bluuebunny/crossref_metadata_2025 huggingface dataset:
FACTORS LIMITING FRUIT AND SEED PRODUCTION OF A TEMPERATE SHRUB, STAPHYLEA TRIFOLIA L. (STAPHYLEACEAE)
Authors: Garwood Nancy C. , Horvitz Carol C.
Published: January 2018

Staphylea trifolia L., the bladdernut, is a self‐incompatible temperate woodland shrub that flowers in May in Illinois. Factors limiting reproduction were studied at four levels: 1) Seeds/fruit. Seed production in open‐pollinated fruit was frequently limited by too few fertilized ovules. Seed production in hand‐cross‐pollinated fruit was limited by resources or dispersal constraints: seed abortion rates were higher in hand‐cross‐pollinated fruits than in open‐pollinated fruits. 2) Fruits/flower and 3) fruits/inflorescence. The number of fruits set and matured per flower and per infloresence in the open‐pollinated treatment was limited by the number of flowers naturally cross‐pollinated. In hand‐cross‐pollinated inflorescences, fruit set was not limited by resources even though fruit set was ten times greater than in the open‐pollinated treatment. Evidence that resources limited fruit maturation in the hand‐cross‐pollinated inflorescences was equivocal. In hand‐cross‐pollinated flowers, fruit set was lowest when cold nights followed pollination, suggesting that cool temperatures limited postpollination physiological processes. 4) Fruits/individual. Early‐flowering individuals matured fewer fruits than later‐flowering individuals. Within the latter group, fruit production increased with plant size, although a relatively small individual matured the maximum number of fruits. Flowering phenologies and size of individuals varied among patches, resulting in differential reproductive success of patches.
PATTERNS OF ENDOTHECIAL WALL THICKENINGS IN ARACEAE: SUBFAMILIES POTHOIDEAE AND MONSTEROIDEAE
Authors: French J. C.
Published: January 2018

A survey of the patterns of endothecial wall thickenings in 106 representative species from 20 genera in the Pothoideae and Monsteroideae was made using cleared anthers, sections and macerations. The wide variety of wall thickenings that is present is based on an annular‐helical pattern. Variations in thickenings are related to differences in cell shape, cell orientation, intergradation between helical and annular patterns, pitch of helices, presence of branched thickenings, and various types of discontinuities in thickenings. Notable exceptions to the annular‐helical pattern include Culcasia, which lacks a differentiated endothecial layer with thickenings, and Acorus, which has a peculiar stellate pattern that is unique in the family. No single pattern consistently characterizes either subfamily, although continuous helices are common in the Monsteroideae, and rare in the endothecium of Pothoideae (except Anadendrum). Monsteroideae frequently exhibit a series of slanted separate thickenings on anticlinal walls, which is absent from Pothoideae except in Heteropsis. The slanted pattern is considered a variation on a rectangular helix, involving discontinuities of thickenings on the periclinal walls. Some monsteroid genera show considerably more interspecific variation (Rhaphidophora) than others (Monstera). Endothecial thickenings constitute an anatomical character that is useful in the systematic study of Araceae; present results support other anatomical studies in identifying Culcasia and Acorus as highly divergent genera in the Pothoideae.
GERMINATION ECOPHYSIOLOGY OF HYDROPHYLLUM APPENDICULATUM, A MESIC FOREST BIENNIAL
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

In north central Kentucky, seeds of the mesic forest biennial Hydrophyllum appendiculatum Michx., are innately dormant at maturity in June. Under natural and simulated seasonal temperature changes, dormancy break occurred in two stages. Root dormancy was broken by high summer temperatures, and shoot dormancy was broken by low winter temperatures. Consequently, roots emerged from seeds during autumn, and cotyledons emerged the following spring. A 90‐day warm (30/15 C) stratification treatment broke root dormancy, but the roots emerged only after transfer to lower temperatures. After the warm stratification treatment, roots emerged from 93, 73, 6 and 9% of the seeds incubated at 5, 15/6, 20/10 and 30/15 C (12/12 hr), respectively. Zero, 28, 56 and 84 days of cold (5 C) stratification of seeds with emerged roots resulted in 9, 21, 49 and 82% cotyledon emergence, respectively, at 20/10 C. Thus, H. appendiculatum exhibits a type of morpho‐physiological dormancy known as epicotyl dormancy. Although many seeds germinate the first year, others remain dormant and germinate in successive years until the fourth season after ripening.
COMPARISON OF HEAVY METALS IN AQUATIC PLANTS ON CHARITY ISLAND, SAGINAW BAY, LAKE HURON, U.S.A., WITH PLANTS ALONG THE SHORELINE OF SAGINAW BAY
Authors: Estabrook George F. , Burk David W. , Inman Dennis R. , Kaufman Peter B. , Wells James R. , Jones John D. , Ghosheh Najati
Published: January 2018

The concentrations of 15 heavy metals in aquatic plants on Charity Island was compared to those in plants on the shoreline of Saginaw Bay, Lake Huron, U.S.A. Heavy metal concentrations were measured by neutron activation analysis. Charity Island was found to have significantly higher levels of nine of fifteen metals investigated. This indicates that distance from known pollution source was not the only factor affecting the heavy metal accumulation of the aquatic plants.
INTRAPOPULATIONAL VARIATION IN LEAFLET MORPHOLOGY OF ZAMIA PUMILA L. IN RELATION TO MICROENVIRONMENT AND SEX
Authors: Newell Sandra J.
Published: January 2018

The cycad Zamia pumila L. was examined for differences in leaflet morphology between sun and shade plants and between males and females within a single population in northern Puerto Rico. Sun leaflets are significantly smaller than shade leaflets in length, width, and surface area; and sun leaflets have a higher length: width ratio than shade leaflets. Also, average densitythickness is greater for sun leaflets than for shade leaflets. Males and females are similar in leaflet size; but the females had a larger number of leaflets per leaf than males.
DIFFERING ONTOGENETIC ORIGINS OF PCR (“KRANZ”) SHEATHS IN LEAF BLADES OF C4 GRASSES (POACEAE)
Authors: Dengler Nancy G. , Dengler Ronald E. , Hattersley Paul W.
Published: January 2018

The origin and early development of procambium and associated ground meristem of major and minor veins have been examined in the leaf blades of seven C4 grass species, representing different taxonomic groups and the three recognized biochemical C4 types (NAD‐ME, PCK, and NADP‐ME). Comparisons were made with the C3 species, Festuca arundinacea. In “double sheath” (XyMS+) species (Panicum effusum, Eleusine coracana, and Sporoboìus elongatus), the procambium of major veins gives rise to xylem, phloem, and a mestome sheath; associated ground meristem differentiates into PCA (“C4 mesophyll”) tissue and the PCR (“Kranz”) sheath. Development in the C3 species parallels this pattern, except that associated ground meristem differentiates into mesophyll and a parenchymatous bundle sheath. In contrast, major vein procambium of “single sheath” (XyMS–) species (Panicum bulbosum, Digitaria brownii, and Cymbopogon procerus) differentiates into xylem, phloem and a PCR sheath; associated ground meristem gives rise to PCA tissue. These observations of major vein development support W. V. Brown's hypothesis that the PCR sheaths of “double sheath” (XyMS+) C4 grasses are homologous with the parenchymatous bundle sheaths of C3 grasses, while in “single sheath” (XyMS–) C4 species they are homologous with the mestome sheath. Although there are some similarities in the development of the major and minor vascular bundle procambium in the C4 species examined, the ontogeny of the smaller minor veins is characterized by a precocious delineation of the PCR sheath layer that may even precede the appearance of the distinctive cytological features of ground meristem and procambium. This contracted development in minor veins appears to be related to their close spacing in mature leaves and to their comparatively late appearance during leaf ontogeny.
A NEW LYGINOPTERID POLLEN ORGAN WITH ALVEOLATE POLLEN EXINES
Authors: Stidd Benton M. , Rischbieter Michael O. , Phillips Tom L.
Published: January 2018

A new lyginopterid pollen organ is described based upon specimens occurring in a single coal ball from the Providence, Kentucky locality. Seven to nine beaked sporangia are fused together at their proximal ends forming a common synangial chamber; synangia are joined together in clusters of two or three. In situ prepollen is similar to Cyclogranisporites and Verrucosisporites sporae dispersae. The thick exine has a lamellate nexine and a prominent alveolate sexine.
THE AURICULATE POLLEN GRAIN OF HYMENOCALLIS QUITOENSIS HERB. (AMARYLLIDACEAE) AND ITS SYSTEMATIC IMPLICATIONS
Authors: Meerow Alan W. , Dehgan Bijan
Published: January 2018

The pollen grain of Hymenocallis quitoensis Herb, is examined with scanning and transmission electron microscopy. The very large, monosulcate grain is characterized by a coarsely reticulate exine surface and solid, auriculate appendages at the equatorial facies. Surface morphology of the pollen grain of H. quitoensis is compared with other representative species of Hymenocallis and supports the inclusion of H. quitoensis within the genus. Meridional exine dimorphism in other species of Hymenocallis is interpreted as a reduction from the well‐defined auriculae of H. quitoensis. Surface morphology of the pollen grain of Hymenocallis sects. Artema Traub and Elisena (Herb.) Traub exhibits divergence from that of sects. Hymenocallis and Ismene (Herb.) Traub. Phylogenetic and paleobotanical implications of the auriculate pollen grain are briefly discussed.
DEVELOPMENT OF THE YOUNG WHEAT SPIKE: A SEM STUDY OF CHINESE SPRING WHEAT
Authors: Gardner John S. , Hess W. M. , Trione E. J.
Published: January 2018

The number of leaves on the main culm was correlated with morphological changes in the wheat spike during development, up to the terminal spikelet stage. The developmental changes were divided into nine stages, which were compared with stages described by other investigators. Several environmental conditions were utilized to determine the consistency of morphological correlations. Although the different environments did influence the length of time required to reach the various stages, the relationship between leaf number and stage of spike development was consistent. Regardless of environmental conditions, all stages were evident. Vernalization period affected the number of spikelets. Plants vernalized 6 wk produced 17–19 spikelets, compared to 21–24 spikelets on plants vernalized 3 wk. There were three major morphological events during spike development: 1) the change from vegetative to reproductive growth, 2) lateral spikelet development, and 3) the initiation and development of the terminal spikelet.
COMPARATIVE ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE METZGERIALES (HEPATICAE). I. THE BLEPHAROPLAST OF PALLAVICINIA LYELLII
Authors: Renzaglia Karen S. , Carothers Zane B. , Duckett Jeffrey G.
Published: January 2018

The blepharoplast in the young spermatid of Pallavicinia is similar to that of other hepatics in that it comprises a four‐layered multilayered structure (MLS) and two staggered, dimorphic basal bodies. The spline, approximately 40 μm in length and extending through nearly two full gyres, comprises 20 parallel microtubules at its anterior end and narrows to 17 at the posterior limit of the subjacent lamellar strip (LS). Behind this, the spline shank, approximately 32 μm in length, is reduced to six tubules. The LS curves around the spermatid, following the anterior one‐third of the first gyre of the spine, and is approximately 7.5 μm in length, the longest yet recorded for the bryophytes. It is spatulate in outline, equaling the width of the spline anteriorly but tapering steeply from the right‐hand side behind the anterior basal body (ABB). It then extends posteriorly as a narrow strip beneath the left‐hand margin of the spline. The basal bodies of the greatly staggered flagella are nonoverlapping and separated by a distance of about 4.4 μm. The subapical ABB and PBB measure (including the ventral triplet extensions and transition zones) 1.2 μm and 2.4 μm in length, respectively. A short, narrow aperture equaling one tubule‐diameter in width is located in the spline directly beneath the ABB. The anterior mitochondrion is about 7 μm long and follows the outline of the overlying LS, while a cupshaped posterior mitochondrion is appressed to the plastid. Comparisons with other taxa indicate that major distinguishing features of metzgerialian blepharoplasts are highly staggered, nonoverlapping basal bodies, greatly elongate anterior mitochondria, and six‐tubule shanks. Great differences between the spermatids suggest wide phylogenetic discontinuities between the genera of the Metzgeriales.
ANTHERIDIAL FORMATION IN ONOCLEA SENSIBILIS L.: GENESIS OF THE JACKET CELL WALLS
Authors: Kotenko Jane L.
Published: January 2018

Antheridial initiation in Onoclea sensibilis L., an advanced leptosporangiate fern, begins with the production of a small, wedge‐shaped cell within the anterior region of the vegetative cell. This is in contrast to previous reports claiming that the initials are formed by a localized protuberance in the cell wall of the vegetative cell (Campbell, 1886; Davie, 1951; Leung and Naf, 1979; Nayar and Kaur, 1971). The mature antheridium of Onoclea is composed of three uniquely shaped jacket cells surrounding spermatogenous cells. The two funnel‐shaped jacket cell walls are shown to form in a lateral circular manner. Except for the production of the antheridial initial cell, jacket cell formation in Onoclea proceeds in accordance with the classical concept of antheridial development in advanced ferns accredited in part to Atkinson (1894), Campbell (1886), Kny (1869), and Strasburger (1869). The classical concept has been contested in more recent years by Davie (1951), Leung and Näf (1979), and Verma and Khullar (1966).
THE VULNERABILITY OF POLLEN AND FUNGAL SPORES TO ANT SECRETIONS: EVIDENCE AND SOME EVOLUTIONARY IMPLICATIONS
Authors: Beattie Andrew J. , Turnbull Christine , Hough Terryn , Jobson Sieglinde , Knox R. Bruce
Published: January 2018

The quality of Brassica and Acacia pollen is adversely affected by exposure to secretions drawn from the metapleural gland of the ant Myrmecia nigriscapa. Ultrastructural studies show that the apparently lipoidal secretions destroy both the plasma membranes and those of the cytoplasmic organelles. Exposure to the integument of this ant prevents the normal hydration of pollen grains. Exposure to the integument of a species of Camponotus, which does not appear to possess metapleural gland openings, also reduces pollen quality. Mycelial development in seven species of soil‐dwelling fungi is inhibited by secretions of the metapleural gland. Two fungal species that are normally entomogenous are most vulnerable to the secretion. It is suggested that the metapleural gland is producing a powerful antibiotic and that the antibiosis that results from its activity, on one hand, alleviates the attacks of microorganisms in nest cavities, while on the other, incidentally kills pollen grains, possibly blocking the evolution of ant pollination systems.
POPULATION AND GENOTYPE NICHE WIDTH IN CLONAL PHLOX PANICULATA
Authors: Garbutt K. , Bazzaz F. A. , Levin D. A.
Published: January 2018

We use a model population comprised of five genotypes of Phlox paniculata L. to investigate the contribution of individuals to the response breadth (niche) of the population on a light gradient and a moisture gradient. Analysis of within‐ and between‐genotype components of population response width showed up to 20% of the response is due to between‐genotype effects, depending upon the character considered. Since the only way a sedentary organism can deal with a variable environment is through plasticity of response, differences in levels of phenotypic plasticity between genotypes on the two resource gradients were also investigated. There was no correlation between level of phenotypic plasticity and success over a range of environments. Niche breadth calculated as Levins' (B) and Roughgarden's (w2) indicated that flowering, and hence sexual reproduction, was limited to a much narrower range of environments than was vegetative growth. We also found significant genotype × environment interactions on both gradients, indicating differences in genetic response to the environment.
SYNAPTONEMAL COMPLEX KARYOTYPING OF TRADESCANTIA ZYGOTENE NUCLEI
Authors: Hasenkampf Clare A. , Menzel Margaret Y.
Published: January 2018

Zygotene synaptonemal complex karyotyping of five strains of diploid Tradescantia was carried out using the whole mount spreading technique. The presence of pairing partner switches in the zygotene preparations suggested the presence of chromosomal structural heterozygosity. Metaphase and Anaphase I analysis confirmed the presence of heterozygous translocations and inversions. Two plants analyzed had large centric fragments. In a nucleus from one, the fragments were completely synapsed; in a nucleus from the other, there was very little synapsis. Difficulties arose in adapting the whole mount spreading technique to the long Tradescantia chromosomes. Variability was encountered in both the contrast obtained and in the degree to which the chromosomal axes were stretched. Possible sources of the variability are discussed.
MECHANISMS OF ALUMINUM TOLERANCE IN TRITICUM AESTIVUM L. (WHEAT). I. DIFFERENTIAL PH INDUCED BY WINTER CULTIVARS IN NUTRIENT SOLUTIONS
Authors: Taylor Gregory J. , Foy Charles D.
Published: January 2018

Twenty winter cultivars of Triticum aestivum L. (wheat) were grown in solution culture with and without aluminum (Al) (74 μM, 2.0 mg L‐1) for 14 days. Exposure to Al increased root growth of the most tolerant cultivar, while both root and shoot growth were depressed in all other cultivars. On the basis of a root tolerance index (RTI = weight of roots grown with Al/weight of roots grown without Al), cultivar tolerance to Al ranged 9‐fold, from 0.13 ± 0.01 to 1.16 ± 0.10. Symptoms of Al toxicity were most evident on roots. Aluminum‐affected roots were relatively short and thick and had numerous undeveloped laterals. Leaves of some cultivars showed chlorosis resembling iron deficiency, and others showed purple stems typical of phosphate deficiency.

Plants of all cultivars grown with and without Al depressed the pH of nutrient solutions, presumably until NH4+ was depleted, at which point the pH increased. Cultivar tolerance, expressed both as the root tolerance index and a shoot tolerance index, was negatively correlated with the negative log of the mean hydrogen ion (H+) concentration, the minimum pH, and the slope of the pH decline, each calculated from pH data collected during the first 9 days of the experimental period before any sharp rises in pH occurred. These results are consistent with the hypothesis that the Al tolerance of a given cultivar is a function of its ability to resist acidification of the nutrient solution and hence to limit the solubility and toxicity of Al.
MECHANISMS OF ALUMINUM TOLERANCE IN TRITICUM AESTIVUM L. (WHEAT). II. DIFFERENTIAL PH INDUCED BY SPRING CULTIVARS IN NUTRIENT SOLUTIONS
Authors: Taylor Gregory J. , Foy Charles D.
Published: January 2018

Twenty spring cultivars of Triticum aestivum L. (wheat) were grown in solution culture with and without aluminum (Al) (74 μM, 2.0 mg L‐1) for 14 days. Root growth and shoot growth were depressed in all cultivars grown with Al; however, symptoms of Al toxicity were most evident on roots. Based on a root tolerance index (RTI = weight of roots grown with Al/weight of roots grown without Al), cultivar tolerance ranged from 0.18 ± 0.02 to 0.85 ± 0.03. Aluminum‐affected roots were relatively short, thick, and had numerous undeveloped laterals. Leaves of some cultivars showed chlorosis resembling iron deficiency and others showed purple stems typical of phosphate deficiency.

Plants of all cultivars induced a progressive decline in nutrient solution pH from the outset of the experiment until Days 10–14. After this initial period, some cultivars rapidly increased solution pH, while others continued to depress solution pH throughout the experiment. Cultivar tolerance expressed as the RTI was negatively correlated with the negative log of the mean hydrogen ion (H+) concentration, the minimum pH, and the slope of the pH decline, each calculated from pH data collected during the first 9 days of the experimental period before any sharp rises in pH. The relationship between solution pH and Al tolerance was similar to that reported previously for winter cultivars of T. aestivum, suggesting that the Al tolerance of a given cultivar is a function of its ability to resist acidification of the nutrient solution and hence to limit the solubility and toxicity of Al.
ULTRASTRUCTURE OF NICOTIANA ALATA POLLEN, ITS GERMINATION AND EARLY TUBE FORMATION
Authors: Cresti M. , Ciampolini F. , Mulcahy D. L. M. , Mulcahy G.
Published: January 2018

Both internal anatomy and external morphology of the mature pollen grain of Nicotiana alata have been studied, together with pollen activation and tube emergence and its cytological zonation.

A peculiar feature of mature pollen is the occurrence in the vegetative cell cytoplasm of a large quantity of stacked cisterns of rough endoplasmic reticulum, which then dissociate during pollen activation.

Pollen tube emergence generally occurs 2 hr 30 min after hydration, while cytological zonation is complete 4 hr 30 min after hydration when the first callosic plug is formed.
IDENTIFICATION OF STARCH IN FROST‐DAMAGED BRASSICA NAPUS (CANOLA) SEEDS
Authors: Van Caeseele L. , MacGregor A. W. , Mills J. T.
Published: January 2018

Frost‐damaged rapeseed, or canola seed, shows a range of symptoms including the presence of white patches on the surface. When a portion of a white patch was teased back, a large number of globular particles were seen within the epidermal cells of the seed. When the globules were treated with α‐amylase they were partially digested and when viewed with polarized light displayed a Maltese cross pattern indicative of an ordered molecular structure like that of starch. This indicates that the white color on frost‐damaged rapeseed was associated with an accumulation of starch granules. Epidermal cells of dark surface areas on frost‐damaged seeds also contained starchlike granules, but relatively few compared to cells in white patches.
MOVEMENT OF CALCIUM ACROSS TIPS OF PRIMARY AND LATERAL ROOTS OF PHASEOLUS VULGARIS
Authors: Moore Randy
Published: January 2018

Calcium (Ca) movement across tips of primary and lateral roots of Phaseolus vulgaris was determined by applying 45Ca2+ to one side of the root and collecting radioactivity in an agar receiver block on the opposite side of the root. The ratios of cpm in receiver blocks on the bottom of primary roots : cpm in receiver blocks on the top of primary roots were 1.87 and 2.47 after 1 and 2 hr, respectively. This polar transport of Ca across tips of primary roots correlated positively with a gravicurvature of 43° after 2 hr. The ratio of cpm in receiver blocks on the bottom of lateral roots : cpm in receiver blocks on the top of lateral roots was 1.20 after 2 hr. The decreased polar movement of Ca across tips of lateral roots correlated positively with lateral roots being nongraviresponsive. These data 1) support the suggestion that gravistimulation induces polar movement of Ca toward the lower side of tips of primary roots, and 2) suggest that the reduced polar movement of Ca across tips of lateral roots may be involved in uncoupling gravistimulation from gravicurvature in lateral roots.
FLAVONOID EVOLUTION IN ROBINSONIA (COMPOSITAE) OF THE JUAN FERNANDEZ ISLANDS
Authors: Pacheco Patricia , Crawford Daniel J. , Stuessy Tod F. , O Mario Silva
Published: January 2018

Leaf flavonoids were isolated and identified from 54 populations representing all seven species of Robinsonia, a genus of dioecious rosette trees endemic to the Juan Fernandez Islands. Fourteen compounds were detected consisting of flavonols, flavones, flavanones and dihydroflavonols. The distribution of these compounds in Robinsonia largely corresponds to specific and sectional limits based on morphological data. The morphologically similar species, R. gayana and R. thurifera, have identical flavonol profiles (derivatives of quercetin). Likewise, the closely related R. evenia and R. masafuerae are unique in the genus by possessing flavones. The inclusion of Rhetinodendron (i.e., R. berteroi) in Robinsonia is supported by its strong flavonoid similarity with species in two other sections of the genus. The morphologically diverse section Eleutherolepis exhibits the greatest flavonoid variation of any section, and only here are found flavones, flavanones and dihydroflavonols. The direction of flavonoid evolution in Robinsonia is hypothesized to be from fewer to more classes of compounds. Biosynthetic considerations suggest that this gain in compounds is due both to a gain of an additional enzymatic step and to the sequestering of precursors. This interpretation of direction of flavonoid evolution is in agreement with several lines of evidence including the flavonoid chemistry of the hypothesized outgroup (i.e., species of Senecio on mainland Chile), the ages of the two islands, and morphological trends.
THE EFFECT OF DELPHINIUM NELSONII POLLEN ON SEED SET IN IPOMOPSIS AGGREGATA, A COMPETITOR FOR HUMMINGBIRD POLLINATION
Authors: Kohn Joshua R. , Waser Nickolas M.
Published: January 2018

Sympatric plant species can compete for pollination services in several ways. For example, pollinators may move between species and deposit heterospecific pollen on stigmas, which in turn may reduce the efficacy of conspecific pollen. We explored this possibility by determining the effect of Delphinium nelsonii pollen on seed set in Ipomopsis aggregata. These montane herbs are pollinated by hummingbirds, experience heterospecific pollen deposition in nature, and suffer reduced seed set in each other's presence. We hand‐pollinated flowers of I. aggregata with either pure conspecific pollen or a mixture of pollen of the two species. Resulting pollen loads on stigmas ranged from 0–865 D. nelsonii grains and from 10–336 I. aggregata grains; mean seed set per flower was 11.3. There was no detectable effect of D. nelsonii pollen load on I. aggregata seed set. It is possible that seed set reductions seen in previous studies of competition for pollination between these species were caused by pollen wastage, pollen layering on the pollinator, or the temporal sequence of pollen arrival at the stigma.
ANALYTICAL RESOLUTION OF THE CRYSTALLINE SAND PYRAMIDS
Authors: Cody A. M. , Horner H. T.
Published: January 2018

Pyramid‐shaped crystals of calcium oxalate comprise the “crystal sand” found in certain flowering plants. They have presented an enigma to both botanists and crystallographers since their description nearly a century ago. Even though it is impossible to build a tetrahedron from the atomic lattice cell units of the mineral, the four‐sided crystals are found within vacuoles of plant cells. Scanning electron microscopy, acid‐etching procedures, x‐ray analysis, and the results of synthetic in vitro crystal‐growth experiments were used to resolve the problem. Individual crystals of crystal sand are shown to be twin and triplet crystals. A newly presented Stability Determination Procedure distinguishes the hydration forms of phytocrystalline calcium oxalate by their stability in oxalic acid. It shows crystal sand to be calcium oxalate monohydrate. Based on information from plant crystal sand, a new twofold rotational twin axis is proposed for the mineral whewellite.
ON RHIZOCLADS IN THE OAK FERN, QUERCIFILIX ZEILANICA
Authors: Bierhorst David W.
Published: January 2018

Stem branches in Quercifilix arise in the axils of roots at their attachment to the parent rhizome or apically upon a new root before it has erupted from the tissues of the rhizome. In either case, they arise from the surface cells of the accessory calyptra. When the new stem arises apically, the root apex and the root cap give rise to a continuous core of procambium. The apical cell of the root becomes a tracheid, more or less retaining its original shape. The root‐shoot axis thus produced is referred to as a rhizoclad.
NUCLEAR DNA CONTENT VARIATION IN HELIANTHUS (ASTERACEAE)
Authors: Sims Lynne E. , Price H. James
Published: January 2018

Nuclear 2C DNA content was microspectrophotometrically determined for 19 diploid (2n=34) species of Helianthus L. DNA amount varied over a fourfold range. Helianthus neglectus had the lowest (53.40 ± 0.51 Feulgen absorbancy units [FAU]) and H. agrestis the highest (216.30 ± 2.30 FAU) DNA content. Chromosome size ranged from 1.1–1.7 μm long in H. neglectus to 3.2‐5.0 μm long in H. agrestis. When the highly divergent H. agrestis was excluded from analyses, the mean of the annual species (70.05 FAU) was significantly different from the mean of the perennials (97.70 FAU). No correlations of DNA content with habitat, soil type, annual precipitation, or geographical location were apparent among species.
REPRODUCTIVE BIOLOGY OF DISTYLOUS PARTRIDGEBERRY, MITCHELLA REPENS
Authors: Hicks David J. , Wyatt Robert , Meagher Thomas R.
Published: January 2018

Long‐styled (pin) and short‐styled (thrum) plants in populations of Mitchella repens from North Carolina and New York displayed strongly clumped spatial dispersion. This distribution pattern results from the tendency of these prostrate perennials to spread by production of trailing stems with adventitious roots. Both morphs, in both populations, exhibited natural fruit set exceeding 86%. This percentage was not increased by hand‐pollination. Although the number of ovules per pair of ovaries was fixed at eight in each morph, numbers of seeds per fruit in naturally pollinated flowers differed significantly between pins (4.3) and thrums (6.4) in the North Carolina population. In the New York population, no significant differences were found (pins had 5.0 seeds per fruit; thrums, 4.4). Artificial pollinations in both populations showed low seed set in intramorph cross‐pollinations as compared with intermorph crosses. The flowers of M. repens were visited by native species of Bombus, which visited many flowers in each patch of plants. These insects moved frequently from patch to patch, effecting intermorph cross‐pollination and maintaining high levels of seed set. Movement among patches may be promoted by the dispersion of nectar rewards, with flowers about to open or just opened providing maximum amounts of nectar. Calculations of functional gender suggested that in the North Carolina population, thrums contributed more than 75% of the genes transmitted by ovule production. This contrasts strongly with previous studies of unequal sexual contributions in distylous taxa, which have demonstrated greater female contributions by pins. In the New York population, however, nearly equal contributions by pins and thrums through pollen and ovule production occurred, a situation similar to that found in most distylous species. This appears to be the first demonstration of variation in functional gender between populations of a single species.
BREEDING SYSTEMS OF CENTRAL AMERICAN APHELANDRA (ACANTHACEAE)
Authors: McDade Lucinda A.
Published: January 2018

Controlled pollinations, followed by germination studies of seeds resulting from self‐ and cross‐pollination, were carried out using plants from 12 populations of nine species of Aphelandra (Acanthaceae), a genus of neotropical shrubs and herbs. These results are combined with data from field studies of flower morphology, phenology, and pollinator relationships to estimate breeding system of each species. All species have floral morphological traits that prevent autogamy. Plants from five populations of five species experience low levels of geitonogamous pollen transfer; they produce few flowers daily and are pollinated by traplining hummingbirds. Excepting A. storkii, these plants are fully self‐compatible (SC), and seeds from selfing are as viable as crossed seeds. Aphelandra storkii is partially self‐incompatible (SI) and produces seeds from selfing that tend to germinate less successfully than crossed seeds. Plants from the remaining populations are profusely flowering shrubs, and even those pollinated by traplining hummingbirds should experience higher levels of geitonogamy. Aphelandra deppeana is pollinated by territorial hummingbirds, which should further increase the incidence of geitonogamy. All shrub species are partially SI, and two species (A. leonardii and A. sinclairiana) show significant reduced germination of selfed vs. crossed seeds. The breeding system of these species is thus modified by postpollination factors that favor the formation and maturation of outcrossed seeds. It is suggested that Aphelandra species, like other herbs and shrubs of tropical forest understory, possess a combination of breeding system traits that promote outcrossing but do not exclude geitonogamy.
CELL DETERMINATION DURING EMBRYOGENESIS IN CITRUS JAMBHIRI. II. EPIDERMAL DIFFERENTIATION AS A ONE‐TIME EVENT
Authors: Bruck David K. , Walker Dan B.
Published: January 2018

Shallow peridermal tissue slices taken from leaves, stems, and roots of various ages and positions resulted in wound periderm formation at the cut surface. The outcome was similar in embryos treated and grown in a nurse ovule culture system. Torpedo and older embryos developed wound periderm, while globular and heart‐shaped embryos formed a disorganized, extensible callus. Epidermis did not regenerate at any time. These responses are consistent with the conclusion that epidermis is normally initiated only one time in the life of the shoot system. They also support our proposal that internal derivatives of the zygote diverge from epidermal differentiation and cannot retreat back to an epidermal pathway.
COLONIZATION AND ESTABLISHMENT OF MISSOURI PRAIRIE PLANTS ON ARTIFICIAL SOIL DISTURBANCES. III. SPECIES ABUNDANCE DISTRIBUTIONS, SURVIVORSHIP, AND RARITY
Authors: Rabinowitz Deborah , Rapp Jody K.
Published: January 2018

We examined the process by which a pool of colonists was reduced to a pool of survivors in 160 small microsites on undisturbed tall‐grass prairie in Missouri. Specifically, did the degree of species dominance shift as mortality proceeded and did rare and common species differ in their survivorship? Over 4 yr, 25 taxa of seedlings appeared and 12 survived until the end of the experiment; these pools contained 550 and 79 identified individuals, respectively. For vegetative shoots, 36 taxa appeared and 20 survived, with 1,750 and 387 identified individuals, respectively. Mean survivorship for seedlings (119 ± 87 days) was briefer than for shoots (165 ± 107 days). While species richness was lower among survivors than colonizers, it was not lower than one would expect based on random mortality. Rare species were not disproportionately lost given their population sizes in the microsites. Taxa that were common in the source pool remained common as survivors. The survivors showed more equitable species abundance distributions than the colonists, due to higher mortality among a few of the more common species. For the entire pool of colonists, there was no relationship between abundance and survivorship. In general, rare species did not have higher mortality than common species. These results do not support the notion of regeneration as a competitive “sorting out” of successful dominant from unsuccessful rarer species. Rather, they portray waves of turnover of tiny plants, with species largely acting independently of one another.
SOIL AGGREGATION BY CRYPTOGAMS OF A SAND PRAIRIE
Authors: Schulten Julia A.
Published: January 2018

Cryptogam‐covered, sandy soils of the Big Sand Mound prairie in southeastern Iowa are significantly more aggregated than bare soils. Soil particles covered by moss are intertwined by rhizoids, whereas cyanobacteria and lichen fungal hyphae adhere to the particles and glue them together. Lichen‐covered samples that were tested and oven dried, then retested 2 yr later, retain their aggregation, indicating that the aggregating material is stable even after the death of the fungus.
DUAL FUNCTION OF THE ELAIOSOME OF CORYDALIS AUREA (FUMARIACEAE): ATTRACTION OF DISPERSAL AGENTS AND REPULSION OF PEROMYSCUS MANICULATUS, A SEED PREDATOR
Authors: Hanzawa Frances M. , Beattie Andrew J. , Holmes Anne
Published: January 2018

It has been suggested that one of the selective advantages of ant dispersal is the burial of seeds in ant nests where predators such as small rodents cannot find them. The elaiosomes of Corydalis aurea (Fumariaceae) are extremely attractive to ants, which assiduously gather the seeds and take them to nests. However, seed production commonly exceeds the gathering capacity of ants so that seeds accumulate beneath the parent plants. In spite of this, no signs of rodent predation are evident. Experiments with a major seed predator, the deer mouse Peromyscus maniculatus, show that when given the choice of seeds with and without elaiosomes, the mice consume significantly more seeds without elaiosomes. This remains true whether or not the intact seeds bear fresh, moist elaiosomes or dry, withered ones. Our experiments strongly suggest that the elaiosome has a dual function, the attraction of the ant seed dispersers and the repulsion of seed predators.
MALE STERILITY IN SOYBEAN (GLYCINE MAX). II. PHENOTYPIC EXPRESSION OF THE ms4 MUTANT
Authors: Graybosch Robert A. , Palmer Reid G.
Published: January 2018

Observations on the reproductive biology of a male‐sterile mutant (ms4) of soybean, Glycine max (L.) Merr., demonstrated that male sterility was the result of a syndrome of abnormalities that influenced the function of the postmeiotic microspore mother cells (MMCs). Cytokinesis following telophase II was absent, incomplete, or disoriented, resulting in cells with different numbers of nuclei. Postmeiotic cells demonstrated various abnormalities in the formation of pollen walls. The nature of the exine ranged from absence through amorphous accumulations of sporopollenin to stratified layers. Infrequently, anther locules functioned properly, and normal pollen was differentiated. The extent and frequency of cytokinesis varied both between and within locules of single anthers. Temperature influenced the frequency of cytokinesis. At temperatures of 35 C day/32 C night, cytokinesis did not occur. Male sterility was concluded to result from the cumulative effects of various abnormalities, all of which involve functions of the postmeiotic MMCs' plasmalemmas.
ABNORMAL DEVELOPMENT OF THE SUSPENSOR IN AN EMBRYO‐LETHAL MUTANT OF ARABIDOPSIS THALIANA
Authors: Marsden Margery P. F. , Meinke David W.
Published: January 2018

Developmental arrest of the embryo proper in aborted seeds from mutant 50B, a recessive embryo‐lethal mutant of Arabidopsis thaliana, was shown to be followed by abnormal growth of the suspensor. Each of the 12 aborted seeds examined in sectioned material contained an abnormally large suspensor and an embryo proper arrested at a preglobular stage of development. Analysis of serial sections revealed that mutant suspensors contained 15–150 cells whereas wild‐type suspensors were composed of only six to eight cells. Development of the mutant endosperm continued to a late nuclear or early cellular stage even in the absence of further development of the embryo proper. These results suggest that the missing gene product in mutant 50B is required for development of the embryo proper but not for continued growth of the suspensor or endosperm tissue. The pattern of abnormal development observed in this mutant provides further evidence that continued growth of the suspensor during normal development is inhibited by the developing embryo proper and that the full developmental potential of cells in the suspensor is expressed only when this inhibitory effect is removed through a mutation or experimental treatment that is lethal only to cells of the embryo proper.
THE CRETACEOUS PTERIDOSPERMS RUFLORINIA AND KTALENIA AND IMPLICATIONS ON CUPULE AND CARPEL EVOLUTION
Authors: Taylor Thomas N. , Archangelsky Sergio
Published: January 2018

The vegetative (Ruflorinia sierra) and fertile (Ktalenia circularis) organs of an Early Cretaceous pteridosperm collected from Santa Cruz Province in Argentina are described. The sterile leaf is at least tripinnate and bears decurrent secondary pinnae with obliquely attached, sharply pointed pinnules. The fertile member arises from the base of the vegetative rachis and bears two types of appendages, cupules and bracts. Bracts are attached to the main axis near cupules and are present in clusters of up to six. Cupules are sessile, spherical, and arranged in opposite or subopposite pairs along the axis. A small lip is present on one surface of the cupule. The number of seeds per cupule may be one or two, with each characterized by a distal nucellar beak and circular, chalazal scar. Cuticular anatomy, including the fine structure of the stomatal complex, is described for both vegetative and reproductive organs. The cupules of Ktalenia and other Mesozoic seed plants are compared, and a discussion presented regarding the possible function of the cupule.
ASSOCIATION OF α‐AMYLASE WITH CELLULAR AUTOLYSIS IN PEA STEM TISSUES
Authors: Davis Bill D.
Published: January 2018

Increased activity of α‐amylase in bean stems occurred during cellular autolysis in the pith region. In etiolated pea seedlings, α‐amylase activity increased sequentially in the first, second, and third internodes. In light‐grown seedlings, the increase was initially observed in the first internode, then simultaneously in the second and third internodes. In all internodes, these changes were observed in regions undergoing cellular autolysis in the cortex region. As in bean hypocotyls, α‐amylase activity occurred in tissues virtually devoid of starch. Sequential accumulation and then decline in protein and sugar concentrations in each internode indicate a remobilization of materials from nongrowing regions of the stem. These results are consistent with the hypothesis that regulation of α‐amylase activity is related to this remobilization.
HISTOLOGY OF SOMATIC EMBRYOGENESIS IN PANICUM MAXIMUM (GUINEA GRASS)
Authors: Lu Chin‐yi , Vasil Indra K.
Published: January 2018

Immature embryos of Panicum maximum Jacq. (Guinea grass) were cultured on Murashige and Skoog's medium containing 2,4‐dichlorophenoxyacetic acid (5 mg/1) and coconut milk (5%). The epidermal and subepidermal cells of the scutellum at the coleorhizal end either formed somatic embryos directly or gave rise to embryogenic callus at several loci. Somatic embryos were formed later also at the periphery of these embryogenic calli. The embryoids originated from single, densely staining, nonvacuolated and starch‐containing cells with thickened walls and developed through characteristic stages of grass embryogeny.
FRUIT RIPENING ASYNCHRONY IS RELATED TO VARIABLE SEED NUMBER IN AMELANCHIER AND VACCINIUM
Authors: Gorchov David L.
Published: January 2018

Two vertebrate‐dispersed woody plants, Vaccinium corymbosum and Amelanchier arborea, were studied in southeastern Michigan to determine the proximate causes of their within‐plant fruit ripening asynchrony. Individual flowers were followed from opening (A. arborea) or fruit initiation (V. corymbosum) to fruit ripening. Fifty‐nine to 100% of the variance in fruit‐ripening dates within V. corymbosum plants was due to variance in the development time; little was due to variance in initiation dates or covariance between these two terms. Similarly, 98% of the variance in fruit‐ripening dates in A. arborea was due to variance in the number of days from flower opening to fruit ripening. Fruit developmental time in V. corymbosum and flower‐fruit interval in A. arborea were significantly correlated with seed number: fruits with more seeds developed faster. I hypothesize that in both species ripening asynchrony is largely a consequence of variability in seed number.
INTROGRESSION IN CENTRAL AMERICAN PHYTOLACCA (PHYTOLACCACEAE)
Authors: Davis Jerrold I.
Published: January 2018

A numerical analysis of morphological variation in Central American Phytolacca distinguishes P. rivinoides Kunth & Bouché from the P. iscosandra complex, which includes elements that have been recognized as P. icosandra L., P. octranda L., P. purpurascens A. Br. & Bouché, P. rugosa A. Br. & Bouché, and P. costaricensis Suesseng. A third and rarely collected taxon, P. meziana H. Walt., is also distinguished. New chromosome counts of 2n = 36 are recorded for P. rivinoides and two representatives of the P. icosandra complex. Nearly half the morphological variation in the sample is summarized by a multivariate axis that separates P. rivinoides from the P. icosandra complex. This axis correlates with a cline in elevation; P. rivinoides occurs between sea level and 2,200 m, and P. rugosa occurs between 1,000 and 3,400 m. It is hypothesized that introgression of the P. rivinoides genome into that of P. rugosa has generated the P. icosandra complex; elements of this complex then migrated northward through Mexico and may have been progenitors of the North American P. americana L.
DIRECT EMBRYOGENESIS FROM CULTURED ANTHERS AND PISTILS OF DACTYLIS GLOMERATA
Authors: Songstad D. D. , Conger B. V.
Published: January 2018

Direct somatic embryoids were initiated from orchardgrass (Dactylis glomerata L.) anthers and unpollinated pistils cultured in the dark at 25 C on Schenk and Hildebrandt (SH) medium supplemented with 30 μM dicamba (3,6 dichloro‐o‐anisic acid). Stereoscopic and scanning electron microscopy indicated that the embryoids originated from anther walls and from ovary and style regions of pistils. Callus initiation from direct embryoids leading to secondary embryogenesis was observed in pistils cultured from 4–6 wk. The ability of these calli to proliferate and initiate new embryoids through the dedifferentiation and redifferentiation of preexisting embryoids suggests long‐term totipotency.
GEOGRAPHIC PATTERNS OF ALLOZYME VARIATION IN JEFFREY PINE
Authors: Furnier Glenn R. , Adams W. T.
Published: January 2018

Genetic structure of seven Jeffrey pine (Pinus jeffreyi Grev. & Balf.) populations restricted to ultramafic soils in the Klamath Mountains of Oregon and California was compared to that of seven populations occurring on a broader range of soils in the rest of the range (Sierra Nevada‐southern California). Patterns of variation at 20 allozyme loci were examined. Eighteen loci were polymorphic in at least one population. Despite discontinuous distribution in the Klamath Mountains, differentiation was limited among the seven populations. Average expected heterozygosity, however, was lower there (mean He = 0.185) than in the Sierra Nevada‐southern California region (mean He = 0.255). Significant differences (P < 0.05) in allele frequencies between the two regions were found at 11 loci. Of Sierra Nevada‐southern California populations, the one on ultramafic soil was most similar to Klamath populations in allele frequencies, which suggests genetic adaptation to such soils. Lower expected heterozygosity in the Klamath region may reflect strong directional selection under harsh soil conditions, genetic drift in an ancestral population, or both.