bluuebunny/crossref_metadata_2025 huggingface dataset:
VARIATION OF SEX ALLOCATION AMONG EIGHT TAXA OF THE MIMULUS GUTTATUS SPECIES COMPLEX (SCROPHULARIACEAE)
Authors: Ritland Carol , Ritland Kermit
Published: January 2018

Characters related to sex allocation and the mating system were studied in eight California taxa of the Mimulus guttatus complex: M. guttatus, M. nasutus, M. glaucescens, M. Tilingii, M. nudatus, M. laciniatus, M. platycalyx, and M. micranthus, ranked in approximate decreasing levels of outbreeding. Dry weights and lengths of floral parts, pollen and ovule number, and timing of stigmatic closure were measured on plants in the growth chamber. As percent of total flower weight, allocation to stamens and corollas was lowest in M. micranthus (28%), intermediate in M. platycalyx, M. Tilingii, and M. laciniatus (50%), and high in other taxa (60%). Among M. micranthus, M. platycalyx, and M. laciniatus, pollen–ovule ratios ranged from 3.9 to 12.0; ratios for other taxa were 19.3 to 26.6. Taxa with increased male biomass allocation generally show increased outcrossing and increased P/O ratios. Stigma‐anther separation and closure of stigma lobes upon touch were positively correlated with outcrossing ratios, P/O ratios, and male allocation. Isozyme variation indicates the inbreeding taxa have been independently derived; thus, these associations of maleness with outbreeding are significant trends in the Mimulus guttatus complex.
RELEASE OF SOMATIC EMBRYOGENIC POTENTIAL FROM EXCISED ZYGOTIC EMBRYOS OF CARROT AND MAINTENANCE OF PROEMBRYONIC CULTURES IN HORMONE‐FREE MEDIUM
Authors: Smith David L. , Krikorian A. D.
Published: January 2018

Excised zygotic embryos, mericarps (“seeds”) and hypocotyls of seedlings of cultivated carrot Daucus carota cv. Scarlet Nantes were evaluated for their ability to generate somatic embryos on a semisolid hormone‐free nutrient medium. Neither intact zygotic embryos nor hypocotyls ever produced somatic embryos. However, mericarps and broken zygotic embryos were excellent sources for somatic embryo production (response levels as high as 86%). Somatic embryo formation was highest from cotyledons, but was also observed on isolated hypocotyls and root tips of mature zygotic embryos. On media containing unreduced nitrogen, somatic embryo formation led to the generation of vigorous cultures comprised entirely of somatic embryos at various stages of development which in turn proliferated still other somatic embryos. However, a medium was devised which when 1–5 mm NH4+ was the sole nitrogen source, led only to a proliferation of globular proembryos. Sustained subculturing of these proembryos at 2–3 week intervals enabled establishment of highly uniform cultures in which no further development into more mature stages of embryonic development occurred. These have been maintained, without decline, as morphogenetically competent proembryonic globules for over ten months. A basal medium containing from 1–5 mm NH4+ as the sole nitrogen source appears not to be inductive to somatic proembryo formation. Instead, such a medium is best thought of as permissive to the expression of embryogenically determined cells within zygotic embryos. By excising and breaking or wounding zygotic embryos, constituent cells are probably released from positional or chemical restraints and thus are able to express their innate embryogenic potential. Once a proembryonic culture is established, this medium containing 1–5 mm NH4+ as the sole nitrogen source provides a nonpermissive environment to the development and growth of later embryonic stages, but it does allow the continued formation and multiplication of globular somatic proembryos. The sequence of events leading from excised broken zygotic embryos to the formation of somatic embryos and the maintenance of somatic proembryos are demonstrated by scanning electron microscopy and histological preparations. Germination levels from intact zygotic embryos on media with varying levels and ratios of unreduced vs. reduced inorganic nitrogen were determined as well and provided baseline or control data on the type of response obtained from nonwounded material.
REPRODUCTIVE BIOLOGY OF A TROPICAL PALM SWAMP COMMUNITY IN THE VENEZUELAN LLANOS
Authors: Ramirez Nelson , Brito Ysaleny
Published: January 2018

The reproductive biology of a tropical palm swamp community, called morichal in the Venezuelan Central Llanos, was studied. Of the 128 woody and herbaceous species of plants recorded, 99 (77.34%) were hermaphrodites, 25 (19.53%) were monoecious, and four (3.13%) were dioecious. The morichal is characterized by a low number of species with obligate cross‐fertilization. The frequencies of species with different breeding systems in a subsample of 26 species showed that eight (30.77%) were self‐incompatible, 14 (53.85%) were self‐compatible, and four (15.38%) were agamospermous. Ten of 14 self‐compatible species were autogamous. Regardless of the self‐incompatibility level estimated, seed and fruit set were greater in self‐fertilized flowers than in hand‐pollinated flowers in three of the nine self‐incompatible species. These results are related to the facts that: 1) the relative isolation of the plant population limits the gene flow among similar communities and enforces the intrapopulation pollen flow; 2) the overlapping flowering patterns and infrequent and unspecialized pollinators may be enforcing self‐compatibility and agamospermy; 3) self‐compatibility is the rule among short‐lived species in the morichal; and 4) three out of four agamospermous species are of the Melastomataceae family.
POLLEN BRUSH OF PAPILIONOIDEAE (LEGUMINOSAE): MORPHOLOGICAL VARIATION AND SYSTEMATIC UTILITY
Authors: Lavin Matt , Delgado S. Alfonso
Published: January 2018

The pollen brush commonly is referred to as a “bearded” or “pubescent” style in taxonomic literature and traditionally is taken to be an aggregation of trichomes on the distal end of the style, and occasionally including the stigma. We present data that support the taxonomic utility of the pollen brush but define it more specifically as a dense aggregation of erect trichomes emanating from the style (not stigma or ovary) and functioning in secondary pollen presentation. We recommend avoiding such vague terminology as bearded or pubescent styles as these refer not only to the pollen brush but also to ciliate and penicillate stigmas and ciliate styles. The latter three conditions have some taxonomic use, and since their occurrence is not necessarily correlated with the presence of a pollen brush, they should be distinguished from it. We estimate that the pollen brush has arisen independently in the following eight taxa: 1)CrotalariaandBolusia(Crotalaraieae), 2) subtribe Coluteinae (Galegeae), 3)TephrosiasubgenusBarbistyla(Millettieae), 4)Adenodolichos(Phaseoleae subtribe Cajaninae), 5)Clitoria(Phaseoleae subtribe Clitoriinae), 6) the subtribe Phaseolinae (Phaseoleae), 7) theRobiniagroup (Robinieae), and 8) the tribe Vicieae. Its hypothesized homology within each of these groups is supported by a cooccurrence with other taxonomic characters, both morphological and molecular.
PATTERNS OF CLONAL DIVERSITY IN THE ANTENNARIA ROSEA (ASTERACEAE) POLYPLOID AGAMIC COMPLEX
Authors: Bayer Randall J.
Published: January 2018

The perennial herbaceous species, Antennaria rosea, is a large, morphologically diverse, polyploid agamic complex that is widespread in the cordillera of western North America. The species consists of triploid and tetraploid, nonpseudogamous, gametophytic apomicts. Populations of A. rosea are gynoecious, consisting almost entirely of pistillate clones. Clonal diversity among 63 populations of A. rosea was studied over a large portion of its range. Isozyme electrophoresis utilizing four polymorphic enzyme systems detected 192 multilocus genotypes among the populations. Populations of A. rosea tend to be composed of one or a few genotypes (range 1–11; mean 3.5), and these genotypes usually occur in only one or a few localized populations. Geographic patterns of clonal diversity may be a result of frequent genesis of new clones in populations that occur in areas where sexual relatives of A. rosea donate compatible pollen to facultatively sexual apomicts. Populations from previously glaciated regions tend to have fewer clones per population than those from unglaciated portions of the range.
EFFECT OF OVULE POSITION ON SEED PRODUCTION, SEED WEIGHT, AND PROGENY PERFORMANCE IN PHASEOLUS COCCINEUS L. (LEGUMINOSAE)
Authors: Rocha Oscar J. , Stephenson Andrew G.
Published: January 2018

We examined the effect of ovule position within the ovary on the probability of seed maturation, on seed weight, and on progeny performance in the outbreeding legume Phaseolus coccineus. Ovaries of P. coccineus possess six linearly arranged ovules (ovule position one = stylar end). We found that in both 1987 and 1988, ovule position had a significant effect on the probability of seed maturation under field conditions. In 1987, ovule positions one. two, and three had a higher probability of maturing seeds than the three most basal ovule positions. In 1988, the probability of producing a mature seed in ovule position one was more similar to the three most basal ovule positions than to ovule positions two and three. The position of the ovule in the ovary had no significant effect on seed weight in 1987, but it had a significant effect in 1988. Overall, seeds from ovule positions one, two, and three tended to produce heavier seeds than the three most basal ovule positions. The effects of ovule position on progeny performance were determined in a greenhouse and a field study. In the greenhouse study, we found no significant overall effect of the position of the ovule that produced the seed on progeny performance. In the field study, we did find a significant ovule position effect on several measures of reproductive performance as well as an overall effect on reproductive performance. In addition, we found a significant interaction between ovule position and number of seeds per fruit. Progeny from the stylar end of the fruit outperformed the progeny from the peduncular end in fruits containing many seeds, whereas there were no significant differences between progeny produced in the stylar and peduncular ends of fruits containing few seeds. Causes of position effects are unknown but hypotheses abound.
MORPHOLOGICAL RESPONSES OF CROP AND WEED SPECIES OF DIFFERENT GROWTH FORMS TO ULTRAVIOLET‐B RADIATION
Authors: Barnes Paul W. , Flint Stephan D. , Caldwell Martyn M.
Published: January 2018

The influence of ultraviolet‐B (UV‐B) radiation (280‐320 nanometers) on the morphology of 12 common dicot and monocot crop or weed species was examined to determine whether any common responses could be found that might, in turn, be useful in predicting possible changes in competitive balance under solar UV‐B enhancement. Under glasshouse conditions, UV‐B exposure (simulating a 20% reduction in stratospheric ozone at Logan, Utah) was found to reduce leaf blade and internode lengths and increase leaf and axillary shoot production in several species. Overall, the directions of these trends were similar in the majority of species that exhibited a significant response. These morphological changes occurred without any significant reduction in total shoot dry matter production. There was no clear distinction in the response of crops and weeds, though monocots were found to be generally more responsive than dicots. Previous work in dense canopies has shown that the photomorphogenetic effects of UV‐B alter leaf placement and thereby influence competition for light. Our results suggest that, under these conditions, changes in competitive balance resulting from increased UV‐B might be expected more frequently when monocots are involved in mixtures, rather than mixtures of only dicots.
EARLY CRETACEOUS TETRADS, ZONASULCULATE POLLEN, AND WINTERACEAE. I. TAXONOMY, MORPHOLOGY, AND ULTRASTRUCTURE
Authors: Doyle James A. , Hotton Carol L. , Ward Jerome V.
Published: January 2018

Ulcerate pollen tetrads from the late Barremian‐early Aptian of Gabon, named Walkeripollis gabonensis gen. et sp. nov., resemble pollen of extant Winteraceae but have finer sculpture and a weakly calymmate tectum, like tetrads reported from the late Aptian‐Albian of Israel. Scanning and transmission electron microscopy reveal additional winteraceous features (tall muri, short columellae, ring of endexine around the ulcus), plus segmented muri recalling the reticulate, zonasulculate to inaperturate genus Afropollis, which is abundant in the Aptian‐Albian of Northern Gondwana. Afropollis also resembles Winteraceae in having tall muri and short columellae, but it has a thicker endexine. The new zonasulculate genus Schrankipollis, including S. mawhoubensis (Schrank) comb. nov. from the Aptian of Egypt and S. microreticulatus (Brenner) comb. nov. from the Potomac Group of Maryland, resembles Afropollis in structure of its muri but differs in its elliptical shape, finer reticulum, and restricted endexine.
EARLY CRETACEOUS TETRADS, ZONASULCULATE POLLEN, AND WINTERACEAE. II. CLADISTIC ANALYSIS AND IMPLICATIONS
Authors: Doyle James A. , Hotton Carol L. , Ward Jerome V.
Published: January 2018

Comparisons with other fossil pollen types and the distribution of pollen characters in modern angiosperms support affinities of Early Cretaceous ulcerate tetrads (Walkeripollis) and zonasulculate pollen (Afropollis, Schrankipollis) with modern Winteraceae. Cladistic analysis of these fossils plus modern Winteraceae and Illiciales, which have been associated with each other, implies that Afropollis and Schrankipollis represent an extinct sister group of Walkeripollis, Winteraceae, and Illiciales, derived from a common ancestor before origin of the tetrad condition. The single tricolpate grains of Illiciales are derived from ulcerate tetrads, which helps explain their thin proximal exine and Garside's Rule aperture arrangement. These results imply that extinct relatives of Winteraceae and Illiciales were an important component of Early Cretaceous tropical floras and extended into Laurasia, and that the present austral temperate distribution of Winteraceae was attained later. They are consistent with recent suggestions that absence of vessels in Winteraceae is due to secondary loss.
SEXUAL REPRODUCTION IN EPHEDRA NEVADENSIS (EPHEDRACEAE): FURTHER EVIDENCE OF DOUBLE FERTILIZATION IN A NONFLOWERING SEED PLANT
Authors: Friedman William E.
Published: January 2018

Since the initial discovery of double fertilization in angiosperms in 1898, a number of reports of double fertilization‐like events in the genus Ephedra have appeared. Until recently, convincing documentation of double fertilization in Ephedra had not been presented. In Ephedra nevadensis, following entry of a single binucleate sperm cell into the egg cell, one sperm nucleus migrates in a chalazal direction to fuse with the egg nucleus. Contemporaneous with this first fertilization event, the ventral canal nucleus regularly migrates from its initially apical position within the egg cell to a more central position within the egg cytoplasm, where it fuses with a second sperm nucleus. Based on quantitative microspectrofluorometric analysis, occasional supernumerary nuclei within the egg cell (derived by migration through pores in the cell walls between jacket cells and the central cell or egg cell) can be ruled out as participating in the second fertilization event. The evolutionary establishment of double fertilization in Ephedra (or its ancestors) was dependent on a number of specific developmental preconditions: 1) persistence of the ventral canal nucleus (which is degenerate in many groups of nonflowering seed plants) through the time of normal fertilization; 2) regular displacement of the ventral canal nucleus from its initially apical position within the egg cell to a position within the egg cytoplasm where fusion of the egg nucleus with the first sperm nucleus earlier occurred; 3) acquisition of egg‐like features by the ventral canal nucleus that allow it to attract and fuse with a sperm nucleus; and 4) consistent entry of a second sperm nucleus into the archegonial cavity to participate in a second fertilization event. Although it cannot be determined definitively whether double fertilization in Ephedra is evolutionarily homologous with double fertilization in flowering plants, comparative evidence is consistent with the hypothesis that double fertilization arose in a common ancestor of the Gnetales and angiosperms.
CHLOROPLAST‐DNA PHYLOGENETICS AND BIOGEOGRAPHY IN A RETICULATING GROUP: STUDY IN POA (POACEAE)
Authors: Soreng Robert J.
Published: January 2018

Cladistic analysis of Poa chloroplast DNA (cpDNA) restriction sites tested previously hypothesized relationships within the genus. Forty‐six taxa representing 19 sections or groups and three subgenera of Poa and two out‐group genera, Puccinellia and Bellardiochloa, are analyzed. Five major and several minor cpDNA groups are identified. The cpDNA cladogram is generally congruent with the subgeneric taxonomy of Poa. Exceptions are reclassified or are discussed in terms of character incompatibilities and possible reticulation events. The cpDNA tree detected relationships among sections that were unresolved using traditional character sets and provides a basis for polarization of morphological character states. An assessment of biogeographic events based on the cpDNA tree suggests: 1) Poa originated in Eurasia; 2) at least six groups of species independently colonized North America; and 3) two of the latter groups colonized South America, and one closely related group colonized New Zealand and Australia. The cpDNA tree provided a conservative estimate of the number of amphi‐neotropical disjunctions when compared to the known number of species disjunctions.
DIVERSITY OF SHOOT MORPHOLOGY IN TYPHONIUM (ARACEAE)
Authors: Murata Jin
Published: January 2018

The details of shoot organization, including number of leaves per shoot, position of foliage leaves and cataphylls, position of the lateral continuation shoot, nature of axillary buds and phyllotaxis, and the pattern of shoot extension were observed and compared in five species of Typhonium, Dracunculus vulgaris, Sauromatum venosum, Arum italicum, and Helicodiceros muscivorus, resulting in the recognition of four types of stems. Three of the four types were found in the genus Typhonium. One type was found in Typhonium giganteum and Sauromatum venosum and is presumably the same in Biarum. Another type, found in T. trilobatum, T. blumei, and T. flagelliforme, is distinct in the position of the lateral continuation shoot, which arises from the axil of the n‐1 leaf and is adnate to the axis to above the n leaf. Based on the results, two groups, one of which is further subdivided into two subgroups, are recognized in subtribe Arinae (subfam. Aroideae tribe Areae).
THE QUADRIPOLAR MICROTUBULE SYSTEM AND MEIOTIC SPINDLE ONTOGENY IN HORNWORTS (BRYOPHYTA: ANTHOCEROTAE)
Authors: Brown Roy C. , Lemmon Betty E.
Published: January 2018

Ontogeny of the meiotic spindle in hornworts was studied by light microscopy of live materials, transmission electron microscopy, and indirect immunofluorescence microscopy. As in monoplastidic meiosis of mosses and Isoetes, the single plastid divides twice, and the four resultant plastids migrate into the future spore domains where they organize a quadripolar microtubule system (QMS). Additionally, a unique axial microtubule system (AMS) was found to parallel the plastid isthmus at each division in meiosis, much as in the single plastid division of mitosis. This finding is used to make a novel comparison of mitotic and meiotic spindle development. The AMS contributes directly to development of the mitotic spindle, whereas ontogeny of the meiotic spindle is more complex. Nuclear division in meiosis is delayed until after the second plastid division; the first AMS disappears without spindle formation, and the two AMSs of the second plastid division contribute to development of the QMS. Proliferation of microtubules at each plastid results in the QMS consisting of four cones of microtubules interconnecting the plastids and surrounding the nucleus. The QMS contributes to the development of a functionally bipolar spindle. The meiotic spindle is comparable to a merger of two mitotic spindles. However, the first division spindle does not terminate in what would be the poles of mitosis; instead the poles converge to orient the spindle axis midway between pairs of non‐sister plastids.
DROUGHT AND THE EVOLUTION OF FLOWERING TIME IN DESERT ANNUALS
Authors: Fox Gordon A.
Published: January 2018

Drought is often thought to stimulate flowering in desert, and sometimes in mesic, annuals. I review experimental studies of the effect of drought on flowering time in both desert and mesic annuals. No convincing experimental evidence presently exists that drought stimulates flowering in any annual plant; some experimental results suggest the opposite. The design and analysis of flowering time studies are also reviewed; most extant studies have serious flaws. Thus, a convincing demonstration of drought‐stimulated flowering will require carefully designed and analyzed experiments.

In light of these results, I examine several ways in which drought may affect the ecology and evolution of flowering time in desert annuals, and suggest directions for research. Several mechanisms probably contribute to phenotypic variation in flowering time and size, including water and nutrient limitation, competition, and variation in seed size and germination time. Phenotypic effects of seed traits suggest that seed and flowering time traits may not evolve independently of one another. Water stress during reproduction can influence seed traits; such maternal effects can influence the outcome of selection both on seed traits and on flowering time. The multivariate character of flowering time evolution suggests that genetic and phenotypic correlations among these traits may present important constraints on the evolution of flowering time.
VESICULAR‐ARBUSCULAR MYCORRHIZAE IN HAWAIIAN ERICALES
Authors: Koske R. E. , Gemma J. N. , Englander L.
Published: January 2018

Vesicular‐arbuscular mycorrhizae (VAM) are reported for the first time in four species of Hawaiian Ericales, Vaccinium calycinum, V. dentatum, and V. reticulatum of the Ericaceae and Styphelia tameiameiae of the Epacridaceae. The coarse roots (> 1.5 mm diam) of many specimens were densely colonized by VAM fungi, with up to 90% of the length of roots containing arbuscules, vesicles, coils, and internal hyphae. Spores of an undescribed Glomus sp. were associated with two species of Vaccinium. The hair roots of all species bore the ericoid mycorrhizae typical of certain families of this order. The high frequency of VAM in Hawaiian populations of Ericales suggests that ancestral Ericales possessed the capacity to form both VA and ericoid mycorrhizae. An evolutionary sequence of mycorrhizal dependency in the Ericales is presented.
EXTRACELLULAR POLYSACCHARIDE AND LEAF CAPACITANCE IN A HAWAIIAN BOG SPECIES, ARGYROXIPHIUM GRAYANUM (COMPOSITAE‐MADIINAE)
Authors: Robichaux Robert H. , Morse Suzanne R.
Published: January 2018

Mature leaves of Argyroxiphium grayanum exhibit an unusual structure‐function relationship. The leaves are traversed by several large channels filled with extracellular polysaccharide. Infrared spectral data suggest that the polysaccharide is mainly pectin, which is consistent with previous data based on its histochemical staining properties. The polysaccharide exhibits a very high water‐holding capacity, which appears to result in a very high leaf capacitance at high water contents and water potentials. The volume‐normalized leaf capacitance of A. grayanum is 0.67 MPa–1 over the water potential range of –0.1 to –0.5 MPa. Coupled with the low time constant for water flux within the leaves (57 sec), the high leaf capacitance of A. grayanum may enable it to avoid rapid declines in leaf water potential. Thus, in its native bog habitat in Hawaii, the high leaf capacitance of A. grayanum may be of benefit in terms of minimizing the development of short‐term leaf water deficits.
EFFECTS OF POLLINATION INTENSITY IN CAMPSIS RADICANS
Authors: Bertin Robert I.
Published: January 2018

I examined effects of pollination intensity on fruit, seed and seedling characteristics in Campsis radicans, and joint effects of pollen donor and pollination intensity on fruit production. Large pollen loads were more likely to initiate fruit production than small pollen loads, and the former fruits contained more seeds and a greater total seed mass. No further increases in seed number or mass occurred for pollen loads above 4,000 grains. The weight of individual seeds was unaffected by pollen load. Effects of pollen donor were generally larger than effects of pollen load, and fruit production from small loads of pollen from one donor were sometimes equal to fruit production from larger pollen loads from another donor. The ratio of pollen grains deposited to resultant seeds increased with pollen load, and several explanations are proposed. Seeds from heavy pollinations emerged better than seeds from light pollinations, but did not differ in speed of germination or in the performance of seedlings up to 126 days. The emergence differences are probably due to differing intensities of pollen tube competition.
CLADISTIC ANALYSIS OF PATTERNS OF ENDOTHECIAL THICKENINGS IN THE POALES/RESTIONALES
Authors: Manning J. C. , Linder H. P.
Published: January 2018

The three‐dimensional structure of the endothecial thickenings in the anthers was investigated in 87 species from 70 genera, chosen to provide representative coverage of the families Cyperaceae, Restionaceae, Anarthriaceae, Ecdeiocoleaceae, Centrolepidaceae, Joinvilleaceae, Flagellariaceae, Poaceae, Xyridaceae, and Eriocaulaceae. There is complex variation in the patterns of endothecial thickening: the Eriocaulaceae, Flagellariaceae, and most Poaceae have thickenings with a complete baseplate; the Cyperaceae and most of the Restionaceae are characterized by helical thickenings; some genera in the Bambusoideae have annular thickenings; and U‐shaped thickenings occur in the Xyridaceae and Eriocaulaceae and in some Poaceae and Restionaceae. Joinvillea and Ecdeiocolea have unique thickening types. Endothecial characters were subjected to cladistic analysis. Including endothecial characters in an existing cladogram of the group indicates that there is no single, well‐corroborated cladogram available for the Poales/Restionales.
ISOZYMATIC VARIATION IN GUATEMALAN RACES OF MAIZE
Authors: Bretting P. K. , Goodman M. M. , Stuber C. W.
Published: January 2018

Isozymatic data taken from 67 Guatemalan collections of maize were subjected to numerical taxonomic analyses to elucidate systematic relationships among the 19 maize races and subraces described for Guatemala by Wellhausen et al. As with Bolivian and Mexican races, isozymatic variation in Guatemalan maize was strongly associated with altitude. Guatemalan lowland races were in general isozymatically distinct from races of higher elevations. Two middle elevation Guatemalan races proved difficult to place taxonomically. As a group, Guatemalan highland races were isozymatically more diverse than races from lower elevations, and were rather weakly differentiated from Mexican highland races. Notably, variational patterns evident from phenetic analyses of isozyme data were generally congruent with those apparent in phylogenetic analyses. The data reported here, and in earlier studies, suggested that divergent combinations of isozymatic, karyotypic, and morphological features have evolved in local maize races from Mexico, Guatemala, and Bolivia, perhaps as the result of the different selective regimens indigenous cultivators have imposed on different regional phylogenetic lineages.
CHLOROPLAST‐DNA AND ALLOZYMIC VARIATION IN DIPLOID AND AUTOTETRAPLOID HEUCHERA GROSSULARIIFOLIA (SAXIFRAGACEAE)
Authors: Wolf Paul G. , Soltis Douglas E. , Soltis Pamela S.
Published: January 2018

Diploid and autotetraploid populations of Heuchera grossulariifolia occur throughout mountainous regions of the Pacific Northwest. Controlled greenhouse crosses indicated that the two cytotypes are largely reproductively isolated. Fourteen diploid and 11 tetraploid populations were analyzed electrophoretically. Individual tetraploid plants expressed up to four alleles per isozyme locus, and tetraploid populations had significantly higher levels of heterozygosity than diploids. Mean observed heterozygosity was 0.159 for tetraploid populations and 0.058 for diploid populations. The patterns of allelic distribution between cytotypes suggested multiple origins of autotetraploids. This hypothesis was supported by restriction‐site analysis of chloroplast‐DNA (cpDNA) variation which indicated that there had been at least three independent origins of tetraploids. Electrophoretic data, in conjunction with a cpDNA‐based phylogeny and geographic distribution of populations, suggest that autopolyploid populations evolved several times as migration of diploids occurred down river systems. This study further supports the contention that autopolyploidy can be a common and successful speciation process in some groups of plants.
A REEVALUATION OF THE ZOSTEROPHYLLOPHYTINA WITH COMMENTS ON THE ORIGIN OF LYCOPODS
Authors: Niklas Karl J. , Banks Harlan P.
Published: January 2018

The primary paleobotanical literature pertaining to Zosterophyllophytina (a now extinct group of Devonian vascular plants) was reexamined for evidence concerning the activity of the apex of fertile shoots as it might be revealed by the presence or absence of terminally located sporangia (terminate or nonterminate axes, respectively). The symmetry of sporangial arrangement (radial or bilateral), the presence or absence of enations, circinate axial tips, and the shape of the vascular strand were also recorded. We found terminate axes usually are (but not invariably) associated with radial symmetry and nonterminate axes are typically bilateral in symmetry. Other morphological features are consistent with this observation, e.g., enations, circinate tips, and (when preserved) elliptic vascular strands are found in association with bilateral symmetry and nonterminate axes. We hypothesize that there are two distinct patterns of fertile axial growth within the Zosterophyllophytina. Nonetheless, all taxa currently assigned to the zosterophyllophytes share a reniform or globose sporangial shape and a distal line of dehiscence. Accordingly, we view Zosterophyllophytina as a monophyletic group of plants, whose members show two distinct patterns of growth in their fertile axes. We speculate that lycopods arose from an early zosterophyllophytelike group characterized by nonterminate, radially symmetrical fertile axes. We speculate that zosterophyllophytes with terminate fertile axes and those with nonterminate, bilaterally symmetrical fertile axes were phylogenetic deadends.
FREE AMINO ACID POOLS, 15N2 FIXATION AND FIXED N2 ASSIMILATION IN LEUCAENA LEUCOCEPHALA VAR. K‐8
Authors: DuBois John D. , Winter Harry C. , Dekker Eugene E.
Published: January 2018

Various organs of Leucaena leucocephala (Lam.) de Wit were analyzed for their levels of total nitrogen and free amino acids as well as for changes in free amino acid pools from the time of germination through nodulation. Also an assessment was made of the sink of fixed N2 (transport product) in the nodules using 15N methodology. L. leucocephala organs showed total nitrogen levels similar to those of other legumes. Asparagine was the most prevalent amino acid in the nodules and roots followed by glutamate and mimosine. Asparagine was the second most common amino acid in the leaves and stems, with mimosine being the most abundant. Strong correlations were found between the total plant levels of aspartate and glutamate, asparagine and NH4+, acetylene reduction and glutamate, and asparagine and plant age. Asparagine amino‐ and amide‐N accounted for over 75% of the fixed 15N2 in nodules. It was concluded that L. leucocephala is an asparagine transporter of fixed N2 in the nodule.
DEVELOPMENTAL ANALYSIS OF LEAF PLASTICITY IN THE HETEROPHYLLOUS AQUATIC PLANT HIPPURIS VULGARIS
Authors: Goliber Thomas E. , Feldman Lewis J.
Published: January 2018

Leaf development was studied in the heterophyllous aquatic plant Hippuris vulgaris in order to characterize the developmental events that lead to the formation of aerial‐ vs. submerged‐type leaves. Recent evidence that abscisic acid regulates leaf development in this species provided a basis for using abscisic acid as a developmental tool to accurately control leaf development. We found that leaf primordia were fully competent to develop into either aerial‐ or submerged‐type leaves until the 10th plastochron, when they were ca. 300 μm long. Also, leaves between about the 10th and 21st plastochron formed sectored transition leaves (i.e., the basipetal portion was composed of aerial‐type tissue and the apical portion was composed of submerged‐type tissue, or vice versa), indicating that tissue determination as one or the other leaf type occurred on a local, as opposed to whole‐leaf, level. Finally, no significant difference was observed between the apical dimensions of aerial or submerged‐type shoots. These results indicate that the final determination of Hippuris vulgaris leaves occurs a) relatively late in leaf development, and b) independently of the shoot apex, and provide a basis for using this plant in further studies concerning leaf determination and pattern formation (e.g., stomates, lateral venation) in plants.
SCANNING ELECTRON MICROSCOPY SURVEY OF LEAF EPIDERMIS OF SORGHASTRUM (POACEAE: ANDROPOGONEAE)
Authors: Dávila Patricia , Clark Lynn G.
Published: January 2018

Scanning electron micrographs of the foliar epidermes of all 17 species of Sorghastrum are presented. A description of foliar epidermal micromorphology for the genus is followed by short descriptions of the individual species, emphasizing their epidermal differences. Papillar morphology is variable but taxonomically informative in distinguishing among the species of Sorghastrum. Based on the absence or presence of papillae, and differences in papillar morphology, three informal groups within Sorghastrum are recognized: 1) the nonpapillate group including S. balansae, S. rigidifolium, S. setosum, S. contractum, S. minarum, and S. viride; 2) the globose‐papillate group including S. elliottii, S. incompletum, S. nudipes, S. nutans, S. scaberrimum, S. secundum, and S. trichopus; and 3) the elongate‐papillate group including S. brunneum, S. stipoides, S. chasae, and S. pellitum. No correlation between papillar development and habitat is evident; however, a correlation exists between papillar development and the geographic distribution of the species of Sorghastrum.
ENDOTHECIUM IN IRIDACEAE AND ITS SYSTEMATIC IMPLICATIONS
Authors: Manning John C. , Goldblatt Peter
Published: January 2018

An examination of the endothecial thickenings in 44 species of Iridaceae, selected from the four subfamilies and all major tribes, provides useful information about generic and tribal relationships in the family. U‐shaped thickenings occur in Nivenioideae and Iridoideae—Sisyrinchieae, the latter the least specialized tribe of its subfamily. The occurrence of helical thickenings in all members examined of Iridiodeae tribes Irideae, Mariceae, and Tigridieae (a putatively monophyletic group) and Ixioideae is consistent with the recognition of these two lines as distinct taxa based on anatomical, morphological, phytochemical, and in the case of Ixioideae, palynological criteria. Baseplate thickenings are restricted to Patersonia. However, the shrubby Cape genera—Nivenia, Klattia, and Witsenia—have U‐shaped thickenings which show a tendency for the bars on the inner periclinal cell walls to anastomose, suggesting a trend towards the baseplate condition in Patersonia. This accords with a suggested relationship between these genera, based on anatomical and flavonoid similarities. The pattern of variation in endothecial thickenings in Iridaceae is consistent with the phylogeny proposed by Goldblatt (1990). The distribution of thickening types within the family does not make it possible to polarize this character, but the most parsimonious interpretation assumes that U‐shapes are basic. However, in at least some other monocotyledonous families the pattern suggests that U‐shaped thickenings are derived from helices.
ROLE OF PSEUDOBULBS IN GROWTH AND FLOWERING OF CATASETUM VIRIDIFLAVUM (ORCHIDACEAE)
Authors: Zimmerman Jess K.
Published: January 2018

In Catasetum viridiflavum Hook., a drought‐deciduous orchid from central Panama that produces unisexual flowers, plants possess up to nine annually‐produced pseudobulbs. I investigated the role of these structures in plant growth and flowering by 1) relating annual shoot size and flower production to the size and number of pseudobulbs possessed by plants, 2) experimentally severing connections between young and old pseudobulbs when plants were dormant and monitoring their subsequent vegetative growth and flowering, and 3) determining the seasonal variation in water content, total nonstructural carbohydrates, nitrogen, and phosphorus in pseudobulbs. In small plants (1 to 3 pseudobulbs) pseudobulb stores appeared important to both vegetative growth and flowering. In larger (= older) plants, pseudobulb number was not related to vegetative growth and experimental separations of young from old pseudobulbs did not affect growth. However, flower production by experimental plants was significantly reduced relative to controls. Male plants were usually smaller than female plants in the areas studied; however, experimental reductions of pseudobulb number did not affect the sex expression of plants. All measured nutritional components of pseudobulbs exhibited significant seasonal variation. Carbohydrates appeared most important for supporting growth immediately following dormancy. Nitrogen and phosphorus were less important for this role and may have been more important for determining the number of flowers produced by plants.
CHLOROPLAST DNA RESTRICTION SITE VARIATION AND THE PHYLOGENY OF COREOPSIS SECTION COREOPSIS (ASTERACEAE)
Authors: Crawford Daniel J. , Palmer Jeffrey D. , Kobayashi Marilyn
Published: January 2018

Restriction site variation in chloroplast DNAs (cpDNAs) of Coreopsis section Coreopsis was employed to assess divergence and phylogenetic relationships among the nine species of the section. A total of fourteen restriction site mutations and one length mutation was detected. Cladistic analysis of the cpDNA data produced a phylogeny that is different in several respects from previous hypotheses. CpDNA mutations divide the section into two groups, with the two perennial species C. auriculata and C. pubescens lacking any derived restriction site changes. The other seven species are united by five synapomorphic restriction site mutations and the one length mutation. These seven species fall into three unresolved clades consisting of 1) the remaining three perennial species, C. grandiflora, C. intermedia, and C. lanceolata; 2) three annual species, C. basalis, C. nuecensoides, and C. nuecensis; and 3) the remaining annual, C. wrightii. The cpDNA data suggest that, although the perennial habit is primitive within the section, the annual species of section Coreopsis have likely not originated from an extant perennial species. The estimated proportion of nucleotide differences per site (given as 100p) for the cpDNAs of species in the section ranges from 0.00 to 0.20, which is comparable to or lower than values reported for other congeneric species. The low level of cpDNA divergence is concordant with other data, including cross compatibility, interfertility and allozymes, in suggesting that species of the section are not highly divergent genetically.
MONOPLASTIDIC CELL DIVISION IN LOWER LAND PLANTS
Authors: Brown Roy C. , Lemmon Betty E.
Published: January 2018

In many bryophytes and vascular cryptogams mitosis and/or meiosis takes place in cells containing a single plastid. In monoplastidic cell division plastid polarity assures that nuclear and plastid division are infallibly coordinated. The two major components of plastid polarity are morphogenetic plastid migration and microtubule organization at the plastids. Before nuclear division the plastid migrates to a position intersecting the future division plane. This morphogenetic migration is a reliable marker of division polarity in cells with and without a preprophase band of microtubules (PPB). The PPB, which predicts the future division plane before mitosis, is a characteristic feature of land plants and its insertion into the cytokinetic apparatus marks the evolution of a cortical microtubule system and a commitment to meristematic growth. Microtubule systems associated with plastid division, the axial microtubule system (AMS) in mitosis and the quadripolar microtubule system (QMS) in meiosis, contribute to predictive positioning of plastids and participate directly in spindle ontogeny. Division polarity in monoplastidic sporocytes is remarkable in that division sites are selected prior to the two successive nuclear divisions of meiosis. Plastid arrangement prior to meiosis determines the future spore domains in monoplastidic sporocytes, whereas in polyplastidic sporocytes the spore nuclei play a major role in claiming cytoplasmic domains. It is hypothesized that predivision microtubule systems associated with monoplastidic cell division are early forming components of the mitotic apparatus that serve to orient the spindle and insure equal apportionment of nucleus and plastids.

“Can it be supposed that cytoplasm would be intrusted with so important a task as the preparation of a chloroplast for each of the four nuclei that are later to preside over the spores before there is any indication that such nuclear division is to take place?”

Bradley Moore Davis, 1899
ZEIN DEGRADATION IN THE ENDOSPERM OF MAIZE SEEDS DURING GERMINATION
Authors: Mohammad Kamaruzaman Bin , Esen Asim
Published: January 2018

The pattern and sequence of zein degradation in the endosperm of germinating maize seeds were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) and by immunostaining Western blots with a monoclonal antibody to α‐zein and polyclonal antibodies to β‐, γ‐, and δ‐zeins. The results indicated: 1) the degradation of the predominant α‐zein fraction (23.8 and 26.7 kD) started on the 5th day after germination (DAG) and continued gradually until the 10th DAG with a small amount remaining undegraded up to the 26th DAG; 2) β‐zein (17 kD) began to be degraded on the 2d DAG, and the degradation of the 17 kD polypeptide was completed by the 7th DAG; 3) γ‐zeins (27 and 18 kD) were the first zeins to be degraded, and the degradations of γ‐zeinl (27 kD) and γ‐zein2 (18 kD) were complete by the 3rd and 4th DAG, respectively; and 4) the degradation of δ‐zein (10 kD) began on the 4th DAG and was complete by the 7th DAG. Based on these results, the following arrangement of zein polypeptides within the protein bodies is postulated, assuming that the proteolytic events start at the periphery and processed towards the core of the protein body: 1) γ‐zeins are situated around the periphery of the protein bodies and are possibly a structural component of the protein body membrane or directly anchored in the membrane; 2) β‐zein would be internal to γ‐zeins; and 3) α‐zein and δ‐zein would be in the protein body core. This arrangement is largely consistent with published data on the immunocytochemical localization of zeins, and it indicates that the different classes of zein are not randomly organized within the matrix of the protein body.
TROPIC RESPONSES CONTROLLING LEAF ORIENTATION IN THE FERN DANAEA WENDLANDII (MARATTIACEAE)
Authors: Sharpe Joanne M. , Jernstedt Judith A.
Published: January 2018

Fertile leaves (sporophylls) of the eusporangiate herbaceous layer fern Danaea wendlandii emerge from the shoot apex with a horizontal orientation. Croziers of sterile leaves (trophophylls) emerge from the terminal bud oriented vertically. Sporophylls maintain a horizontal orientation as the leaflets uncoil and the rachis unrolls. This is followed by formation of a petiolar hook and vertical reorientation of the mature sporophyll. Both the vertical orientation of young trophophylls and the horizontal orientation of young sporophylls are gravitropic responses. Neither type of leaf responds to directional light stimulus. Negative gravitropism causing downward curvature of young sporophylls occurs only in the light, and in the absence of light, sporophyll croziers curve upward. Amyloplast sedimentation patterns in cells of the petiole and rachis indicate that a statolith mechanism may be involved in the orientation of young leaves of D. wendlandii.
POLLEN DEVELOPMENT IN OENOTHERA BIENNIS (ONAGRACEAE)
Authors: Takahashi Masamichi , Skvarla John J.
Published: January 2018

Development of the exine and viscin threads in Oenothera was studied by a combination of transmission electron microscopy and field emission scanning electron microscopy. Exine formation is initiated in the early tetrad stage by plate‐like structures of preexine formed evenly around the microspore within a callosic wall. In the late tetrad stage, an endexine accumulates on white‐lined lamellae underneath the preexine. After dissolution of the callosic wall, the preexine develops into beaded ektexine which is differentiated into an undulate tectum‐like layer and columellae‐like components. Interwoven fibrous strings connect the developing ektexine and the surface of the tapetal cells, and later develop into the viscin threads. These developmental processes imply that the columellae‐like components are different in structure from the columellae of other angiosperms and that the formation of viscin threads is associated with the tapetal cells.
ANATOMICAL AND PHYSIOLOGICAL ACCLIMATION OF FATSIA JAPONICA LEAVES TO IRRADIANCE
Authors: Vidal Dolors , Griera Elvira , Marin Pilar , Sabido Joan
Published: January 2018

Anatomical and physiological leaf characteristics and biomass production ofFatsia japonicaplants were studied. Plants were grown in a growth chamber at 300 μmol m‐2s‐1(high light) and 50 μmol m‐2s‐1(low light) photosynthetic photon flux density. Plants grown under high light showed a net maximum photosynthetic rate 44% higher than plants grown under low light; the light compensation point and the light saturation point were also higher in high‐light plants. Photosynthetic oxygen evolution in isolated chloroplasts was about 40% higher in high‐light plants. However, chlorophyll content on a dry weight basis, on a leaf area basis, and per chloroplast was greater in plants grown under low light. Leaf thickness in high‐light plants was 13% higher than in low‐light plants. The number of chloroplasts was 30% higher in high‐light leaves, while chloroplast size was only slightly higher. Chloroplast ultrastructure was also affected by light. Leaf dry weight, leaf area, and biomass production per plant were drastically reduced under low light. Thus,F. japonicais a plant that is able to acclimate to different photosynthetic photon flux density by altering its anatomical and physiological characteristics. However, low‐light acclimation of this plant has a considerable limiting effect on biomass production.