting from self‐ and outcross‐pollinations. The outcross pollinations included three interplant distance classes: near (within genetic neighborhood, ca. 1 m), far (between far neighborhoods and within subpopulation, ca. 20 m), and distant (between neighborhoods and adjacent subpopulations, ca. 50–100 m). Our results show that pollen tube growth was not affected by genetic relatedness, by differences between self and outcross, nor by differences due to phenotypic variation among pollen donors. In contrast, maternal environment had a strong impact on pollen tube growth. These results suggest a lack of gametophytic competition and indicate little opportunity for sexual selection on pollen tube growth in C. fasciculata.
SYSTEMATIC OCCURRENCE OF STEROLS IN LATEX OF ARACEAE: SUBFAMILY COLOCASIOIDEAE
Authors: Fox M. G. , French J. C.
Published: January 2018

Latex from representative New and Old World colocasioid species was analyzed by combined gas chromatography‐mass spectrometry for the presence of sterols. Free sterols were detected in latex of all New World species examined, and were localized in ca. 1 μm terpenoid particles which are abundant and account for the white‐opaque appearance of the latex. The sterol profiles were qualitatively and/or quantitatively distinct for each of the New World species examined. No free sterols were detected in latex of Old World genera examined, which are consistently clear to cloudy, and lack terpenoid particles. The presence of free sterols as small particles is typical of New World Colocasioideae with white latex. The results of this study provide chemical evidence for distinguishing Old and New World groups of Colocasioideae, which was recently proposed based on stem vasculature, pollen, and leaf type. This is the first report of sterol‐rich latex in a monocotyledon.
SURVEY OF POLLEN AND POLLENKITT LIPIDS–CHEMICAL CUES TO FLOWER VISITORS?
Authors: Dobson Heidi E. M.
Published: January 2018

A chemical survey of pollen lipids was carried out to examine the composition of pollenkitt in relation to that of whole pollen and to evaluate the possible role of pollenkitt as the principal carrier of chemical cues used by flower visitors. Investigated pollen was collected from 69 angiosperm species (28 families) in California. Lipid extracts of pollenkitt and of the internal portion of pollen were analyzed for each species using thin‐layer chromatography. Neutral lipids (energy storage and essential oil constituents) were most diverse in pollenkitt, while polar lipids (mostly membrane constituents) were found almost exclusively in the internal pollen fraction. Patterns in neutral lipid compositions suggest that pollenkitt may provide pollen with species‐specific odors. Yellow pigments were observed in pollen of most species, with carotenoids predominating in pollenkitt and flavonoids in the internal fraction. Phenolic and heterocyclic nitrogen compounds were found in the lipid extracts of several species.
ANTHER AND POLLEN DEVELOPMENT IN RICE (ORYZA SATIVA)
Authors: Raghavan V.
Published: January 2018

Investigations of the growth of anthers and ontogeny of pollen grains of Oryza sativa (rice) IR‐30 were undertaken for the purpose of 1) providing a set of growth measurements and 2) describing stable cytological features of anther and pollen development. Correlations exist between elongation of the floret and growth parameters of the anther such as its length, width, fresh and dry weights and cytological stage of pollen development. In the early ontogeny of the anther, hypodermal archesporial initials divide periclinally to form primary parietal cells and primary sporogenous cells. Each of the latter divides twice mitotically to generate four microspore mother cells, which undergo meiosis. The anther wall is formed by anticlinal and periclinal divisions of the primary parietal cells as well as of cells surrounding the primary sporogenous cells. Subsequent cytological features in the development of anther and pollen grains of rice have much in common with anther and pollen developmental biology of other members of Gramineae.
ARTIFICIAL HYBRIDIZATION OF RUBBER‐BEARING GUAYULE WITH COLD‐TOLERANT PARTHENIUM LIGULATUM
Authors: Hashemi Ahmad , Estilai Ali , West Jan E. , Waines J. Giles
Published: January 2018

ABSTRACT

Caespitose and cold‐tolerant plants of Parthenium ligulatum (Jones) Barneby (Asteraceae) from a native population in the Uinta Basin, Utah, were uprooted, potted, and transferred to a greenhouse in California. Approximately two years after transfer, the plants flowered and subsequently were crossed to diploid guayule (Parthenium argentatum Gray), the rubber‐bearing species, native to the state of Durango, Mexico. Only female guayule × male P. ligulatum crosses produced F1 hybrids. Only crosses involving guayule as female parent and F1 plants as male parents produced backcross (BC,) plants. Hybrid plants were variable with respect to their growth habit, inflorescence, and leaf shape. Both parents and F1 hybrids had 2n = 36 chromosomes. Unlike the parents, however, meiosis was irregular in the hybrids which showed a range of 0–5 and an average of 2.1 univalents at metaphase I. Hybrids averaged 0.87 laggards at anaphase I and 0.83 micronuclei at the tetrad stage. The crossability of guayule and P. ligulatum, the high degree of chromosome pairing of the F1 hybrids, and the production of BC1 plants indicate that the two species are related in spite of their distinct morphological and ecological differences. This study suggests that the cold‐tolerance trait of P. ligulatum may be transferred to guayule through interspecific hybridization followed by backcrossing. The development of cold‐tolerant guayule cultivars is expected to expand the areas of guayule production beyond that of the Chihuahuan desert and similar climates.
AN ELECTROPHORETIC INVESTIGATION OF INTRAGAMETOPHYTIC SELFING IN EQUISETUM ARVENSE
Authors: Soltis Douglas E. , Soltis Pamela S. , Noyes Richard D.
Published: January 2018

Because homosporous pteridophytes (Psilotophyta, Arthrophyta, most Microphyllophyta and Pteridophyta) produce bisexual gametophytes, it was maintained that high levels of inbreeding would characterize these plants. Electrophoretic evidence was used to estimate the frequency of intragametophytic selfing in Equisetum arvense (Arthrophyta). A total of 669 samples from 17 populations was examined from western North America. Although some populations exhibited as many as seven or eight genotypes, 10 populations were each characterized by only a single genotype; eight of these populations were heterozygous for one or more loci. For most populations, estimates of intragametophytic self‐fertilization are 0.000, indicating that virtually all matings involve different gametophytes. Genetic data corroborate predictions based on earlier field and laboratory investigations of Equisetum gametophytes. These detailed studies demonstrated that in many species, including E. arvense, gametophytes are initially either male or female; only later and in the absence of fertilization do some gametophytes become bisexual. Our findings join a growing electrophoretic data base which demonstrates that homosporous pteridophytes are not highly inbreeding as previously suggested.
SHOOT TIP ABORTION AND SYMPODIAL BRANCH REORIENTATION IN BROWNEA ARIZA (LEGUMINOSAE)
Authors: Mueller Richard J.
Published: January 2018

The growth of the tropical tree Brownea ariza Benth. is modular and conforms to Troll's model. Distinctive anatomical features of its shoot development were investigated. Each module consists of from 6–10 compound leaves and terminates its growth by shoot tip abortion. Sympodial branch systems are formed by renewal growth from the most distal (pseudoterminal) 1–2 buds. New modules are wholly preformed within large (15–28 cm) buds. The flush occurs without a resting period and full shoot expansion is completed within one day. A distinct abscission zone develops in the stem just distal to the node of the last expanded leaf. Abortion of the shoot apex and 5–6 embryonic leaves occurs 2–3 days after the flush begins. This tissue vacuolates and begins to become necrotic prior to actual abscission. New flushes are pendent but are reoriented to a plagiotropic or upright position to create an arborescent form. Reorientation begins quickly (10° within 2 days) due to maturation of primary and secondary tissues and continues throughout the life of the branch by means of reaction wood formation on the upper surface.
BRANCHING PATTERNS OF SALICORNIA EUROPAEA (CHENOPODIACEAE) AT DIFFERENT SUCCESSIONAL STAGES: A COMPARISON OF THEORETICAL AND REAL PLANTS
Authors: Ellison Aaron M. , Niklas Karl J.
Published: January 2018

Salicornia europaea L. (Chenopodiaceae) is an annual succulent halophyte that lacks leaves, is photosynthetically active over its entire surface, and branches in a predictable manner. A computer model based on that of Niklas and Kerchner (1984) was used to generate S. europaea‐like branching patterns. The model was used to predict the morphology of S. europaea that could maximize light interception and minimize the total bending moment. The optimal branching pattern generated by the computer corresponded very closely to the form of S. europaea found in late‐successional populations. The progression of model forms from the least efficient (lowest total projected surface area and highest bending moment) to the most efficient (highest projected surface area and lowest bending moment) parallels the observed phenotypic changes in morphology of S. europaea over the course of succession in New England salt marshes. Based on computer simulations, we conclude that morphological changes in the branching patterns of S. europaea during succession correspond to alterations of shape capable of coincidentally maximizing the interception of light and minimizing the total bending moment.
FLOWER CULTURE OF A MALE STERILE STAMENLESS‐2 MUTANT OF TOMATO (LYCOPERSICON ESCULENTUM)
Authors: Rastogi Rajeev , Sawhney Vipen K.
Published: January 2018

Young floral buds of a male sterile stamenless‐2 (sl‐2/sl‐2) mutant of tomato were cultured, at the sepal primordia stage, in a liquid Murashige and Skoog medium containing either benzylaminopurine (BAP) or gibberellic acid (GA3) or both. In the basal medium (BM), the buds initiated petal and stamen primordia only and they showed limited development. In buds grown in BM supplemented with 10–6 M BAP, all types of organ primordia were initiated but the petals remained small and the stamens and carpels were immature. Well‐developed flowers with a normal complement of floral organs were, however, produced in a medium containing both BAP (10–6 M) and GA3 (10–7 M to 10–5 M). The development of stamens was variable and ranged from the complete absence of microsporogenesis to the formation of abnormal pollen. Gynoecium development was normal and ovules with megaspores were produced in the ovary. The results show that male sterility in the sl‐2/sl‐2 mutant can be expressed in vitro and that GA3 is essential for the in vitro growth and development of all the floral organs of this mutant.
EVALUATION OF RELATIONSHIPS WITHIN ERIODICTYON (HYDROPHYLLACEAE) USING TRICHOME CHARACTERISTICS
Authors: Hannan Gary L.
Published: January 2018

All 13 taxa of Eriodictyon Bentham (Hydrophyllaceae) were examined to determine the range of variation in trichome characters within the genus. Four simple trichome types were found: short and straight, intermediate length and straight, long and straight, long and wavy. Glandular capitate trichomes were also found in some species. Sessile glands were also observed but not included in the study. Most taxa displayed unique combinations of trichome types on stems, leaves, inflorescence axes and flower parts that allowed those taxa to be identified using trichome types alone. Trichome data support most previous taxonomic treatments, but suggest that 1) the two varieties of E. traskiae are extremely similar, 2) the rare E. altissimum is most similar to the widespread E. californicum, 3) the rare E. capitatum is allied with E. crassifolium var. nigrescens or perhaps E. angustifolium, 4) E. crassifolium var. denudatum and E. crassifolium var. nigrescens are essentially indistinguishable using trichome characters and, coupled with variation in other characters, are best combined under the name E. crassifolium var. nigrescens. Trichome characters provide a wealth of taxonomically useful information and may prove useful in the study of related genera of Hydrophyllaceae.
APHIDS LIMIT FECUNDITY OF A WEEDY ANNUAL (RAPHANUS SATIVUS)
Authors: Snow Allison A. , Stanton Maureen L.
Published: January 2018

Few previous studies document effects of herbivores on the reproduction of wild plants in situ. We examined the impact of aphids on seed production in wild radish (Raphanus sativus L.), an annual herb. Aphid infestation increased during the three‐month flowering period. Flower and fruit production declined during the season, in part due to aphids. Inflorescences of late‐blooming plants more than doubled their fruit production when aphids were removed. Thus, aphids curtailed the blooming period of wild radish, perhaps conferring a selective advantage on early‐flowering plants. A few individuals were not susceptible to aphid colonization.
PHENOTYPES MEDIATED BY THE IOJAP GENOTYPE IN MAIZE
Authors: Coe Edward H. , Thompson Deborah , Walbot Virginia
Published: January 2018

The phenotype of maize plants that are homozygous recessive for the nuclear gene iojap is commonly an “anemic,” grainy green appearance accompanied by white leaf stripes, white leaf margins, and reduced growth. In plants in which the iojap effect is occurring (homozygous ij/ij), we find affected tissue varies in extent, from wide, discrete striping to layered striping to short striations; and in distribution, from white leaves to boldly white‐patterned to white‐margined. In homozygous iojap plants the patterns are predictable and are consistent within a particular genetic background.

Leaf striping patterns in iojap seedlings and plants are expressed primarily in the leaf margins, in positional patterns that are inconsistent with cellular proliferation. Reversion sectors on iojap plants (green stripes resulting from nuclear reversion of the ij gene), however, follow clonal cell lineages and indicate either that the iojap defects do not arise until after a leaf differentiates, or that they remain correctable in leaf tissue.

On transmission through the egg, iojap‐affected plastids become altered to a stable, nongreening state and can be transmitted maternally to subsequent generations. Defects in eggs borne on iojap ears, as revealed by ear maps of seedling progeny, have positional rather than clonal distributions on the ear. The expression of striping nonetheless is clonal in the occasional sectored plants that occur among such maternal progeny. The contrast of maternal sectorials with iojap plants is profound, and shows the period of meiosis and gametogenesis to be a critical passage for plastids in the egg as well as in the pollen.

In some genetic backgrounds aborted embryos occur at variable stages in embryo development in ij ij zygotes and in the maternal progeny from ij ij plants. These effects presumably reflect a participation of the organelles in embryogenesis that is subject to the influence of nuclear genes.

We conclude that the functional basis of the effects of the iojap gene must be 1) position‐dependent (i.e., dependent on the location of a cell in the meristem or organ at a particular time in development of an organ) and 2) differentiation‐dependent (i.e., dependent on the attainment of a certain state, specific to the genetic background). The iojap phenotype is thus a reflection of developmental progression of the organ rather than cell‐specific, clonal changes. The rate of cell proliferation and growth of one portion of an organ vs. another is related to position‐specific and background‐specific expressions, and the range of iojap expression is similarly related. Maternally inherited sectoring, on the other hand, shows phenotypes that are derived from clonal changes specific to each cell lineage, presumably attributable to sorting of mixed organelles in the apical meristem cells.
STOMATA OF ALETHOPTERIS SULLIVANTI: A NEW STOMATAL TYPE AMONG SEED FERNS AND VASCULAR PLANTS
Authors: Stidd Benton M.
Published: January 2018

Observations based on new preparations confirm the presence of four cells in parallel alignment in A. sullivanti stomata but not with two flanking subsidiary cells as in paracytic stomata. Rather, each guard cell contains in its interior a smaller inner cell. The stomatal pore is formed by walls of the larger cells and it is not known what role, if any, the interior cells may have played in opening and closing the pore. This cell‐within‐a‐cell arrangement is unknown among stornata elsewhere in the plant kingdom. The inner cells have the appearance of guard cells, especially when the poral walls of the larger cells are removed, and were so designated by Oestry Stidd and Stidd (1976). Cuticle preparations (Reihman and Schabilion, 1985) leave most of the cell structure of the stomatal apparatus intact among other leaf tissues (are not removed with the cuticle) and therefore do not reveal essential features.
EFFECT OF WATER STRESS ON STOMATAL AND PHOTOSYNTHETIC RESPONSES IN SUBALPINE PLANTS TO CLOUD PATTERNS
Authors: Knapp Alan K. , Smith William K.
Published: January 2018

Daily cloudcover is a frequent and persistent environmental feature of subalpine habitats. Response patterns in net photosynthesis (A), stomatal conductance to water vapor diffusion (g), transpiration (E), and water use efficiency (WUE = A/E) to intermittent cloudcover were evaluated for two subalpine species to determine if their responses supported the hypothesis that species that undergo water stress during sunlit intervals may have more rapid and greater stomatal responses to irradiance fluctuations than species under little apparent water stress. In Helianthella quinquenervis, a herbaceous perennial with midday xylem pressure potential < –2.0 MPa, responses in both A and g to simulated changes in natural irradiance occurred almost simultaneously and were relatively rapid. Although A was reduced by 22% during periods of shade compared with full sunlight periods, E was similarly reduced, and thus, no reduction in WUE occurred. In contrast, the riparian herb Senecio triangularis was under little apparent water stress and g was relatively insensitive to fluctuations in irradiance. As a result, periods of cloudcover led to a smaller reduction in A of only 15% relative to full sunlight with little concurrent reduction in E, leading to a corresponding 12% decrease in WUE compared with steady state values under full sunlight. These data suggest that species that experience apparent water stress during sunlit intervals may maintain higher WUE during intermittent cloudcover through water conservation at the expense of carbon gain. In contrast, species in which water stress does not occur during sunlit intervals can maximize carbon gain at the expense of reduced WUE. The degree of competition for water and sunlight in a habitat may determine the particular physiological response pattern expressed during natural cloudcover regimes.
CRYO SEM EXAMINATION OF GEMMA FORMATION IN VITTARIA GRAMINIFOLIA
Authors: Sheffield E. , Farrar D. R.
Published: January 2018

Production of gemmae by gametophytes of Vittaria entails regularity of pattern relevant to systematic comparisons and unusual cellular differentiation relevant to studies of cellular morphogenesis. Cryo SEM allows critical three dimensional analysis of these delicate structures. In Vittaria graminifolia, gemmifer cells initiated by the apical meristem typically support two gemma pairs with the terminal gemma of each pair oriented at right angles to the subterminal gemma. Mature gemmae consist of a uniseriate filament of four body cells with rhizoid primordial cells at each end. Cellular differentiation during gemma production includes growth from specific, localized areas, constricted connections between cells, reorientation of the polarity of cell growth, temporary suppression of cell growth and division, abscission between cells, and deposition of surface material on mature gemmae.
EFFECTS OF POLLEN AND RESOURCES ON SEED NUMBER AND OTHER FITNESS COMPONENTS IN AMELANCHIER ARBOREA (ROSACEAE: MALOIDEAE)
Authors: Gorchov David L.
Published: January 2018

Most Amelanchier arborea flowers have 10 ovules, but the number of filled (embryo‐containing) seeds per fruit is usually less than 10 and is highly variable within each individual plant. Because fruit developmental time correlates with seed number, this variation in seed number results in asynchronous fruit ripening. Field experiments tested whether seed number was pollen‐ or resource‐limited. Manipulation of resources in the shoot at the time of fruit initiation by defoliation, girdling, fruit thinning, or foliar feeding had no significant effect on seed number per fruit, although fruit set and seed weight were affected. Supplemental cross‐pollination also had no demonstrable effect on seed number. Most ovules that do not become filled seeds are visible as small “undeveloped seeds”; these are not necessarily aborted seeds as this was also the fate of ovules in unpollinated carpels. Alternative hypotheses for the determination of seed number are proposed and discussed.
INTRASPECIFIC VARIATION IN GERMINATION REQUIREMENTS AND GROWTH IN AMARANTHUS DUBIUS
Authors: Wulff Renata D.
Published: January 2018

Seeds collected from five Amaranthus dubius plants of the same population were weighed and tested in continuous light or darkness at three temperatures in controlled conditions. Different seed families differed in weight, germination percentages and rate, and responded differently to an increase in temperature from 25 to 38 C. Plants derived from these seed families and grown outdoors, either singly or in mixtures, differed in several growth characteristics and in time to flowering. Significant interactions between growth characteristics and growth conditions, as measured with a two‐way ANOVA, suggest that plants derived from different individuals differ in their competitive ability. The progeny of different individuals may thus be favored in different environmental conditions.
INITIAL TWIG INJURY TO HIGH ELEVATION PICEA RUBENS IN EASTERN NORTH AMERICA CAUSED BY INADEQUATE PERIDERM FORMATION
Authors: Evans Lance S. , Biesemeyer Peter T.
Published: January 2018

Apical dieback is the predominant injury symptomatology associated with growth declines of high elevation Picea rubens Sarg, trees in North America. Histological observations of uninjured tissues and of initial injury to tissues were made to understand the mechanism of injury to this species. Observations were made of hundreds of grab samples of apparently uninjured tissues and of uninjured twigs from trees growing on mountains of the Adirondack Mt., NY; Mount Mansfield, VT; Mt. Mitchell, NC; and Clingman's Dome, TN, from March 1985 to April 1986. In the normal growth pattern of red spruce, three buds elongate from each twig terminus during spring. These buds expand into shoot increments during the growing season and three new buds will form at the tip of each of the three elongated increments. The timing of developmental events varied markedly among buds of individual trees and among trees. Bud break occurred between mid‐June to the end of July. Most shoot elongation was completed and periderm formation began near the end of August or in early September. A phellogen, one cell thick, formed and a phellem layer developed from phellogen derivatives during autumn 1985. Many twig samples taken in October and November had produced only one, or at most two, phellem layers external to the phellogen during the relatively short growing season. In some samples, three or more phellem layers were present between November 1985 and March 1986. In some cases a distinct phellem was not developed at all. Usually a phelloderm one cell thick developed in autumn of the first year. Tissue necrosis occurred in twigs during their first overwintering period. Injured twigs with necrotic tissues had only one or two continuous or discontinuous phellem layers. In samples that exhibited initial injury, necrotic tissues consisted mostly of cortical cells and phloem subjacent to this meager periderm. Frequently, necrotic tissues developed initially near the bases of needles and at branch “nodes” (transition zone tissues with older twigs). In contrast, twigs of healthy appearance had two or more continuous phellem layers external to the phellogen.
NEW INTERPRETATION OF THE INFLORESCENCE OF FAGUS DRAWN FROM THE DEVELOPMENTAL STUDY OF FAGUS CRENATA, WITH DESCRIPTION OF AN EXTREMELY MONSTROUS CUPULE
Authors: Okamoto Motoharu
Published: January 2018

The inflorescence of Fagus is generally considered to be a determinate one, i.e., an axillary dichasium, in contrast to those of most genera in the family, which are indeterminate, dichasial, or simple catkins. To understand the relationship between the two types, ontogenetic development of the inflorescence of Fagus crenata was investigated. The early developmental stages are similar in both the male and the female inflorescences. At first, the inflorescence is oval‐shaped, then a swelling forms at the distal side of it. Subsequently, another swelling forms at the proximal side. The more or less conspicuous residual part of the primary inflorescence axis remains between the two swellings. The inflorescence becomes heart‐shaped and the first flower forms at the summit of each swelling. Subsequently, higher‐ordered flowers form dichasially in the male inflorescence, and the cupule valves differentiate in the female one. This organogenetic manner suggests that the inflorescence of Fagus is an indeterminate one, consisting of two dichasia arranged alternately on the primary axis. The scale leaves surrounding the inflorescence were also given a new interpretation. They were considered to be stipules of the bracts, because sometimes they constitute a continuous structure, together with an inconspicuous swelling between them. A proliferous‐type monstrous cupule was interpreted as supporting evidence for the hypothesis.
TWO‐DIMENSIONAL POLLINATION IN HYDROPHILOUS PLANTS: CONVERGENT EVOLUTION IN THE GENERA HALODULE (CYMODOCEACEAE), HALOPHILA (HYDROCHARITACEAE), RUPPIA (RUPPIACEAE), AND LEPILAENA (ZANNICHELLIACEAE)
Authors: Cox Paul Alan , Knox R. Bruce
Published: January 2018

In most plant species with abiotic pollination systems, pollen is dispersed in three dimensions. Theoretical considerations suggest, however, that there are significant advantages for two‐dimensional pollination systems over three‐dimensional systems, especially if pollen is dispersed in conveyances or aggregations of large diameter. We report that two‐dimensional pollination systems occur in the genera Halodule, Halophila, Lepilaena, and Ruppia, where pollen grains are not transported through the water singly, but in rafts or search vehicles. These genera possess unusual pollen morphologies which facilitate assemblage of pollen grains into search vehicles. These floating search vehicles have large diameters, thus greatly increasing probability of encountering a stigma. The grains have a hydrophobic surface that appears to mediate adhesion by an external coating of proteins and carbohydrates. Similar adaptations to two‐dimensional pollination are found in the target organs, the stigmas. The long filamentous stigmas of the marine genera float, as do the indusiate stigmas of the freshwater genera, creating small depressions in the water surface. Pollination occurs through the collision of a moving search vehicle with a floating stigma. The existence of similar pollen search vehicles, stigma morphologies, and flowering phenologies in these unrelated hydrophilous genera evidences convergent evolution towards efficient search strategies in surface‐pollinated aquatic plants.
IMMUNOLOGICAL AFFINITIES AMONG SUBFAMILIES OF THE POACEAE
Authors: Esen Asim , Hilu Khidir W.
Published: January 2018

Immunological affinities were investigated among twenty taxa belonging to the grass subfamilies Pooideae, Chloridoideae, Panicoideae, Oryzoideae, and Bambusoideae. Antisera were raised to the prolamin fraction of seed proteins from species of eleven grass genera (Hordeum, Bromus, Festuca, Phleum, Elensine, Panicum, Pennisetum, Tripsacum, Dendrocalamus, and Oryza) and reacted with their homologous antigens and nineteen different heterologous antigens in Enzyme‐Linked Immunosorbent Assay (ELISA). The immunological cross‐reactivity among the eleven taxa whose prolamin was used for antisera production was analyzed quantitatively by generating matrices of averaged cross‐reactivities, Q correlation and distance. The averaged cross‐reactivity matrix was calculated from averaging reciprocal immunological reactions while the two other matrices were computed by considering each antiserum as a character and antigens as OTUs. The three matrices were subjected to clustering by the Unweighted Pair Group Method using Arithmetic Averaging (UPGMA). The phenogram based on the averaged similarity matrix showed some distortion, while the other two phenograms were similar in topology and were informative. A phenon line at r = 0.17 divided the phenogram based on Q correlation into four major groups: Pooideae, Oryzoideae, Bambusoideae, and Chloridoideae‐Panicoideae. The two subfamilies in the Chloridoideae‐Panicoideae group clustered at a correlation coefficient of 0.22. Within the Pooideae, the tribes Aveneae and Agrostideae were closely grouped together (r = 0.85), but they were quite distinct (r = 0.16) from the tightly clustered (r = 0.84–0.85) Bromeae, Poeae, and Triticeae. The Oryzoideae and Bambusoideae showed low immunological similarity (r = –0.07). The two tribes of the Panicoideae, Paniceae and Andropogoneae, displayed extensive immunological similarity clustering tightly at r = 0.84–0.86. The immunological data revealed a possible trend in grass evolution encompassing the chloridoid‐panicoid groups and provided insights into the phylogenetic affinities of the bambusoid and oryzoid grasses. The results also underscored the heterogeneity of the taxa within the Pooideae.
INCOMPATIBILITY IN AMSINCKIA GRANDIFLORA (BORAGINACEAE): DISTRIBUTION OF CALLOSE PLUGS AND POLLEN TUBES FOLLOWING INTER‐ AND INTRAMORPH CROSSES
Authors: Weller Stephen G. , Ornduff Robert
Published: January 2018

The distribution of callose plugs and pollen tubes was investigated following inter‐ and intramorph crosses of Amsinckia grandiflora (Boraginaceae), a distylous species possessing cryptic self‐incompatibility. Callose plug distribution provided a good indication of the distribution of pollen tubes. Compared to intramorph crosses, many more callose plugs and pollen tubes were found in basal stylar regions following intermorph crosses, indicating that differential pollen tube growth is a likely cause of cryptic self‐incompatibility. The incompatibility response differed for the floral morphs: in the pin (long‐styled) morph pollen tubes were most likely to cease growth in the midstylar region, while inhibition was more likely to occur in the upper stylar region of the thrum (short‐styled) morph. There was no evidence of stigmatic inhibition of pollen tubes for either morph, although the incompatibility response in the Boraginaceae is normally located in the stigmatic region.
BREEDING SYSTEM OF A HYBRID BETWEEN A SEXUAL AND AN APOMICTIC SPECIES OF AMELANCHIER, SHADBUSH (ROSACEAE, MALOIDEAE)
Authors: Weber Jill E. , Campbell Christopher S.
Published: January 2018

Amelanchier bartramiana, which has been shown to be sexual and self‐incompatible, and A. laevis, in which apospory and self‐compatibility occur, grow in a mixed population in western Maine. Also present there is the putative interspecific hybrid, A. × neglecta. Principal components and canonical discriminant analyses of seven morphological characters from 96 parental and putative hybrid individuals substantiate morphological intermediacy of the hybrids. A Nomarski differential interference microscopy study of megasporogenesis and megagametogenesis in five hybrid plants shows a predominantly aposporous mode of reproduction, and controlled pollinations indicate that seed formation between A. bartramiana and A. laevis is possible and that the hybrids are self‐compatible. The hybrids, which are tetraploids (n = ca. 34) like both parents in Maine, produce viable pollen and seed, but there is little evidence for backcrossing with either parent.
POPULATION BIOLOGY OF BONAMIA GRANDIFLORA (CONVOLVULACEAE): EFFECTS OF FIRE ON PLANT AND SEED BANK DYNAMICS
Authors: Hartnett David C. , Richardson Donald R.
Published: January 2018

The effects of disturbance on reproduction and plant and seed bank dynamics in the perennial herb Bonamia grandiflora were studied by comparing populations in recently burned, mechanically disturbed, and undisturbed habitats in central Florida over a 3‐year period. Plant densities, seed production, and the occurrence of herbivory and predispersal seed predation varied considerably between sites and between years, with recently disturbed sites supporting the densest and most dynamic populations. Death of established plants was rare in all sites. In each site, the soil seed bank was several‐fold larger than single season seed rains suggesting that B. grandiflora seeds are long‐lived and accumulate in the soil. There was no evidence that postdispersal predation or pathogens have any significant influence on the seed bank dynamics. Fire resulted in large increases in stem densities due to both increased clonal stem production and new genet recruitment from seed. Burning also caused significant increases in the percentage of flowers producing seed and the numbers of capsules and seeds per plant. The seed rain was ten to thirty times greater in the burned site relative to adjacent unburned site during the 3 years after burning. However, additions to the seed bank from the postfire seed rain were balanced by equivalent losses due primarily to seed mortality during fire, and to a much lesser extent due to germination and new genet establishment. As a result, the subsequent densities of seeds stored in the soil in these two sites were similar, indicating that fire results in a significant turnover in the seed bank population but no immediate change in its size. These effects on seed bank dynamics, in addition to new genet recruitment, suggest that periodic fires may play an important role in the maintenance of genetic variability as well as the size of these populations.
FOSSIL FUNGI (ENDOGONACEAE) FROM THE TRIASSIC OF ANTARCTICA
Authors: Taylor Thomas N. , White James F.
Published: January 2018

Fungal sporocarps are described from Triassic silicified peat deposits from Antarctica. Sporocarps possess a two‐layered wall and contain a single spore. The outer layer is mycelial; the inner layer, noncellular. The combination of primitive and advanced features suggests that this fungus is intermediate in complexity between the lower and evolutionarily more advanced fungi. The Antarctic fungus and morphologically similar fossils resemble extant members of the Endogonaceae, but appear to have been saprophytes rather than mycorrhizal symbionts.
INBREEDING DEPRESSION IN SCHIEDEA GLOBOSA AND S. SALICARIA (CARYOPHYLLACEAE), SUBDIOECIOUS AND GYNODIOECIOUS HAWAIIAN SPECIES
Authors: Sakai Ann K. , Karoly Keith , Weller Stephen G.
Published: January 2018

Progeny produced by inbreeding were compared to progeny derived from outcrosses for gynodioecious Schiedea salicaria and subdioecious S. globosa to assess fitness consequences of breeding system on parental fecundity (seeds per capsule) and progeny measures of fitness (germination, survival, biomass, and number of flowers). Results from both species indicated that inbreeding depression occurred at all measured stages of the life history. In both species, different females showed different levels of inbreeding depression. Multiplicative fitness functions of the ratio of values for selfed and outcrossed progeny in S. salicaria resulted in inbreeding depression values of 0.62–0.94. Within‐ vs. between‐family crosses of S. globosa also resulted in inbreeding depression values as high as 0.49. These values suggest that inbreeding depression may promote the evolution of dioecy within S. globosa and S. salicaria, depending on the levels of natural outcrossing.
ROOTCAP STRUCTURE IN WILD TYPE AND IN A STARCHLESS MUTANT OF ARABIDOPSIS
Authors: Sack Fred D. , Kiss John Z.
Published: January 2018

Rootcaps of the wild type (WT) and of a starchless, gravitropic mutant (TC7) of Arabidopsis thaliana L. were examined by electron microscopy to identify cellular polarities with respect to gravity. In columella cells, nuclei are located proximally, and the nuclear envelope is continuous with endoplasmic reticulum (ER) that is in turn connected to nearby plasmodesmata. Impregnation of ER with osmium ferricyanide revealed numerous contacts between columella plastids and ER in both genotypes. ER is present mostly in the outer regions of the columella protoplast except in older columella cells that are developing into peripheral cells. In vertical roots, only columella cells that are intermediate in development (story 2 cells) have a higher surface density (S) of ER in the distal compared to proximal regions of the cell. The distal but not the proximal S of the ER is constant throughout columella development. Plastids are less sedimented in TC7 columella cells compared to those of the WT. It is hypothesized that plastid contact with the ER plays a role in gravity perception in both genotypes.
HISTOCHEMISTRY AND ULTRASTRUCTURE OF RICE (ORYZA SATIVA) ZYGOTIC EMBRYOGENESIS
Authors: Jones Todd J. , Rost Thomas L.
Published: January 2018

Rice embryo development was examined, histochemically and ultrastructurally, from the time of fertilization to embryo maturity. At the time of fertilization, the megagametophyte consists of an antipodal mass of 10–15 cells, parietally positioned along the placental side of the central cell, and, at the micropylar end, two partly fused polar nuclei and the egg apparatus. Hydrolysis of adjacent nucellar tissue suggests the secretion of hydrolytic enzymes by the antipodal mass. The antipodal cells stain intensely for RNA and protein, indicating that they are metabolically active. The egg, supported by two overarching synergids, occupies a small, wall ingrowth‐lined pocket of the central cell that quickly fills with cellular endosperm after fertilization. The endosperm cells, initially supplied with nutrients from wall ingrowth‐derived vesicles, are digested and utilized by the embryo as a nutritive source. The developing embryo is also supplied with assimilates via the nucellus at the base of the embryo until about 8 days after fertilization. After 8 days, the embryo is no longer connected to the nucellus, and the nucellar cells at the base of the embryo are crushed. The zygote is not structurally polarized and contains a central nucleus, amyloplasts, lipid bodies, dictyosomes and extensive dilated ER. The first division of the zygote is transverse and unequal and occurs about 4 hours after fertilization. Embryo development is rapid, and within 24 hr, the embryo consists of 5–8 cells. Organ development begins with scutellum emergence in the 3‐day‐old embryo. The shoot apex organizes and the coleoptile develops from scutellum tissue at 4 days postfertilization, the epiblast emerges at 5 days, and the vascular bundle and root apex differentiate by 6 days after fertilization. Starch begins to accumulate in the basal cells of the 3‐day‐old embryo and deposition proceeds acropetally over the next 9–10 days. Lipid accumulation begins in the basal scutellum in the 6‐day‐old embryo and also proceeds acropetally. Storage protein synthesis is first detected in 6‐day‐old embryos and accumulation again proceeds acropetally, reaching the apex of the scutellum of the 25‐day‐old embryo. The ultrastructure of the 24‐hr‐old embryo is distinctive. The cells are characterized by numerous vesicles, heterochromatin and extensive nuclear evaginations.
EVIDENCE FOR APICAL INITIAL CELLS IN THE VEGETATIVE SHOOT APEX OF HEDERA HELIX CV. GOLDHEART
Authors: Rogers Scott O. , Bonnett Howard T.
Published: January 2018

We examined changes in the pattern of leaf variegation in a periclinal chloroplast chimera of Hedera helix L. cv. Goldheart to determine whether stable apical initials exist in the shoot apex. Additional data were obtained by histological analyses. All of the data indicate that four apical initials are present in the third layer of the apex, supporting the model of a structured apical meristem.
TECHNIQUES FOR MEASURING VESSEL LENGTHS AND DIAMETERS IN STEMS OF WOODY PLANTS
Authors: Ewers Frank W. , Fisher Jack B.
Published: January 2018

Results were compared between the latex paint and compressed air methods for determining total vessel lengths, and between the sectioning and maceration methods for determining vessel diameters. The minimum, mean, median, and maximum vessel diameters were less with the sectioning method than with the maceration technique. Vessel diameter distributions were always nonnormal and had roughly similar patterns with the two techniques, but were statistically different from one another. In all six species where the paint and air methods for determining vessel length were compared, both methods showed a similar skewed vessel length distribution, with many short vessels and few long ones. Although there was no consistent pattern to the difference in results with these two methods, the vessel length frequency distributions were statistically different from one another. With the paint method, many vessels, especially many of the narrowest ones, were not paint‐filled at the paint infusion port. The air method utilized the paint method, in part, and, in addition, is based upon the incorrect assumption that all vessels in the stem are the same diameter. Both techniques tended to exclude vessel lengths of the narrowest vessels. However, the narrow vessels, although numerous, contributed an insignificant amount to the total theoretical hydraulic conductance in stems.
STRANGLER FIG ROOTING HABITS AND NUTRIENT RELATIONS IN THE LLANOS OF VENEZUELA
Authors: Putz Francis E. , Holbrook N. Michele
Published: January 2018

The strangler figs, Ficus pertusa and F. trigonata, are abundant in the seasonally flooded palm savanna (llanos intermedio) near Calabozo, Venezuela. The most common host tree for the hemiepiphytic figs is the palm Copernicia tectorum; nearly half of the palms support either an epiphytic or a ground‐rooted fig. During their epiphytic stage the figs are rooted behind the palms' marcescent leaf bases. Material trapped behind the leaf bases is higher in organic matter, nitrogen, magnesium, and potassium than soil from the ground near the palms. The suggestion that nutrient availability to epiphytes is high is supported by the observation that concentrations of several nutrients, including N, P, and K, are significantly higher in epiphytic leaves than in tree leaves. Figs retain access to the epiphytic medium by producing upwardly growing (apogeotropic) roots that remain attached in the host palm's crown long after the fig has become firmly rooted in the ground. Although upward growing roots are expected to be more important in nutrient than water uptake, there are no obvious differences in the xylem anatomy of upward and downward growing fig roots. Terrestrial roots of fig trees are generally infected with vesicular‐arbuscular mycorrhizae, but the epiphytic roots of the same individuals are not infected.
DROUGHT STRESS RESPONSES OF MICROSERIS SPECIES DIFFERING IN NUCLEAR DNA CONTENT
Authors: Castro‐Jimenez Y. , Newton R. J. , Price H. J. , Halliwell R. S.
Published: January 2018

Anatomical and physiological responses to drought stress were compared in two Microseris species differing in DNA content and originating from contrasting habitats relative to water availability (M. bigelovii, DNA = 2.6 pg nucleus–1, more xeric; M. laciniata, DNA = 6.8 pg nucleus–1, mesic). Leaf mesophyll cell volume was positively correlated with DNA content and negatively correlated with tissue elasticity, i.e., low ϵ̄ and thin cell walls. Drought stress increased leaf tissue elasticity (lower ϵ̄, thinner cell walls). Cell volume, cell wall thickness, cell number, and leaf area were decreased most by drought stress in M. laciniata. Osmotic adjustment with a 20% increase in total solutes (mostly amino acids) after stress was observed in both species, but their estimated contribution to the change in osmotic potential was larger in M. bigelovii. These findings indicate that the Microseris species studied respond to low water availability by maintaining turgor with 1) small cell volumes, 2) elastic tissues (low ϵ̄, thin cell walls), and 3) osmotic adjustment. Both enhanced tissue elasticity and small cell volume appear to be inherent characteristics in M. bigelovii and drought‐induced responses in M. laciniata. These data are compatible with the hypothesis that natural selection may influence DNA content through differential sensitivity of cell growth to environmental stress.