bluuebunny/crossref_metadata_2025 huggingface dataset:
LIFE‐HISTORY STRATEGIES AND SEX RATIOS FOR A CULTIVAR AND A WILD POPULATION OF BUCHLOE DACTYLOIDES (GRAMINEAE)
Authors: Quinn James A. , Engel Jean L.
Published: January 2018

Buchloe dactyloides (Nutt.) Engelm. is a perennial, sod‐forming shortgrass of the grasslands of central North America from Montana to northern Mexico. The objectives of this research were to compare a cultivar (Sharps Improved) and a wild population from the Oklahoma panhandle, both in the field and in the greenhouse over several growing seasons, in regard to life‐history strategies, sex ratios, and constancy of sex expression. Sex ratios of offspring from individual burs (usually 1–5 seeds per bur) and for all surviving plants germinated from seeds in the greenhouse were markedly different for the two populations. The wild population exhibited a 1: 1 male/female ratio with no monoecious plants and complete stability in sex expression over 3 yr of study in the greenhouse. In contrast, 13% of the cultivar plants were monoecious, and its unisexual plants showed a female bias. Burs of the two populations, in flats exposed to three separated month‐long periods of favorable moisture with intervening “drought” periods, showed differential germinability of seeds within burs. The cultivar had less dormancy and produced a greater number of seedlings in the first and second periods; wild burs significantly exceeded cultivar burs in the number of seedlings during the third period and in the number of burs giving rise to seedlings in all three periods. Field and greenhouse measurements of vegetative (VRE) and sexual reproductive effort (SRE) per plant indicated that SRE was minimal (ca. 2% of aboveground biomass) in relation to asexual ramet propagation by rapidly growing stolons (VRE = ca. 80%). Mean SRE and VRE were not only similar for the populations, but also for the males and females within a population, although the values for individual plants were highly variable. It is concluded that Buchloe dactyloides is largely dioecious, with at least some wild populations showing a 1: 1 male/female ratio and constancy of sex expression, and that the bur as a dispersal unit containing 1–5 seeds is particularly appropriate for the breeding system and habitat ecology of Buchloe dactyloides.
EFFECTS OF ENVIRONMENTAL STRESS ON COMPONENTS OF REPRODUCTION IN CLARKIA UNGUICULATA
Authors: Smith‐Huerta Nancy L. , Vasek Frank C.
Published: January 2018

The effects of stress on reproduction in Clarkia unguiculata were investigated by monitoring flower number, seed number and seed wt after subjecting plants to drought and heavy fruit loads, and by monitoring seed number after pollinating overage flowers. Fewer main‐stem flowers were produced in drought stressed plants than in non‐stressed plants. Drought stress did not affect overall seed numbers and seed wt in 1981, but did significantly affect seed number and wt in different flower age classes. Overall seed numbers were not affected by drought stress in 1982, but seed wt was significantly lower in plants with stressed ovules. Fewer flowers but more seeds per pollination were produced by plants in which all or ½ the flowers were pollinated than by plants in which ¼ or 1/6 of the flowers were pollinated. Seed wts were lowest in plants with a full fruit load and in fruits produced late in the growth cycle. Seed number was variable but high following pollination of flowers with 1–7 day old stigmas, and much lower in flowers with older stigmas.
EFFECT OF SHORT‐TERM SHADING ON THE CYTOLOGY OF PALISADE TISSUE IN MATURE LEAVES OF THE SUNFLOWER HELIANTHUS ANNUUS
Authors: Fagerberg Wayne R.
Published: January 2018

Mature sunflower leaves were exposed to partial shading (35 or 14% of normal sun) or darkness (0% of normal sun) for approximately 8 hr. During this period one‐half of each test leaf was shaded; the other half was used as a normal sun control. Palisade cell structure from both halves of each leaf was compared. Shading of leaves had little effect on organelle percent volume values (Vv) with exception of the starch compartment which decreased as shading increased. The surface to volume ratio (Sv) of the chloroplast thylakoids increased while the Sv of the mitochondrial membranes decreased as shading increased. Palisade cell volume did not change in shaded portions of the leaf, except in the fully shaded (dark) tissues where cell volume decreased. Changes in the actual volume of organelle compartments were strongly correlated with changes in cell volume. Thus a general osmotic response may account for some of the volume changes associated with differences in light intensity. Shading increased thylakoid surface areas 10–30% over the full sun controls. The ratio of stromal to granal thylakoid surface area remained constant in both the control and partially shaded samples. However, in darkened samples this ratio decreased as stromal membranes increased more than granal membranes. Changes observed in thylakoid surface areas associated with shading did not support thylakoid models which propose the interconversion of granal membranes to stromal membranes and vice versa.
SOYBEAN GROWTH RESPONSES TO ENHANCED LEVELS OF ULTRAVIOLET‐B RADIATION UNDER GREENHOUSE CONDITIONS
Authors: Teramura Alan H. , Sullivan Joe H.
Published: January 2018

Soybean (Glycine max [L.] Merr. cv. Essex) was grown in an unshaded greenhouse under three levels of biologically effective ultraviolet‐B (UV‐BBE) radiation (effective daily dose: 0, 11.5 and 13.6 kJ m–2) for 91 days. Plants were harvested at regular intervals beginning 10 days after germination until reproductive maturity. Mathematical growth analysis revealed that the effects of UV‐B radiation varied with plant growth stage. The transition period between vegetative and reproductive growth was the most sensitive to UV‐B radiation. Intermediate levels of UV‐B had deleterious effects on plant height, leaf area, and total plant dry weight at late vegetative and reproductive stages of development. Specific leaf weight increased during vegetative growth but was unaffected by UV‐B during reproductive growth stages. Relative growth, net assimilation, and stem elongation rates were decreased by UV‐B radiation during vegetative and early reproductive growth stages. Variation in plant responses may be due in part to changes in microclimate within the plant canopy or to differences in repair or protection mechanisms at differing developmental stages.
DIASPORE SIZE, SHAPE, AND FALL BEHAVIOR IN WIND‐DISPERSED PLANT SPECIES
Authors: Matlack Glenn R.
Published: January 2018

Seeds and fruit of 38 anemochorous species were dropped in still air to simulate their descent under natural conditions. Fall rate and lateral distance were recorded as indices of wind‐borne dispersal capability. Differences in fall rates among plumed species were dependent on interspecific variation in diaspore weight and plume area, while fall rates of winged species were strongly differentiated by contrasting wing shapes. In Acer platanoides and Asclepias syriaca, representing wing and plume architectures, respectively, the range of diaspore weight was artificially extended by removing embryos or adding lead weights. In both of these species, rate of descent of altered diaspores was controlled by weight relative to wing or plume area. The wing morphology of A. platanoides showed lower fall rates than the plumed A. syriaca above 45 mg, while the plume morphology of A. syriaca achieved lower fall rates below this weight. Compared with wide variation in diaspore weight, members of the Compositae showed relatively low variation in plume loading (diaspore weight/plume area) and fall speed. These observations suggest functional and phyletic constraints on diaspore architecture. Such constraints may limit evolutionary change in diaspore size and performance.
CHANGES IN GLYCERALDEHYDE 3‐PHOSPHATE DEHYDROGENASE ACTIVITY IN SHOOT APICAL MERISTEMS OF BRASSICA CAMPESTRIS DURING TRANSITION TO FLOWERING
Authors: Orr Alan R.
Published: January 2018

An assay system has been developed for the histochemical determination of glyceraldehyde 3‐phosphate dehydrogenase (G3PD) activity to indicate glycolytic pathway capacity during evocation in the shoot apical meristem of Brassica campestris L. G3PD activity was differentially distributed in a zonate pattern within the meristems at the vegetative, the transition, and the floral stages. The activity of G3PD changed in all apical zones of evoked apices, but especially in the central and the peripheral zones of apices at the prefloral stage. In the prefloral stage of development heavy enzyme activity was localized in island‐like areas within the peripheral zone. These results indicate that 1) the capacity of glycolysis fluctuates during evocation, 2) during floral evocation the capacity of the glycolytic pathway parallels the capacity of the citric acid cycle and the electron transport system only at the prefloral stage, and 3) G3PD activity marks incipient floral primordia. It is proposed that the enzymic marking of an incipient floral primordium indicates the end of evocation in Brassica.
GAMETOPHYTIC SELF‐FERTILIZATION IN HOMOSPOROUS PLANTS: DEVELOPMENT, EVALUATION, AND APPLICATION OF A STATISTICAL METHOD FOR EVALUATING ITS IMPORTANCE
Authors: Holsinger Kent E.
Published: January 2018

The methods described here make it possible to use data on sporophytic genotype frequencies to estimate the frequency of gametophytic self‐fertilization in populations of homosporous plants. Bootstrap bias reduction is effective in reducing or eliminating the bias of the maximum likelihood estimate of the gametophytic selfing rate. The bias‐corrected percentile method provides the most reliable confidence intervals for allele frequencies. The percentile method gives the most reliable confidence intervals for the gametophytic selfing rate when selfing is common. The maximum likelihood intervals, the percentile intervals, the bias‐corrected percentile intervals, and the bootstrap t intervals are all overly conservative in their construction of confidence intervals for the gametophytic selfing rate when self‐fertilization is rare. Application of the recommended methods indicates that gametophytic self‐fertilization is quite rare in two sexually reproducing populations of Pellaea andromedifolia studied by Gastony and Gottlieb (1985).
NEAR‐VESSELLESSNESS IN EPHEDRA AND ITS SIGNIFICANCE
Authors: Carlquist Sherwin
Published: January 2018

Wood of two specimens of Ephedra from high alpine localities is nearly vesselless: E. gerardiana from 4,750 m in Tibet, and E. rupestris from 4,300 m in Argentina. Ephedra gerardiana from lower elevations in the Himalayas has more vessels, although even there they are not abundant. Instances in other species of Ephedra in which extensive areas of latewood or even entire growth rings are vesselless are cited; these tend to occur in high deserts with climates somewhat less extreme than those of the alpine localities. Near‐vessellessness is interpreted as an adaptive condition in which the proportion of tracheids, conductively safer than vessel elements, reaches a maximum. Near‐vessellessness in Ephedra wood is probably reversible within limits, and should be likened to production of latewood to the exclusion of earlywood. Comparisons are offered to dicotyledons in which abundance of vessels is lowered with respect to ecological extremes.
CYTOLOGICAL CONSEQUENCES OF DNA AMPLIFICATION IN AN ANTHER CULTURE‐DERIVED DOUBLED HAPLOID LINE OF NICOTIANA TABACUM
Authors: Reed Sandra M. , Burns Joyce A.
Published: January 2018

An increase in nuclear DNA, without an increase in chromosome number, has been found to occur as a result of anther culture in Nicotiana tabacum L. The objective of this study was to determine the cytological consequences of this DNA amplification in F1 hybrids between a doubled haploid that had undergone a substantial increase in DNA and the cultivar from which that doubled haploid was derived. Mitotic and meiotic analyses were performed on plants obtained from reciprocal crosses of N. tabacum cv. NC95 and NC95 SCDHL 12, a doubled haploid line that has 41% more DNA than the parental cultivar. While no cytological abnormalities were observed in either parental line, numerous abnormalities were seen in both somatic and meiotic tissues of the F1 hybrid. Chromosome losses, which appeared to result from spindle errors, were observed in these tissues. It is speculated that the spindle errors may be the result of a genetic unbalance caused by combining genomes with widely differing amounts of DNA. In addition to the spindle errors, a quadrivalent with an atypical morphology was observed in meiotic diplotene and metaphase I cells of the hybrid. The quadrivalent configuration was interpreted to represent pairing between amplified homologous regions in homeologous chromosomes. Further investigations of additional doubled haploid × cultivar lines is required before the significance of these findings to the anther culture process in N. tabacum can be fully assessed.
LEAF OF SPINACIA OLERACEA (SPINACH): ULTRASTRUCTURE, AND PLASMODESMATAL DISTRIBUTION AND FREQUENCY, IN RELATION TO SIEVE‐TUBE LOADING
Authors: Warmbrodt Robert D. , Woude William J. VanDer
Published: January 2018

Minor veins and contiguous tissues of the Spinacia oleracea leaf were analyzed by electron microscopy to determine the characteristics of the component cells and the structure, distribution, and frequency of plasmodesmata between the various cell types of the leaf. Mesophyll and bundle‐sheath cells contain components typical of photosynthetic cells although the latter cell type contains smaller chloroplasts and fewer mitochondria and microbodies than the mesophyll cells. In addition, the mesophyll cells contain numerous invaginations of the plasmalemma bordering the chloroplasts and evaginations of the outer membrane of the opposing chloroplast envelope. In places, these membranes appear continuous with each other. The minor veins consist of tracheary elements, xylem parenchyma cells, sieve‐tube members, companion and phloem parenchyma cells, and other cells simply designated vascular parenchyma cells. The companion and phloem parenchyma cells are typically larger than the sieve‐tube members with the companion cells containing a much denser cytoplasm that the phloem parenchyma. Cytoplasmic connections occur along all possible routes from the mesophyll to the sieve‐tube members and consist of either simple or branched plasmodesmata between parenchymatic elements or pore‐plasmodesmata between the sieve‐tube members and parenchyma cells. The highest frequency of plasmodesmata occurs between the sieve‐tube members and companion cells, although the value is essentially the same as between the various parenchymatic elements of the phloem. Compared to several previously studied species, the frequency of plasmodesmata between cell types of the spinach leaf is low. These results are discussed in relation to apoplastic vs. symplastic solute transport and sieve‐tube loading in this species.
SPECIES‐AREA RELATIONSHIP DURING PRIMARY SUCCESSION IN GRANITE OUTCROP PLANT COMMUNITIES
Authors: Houle Gilles
Published: January 2018

The species‐area relationship and its underlying explanatory mechanisms were investigated in a primary successional sere on a southeastern (United States) granite outcrop. There, plant communities occupy soil‐filled depressions separated from one another by areas of bare rock. They have been termed “island communities.” Soil depth and area increase as succession proceeds from Sedum smallii, to lichen‐annual, to annual‐perennial, and to herb‐shrub‐tree stages. Although plant species richness is significantly and positively correlated with island area in the system studied (all successional stages considered), the relationship between species richness and island maximum soil depth is stronger. However, island maximum soil depth and area are significantly and positively correlated. The exponential function describes the speciesarea relationship better than the transformed power function. Within successional stage, species richness shows no significant relationship with area or depth, except for late‐successional island communities. Processes related to community successional development may explain the species‐area relationship that exists when islands of all stages are considered. However, mechanisms related to equilibrium between extinction and immigration may be responsible for the speciesarea relationship for late‐successional island communities.
REPRODUCTIVE BIOLOGY OF THE YELLOW‐FRINGED ORCHID, PLATANTHERA CILIARIS
Authors: Robertson Judith L. , Wyatt Robert
Published: January 2018

Platanthera ciliaris is a butterfly‐pollinated, terrestrial orchid with a loose terminal raceme of 10–50 orange flowers, characterized by a long nectariferous spur. In the southeastern United States, P. ciliaris occurs in the Appalachian Mountains and Coastal Plain physiographic provinces, but rarely in the intervening Piedmont. Of 153 plants that flowered in a Mountain population in 1983, 54 (35.2%) flowered again in 1984; in a Coastal Plain population, only 51 of 306 (16.7%) flowered in both years. Experimental pollinations showed that P. ciliaris is self‐compatible but not autogamous. Nectar volume increased over the 6‐ to 7‐day life span of a flower, reaching a maximum of 4 μl and 1.0 mg of sugar (Mountains) or 6 μl and 1.2 mg of sugar (Coastal Plain). Nectar concentrations were relatively constant in flowers of all ages and averaged 23% in the Mountains and 19% in the Coastal Plain. Diurnal patterns of nectar secretion were not well‐defined, but most nectar appeared to be produced overnight. In the Mountains Papilio troilus (spicebush swallowtail) was the most frequent and effective pollinator, whereas in the Coastal Plain P. palamedes (palamedes swallowtail) was the predominant pollinator. These large butterflies were most active in the late morning (0930–1030) and early afternoon (1230–1400). Levels of pollinator service, as assessed by rates of removal and insertion of pollinia, were higher in the Mountains (0.81, 0.86) than in the Coastal Plain (0.63, 0.67). These values were reflected in higher levels of fruit‐set in Mountain (83.9% in 1983, 86.5% in 1984) than in Coastal Plain (63.8, 65.5%) populations. Combining these observations with the fact that hand pollination increased fruit‐set of Coastal Plain flowers 6.5–13.5% above open‐pollinated controls, it appears that fruit‐set in P. ciliaris is pollen‐limited.
MOLECULAR EVIDENCE FOR THE ORIGIN OF THE S‐DERIVED GENOMES OF POLYPLOID TRITICUM SPECIES
Authors: Talbert L. E. , Magyar G. M. , Lavin M. , Blake T. K. , Moylan S. L.
Published: January 2018

The genus Triticum includes several polyploid species that arose due to hybridization between two or more diploid species. Section Sitopsis is comprised of five diploid species given the genome designation S. Four polyploid species are recognized that contain an S or S‐derived genome. We have used two repetitive DNA sequences found primarily in the S genomes of Triticum to determine the likely diploid progenitors of the polyploid species. Comparison of restriction fragments that hybridize to probes for these sequences suggests that T. speltoides is distinct from other members of section Sitopsis (i.e., T. longissimum, T. bicorne, T. searsii, and T. sharonense). The S‐derived genome of T. aestivum is more closely related to T. speltoides than to the other Sitopsis diploids. The restriction fragment pattern of T. timopheevii is 98% identical to that of T. speltoides, while those of T. kotschyi and T. syriacum are identical to the group of diploids represented by T. longissimum, T. bicorne, T. searsii, and T. sharonense. Our results are compatible with previous molecular and biochemical data regarding relationships among Triticum species containing an S or S‐derived genome.
EVOLUTION OF DIOECY IN BUCHLOE DACTYLOIDES (GRAMINEAE): TESTS FOR SEX‐SPECIFIC VEGETATIVE CHARACTERS, ECOLOGICAL DIFFERENCES, AND SEXUAL NICHE‐PARTITIONING
Authors: Quinn James A.
Published: January 2018

Buchloe dactyloides is a perennial dioecious grass in which male and female inflorescences are so strikingly dimorphic that they were originally assigned to different genera. The objective of this paper is to present the results of tests for sex‐specific vegetative characters, ecological differences, and sexual niche‐partitioning, combining them with prior information on the reproductive biology of Buchloe for an evaluation of the key factors leading to the evolution of dioecy and sexual dimorphism. Field and greenhouse data were collected from Oklahoma and Kansas populations on vegetative characters, allocation to reproduction, and relative growth and competitive success along resource gradients. Except for greater susceptibility to leaf rust by males, there were no significant differences between males and females in vegetative characters, total biomass, or reproductive effort. Field studies of spatial distributions of males and females failed to show any relation to soil, topography, or soil moisture. In a 45‐month greenhouse experiment starting at the seedling stage, the relative growth and competitive success of randomly paired individuals showed no evidence for differential competitive success or for niche‐partitioning of males and females. The “outcrossing advantage” and subsequent sexual specialization of the female inflorescence appear to be the major factors underlying this dimorphic system.
ROLE OF THE NITROGEN‐FIXING BACTERIAL MICROFLORA IN THE EPIPHYTISM OF TILLANDSIA (BROMELIACEAE)
Authors: Brighigna Luigi , Montaini Paola , Favilli Franco , Trejo Alfonso Carabez
Published: January 2018

Nitrogen‐fixing activity in the phyllosphere of 12 species of Tillandsia from different Mexican habitats was evaluated by the acetylene reduction assay, and nitrogen‐fixing microorganisms were isolated and characterized. The leaves from eight of the 12 Tillandsia species examined exhibited nitrogenase activity in enrichment cultures. Among the microorganisms implicated—Agrobacterium, Bacillus, Erwinia, Pseudomonas, Rahnella, Vibrio, and Xanthomonas—only Bacillus megatherium reduced acetylene in pure culture. Our findings suggest that nitrogen fixation in the phyllosphere of the sampled epiphytes occurs under suitable conditions and that most of the bacteria involved are primarily soil and water inhabitants. The results also suggest a relationship between the composition of the nitrogen‐fixing microbial communities grown on the leaf and the different development of the leaf area in Tillandsia due to the aerial components (wings) of the trichomes.
VARIATION IN THE CHLOROPLAST GENES RPOC1 AND RPOC2 OF THE GENUS ASTRAGALUS (FABACEAE): EVIDENCE FROM RESTRICTION SITE MAPPING OF A PCR‐AMPLIFIED FRAGMENT
Authors: Liston Aaron
Published: January 2018

A 4,100‐base pair (bp) region of the chloroplast genome, amplified via the polymerase chain reaction, was obtained from 14 species of the genus Astragalus and mapped with 23 restriction enzymes. The amplified region encompassed the chloroplast genes RNA polymerase Cl (rpoCl; 90.8% of the gene) and RNA polymerase C2 (rpoC2; 32.7% of the gene) including the intron in rpoC1 and the intergenic spacer between the two genes. Approximately 144 sites (615 bp) were identified; 37 restriction site mutations and one 10‐bp length mutation were detected. Estimated interspecific sequence divergence values ranged from 0.00% to 3.92%. Phylogenetic analysis with Wagner and Dollo parsimony both resulted in a single 41‐step tree with a consistency index of 0.951. The relative positions of 115 restriction sites were mapped. The insertion and ten of the restriction site mutations mapped to the intron in rpoC1, 18 site mutations mapped to the rpoC1 exons, three site mutations mapped to rpoC2, three site changes mapped to the intergenic spacer, and four site changes were not mapped. This study demonstrates the utility of restriction site analysis of PCR‐amplified chloroplast DNA to the study of plant phylogenetic relationships and molecular evolution.
SPHENOPTERIDIUM AND TELANGIOPSIS IN A DIPLOPTERIDIUM‐LIKE ASSOCIATION FROM THE VIRGILIAN (UPPER PENNSYLVANIAN) OF NEW MEXICO
Authors: Mamay Sergius H.
Published: January 2018

The highly fossiliferous Virgilian (Upper Pennsylvanian) shales of the Kinney Brick Company quarry near Albuquerque, New Mexico, contain a diversified flora dominated by walchian conifers and neuropterid pteridosperms. Its other components include a specimen of Telangiopsis sp. and abundant material of Sphenopteridium manzanitanum, n. sp., a highly variable foliar form. Both genera are characteristically restricted to the Upper Mississippian, with the exception of one basal Pennsylvanian occurrence. Their occurrence together in the Kinney sediments and their possession in common of distinctive surficial ornamentation suggest that they represent dissociated parts of Diplopteridium, a very rare European Lower Carboniferous taxon. Other associated plants show later Paleozoic or even Early Mesozoic characteristics, which, together with the Mississippian elements, distinguish the Kinney site as paleobotanically unique.
FOSSIL EXTRAFLORAL NECTARIES, EVIDENCE FOR THE ANT‐GUARD ANTIHERBIVORE DEFENSE IN AN OLIGOCENE POPULUS
Authors: Pemberton Robert W.
Published: January 2018

Extrafloral nectaries are secretory glands, usually found on leaves, that have been shown to promote ant defense against the insect herbivores of many modem day plants. Extrafloral nectaries were found on the 35‐million‐year‐old fossil leaves of the extinct Populus crassa from Florissant, Colorado. Extinct ant species (belonging to five still extant genera that have modem ant‐guard species), and other predators and parasitoids (whose modem relatives frequent extrafloral nectaries) also lived at Florissant. The extrafloral nectaries of P. crassa (and perhaps other plants) probably operated to attract ants and/or other arthropod defenders as early as the Oligocene.
HIGH‐RESOLUTION LEAF X‐RADIOGRAPHY IN SYSTEMATICS AND PALEOBOTANY
Authors: Wing Scott L.
Published: January 2018

The foliar vein nets of many seed plants and ferns display systematically informative characters. These venation characters traditionally have been observed by chemically clearing and staining leaves, a process that is slow, involves toxic chemicals, and yields delicate, glass‐mounted specimens that require long‐term maintenance to prevent or correct bubbling or crystallization of the mounting medium. A technique that uses X‐rays and photographic film to produce images of leaf venation consistently shows veins that are 50–100 μm thick. Although the X‐ray images are slightly less detailed than the best cleared and stained leaves, the images can be made much more quickly, are more easily stored and reproduced, and do not require permanent alteration of the original herbarium specimen. The technique should facilitate the use of vein characters in systematics, and the identification and systematic analysis of fossil leaves.
ANALYSIS OF POLYPEPTIDES ASSOCIATED WITH SHOOT FORMATION IN TOBACCO CALLUS CULTURES
Authors: Bertrand‐Garcia Ralph , Walling Linda L. , Murashige Toshio
Published: January 2018

Callus lines of Nicotiana tabacum were selected for competence and lack of competence in shoot formation. Changes in total and chromosomal polypeptides in these shoot‐forming and nonshoot‐forming tobacco cultures were examined by twodimensional polyacrylamide gel electrophoresis. Qualitative and quantitative differences in total, nonhistone chromosomal, and basic chromosomal polypeptides were evident throughout the 7‐d test period. The analysis of total proteins identified polypeptides specific to shoot‐forming and nonshoot‐forming tissue during the 7‐d sampling period. A small number of basic chromosomal proteins were found solely in shoot‐forming or nonshoot‐forming tissue. One basic chromosomal protein was detected in only nonshoot‐forming tissue at all sampling times. Two proteins, although present in shoot‐forming tissue, were present at elevated levels in the nonshoot‐forming cultures. No temporal changes in basic proteins over the 7‐d incubation period were observed. Qualitative differences in total nonhistone chromosomal polypeptides in the shoot‐forming and nonshoot‐forming tissue were also observed. Differences in chromosomal polypeptides were observed. In contrast to the basic chromosomal proteins, temporal variation in the nonhistone chromosomal polypeptides was demonstrated. Throughout the 7‐d sampling period, 29 and 12 nonhistone chromosomal polypeptides varied qualitatively in shoot‐forming and nonshoot‐forming callus cultures, respectively. In vitro labeling with 32P‐orthophosphate indicated that approximately 1.0% and 0.3% of the nonhistone chromosomal proteins were phosphorylated in the shoot‐forming and nonshoot‐forming cultures. Of these phosphorylated polypeptides, one was present in nonshoot‐forming tissue and three were detected only in the shoot‐forming tissue. Phosphorylation occurred at serine or threonine residues.
REPRODUCTIVE BIOLOGY, POLLEN AND SEED DISPERSAL, AND NEIGHBORHOOD SIZE IN THE HUMMINGBIRD‐POLLINATED ECHEVERIA GIBBIFLORA (CRASSULACEAE)
Authors: Parra Victor , Vargas C. Fabian , Eguiarte Luis E.
Published: January 2018

Little is known about the reproductive biology of the Crassulaceae. We studied a population of Echeveria gibbiflora in the Pedregal de San Angel ecological preserve in Mexico City, Mexico. Each flower is open and producing nectar 7 to 8 days. On the days of maximum nectar production (flowers 4–6 days old) an average of 14.5 μl accumulates in a flower per day. The maximum rate of nectar production is between 0700 and 0900 hours. The average sugar concentration in the nectar is 43.7%. In a given flower, pollen is exposed and the stigmas are receptive at the same time. The average natural fruit‐set and seed‐set are 56.6% and 35.5%, respectively. The pollen‐ovule ratio is 124, and the plants are fully self‐compatible. The flowers are pollinated by only one species of hummingbird (Cynanthus latirostris) and are never visited by insects. Pollen movement is very limited (mean of pollinator flight distances = 0.72 m, mean distance fluorescent dyes = 0.92 m). Seed dispersion is by gravity and wind, and also is very limited (an average of 1.07 m). The total genetic neighborhood area is 15 m2 to 17 m2, producing a neighborhood effective population size (Nb) of 5.01 to 39.7 individuals. This is a very small Nb, indicating that genetic drift may be a dominant force in the evolution of this species.
DIASPORE MORPHOLOGY AND SEED DISPERSAL IN SEVERAL WIND‐DISPERSED ASTERACEAE
Authors: Andersen Mark C.
Published: January 2018

I made measurements of morphology and settling velocity on seeds of 19 species of wind‐dispersed Asteraceae. From the morphological measurements I calculated Reynolds numbers and approximate plume loadings for the species. Diaspore settling velocity increases linearly with the square root of plume loading. This relationship varies among species and among subfamilies, but not among life history types. Reynolds number is highly variable among subfamilies, less so within subfamilies. Diaspores with beaked achenes have significantly lower settling velocities than diaspores with unbeaked achenes, even though beaked and unbeaked achenes do not differ in plume loading or in Reynolds number. Reynolds numbers of all diaspores examined are well above the range in which Stokes' Law applies. I recommend that the use of formulae based on Stokes' Law be curtailed in studies of the relationship between plume loading and settling velocity. The results suggest that many seed characters may have evolved due to selection on dispersal ability. This is in spite of phyletic constraints on morphology reflected in the relative uniformity of Reynolds numbers within subfamilies.
INCIDENCE OF MONOECY AND DICHOGAMY IN RELATION TO SELF‐FERTILIZATION IN ANGIOSPERMS
Authors: Bertin Robert I.
Published: January 2018

The evolution of many floral traits, including monoecy and dichogamy, has been attributed to selection for avoidance of self‐fertilization. If this explanation is correct, monoecy and dichogamy should be uncommon among self‐incompatible species because physiological barriers prevent self‐fertilization in such species. In fact, self‐fertility was independent of sexual system in a sample of 588 hermaphroditic and monoecious angiosperms. Overall, dichogamy was also equally common among self‐incompatible and self‐compatible species. When the different forms of dichogamy were analyzed separately, only intrafloral protogyny was associated with self‐compatibility. This form of dichogamy is less common among angiosperms than intrafloral protandry, which is probably less effective at reducing self‐fertilization. Thus, avoidance of self‐fertilization has probably been less important in the evolution of monoecy and most forms of dichogamy than other factors, such as avoidance of pollen‐pistil interference, and flexibility of resource allocation to male and female functions.
BUZZ‐POLLINATION AND PATTERNS IN SEXUAL TRAITS IN NORTH EUROPEAN PYROLACEAE
Authors: Knudsen Jette T. , Olesen Jens Mogens
Published: January 2018

Flower biology and pollination of Moneses uniflora, Orlhilia secunda, Pyrola minor, P. rotundifolia, P. chlorantha, and Chimaphila umbellata are described and discussed in relation to patterns in sexual traits and possible evolution of buzz‐pollination within the group. The large number of pollen grains are packed into units of monads in Orthilia, tetrads in Moneses and Pyrola, or polyads in Chimaphila. Pollen is the sole reward to visiting insects except in the nectar‐producing O. secunda and C. umbellata. Correlations are present between several sexual traits. Pollen: ovule ratios are very low, indicating efficient pollen transfer. Use of polyads may reduce the number of siring males. This trend may be counteracted by larger stigmas as in C. umbellata. Increasing pollen unit size may enhance relatedness of seeds, reduce abortion, and improve seed set. This may explain the evolution, within the Pyrolaceae and other families, of higher ovule numbers with larger pollen units. The plants are mainly pollinated by bumblebees. Chimaphila umbellata is visited by nectar‐collectors; Moneses uniflora, Pyrola minor, P. rotundifolia, and P. chlorantha are visited exclusively by pollen‐buzzers; and Orthilia secunda is visited by both nectar‐collectors and pollen‐buzzers. Nectar secretion is suggested to be an ancient attractant in the group with C. umbellata having the least specialized pollination system, and buzz‐pollination in M. uniflora and in the studied Pyrola species regarded as an advanced system.
Reassessment of tetrazolium bromide as a viability stain for spores of vesicular‐arbuscular mycorrhizal fungi
Authors: Meier R. , Charvat I.
Published: January 2018

Techniques for the determination of viability of field‐collected vesicular‐arbuscular mycorrhizal spores must be valid for spores of different ages and of varying levels of peridium (outer wall of unispored sporocarp) development. The use of the dehydrogenase‐activated stain 3‐(4,5‐dimethylthiazol‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide (MTT) for determining viability of endogonaceous spores was reassessed. Freshly isolated and stored spores of three isolates of Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe were stained using two different protocols: Miller, Torres, and McClean (Mycological Research, in press) and An and Hendrix (Mycologia 80: 259–261). Time course results from selected experiments were analyzed graphically, and pooled results from all experiments were analyzed by factorial analysis of variance to determine statistically significant differences among the protocols, storage regime of spores, control killing method, and the effect of added cobalt ions. Significant nondehydrogenase‐specific staining occurred in both types of controls of freshly isolated spores using Miller, Torres, and McClean's method, rendering it inadequate for viability determination. With An and Hendrix's protocol, fresh nonkilled spores stained significantly more than ethanol‐treated spores, although these results underestimated viability as determined by two other assessment procedures, and autoclaving of fresh spores was not a satisfactory control treatment. Addition of cobalt to the incubation solution effectively drove all formazan production to the blue color but did not change the total percentage of colored spores produced, regardless of protocol used. Results corroborate the use of An and Hendrix's protocol with stored spores if color interpretation was corrected to include both blue and red colors as indicators of viability, results were read before nonspecific staining starts, and timing was extended to 75 hours. Both staining methods work with uniformly stored spores using specific incubation times, but not with spores of mixed ages, which could include young spores, making MTT not useful as a viability stain for field‐isolated spores.
Comparison of water‐use efficiency and internal leaf carbon dioxide concentration in juvenile leaves and phyllodes of Acacia koa (leguminosae) from Hawaii, estimated by two methods
Authors: Hansen David , Steig Eric
Published: January 2018

To gain further insight into comparative ecophysiology of different leaf types, water‐use efficiency (WUE) and internal leaf carbon dioxide concentration (Ci) were estimated in the field for juvenile leaves and phyllodes of Acacia koa by carbon dioxide and water vapor exchange using a closed system infrared gas analyzer and humidity sensor, and by δ13C measurements. Both methods indicate that phyllodes possessed higher WUE and lower Ci than juvenile leaves. However, Ci predicted by δ13C for juvenile leaves and phyllodes was lower than the average gas exchange estimated values of Ci and closer to minimal gas exchange estimated values of Ci. It is suggested that δ13C may be influenced more during times of maximal assimilation and leaf expansion than during maintenance.
The pollen‐collecting hairs of Campanula (Campanulaceae). I. Morphological variation and the retractive mechanism
Authors: Nyman Yvonne
Published: January 2018

The pollen‐collecting hairs (PCHs) of Campanula have been a subject of intense debate for the past two centuries. Although several morphological studies have been made on these hairs, detailed comparative studies among species are still lacking, their function and adaptive significance being an unsolved question. The present study comprises two microscopy techniques: scanning electron microscopy and confocal scanning laser microscopy. The aim of the present study is to elucidate: 1) the variation in morphology of the PCHs, 2) the variation in presence/absence of the PCHs by the time of spreading of the stigmatic lobes, 3) the variation in the retractive mechanism of the PCHs, and 4) the correlation between pollination and the retraction of the PCHs. In several species PCHs of various lengths are found. Despite the variations in length of the hairs, the same retractive mechanism is found in all species studied. In most species the hairs retract into basal cavities within the style late in anthesis. The cells into which the hairs retract differ in length among species. Pollen grains are often found within the cavities together with the retracted hairs, a mechanism considered to prevent self‐pollination. Pollen germination within the cavities was not observed. In a few species, the PCHs are still present at stigma receptivity. Differences in the shape and size of the cells surrounding the PCHs are documented. The diameter of the pits and the pollen grains vary among species. Other types of hairs on the style are recognized in some species, being of various lengths. These other types do not retract at stigma development and should not be regarded as pollen‐collectors. They possibly facilitate for visiting insects to reach the nectar glands, present at the top of the ovary.
Floral determination in adventitious shoot meristems regenerated from leaves of day‐neutral tobacco
Authors: Rivers Bruce A. , Marcotrigiano Michael
Published: January 2018

The developmental patterns of adventitious shoots regenerated from cultured leaf tissue and the petioles of leaf cuttings of flowering day‐neutral tobacco plants were assessed. Leaf tissue, removed from leaves within the inflorescence, was cultured on hormone‐free medium and produced a limited number of adventitious shoots. These shoots produced the same number of nodes that would be produced by a seedling meristem. Most leaf‐cutting derived shoots produced the same number of nodes that would be produced by a seedling meristem prior to flowering, while a few shoots produced very few nodes and flowered. Some plants appeared to be intermediate in response. Results indicated that the developmental state or the developmental response of all petiole cells is not the same. The influence of position and the potential reversibility in developmental fate of cell populations within leaves is discussed in the context of existing theory.
Resin‐casting: a method for investigating apoplastic spaces
Authors: Mauseth James D. , Fujii Tomoyuki
Published: January 2018

A method has been developed in which liquid resin can be injected or infiltrated into spaces within a plant body, for example the lumens of vessels, fibers, and intercellular spaces. After polymerization of the resin, plant tissues are digested away with two solutions used in sequence: first, equal parts concentrated hydrogen peroxide and glacial acetic acid; second, concentrated sulfuric acid. Complete digestion renders three‐dimensional casts of the spaces in the original tissue. These can be examined with scanning electron microscopy, light microscopy, or a dissecting microscope. Casts have such high fidelity and high resolution that details of pit canals, pit chambers, and perforation plates can be studied. Vessel casts over 15 cm long and revealing the details of several thousand constituent vessel elements have been obtained easily. Casts of the lumens of all cell types and of narrow intercellular spaces are obtained by prolonged infiltration with a low‐viscosity resin solution. Alternatively, rapid, brief injection of the resin by vacuum produces casts predominantly of just those spaces that were open to the resin at the cut ends of the sample, for example the lumens of vessels and secretory ducts or the intercellular space network of an aerenchymatous parenchyma.
Floral nectary structure and nectar composition in Eccremocarpus scaber (Bignoniaceae), a hummingbird‐pollinated plant of central Chile
Authors: Belmonte Eliana , Cardemil Liliana , Arroyo Mary T. Kalin
Published: January 2018

Surface features, anatomy, and ultrastructure of the floral nectary of Eccremocarpus scaber (Bignoniaceae), pollinated predominantly by the largest‐known hummingbird (Patagona gigas gigas), were studied together with nectar sugar content and secretion rate. The annular disk nectary comprises epidermis, secretory and ground parenchyma with intercellular spaces, and branched vascular bundles terminating in the secretory parenchyma where only phloem is found. Amyloplasts and vacuoles increase in size throughout development, the latter becoming sites of organelle degradation. Transferlike cells in nectary phloem and P‐proteinlike fibrillar material in phloem parenchyma were observed. Flowers produced around 32 μl of nectar (mostly after anthesis) with 11 mg of sugar composed of fructose, glucose, sucrose, and maltose in a ratio of 0.34:0.32:0.17:0.17. Morphological studies as well as the presence of maltose and glucose in nectar suggest storage of the originally phloem‐derived sugars as starch with its subsequent hydrolysis. The low sucrose/hexose ratio (0.25) and high nectary secretion force (nectar per flower biomass) observed places E. scaber close to large‐bodied bat‐pollinated plants. A hypothesis based on nectar origin and nectar secretion is advanced to explain pollinator‐correlated variation in sucrose/hexose ratio.
Early events of multiple bud formation and shoot development in soybean embryonic axes treated with the cytokinin, 6‐benzylaminopurine
Authors: Buising Charisse M. , Shoemaker Randy C. , Benbow Robert M.
Published: January 2018

Early events of multiple bud formation and shoot development in germinating soybean embryonic axes treated for 24 hr with the cytokinin, 6‐benzylaminopurine (BAP), were compared to the development of untreated control axes using four different techniques: photomicrography, scanning electron microscopy, histology, and autoradiography. Shoot apex development in BAP‐treated embryonic axes was delayed by about 9 to 15 hr. A transient inhibition of DNA synthesis in the primary apical meristem and axillary buds was observed with subsequent changes in the timing of cell division patterns in these regions. Meristematic regions (supernumerary vegetative buds) were observed in BAP‐treated axes around the perimeter of the apical dome at and above the level of the axillary buds. Cells elongated from some of the BAP‐induced meristematic regions to form four to six shoots. In the absence of BAP, excision of the primary apical meristem and/or axillary buds did not result in multiple bud formation. These results suggest that transient exposure to BAP interrupted chromosomal DNA replication and reprogrammed the developmental fate of a large number of cells in the shoot apex. We postulate that interruption of DNA synthesis, either directly, by interfering with DNA replication, or indirectly, by preventing entry into S‐phase, effected redetermination of the shoot apex cells.
GENETIC DIVERGENCE AMONG MEDITERRANEAN AND MACARONESIAN GENERA OF THE SUBTRIBE CHRYSANTHEMINAE (ASTERACEAE)
Authors: Francisco‐Ortega Javier , Crawford Daniel J. , Santos‐Guerra Arnoldo , Sa‐Fontinha Susana
Published: January 2018

Genetic variation at 17 isozyme loci was used to assess divergence among the four genera comprising subtribe Chrysantheminae (Anthemideae: Asteraceae). The Macaronesian endemic genus Argyranthemum is supported as monophyletic and is about equally divergent at isozyme loci from the other three genera of the Chrysantheminae, Chrysanthemum, Heteranthemis, and Ismelia. Chrysanthemum is native to the Mediterranean whereas Heteranthemis occurs in southern Iberia and Morocco, and Ismelia is endemic to Morocco. The genera Chrysanthemum and Ismelia have a genetic identity of 0.9283, which is comparable to values often seen for congeneric species and indicates that they should be treated as one genus. The isozyme data indicate that three lines consisting of Argyranthemum, Chrysanthemum‐Ismelia, and Heteranthemis radiated rapidly from a common ancestor. Divergence times estimated from isozyme data suggest that the initial radiation of the three lines occurred 2.5–3.0 mya. If this is so, then Argyranthemum or its ancestor arrived in Macaronesia after all the islands except La Palma and El Hierro were formed. The evolutionary history of the subtribe is discussed in relation to the climatic and geological events that took place in the Western Mediterranean between the Tertiary and Quaternary, i.e., the first Northern Hemisphere glaciation and desertification of the Sahara region. The high mean genetic identities between species of Argyranthemum suggest that it might have subsequently undergone a second more recent radiation in the Macaronesian Islands. Also, the high mean identity (0.860) between populations in Chrysanthemum and Ismelia suggest that these continental genera might be in the early stages of secondary speciation.