bluuebunny/crossref_metadata_2025 huggingface dataset:
DETECTING SHAPE VARIATION IN OAK LEAF MORPHOLOGY: A COMPARISON OF ROTATIONAL‐FIT METHODS
Authors: Jensen Richard J.
Published: January 2018

Rotational‐fit methods were used to examine shape variation in oak leaf morphology by reference to a set of 14 landmarks for each leaf. Within‐tree, between‐tree, and between‐species variations were examined. Generalized least‐squares and generalized resistant‐fit analyses revealed patterns of landmark variation that could be related to leaf architecture. The two species (Quercus palustris and Q. velutina) did not illustrate the same patterns of within‐tree variability nor did they reveal similar degrees of between‐tree variability. Incorporating an affine transformation algorithm resulted in little insight in some comparisons but suggested strong uniform shape change in other comparisons (especially between species). Resistant‐fit mean square statistics were equally variable 1) in upper vs. lower crown samples within trees, 2) between trees within each species, and 3) between species. In addition, resistant‐fit mean square statistics were found to be a poor measure of similarity, whether derived by comparison to a single reference object or by way of pairwise comparisons. Fundamental species differences in leaf shape are suggested by relationships among particular sets of landmarks, although overall shape differences cannot be explained fully by these analyses.
SEED SIZE AND HABITAT EFFECTS ON THE WATER‐DISPERSED PERENNIAL, CRINUM ERUBESCENS (AMARYLLIDACEAE)
Authors: Manasse Robin S.
Published: January 2018

Crinum erubescens (Amaryllidaceae), a water‐dispersed herbaceous perennial occupying the margin between land and freshwater lakes and swamps in Panama, produces seeds of highly variable size (0.1–66.5 g). Seeds were grown under conditions mimicking natural habitat types (water; saturated, undrained soil; moist, drained soil; and drained soil, saturated every third day) to determine whether either small or large seeds perform better in some habitats. Time to germination and percent germination are not related to seed size in any habitat type. Small seeds are less likely to survive in water, but not in other habitat types. Growth is positively associated with seed size in all habitat types and is greatest in saturated soil. Unlike studies with terrestrial plants, the benefits of having a large seed are demonstrated in the absence of competition.
DEVELOPMENTAL CHANGES IN THE COTYLEDONS OF LUPINUS LUTEUS L. DURING AND AFTER GERMINATION
Authors: Asghar Rehana , DeMason Darleen A.
Published: January 2018

Cotyledons of Lupinus luteus were sampled from 1 to 21 days after sowing and processed for light microscopy and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). Length, width, and surface area of the cotyledons increased gradually until day 10. The thickness of the cotyledons increased from day 7 to day 12 and decreased thereafter. Morphometric analyses showed that the increase in length, width, and thickness of the cotyledon was due to cell expansion, and the decrease in thickness of the cotyledon was due to the decrease in the length of abaxial cells and in the total number of cells. Mesophyll development accompanied schizogenous and lysigenous air space formation. There were two structurally distinct types of protein bodies. Protein bodies in five to six layers of cells on the abaxial side did not contain globoids, while globoids were prominent in protein bodies in the center and adaxial side. Storage protein mobilization occurred first in the abaxial side of the cotyledon and proceeded toward the adaxial side. SDS‐PAGE analysis showed that proteins ranged from 97 to 14 kD. High molecular weight α‐ and ß‐conglutinins were more abundant in the abaxial region, whereas γ‐conglutinin occurred in both abaxial and adaxial regions. In addition, there were five minor bands between 97 and 43 kD unique to abaxial region and five minor bands between 43 and 14 kD unique to adaxial region in the nonreduced protein profiles. The α‐ and ß‐conglutinins began to decrease after imbibition and disappeared by day 7 after sowing. At this stage the subunits of ribulose‐l,5‐bisphosphate carboxylase/oxygenase and four new minor bands appeared.
AN EXAMINATION OF POLYPLOIDY AND PUTATIVE INTROGRESSION IN CALOCHORTUS SUBSECTION NUDI (LILIACEAE)
Authors: Ness Bryan D. , Soltis Douglas E. , Soltis Pamela S.
Published: January 2018

Calochortus subsection Nudi (section Calochortus) comprises four extant species distributed from central California to southern Oregon. To elucidate relationships within this group, morphological, cytological, and electrophoretic investigations were undertaken. Allozyme data revealed two distinct groups in subsection Nudi: a coastal group, comprising C. uniflorus and C. umbellatus; and a Sierran group, comprising C. minimus and C. nudus. Calochortus uniflorus consists of diploids (n = 10) and tetraploids (n = 20). Several lines of evidence suggest that tetraploid C. uniflorus may be an autotetraploid: 1) quadrivalents were observed during meiosis in tetraploid C. uniflorus; 2) the mean genetic identity between the diploid and tetraploid cytotypes was much higher (Ī = 0.963) than between either cytotype and C. umbellatus (Ī = 0.903 and 0.904 for 2x and 4x, respectively); 3) diploid and tetraploid individuals of C. uniflorus were indistinguishable morphologically; and 4) both cytotypes of C. uniflorus occupy vernal meadows, whereas C. umbellatus occupies exposed serpentine ridges. Data from morphology and enzyme electrophoresis suggest that introgression, or at least extensive hybridization, has occurred between C. minimus and C. nudus. Principal coordinate analysis showed that pure C. minimus and C. nudus are morphologically distinct and that putatively introgressive populations are morphologically intermediate. Most putatively introgressive populations displayed reduced pollen viability relative to pure C. minimus and C. nudus. Allozyme data are consistent with the concept that hybridization and possibly introgression may have occurred between C. minimus and C. nudus. When allozyme data were analyzed by the unweighted pair‐group method of cluster analysis using arithmetic means, most putatively introgressive populations were placed between the C. minimus and C. nudus populations.
METAMORPHOSIS IN THE ARACEAE
Authors: Ray Thomas S.
Published: January 2018

In the Araceae, as in many other monocotyledons, the stem undergoes gradual thickening as successive internodes are produced. Along with this primary thickening of the stem, successive foliage leaves will be larger and often more complex. In many species, in addition to these and other gradual changes, there are abrupt changes, metamorphoses, that occur under certain conditions. Some metamorphoses are the result of endogenous cycling (e.g., Syngonium, Rhektophyllum, Philodendron linnaei), some are a response to changes in conditions in the environment, usually the gain or loss of contact with a substrate (e.g., Syngonium, Monstera, Rhodospatha, Philodendron section Pteromischum), and some occur when the plant reaches a certain level of maturity (e.g., Monstera). Some of these latter changes are associated with a transition from monopodial to sympodial growth (e.g., Philodendron, Anthurium). Metamorphosis enhances the developmental plasticity of the Araceae in two distinct ways: it allows for a more complex relationship between size and shape in the development to maturity, and it allows shoots to engage in dispersal activities and developmental holding patterns when conditions are not suitable for development to the adult form and reproduction.
ORGANIZATION OF ISOLATED EMBRYO SACS AND EGGS OF PLUMBAGO ZEYLANICA (PLUMBAGINACEAE) BEFORE AND AFTER FERTILIZATION
Authors: Huang Bing‐Quan , Russell Scott D. , Strout Gregory W. , Mao Lian‐Ju
Published: January 2018

The organization of isolated embryo sacs and eggs of Plumbago zeylanica was described before and after fertilization using microscopic cytochemistry and scanning electron microscopy. Major developmental events of fertilization, including preferential fertilization and early embryogenesis, are described in isolated embryo sacs. The two sperms, one unassociated with vegetative nucleus (Sua) and the other physically associated with the vegetative nucleus (Svn), fuse with nuclei of egg and central cell, respectively. The zygote divides asymmetrically to form a two‐celled embryo, consisting of a massive suspensor occupying most of the micropylar portion of the embryo during early embryogenesis. Plastids are distributed in the perinuclear and micropylar regions of the egg cell and in cytoplasmic strands of the central cell before fertilization. Calcofluor white‐positive fibrillar material in the filiform apparatus (presumed β‐1,4 linked glucans) was investigated using scanning electron microscopy. The egg of P. zeylanica can easily be divided into three cytologically distinct regions: 1) perinuclear cytoplasm, 2) lateral cytoplasm, and 3) micropylar cytoplasm. Cytological differences are evident in the organization of the cell walls, general degree of vacuolization, and the distribution of heritable organelles, storage bodies, and microtubules. The present study supports the concept that the egg of P. zeylanica plays combined synergid and gamete functions.
ECOLOGICAL CONSTRAINTS TO SEEDLING ESTABLISHMENT ON THE PUMICE PLAINS, MOUNT ST. HELENS, WASHINGTON
Authors: Wood David M. , Morris William F.
Published: January 2018

For both Epilobium angustifolium and Anaphalis margaritacea, the two dominant species in primary succession on the Pumice Plains on Mount St. Helens, density of the seed rain far exceeds the density of colonists. To test the hypothesis that colonization rate is limited by processes occurring during seedling establishment, we investigated the effects of subsurface moisture (using a wet and a dry site), microtopography (fine and coarse pumice particles), and seed size (five size classes), and monitored the fates of seedlings originating from experimentally sown seed for 2 years. Subsurface moisture had the strongest effect on seedling emergence and survival. By the second year there were over 20 times as many seedlings in the wet site as in the dry site; survival in the latter site was nearly zero. Coarse pumice plots had greater establishment than did fine pumice plots. Emergence rate increased significantly with increasing seed size, but this initial difference disappeared by the second year. A. margaritacea established under a wider range of conditions than did E. angustifolium. We conclude that colonization by these species, and hence rate of primary succession, is limited by availability of safe sites for germination and establishment and not by seed dispersal. Safe sites are defined primarily by the level of subsurface moisture and secondarily by microtopography and seed size, and have a greater effect on seedling emergence than on seedling survival.
EFFECTS OF SOIL WATER DISTRIBUTION ON THE LATERAL ROOT DEVELOPMENT OF THREE SPECIES OF CALIFORNIA OAKS
Authors: Callaway Ragan M.
Published: January 2018

The responses of seedling root systems of three species of oaks in California to two experimental soil moisture regimes were studied by comparing lateral root development, root and shoot weights, and root: shoot ratios. In the first soil moisture treatment the taproot was allowed to extend into moist soil throughout the duration of the experiment (control), while in the second treatment (shallow) the taproot grew into a dry substrate below 30 cm of moist soil. The treatments were intended to approximate soil moisture conditions experienced by oak seedlings in the field when deep soil water sources vary in their accessibility (control: accessible, shallow: inaccessible). Lateral root growth of Quercus agrifolia did not increase significantly when the primary root tip died in the shallow treatment, resulting in an overall decrease in the percent of the root system composed of lateral roots. Q. douglasii and Q. lobata increased lateral root weights by 80% and 70%, respectively, on the upper 30 cm of the primary root when the primary root tip died. Q. lobata was the only species that decreased in shoot and root weight (25% and 21%, respectively) with the loss of the root tip, indicating that, unlike the other species, it was dependent on the primary root for maximum growth. The morphological responses of these species correspond with their distributions and also may be a factor that influences their interactions with other species.
A METHOD FOR DETERMINING PLASTOCHRON INDICES DURING HETEROBLASTIC SHOOT GROWTH
Authors: Hill Jeffrey P. , Lord Elizabeth M.
Published: January 2018

A plastochron is defined as the time interval between two successive recurring events during the growth of plant shoots, such as leaf initiation. The plastochron index (PI) formulated by Erickson and Michelini (1957, American Journal of Botany 44: 297–305) provides a method for determining 1) morphological equivalence in a developmentally variable sample of shoots and 2) rates of development in microscopic tissues and organs, by expressing shoot age as a function of plastochron number. The PI assumes that homologous organs at successive nodes grow exponentially, at equal rates, and the plastochron remains constant. These three conditions are not met in many shoots that exhibit heteroblasty in their plastochron and the growth rate of organs at successive nodes. An alternative computational method for the PI is presented that uses two measurements taken at different times from the same organ during its exponential growth phase. The method does not assume that the PI is a linear function of time. Results of an analysis of cyme internode growth in two races of Arenaria uniflora (Caryophyllaceae) demonstrate that the method proposed is in good agreement with Erickson and Michelini's (1957) method when shoot growth is not markedly heteroblastic. The current method is also used to determine the nonlinear relation between PI and time in a race of A. uniflora that has heteroblastic cyme growth. The results generalize the PI for use in studies of heteroblasty, and for shoots where the relative plastochron rate cannot be directly determined.
WOOD ANATOMY AND RELATIONSHIPS OF LACTORIDACEAE
Authors: Carlquist Sherwin
Published: January 2018

Mature wood of Lactoris, not previously available for study, reveals ten distinctive characters: vessels with simple perforation plates; vessels in pore multiples; vessel‐to‐axial parenchyma pits scalariform or transitional, vessel‐to‐vessel pits alternate; fiber‐tracheids with vestigial pits; fiber‐tracheids, vessels, and axial parenchyma storied; axial parenchyma vasicentric scanty; axial parenchyma either not subdivided or, if subdivided, with thin nonlignified walls between the cells (like the septa in septate fibers); rays wide and tall, little altered during ontogeny; ray cells upright; and ray cells taller adjacent to fascicular areas. All of these features occur in woods of Piper and other Piperaceae. The systematic position of Lactoris is therefore reassessed. Evidence available to date is consonant with placement of Lactoridaceae in Piperales, in which it would be more primitive than Piperaceae or Saururaceae. Features cited as evidence for alternative placements of Lactoridaceae are reviewed.
CHASMOGAMY/CLEISTOGAMY IN TRIODANIS PERFOLIATA (CAMPANULACEAE): SOME CH/CL COMPARISONS IN FITNESS PARAMETERS
Authors: Gara Brian , Muenchow Gayle
Published: January 2018

The chasmogamous/cleistogamous (CH/CL) breeding system has evolved independently many times, but its ecological role has been studied in few species. In Triodanis perfoliata, we studied the natural phenology of flowering and seed set, how successful CH flowers were at setting seed, whether seed from CH and CL flowers differed in germination behavior, and whether plants derived from these two seed types differed in vigor. Most notably, we found that the later the CH flowers were produced, the fewer seed they successfully matured. In general the two seed types did not show differences in germination behavior, but for some maternal parents the two seed types differed. For these, the CL seed germinated less readily. Finally, there was some indication that plants from CL seed were not as vigorous as those from CH seed.
ACTIN MICROFILAMENTS IN PRESUMPTIVE STATOCYTES OF ROOT CAPS AND COLEOPTILES
Authors: White R. G. , Sack F. D.
Published: January 2018

Rhodamine‐phalloidin was used to determine the distribution of actin microfilament bundles (mfb) in cells thought to be the site of gravity perception (statocytes) in coleoptiles and root caps ofZea maysandHordeum vulgare.In coleoptile cells, amyloplasts were usually observed in close proximity to thick mfb, which often appeared to divide into finer mfb adjacent to individual amyloplasts. The nucleus in these cells was surrounded by an extensive network of mfb, which were connected to thicker transvacuolar mfb. Columella cells of the root cap contained an extensive reticulum of fine mfb throughout the protoplast, but lacked the much thicker mfb seen in coleoptile cells. The distribution and extent of mfb observed in fixed cells correlates with patterns of streaming and amyloplast movement seen in living cells. A possible role for actin mfb in the perception of gravity is discussed.
LEAF DEVELOPMENT IN THE NORMAL AND SOLANIFOLIA MUTANT OF TOMATO (LYCOPERSICON ESCULENTUM)
Authors: Sekhar K. N. Chandra , Sawhney V. K.
Published: January 2018

Leaf development in the normal (lobed margin) and the solanifolia (sf/sf) mutant (entire margin) of tomato (Lycopersicon esculentum) was compared at the light and scanning electron microscope levels. The shoot apices of the mutant plants contained microbodies near the axil of the youngest leaf, which were absent in the normal plants. The structural and morphological events in the initiation of leaf primordia were similar in the two genotypes. The pattern of leaflet emergence was also similar in the two types of plants, but the timing of leaflet production was different. The first pair of leaflet primordia in the normal plants was produced on P3, whereas in the mutant it was not produced until P5. The adult leaves of sf/sf plants were larger than those of normal, and the greater leaf area in the mutant was associated with a greater adaxial epidermal cell and areole area. A continuous marginal fimbriate vein (MFV) was present along the margin of each of the normal leaflets. However, a continuous MFV was absent in the mutant leaflets. It is suggested that the absence of a continuous MFV in the mutant might alter the nutritional and hormonal supply to the leaf margin, which ultimately leads to a modified leaf, i.e., with an entire margin.
PHYLOGENETIC IMPLICATIONS OF DIFFERENCES IN NUMBER OF PLASTID PHOSPHOGLUCOSE ISOMERASE ISOZYMES IN NORTH AMERICAN COREOPSIS (ASTERACEAE: HELIANTHEAE: COREOPSIDINAE)
Authors: Crawford Daniel J. , Smith Edwin B. , Roberts Marvin L. , Benkowski Maryan , Hoffman Melinda
Published: January 2018

Enzyme electrophoresis was employed to ascertain the number of loci encoding plastid phosphoglucose isomerase (PGI) in species representing all sections of North American Coreopsis. Several species from each of the closely related genera Bidens, Coreocarpus, Cosmos, and Thelesperma were also examined. Species in nine of the 11 sections of North American Coreopsis have two isozymes for plastid PGI, and nearly all species examined in the four other genera also have two (one species has three) isozymes. Since most diploid vascular plants have one plastid PGI isozyme, a gene duplication probably occurred in an ancestor that is common to Coreopsis and the other four genera. That is, two isozymes represent the ancestral number for Coreopsis. The two sections (Electra and Anathysana) apparently lacking the duplication are closely related woody plants restricted largely to Mexico. One gene encoding plastid PGI ostensibly was silenced in a common ancestor of these two sections. This is concordant with other data suggesting a close relationship between the two sections, i.e., they appear to represent a monophyletic group. The electrophoretic data also indicate that 1) the enigmatic monotypic section Silphidium is more closely related to eastern North American sections and not derived from section Electra; and 2) section Anathysana is not ancestral to the three California sections Leptosyne, Pugiopappus, and Tuckermannia; rather, it represents a terminal element closely related to and possibly derived from section Electra.
ANATOMY OF THE CARYOPSIS OF BRIZA MAXIMA (POACEAE)
Authors: Rost Thomas L. , de Artucio Primavera Izaguirre , Risley Edward B.
Published: January 2018

Briza maxima (quaking grass) is a cosmopolitan grass common to Europe and North and South America. It grows in disturbed soils and on roadsides. The hemispherical caryopsis is embedded between a leaflike lemma and flattened palea. The embryo is of the festucoid type. The scutellum shows two surrounding ridges at the edge of the scutellum/endosperm boundary, and has lateral lobes. A broad epiblast extends toward the embryo apex and is continuous with the dorsal surface of the coleorhiza. The single‐layered aleurone surrounds the starchy endosperm and is discontinuous around the embryo. The caryopsis coat is thin, except at the placental pad where it is thickened by the pigment strand and the nucellar projection.
SHADE TOLERANCE AND ITS EFFECT ON THE SEGREGATION OF TWO SPECIES OF LOUISIANA IRIS AND THEIR HYBRIDS
Authors: Bennett Bobby D. , Grace James B.
Published: January 2018

Iris fulva Ker. Gawler and Iris hexagona Walter have overlapping geographic ranges in Louisiana. In areas of overlap hybrids are fairly common. Iris hexagona occupies the borders of freshwater marshes of southern Louisiana while I. fulva can be found farther north along edges of natural levees, canals and swamps. Where the natural levee penetrates the marsh, natural hybridization can occur between I. hexagona and I. fulva. It has been suggested that one principal explanation for the segregation of the two species is that I. fulva grows best in semishade and I. hexagona grows best in full sun. A greenhouse study was conducted using rhizomes collected from the field to test this hypothesis and determine the relative shade tolerance of two natural hybrid types. Iris fulva, I. hexagona, and the two hybrid taxa were grown under 0% (control), 50% (medium shade), and 80% (high shade) reduction of sunlight for 6 months and then harvested. Iris fulva was found to be more tolerant of shading than I. hexagona and the two hybrids. Further, I. fulva was found to grow as well in control as in medium shade. Both hybrid taxa were more shade tolerant than I. hexagona. Iris hexagona was greatly affected by all levels of shade. In general, the results suggest that these hybrids are intermediate to the parental taxa in terms of shade tolerance.
POLLEN‐POLLEN AND POLLEN‐STYLE INTERACTIONS DURING POLLEN TUBE GROWTH IN ERYTHRONIUM GRANDIFLORUM (LILIACEAE)
Authors: Cruzan Mitchell B.
Published: January 2018

Using pairs of pollen donors, I analyzed the growth of pollen tubes growing in different channels of the same style in Erythronium grandiflorum. After 24 hr the length of pollen tubes of randomly selected pollen donors was affected by the presence of other donors. The mean pollen tube lengths of donors did not differ when taken across all of the donor pairings, but in individual pairs, pollen from one donor was often significantly longer than pollen from the other donor when tested across several recipients. Pollen tube lengths were also consistently longer for pollen paired with pollen from the same donor than when paired with pollen from other donors, apparently because of mutual stimulation between the pollen populations from the same plant. In a second experiment, the amount of pollen tube attrition after five days of growth of pollen from a donor growing near (within 3 m) the recipient depended upon the source of other pollen growing in the same style. Local pollen experienced more attrition paired with self pollen than when paired with outcross pollen. Pollen from different outcross distances also modified the attrition of local pollen, but local pollen usually outcompeted pollen from greater distances. Since the growth of local pollen was modified depending upon the source of other pollen growing in the same style, it is probable that recipient styles are selectively inhibiting pollen tubes to produce the patterns of pollen tube interaction observed. The results from these two experiments indicate that the amount of attrition for pollen can be dependent on the composition of the pollen pool. Both direct pollen tube interactions and mediation by the stylar tissue appear to affect the growth rate and attrition of pollen in Erythronium.
INFLORESCENCE DEVELOPMENT IN TWO ANNUAL TEOSINTES: ZEA MAYS SUBSP. MEXICANA AND Z. MAYS SUBSP. PARVIGLUMIS
Authors: Sundberg Marshall D. , Orr Alan R.
Published: January 2018

The ontogeny of tassels and ears in two annual Mexican teosintes, Zea mays subsp. mexicana and Z. mays subsp. parviglumis, was examined using scanning electron microscopy and light microscopy. Ear development in these annual teosintes follows a pattern previously described as leading to the bisexual mixed inflorescence in Z. diploperennis. Common bud primordia are initiated in the axils of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired sessile and pedicellate spikelet primordia. Development of pedicellate spikelets is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. Development of the central tassel spike is similar to that previously described in the Z. diploperennis tassel, except that the first formed axillary bud primordia form precocious tassel branches. The origin of these tassel branches suggests a possible mechanism for the transition from a distichous spike, characteristic of teosinte, to a polystichous spike, typical of maize.
PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. III. GENERA PHYSOCALYMMA THROUGH WOODFORDIA, ADDENDA, AND CONCLUSIONS
Authors: Graham Alan , Graham Shirley A. , Nowicke Joan W. , Patel Varsha , Lee Sangtae
Published: January 2018

Pollen of the 27 genera presently recognized as comprising the family Lythraceae have been surveyed with light microscopy and scanning and transmission electron microscopy. Results for five genera (Physocalymma, Pleurophora, Rotala, Tetrataxis, Woodfordia), in addition to Duabanga, Sonneratia, and Punica (assigned to the Lythraceae in some classifications), are presented here; the remaining genera were treated previously in the series. The family is revealed as the most diverse palynologically of the order Myrtales. The most simple pollen type and the one common to the largest number of genera is prolate‐spheroidal to prolate; tricolporate, without pseudocolpi; psilate, scabrate or finely verrucate; and 16–28 μm or less in length. Specializations include oblate grains, development of pseudocolpi (three or six in number), diversification of exine sculpturing, broadening of the colpal and pseudocolpal areas, and reduction in the conspicuousness of the colpi. Pollen evidence provides qualified support for inclusion of Punica in the Lythraceae, the generalized nature of the pollen tempering the conclusion, and little support for inclusion of Sonneratia and Duabanga in the family. Completion of the survey provides a data base of pollen characters that will be integrated in future studies with other evidence into an overall phenetic and cladistic assessment of the family leading to production of a more natural classification.
BIOCHEMISTRY OF FERN SPORE PROTEINS: GLOBULIN STORAGE PROTEINS IN ONOCLEA SENSIBILIS AND OSMUNDA CINNAMOMEA
Authors: Templeman Thomas S. , DeMaggio Augustus E.
Published: January 2018

Onoclea sensibilis was found to contain globulin storage proteins of 2.0S and 11.3S. These globulins, comparable in size and subunit composition to the spore storage proteins characterized in Matteuccia struthiopteris (Templeman, DeMaggio, and Stetler, 1987), declined during imbibition and the initial stages of spore germination. Osmunda cinnamomea, a fern that is only distantly related to Matteuccia, also contained globulin proteins, but these had S values of 5.5 and 11.3. SDS‐PAGE analysis revealed extensive differences in banding patterns of the 11.3S protein between Onoclea and Osmunda. This work indicates that while globulin proteins are important storage materials in a variety of ferns they exhibit considerable molecular heterogeneity. The observed heterogeneity in the globulin proteins may be a useful tool to explore evolutionary relationships in the ferns.
ECOLOGIC DIFFERENCES HAVE SEPARATED PINUS REMORATA AND P. MURICATA SINCE THE EARLY PLEISTOCENE
Authors: Axelrod Daniel I.
Published: January 2018

Pure stands of Pinus remorata regularly occur in more equable sites than those occupied by P. muricata. The fossil record suggests that this relationship has existed since at least the earliest Pleistocene. It apparently was the spread of drier, less equable, postglacial climate that opened new, intermediate coastal sites that favored hybrids of P. muricata × P. remorata, the latter a relict species closely allied to P. radiala var. cedrosensis.
ACACIA CONSTRICTA (FABACEAE: MIMOSOIDEAE) AND RELATED SPECIES FROM THE SOUTHWESTERN U.S. AND MEXICO
Authors: Clarke H. David , Seigler David S. , Ebinger John E.
Published: January 2018

Vegetative, fruit, and floral characters of more than 200 herbarium specimens of Acacia constricta and closely related species from the Southwestern U.S. and Mexico were scored and analyzed by principal components analysis (PCA) and stepwise discriminant analysis (SDA). The results show that all of the 5 species of this group are distinct and form nonoverlapping groups in plots of the first three principal components. All taxa were found to be quite homogeneous as indicated by the tight clusters formed in the PCA plots. Acacia pacensis, whose relationship to the species of this group has been questioned, is confirmed to be more closely related to A. farnesiana and related species. Some specimens with a combination of characters from A. constricta, A. neovernicosa, and A. schottii were positioned intermediate to the putative parental species groups in the PCA and SDA plots, suggesting hybridization among these taxa.
DEVELOPMENT OF DIFFERENCES IN LEAF SHAPE IN BEGONIA DREGEI (BEGONIACEAE)
Authors: McLellan Tracy
Published: January 2018

There is a wide range of variation among individuals in the degree of incision of leaf margins in the African Begonia dregei. The development of adult leaves was examined in six varieties of B. dregei. There are several types of differences in development that correlate with the shapes of mature leaves. The shoot apex is larger and the leaf primordia are broader soon after initiation in a variety with entire margins than in those with more incised leaves. One variety differs from the others in the temporal pattern of initiation of the lobes, corresponding to differences in the relative sizes of the lobes of the mature leaves. The differences among varieties in the extent of incision of the margin are apparent during the first plastochron, before the primordia are 300 μm in length. All are more deeply incised early than when mature. Growth rates of the different parts of the leaves change with respect to each other during development in the more deeply incised varieties. The leaves of the three least incised varieties reach similar mature shapes by two different developmental pathways. Differences in the relative timing of developmental processes provide a description of some of the evolutionary changes responsible for differences in shape. However, simple heterochrony does not describe all aspects of the diversification of leaf shape in this species.
SIZES OF NATURAL MICROGAMETOPHYTE POPULATIONS IN PISTILS OF PHLOX DRUMMONDII
Authors: Levin Donald A.
Published: January 2018

The numbers of microgametophytes in the stigmas of the outcrossing Phlox drummondii were determined in 19 natural populations. Microgametophyte numbers per stigma ranged from 0 to over 40 in each population. The number of flowers per plant, distance to the nearest‐neighbor, and number of plants within 1 m of the focal plants explained about 23% of the variation in microgametophyte numbers within 2 of the populations. The mean number per stigma across all populations was 14.34; and the mean number per population varied from 7.77 to 19.52. Given that there are 3 ovules per flower, there was an average of 4.73 microgametophytes per ovule. Sixty‐nine percent of all pistils contained more than 3 microgametophytes, thereby presenting an opportunity for intergametophytic competition.
SUBSTRATE HETEROGENEITY AND REGENERATION OF A SWAMP TREE, NYSSA AQUATICA
Authors: Huenneke Laura Foster , Sharitz Rebecca R.
Published: January 2018

We investigated physical characteristics of several substrate types in a South Carolina riverine swamp forest, and the effect of those characteristics upon germination and seedling growth of the dominant swamp tree, Nyssa aquatica (water tupelo). Substrates were categorized as emergent (surfaces of trees, living cypress knees, stumps, or logs), protected (submerged sediment adjacent to an emergent object), or open (sediment > 50 cm from any emergent object and fully submerged during the growing season). Water tupelo seeds germinated best (>25% in 16 days) on emergent substrates, but seed predation was extremely high on these same substrates. Substrate types differed significantly in permanence and in rates of sediment loss or deposition. Growth rates of transplanted seedlings did not differ among substrate types. The results suggest that mortality due to erosional scour or impermanent rooting zones, superimposed on germination patterns, is responsible for the observed nonrandom distribution of woody plant seedlings among substrate types in the swamp forest.
CYTOLOGICAL BASIS FOR CYTOPLASMIC INHERITANCE IN PSEUDOTSUGA MENZIESII. I. POLLEN TUBE AND ARCHEGONIAL DEVELOPMENT
Authors: Owens John N. , Morris Sheila J.
Published: January 2018

Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) ovules were used to study the method of pollen tube formation and penetration of the nucellus, the movement of the body cell down the pollen tube and development of the archegonia. No pollination drop forms but nucellar tip cells produce a minute secretion that may initiate pollen tube formation. Pollen tubes penetrate the nucellus causing degeneration of nucellar cells in contact with the pollen tube tip. The body cell becomes highly lobed and the tube cytoplasm forms thin sheets between the lobes. This may be the mechanism by which the large body cell is pulled down the narrow pollen tube. Body cell plastids and mitochondria remain unaltered during pollen tube growth, whereas tube cell organelles show signs of degeneration. The pollen tube penetrates the megaspore wall and settles in the archegonial chamber. During pollen elongation and pollen tube growth the egg matured. Egg cell plastids were transformed into large inclusions which filled the periphery of the egg while mitochondria migrated to the perinuclear zone. The neck cells, ventral canal cell and archegonial jacket cells are described. The significance of the body cell and egg cell ultrastructure is discussed in light of recent restriction fragment length polymorphism studies of plastid and mitochondrial inheritance in the Pinaceae.
ROOT ANATOMY OF THE BAMBUSOIDEAE (POACEAE)
Authors: Raechal Luther J. , Curtis John D.
Published: January 2018

Root anatomy was examined for 15 species, in 6 of the 11 tribes of the Bambusoideae. Wide ranges of anatomical variation were found in epidermis, exodermis, cortex, endodermis, pericycle, phloem, xylem, and pith. Although roots of most species seem to resemble the Panicoid type, our study shows much more variation than was described by Goller (1977). These variations could play a role in characterizing taxa within tribes.
GEOGRAPHIC DIFFERENTIATION IN ATRIPLEX CONFERTIFOLIA
Authors: Sanderson S. C. , Stutz H. C. , McArthur E. D.
Published: January 2018

Atriplexconfertifolia (Chenopodiaceae) consists of ploidy races extending from diploid through decaploid and is dissected into many racial groups by cytological and flavonoid relationships. On the basis of morphology, the species can be divided into two major subdivisions, one centered in western Nevada and inhabiting chiefly the Great Basin, and one centered in the Colorado Plateau. Western Nevada plants are distinguished by smaller and narrower leaves, as well as by darker spines and other charactristics. Because western Nevada is situated in the lee of the Sierra Nevada Range, it received reduced amounts of rainfall during Pleistocene and Holocene times. These reduced leaf dimensions of A. confertifolia of the rain shadow zone may thus reflect an evolutionary response to aridity.
COMPARISON OF EARLY LATERAL VEIN FORMATION IN LINUM USITATISSIMUM LEAVES WITH THEORETICAL NETWORK MODELS
Authors: Meicenheimer Roger D. , Leonard Joan McElfresh
Published: January 2018

The plastochron age of the Linum leaf that first exhibited lateral leaf vein divergences, the divergent leaf, increased through shoot ontogeny, but the size of the divergent leaf remained constant. There were progressive decreases in the plastochron and relative plastochron rate of leaf elongation, but no significant change in relative chronological rate of leaf elongation, through ontogeny. Thus, divergent leaves of similar sizes occupied different relative positions in the array of leaves on stems of different plastochron ages. These observations are partially consistent with theoretical network model predictions on early leaf vein development. The empirical data of this study suggest additional features of leaf development that should be incorporated into future simulation models for leaf vein development.
ENVIRONMENTAL AND PHYSIOLOGICAL FACTORS INFLUENCING THE NATURAL DISTRIBUTION OF EVERGREEN AND DECIDUOUS ERICACEOUS SHRUBS ON NORTHEAST‐ AND SOUTHWEST‐FACING SLOPES OF THE SOUTHERN APPALACHIAN MOUNTAINS. II. WATER RELATIONS
Authors: Lipscomb M. V. , Nilsen E. T.
Published: January 2018

Three species of shrubs (Ericaceae) were found to segregate upon the northeast and southwest slopes of spur ridges on Brush Mountain, in southwestern Virginia. Rhododendron maximum was found only in valleys and lower northeast slopes, Rhododendron periclymenoides = R. nudiflorum) was found on northeast slopes while Kalmia latifolia was most abundant on southwest slopes. Previous vegetation studies indicated that these partially segregated distributions were related to irradiance and water availability. In field studies of water potential, R. periclymenoides had the lowest diurnal leaf water potentials and the largest seasonal variation in midday leaf water potential. Kalmia latifolia had the highest leaf conductance in field and phytotron experiments. Rhododendron maximum had the greatest seasonal osmotic adjustment followed by R. periclymenoides and K. latifolia. In phytotron experiments, the photosynthetic capacity of R. maximum was the most sensitive to water stress followed by R. periclymenoides and K. latifolia. Kalmia latifolia was able to modify its conductance rates to reduce water loss and maintain constant leaf water potential minimizing photosynthetic inhibition. Rhododendron periclymenoides showed extreme luxury spending of water indicated by high conductance and low photosynthesis. The ecophysiological responses to water and irradiance provided an explanation for the distributions of the three species. For example, R. maximum leaves are sensitive to elevated irradiance, and carbon gain is strongly influenced by water stress. Thus, R. maximum will perform best in low irradiance environments with ample water, such as valley sites. Each species had a unique set of adaptations for performing best in their optimum habitat.
DIOECY AND A REEVALUATION OF LEPIDOCORDIA AND ANTROPHORA (BORAGINACEAE: EHRETIOIDEAE)
Authors: Miller James S. , Nowicke Joan W.
Published: January 2018

The close relationship between two monotypic genera, Lepidocordia from northern South America, and Antrophora from Central America, is reevaluated in light of numerous recent collections. It was discovered that Lepidocordia punctata and A ntrophora williamsii are dioecious and each species appears to have two floral morphs, pistillate and staminate. The original descriptions of L. punctata and of A. williamsii were based on very limited collections that represented only opposite morphs, thus creating an exaggerated and artificial distinction between the two genera. New data from leaf architecture, pollen morphology, and fruit anatomy, as well as this distinctive breeding system, support their congeneric treatment. Antrophora is reduced to Lepidocordia, and A. williamsii now becomes L. williamsii. Lepidocordia is best retained in the Ehretioideae, but it and Rochefortia (3 spp) are the only dioecious genera in this subfamily, and thus quite distinct.
POLLINATION AND POLLEN ENERGETICS IN MEDITERRANEAN ECOSYSTEMS
Authors: Petanidou Theodora , Vokou Despina
Published: January 2018

Most plants in Mediterranean ecosystems are insect pollinated, with pollen being the main reward to pollinators. The great majority of pollinators (70%) are bees and flies. We measured the energy content of pollen from 40 plant species in these ecosystems that represent abiotic and biotic pollination modes as well as the number of species of their pollinators. Pollen energy content correlates with pollinator diversity. Pollen of wind‐pollinated plants contained less energy than that of insect‐pollinated plants; there was no difference between insect‐pollinated dicots and insect‐pollinated monocots. The median date of flowering (from 1 January) estimated for each of the plant species did not vary significantly either with the number of pollinator species or with the energy content of pollen. The reasons for the differing values of pollen energy content are discussed; in particular, its relation to the type of pollen reserves, length of the flower style, and pollination enhancement.
AN EXPERIMENTAL STUDY OF COMPETITIVE PERFORMANCE IN BRASSICA RAPA (CRUCIFERAE)
Authors: Miller Thomas E. , Schemske Douglas W.
Published: January 2018

Growth chamber experiments with rapid‐cycling Brassica rapa were designed to estimate the signs and magnitudes of the genetic correlations for plant performance in each of three conditions: no‐competition (isolated plants), intraspecific competition, and interspecific competition with Raphanus sativa. Biomass and flower number were highest in the no‐competition treatment, intermediate under intraspecific competition, and lowest under interspecific competition. Significant among‐family variation in biomass and flower number was found under each regime. The mean family performance (biomass or flower number) in the no‐competition treatment was significantly positively correlated with the performance in only one of the competitive treatments (for biomass in the intraspecific treatment). For both biomass and flower number there was a significant positive correlation between family means in the intra‐ and interspecific regimes. These correlations were greater in magnitude than those for the comparison between no‐competition and competition (intra‐ or interspecific) treatments. Our results suggest that the importance of traits affecting plant performance is environment‐dependent; the performance of a family grown without competition was a poor predictor of performance with competition, while the performance of families grown under intra‐ and interspecific competition was positively correlated.
KARYOTYPIC DATA ON NORTH AND CENTRAL AMERICAN ZAMIACEAE (CYCADALES) AND THEIR PHYLOGENETIC IMPLICATIONS
Authors: Moretti Aldo
Published: January 2018

Chromosome numbers and karyotypes of species from four American Zamiaceae (Cycadales) are reported. Zamia shows interspecific and intraspecific chromosome variation, whereas Microcycas, Ceratozamia, and Dioon have constant karyotypes within each genus. In Zamia, all karyotypes have the same number of submetacentric and acrocentric chromosomes, but they differ in the number of metacentric and telocentric chromosomes. Centric fission of metacentric chromosomes is proposed to explain the karyotypic variation in this genus. Zamia shows karyological relationships with Microcycas and Ceratozamia, whereas Dioon appears very distinct from the other American cycad genera. Affinity among Zamia, Ceratozamia, and Microcycas karyotypes and distinctiveness of Dioon karyotypes are supported by comparative analysis of phenotypic characters in the four genera.
LEAF GROWTH AND PHENOLOGY OF THE DIMORPHIC HERBACEOUS LAYER FERN DANAEA WENDLANDII (MARATTIACEAE) IN A COSTA RICAN RAIN FOREST
Authors: Sharpe Joanne M. , Jernstedt Judith A.
Published: January 2018

Leaf growth and spore release inDanaea wendlandiiwere monitored under temperate greenhouse conditions and in a rain forest at the La Selva Biological Station in Costa Rica. Sterile leaf (trophophyll) growth occurs in four phases, and fertile leaf (sporophyll) growth occurs in five phases. Trophophylls show an initial rapid increase in length for a 4‐week period, attain full maturity at 8 weeks, and remain on the plant for about 3 years. There appears to be a seasonal pattern of trophophyll growth, with crozier emergence rates in May and June three times higher than the mean annual rate. Sporophyll growth shows a double sigmoid pattern. For about 3 weeks after crozier emergence, there is a rapid increase in length. This phase is followed by a 10‐week period with no appreciable change in length. Rapid elongation over a 2‐week period precedes spore release; this is followed within 2 weeks by disappearance of the sporophyll. Sporophylls in the rain forest are subject to 14% mortality prior to maturation, with most mortality occurring in later stages of growth. A projected phenology based on the sporophyll growth curve shows peaks in spore release late in the wet season with a concomitant peak in sporophyll emergence early in the wet season during the 15‐month period from June 1986 through September 1987.
MEGAGAMETOPHYTE DEVELOPMENT IN LOTUS CORNICULATUS, L. CONIMBRICENSIS, AND THEIR PROTOPLAST FUSION HYBRID
Authors: Rim Y. W. , Beuselinck P. R. , McGraw R. L. , Somers D. A.
Published: January 2018

The development of early ovules, megasporogenesis, and megagametogenesis in Lotus corniculatus L. (2n = 4x = 24), L. conimbricensis L. (2n = 2x = 12), and their protoplast fusion hybrid were studied. The protoplast fusion hybrid plant was known to be completely male sterile and appeared female sterile. The objectives of this study were to examine the development of the ovules and megagametophytes of the protoplast fusion hybrid of L. corniculatus × L. conimbricensis and to compare the development of the ovules and megagametophytes of the fusion hybrid with that of the parent types. The normal development of the ovules and megagametophytes of L. corniculatus, L. conimbricensis, and their protoplast fusion hybrid were similar to those of several other species of Fabaceae. Approximately 24% of the protoplast fusion hybrid ovules developed into apparently normal megagametophytes beyond the critical reduction divisions. The abortion of ovules in the protoplast fusion hybrid occurred at any stage of megasporogenesis or megagametogenesis, but most abortions appeared to be due to postmeiotic failures. Evidence that normal‐appearing megagametophytes of the fusion hybrid are capable of being fertilized and forming zygotes is needed.