bluuebunny/crossref_metadata_2025 huggingface dataset:
A NEW STRUCTURALLY PRESERVED PENNSYLVANIAN CORDAITEAN POLLEN ORGAN
Authors: Daghlian Charles P. , Taylor Thomas N.
Published: January 2018

Permineralized specimens of the pollen organ Gothania (Hirmer) consist of a primary axis bearing pollen cones in the axils of bracts that are four ranked. The bilaterally symmetrical primary axis consists of a uniform parenchymatous pith surrounded by up to 15 endarch‐mesarch axile bundles. The cortex is two‐parted and consists of an inner zone of subepidermal fibers. Bract traces arise from the ends of the ellipsoid stele. Traces to the cones are derived from the open ends of the stele, and at higher levels form a centrarch‐medullated vascular system. Each pollen cone is constructed of up to 25 helically arranged scales, each vascularized by a single trace that may dichotomize. Scales are elongate and broad, and histologically composed of mesophyll parenchyma and fibrous layers. Stomata are restricted to the adaxial surface between rows of fibers. Up to 10 distal scales may be fertile, each with 4 elongate pollen sacs at the tip. Large monosaccate grains of the Felixipollenites‐type are densely packed in each pollen sac. The well‐preserved specimens of Gothania provide an opportunity to compare this genus with pollen cones assigned to the genus Cordaianthus, and to relate isolated plant organs to the Cordaitales.
FLORA OF THE BRANDON LIGNITE. IV. ILLICIACEAE
Authors: Tiffney Bruce H. , Barghoorn Elso S.
Published: January 2018

Illicium avitum is described from the Early Oligocene Brandon Lignite of Vermont. The remains consist of immature fruiting axes, preserved shortly after fertilization. The short pedicel terminates in a torus bearing 13 conduplicate carpels in a single whorl. These are surrounded by two whorls of approximately 20 to 30 staminal scars each, which are in turn surrounded by 24–40 perianth scars. The immature seeds within the carpels possess developing embryos and seed coats. Although comparisons with certain modern species are possible, the available characters are not sufficient to permit its association with any one modern species or group of species. The fossil material provides limited evidence for a reduction in the numbers of floral parts through time in Illicium.
SOME ASPECTS OF CARPEL STRUCTURE IN CALTHA PALUSTRIS L. (RANUNCULACEAE)
Authors: Peterson R. L. , Scott M. G. , Miller Susan L.
Published: January 2018

Caltha palustris L. carpels obtained from closed flower buds, from flowers that had just reached anthesis, and from older flowers were examined by light and electron microscopy. Trichomes located on either side of the cleft towards the base of each carpel, cells along the margins of the carpel cleft, and transfer cells along the locule lining immediately beneath the micropyle of the anatropous ovule were examined. Numerous, smooth endoplasmic reticulum cisternae and dictyosomes, the presence of material between the cell wall and cuticle, and droplets of material in the region of trichomes is evidence that the trichomes are nectaries. The cells lining the cleft and the transfer cells which have wall ingrowths along the tangential wall facing the locule may be involved in the secretion of substances for pollen tube growth.
PATTERNS OF VARIATION IN FOLIAR TRICHOMES OF EASTERN NORTH AMERICAN QUERCUS
Authors: Hardin James W.
Published: January 2018

Scanning electron microscopy of leaf trichomes of the forty two native species of oaks in eastern North America indicates five patterns of variability: 1) Eight trichome types are evident among the species and each species possesses a definite complement of trichome types. Certain trichomes are restricted to particular subgenera and series. 2) An obvious seasonal loss of trichomes occurs during leaf maturation. This loss may be both quantitative in terms of trichome density and qualitative in terms of trichome type. 3) There is an obvious difference between the adaxial and abaxial surfaces. The adaxial side of most oak leaves is dark green, lustrous, and glabrous or glabrate. The abaxial surface either remains pubescent, becomes glabrate or glabrous, or maintains trichomes along the midrib or in the axils of major secondary veins. There are also initial quantitative and qualitative trichome differences between the two sides. 4) Geographical and ecological variations are due in part to non‐genetic ecophenic modifications, ecotypic differentiation, and random genetic differences not necessarily correlated with environmental conditions. Trichome types are considered to be less affected by environment than is trichome density. 5) Hybridization and introgression within a subgenus leads to localized variability. Trichomes of hybrids are usually a combination of the parental types. These five patterns of variation are predictable and appear to be held within rather narrow limits. The complement of foliar trichomes, therefore, is a reliable character in the taxonomy of the oaks.
STARCH IN ANGIOSPERM POLLEN GRAINS AND ITS EVOLUTIONARY SIGNIFICANCE
Authors: Baker Herbert G. , Baker Irene
Published: January 2018

Pollen grains of 990 species were examined and measured to test four predictions: (1) “Primitive” angiosperms will have starch‐containing pollen; more advanced families will have starchless pollen. (2) Where Hymenoptera and Diptera use pollen nutritionally, there will be selection of starchless (oilcontaining) pollen, particularly where pollen is the only reward for visitors. (3) Conversely, in autogamous species, anemophilous species, and those pollinated by Lepidoptera or birds, the energetically more economical accumulation of starch will be seen. (4) Small pollen grains will be more likely to be starchless (oil‐rich); starch‐containing grains will tend to be larger. Prediction 1 is only partially supported by the results; contemporary representatives of primitive families often show starchless grains, and so do most “advanced” families. Strong intra‐familial resemblances are found (and some between groups of families), but other families show mixtures of “starchy” and “starchless” species. The latter are more likely to show a fit between food reserve and pollination system. Prediction 2 is well supported. Prediction 3 is supported in that autogamous and anemophilous species show relatively high proportions of starchy grains, but the picture is complicated for them by apparent selection for starchlessness (oil‐richness) in small pollen grains (prediction 4), and for the lepidopteran‐ and bird‐pollinated species by selection for large starchless (or very large starchy grains) in species whose pollen tubes must traverse long styles.
ULTRASTRUCTURAL OBSERVATIONS ON THE TRICHOBLASTS OF EQUISETUM
Authors: Harris William M.
Published: January 2018

Equisetum trichoblasts are densely cytoplasmic, containing numerous starch‐containing plastids, mitochondria, and concentrations of rough endoplasmic reticulum with attached polysomes. Numerous vesicles of Golgi origin are present, containing a lightly staining fibrillar material; these vesicles appear to fuse with the wall. The outer tangential and radial walls become thickened while the inner tangential wall remains thin with numerous plasmodesmata. As the trichoblasts develop into root hairs, vacuolation occurs, resulting in large vacuoles. This may represent autolytic vacuolation. The cytoplasm of the root hairs is similar to that of the trichoblasts.
GENETIC AND HORMONAL REGULATION OF GROWTH, FLOWERING, AND SEX EXPRESSION IN PLANTS
Authors: Chailakhyan M. Kh. , Timiriazev K. A.
Published: January 2018

The interaction of the genetic and hormonal regulation of growth, flowering, and sex expression in plants is discussed. The genetic control of these processes is characterized, and data on their hormonal regulation are supplied. The interaction of genetic and hormonal regulation is considered with reference to tall‐growing and genetic dwarf forms of the pea and wheat plants. It is shown that in the dwarf forms of the pea plant and in many other varieties, growth stimulation in response to treatment with the phytohormone gibberellic acid is clearly manifested and the expression of genetic dwarfism is eliminated, whereas in dwarf wheats it is expressed only slightly, if at all. At the same time both tall‐growing and dwarf forms of both pea and wheat show a clearly defined growth retardation response to treatment with the growth inhibitor, abscisic acid, which causes the expression of physiological dwarfism. The short‐ and long‐day characteristics of the photoperiodic response of plants are described as genetically controlled features, and data are given on the induction of flowering of a long‐day variety coneflower grown under short‐day conditions with the aid of gibberellins extracted from leaves of long‐day vegetative plants of short‐day Mammoth tobacco. Data are also supplied on the induction of flowering of a short‐day variety, red‐leaved goosefoot, grown under continuous light with the aid of metabolites extracted from leaves of the same Mammoth tobacco plants flowering under short‐day conditions. This demonstrates the possibility of hormonal regulation of the genetically controlled long‐day and short‐day characteristics in photoperiodically sensitive plants. Genetic and hormonal regulation of sex expression in two dioecious plants, hemp and spinach, is discussed. It is shown that sex expression in these plants is regulated by gibberellins which are synthesized in leaves and cause male sex expression and by cytokinins which are synthesized in the roots and cause female sex expression. These data indicate that sex expression in dioecious plants is the result of interaction between the genetic apparatus and phytohormones.
MORPHOLOGY, VASCULAR ANATOMY AND EMBRYOLOGY OF PISTILLATE AND STAMINATE FLOWERS OF ASPARAGUS OFFICINALIS
Authors: Lazarte Jaime E. , Palser Barbara F.
Published: January 2018

Flowers of three pistillate (female), two heterogametic staminate (male) and two homogametic male genotypes of Asparagus officinalis L. were compared for morphology and vascular anatomy of the flower and for embryological development to the stage of mature ovules and pollen. Flowers are liliaceous, the staminate with rudimentary pistils and the pistillate with collapsed anthers. The uncomplicated vascular pattern differs between staminate and pistillate flowers only in the size and degree of maturation of bundles to stamens and carpels. Longer styles appear to be correlated with a greater extent of ovule development in ovaries of staminate flowers. Microsporogenesis in males is normal with wall development corresponding to the Monocotyledonous type. The tapetum is glandular and binucleate, cytokinesis successive, the tetrads isobilateral or occasionally decussate, and the mature pollen grain two‐celled. A pair of heteromorphic, possibly sex, chromosomes was observed in heterogametic male plants. Anther development is initially the same in pistillate flowers, but the tapetum degenerates precociously followed by collapse of microspore mother cells. In pistillate flowers the ovules are hemitropous, bitegmic, and slightly crassinucellate. Megasporogenesis‐megagametogenesis conforms to the Polygonum type. In staminate flowers ovule development is like that in pistillate flowers until degeneration starts in nucellar and integumentary cells at the chalazal end. Ovules in both homogametic male genotypes rarely complete meiosis, while in the heterogametic males it is normally completed with about one ovule in 20 flowers forming a mature megagametophyte. Since manipulation of sex expression in Asparagus could be important in developing inbred male and female lines for breeding purposes, those aspects of the morphological and embryological observations presented which might be useful in planning experiments to induce sex changes are discussed briefly.
TRICHOME MORPHOLOGY AS AN INDICATOR OF HIGH RUBBER BEARING GUAYULE (PARTHENIUM ARGENTATUM GRAY) PLANTS IN NATIVE POPULATIONS
Authors: Mehta Indira J. , Dhillon Surinder P. , Hanson George P.
Published: January 2018

Parthenium argentatum Gray (guayule) and P. incanum (mariola) grow in close associations in their native habitat of Mexico. Variation in rubber concentration and morphology of guayule has been known for a long time. Studies of over 75 native guayule plants indicated the presence of at least three prominent forms of guayule plants. Group I guayule plants have oblanceolate leaves and leaf margins are entire to two‐toothed. T‐shaped leaf trichomes are with centrally attached stalk and cap cell with two blunt ends. Plants in this group are high in rubber, containing on the average 17% rubber. Group II guayule plants have narrow elliptic leaves and leaf margins are entire to four‐toothed. T‐shaped trichomes have an acentrally attached stalk and a cap cell with short end blunt, long end pointed and straight. Rubber content in these plants averages 10%. Group III guayule plants have ovate leaves and leaf margins are four‐ to eight‐toothed. T‐trichomes have an acentrally attached stalk and a cap cell with short end blunt, long end pointed and wavy or curved. These plants on the average contain 6% rubber. Morphological as well as biochemical data indicate the presence of mariola genes in the last two groups of plants and this has resulted in an increase in trichome length and a decrease in the rubber content. Group II guayule plants are of more common occurrence than the others. Based on the data presented here, high rubber bearing guayule plants in native stands can be easily selected by analyzing trichome morphology.
ABUNDANCE AND NEIGHBORHOOD STRUCTURE FOR SPARSE AND COMMON GRASSES IN A MISSOURI PRAIRIE
Authors: Rabinowitz Deborah , Bassett Barbara K. , Renfro Gregory E.
Published: January 2018

Biomass abundance and distance from a random point to the nearest flowering culm were measured during two seasons for eight species of native perennial grasses on a continuum from locally rare to common in a Missouri tall prairie. Mean abundance from the most common to the most rare ranges over three orders of magnitude (nine octaves) from 73 to .25 g/m2. The means of the distance to a culm range over two orders of magnitude (four octaves) from 0.3 m to 5.0 m. The logarithm of distance to a culm is linearly correlated with the logarithm of abundance. Distance to an inflorescence is greater for sparse species than for common species.
VISCIN THREADS, POLLINATION EFFICIENCY AND LOW POLLEN‐OVULE RATIOS
Authors: Cruden Robert William , Jensen Kenneth G.
Published: January 2018

Some Onagraceae are characterized by quite low pollen‐ovule ratios. We suggest they are an evolutionary response to highly efficient pollination, mediated through viscin threads, which hold large numbers of pollen grains together, and by stigmas, which are large relative to the area of the pollinator over which the pollen is spread. The pollen grains of some Leguminosae are joined by “exinal connections” which are chemically and morphologically similar to viscin threads. In the legumes the area of the stigma is small relative to the area of pollen on the pollinator and pollination is facilitated by short connections which hold small numbers of pollen grains together.
DIFFERENTIAL RESPONSES OF PLANT FOLIAGE TO SIMULATED ACID RAIN
Authors: Evans Lance S. , Curry Thérèse M.
Published: January 2018

Experiments were performed to show the responses of foliage of several clones of Tradescantia sp., Pteridium aquilinum, Quercus palustris, and Glycine max to simulated acid rain. These experiments were performed to (a) predict the relative sensitivities of foliage of these plants to acid rain, and (b) identify leaf surface and anatomical alterations to simulated acid rain that may be used to diagnose acid rain injury. Plants were exposed to simulated rain at pH levels of 5.7, 3.4, 3.1, 2.9, 2.7, 2.5, and 2.3. Sporophyte leaves of bracken fern {P. aquilinum) were most sensitive to simulated acid rain among the species tested. About 10% of the surface area of older leaves of P. aquilinum was injured after exposure to 10 rainfalls at pH 2.5 (a single 20‐min rainfall daily). Foliage of pin oak (Q. palustris) exhibited less than one‐percent leaf area injury after exposure to simulated rain at pH 2.5 after 10 rainfalls (one 20‐min rainfall daily). The responses of soybeans (G. max) and spiderwort (Tradescantia sp.) were intermediate between these two extremes. Histological observations show that lesion development results in collapsed leaf tissue in all four species. Gall formation that resulted from both cell hypertrophy and hyperplasia occurred in lesions of Tradescantia, and Q. palustris. Limited hyperplastic and hypertrophic reactions occurred in G. max foliage after exposure to simulated acid rain but no leaf galls resulted. Sporophyte foliage of P. aquilinum exhibited a “granular” type abnormality in the cytoplasm prior to the collapse of some epidermal cells injured by simulated rain. Injury occurred most frequently near vascular tissues and trichomes in all four species. In general, plant species that show cell hyperplasia and hypertrophy of leaf tissues after exposure to simulated acid rain are injured less than species that do not show these responses.
LEAF DEVELOPMENT OF PHASEOLUS VULGARIS L. IN LIGHT AND IN DARKNESS
Authors: Verbelen J. P. , De Greef J. A.
Published: January 2018

Development of the primary bean leaf in the dark and under continuous white light was studied during 14 days after sowing. The increase in surface area of the blade is the result of a number of sequential processes. Both in the darkness and under illumination, leaf growth is characterized by an initial cell enlargement followed by intensive cell division. Cell division in etiolated leaves continues for one day longer than in illuminated ones, but it proceeds at a slower rate. Mature leaves grown under white light undergo a phase of cell enlargement after cell division has stopped. This increases their surface area up to 800 times when compared with the blade area of the embryo. This enlargement phase is almost absent in dark‐grown seedlings. Consequently the blade area of etiolated leaves is only 50 times that of the embryonic state. Thus light appears to have a dual effect on leaf development: it activates cell division and induces cell expansion.
THE SEED BANK OF A FRESHWATER TIDAL MARSH
Authors: Leck M. A. , Graveline K. J.
Published: January 2018

Presence of buried viable seeds at three depths in freshwater marsh soils was determined by observing seedling emergence in the greenhouse. These results were compared with field germination. For the greenhouse study soils were collected in December 1976, and March 1977, from six vegetation types in the Hamilton Marshes near Trenton, New Jersey. Three to five times more seeds and almost three times as many species germinated in the greenhouse than in the field. Of the ten most numerous species in greenhouse samples, 7.2 ± 0.2 SE species were also observed as seedlings at that site in the field. Annuals comprised seven of the ten most numerous species in both the greenhouse and in the field. Estimated seed densities for the top 10 cm of marsh soil ranged from 6,405 to 32,400 seeds m−2. Germination in soils collected in March was 31% greater than for those collected in December. Decrease in species number with depth was significant for March soils. While seedling numbers also decreased with depth, considerable variability occurred and the differences were not significant. The seed bank profile suggests that viability and/or dormancy are prolonged in these freshwater tidal marsh soils.
FACULTATIVE MUTUALISM BETWEEN WEEDY VETCHES BEARING EXTRAFLORAL NECTARIES AND WEEDY ANTS IN CALIFORNIA
Authors: Koptur Suzanne
Published: January 2018

Vetches (Vicia spp.) were studied in the San Francisco Bay Area of California in the spring of 1978. The stipular nectaries of the vetches are visited by the Argentine ant, Iridomyrmex humilis Mayr. The nectaries were removed to exclude ants in controlled experiments to determine if these ants protect the vetches from herbivores or seed predators. Plants with excised nectaries suffered substantially greater damage to their foliage than control plants, indicating that ants protect the foliage. There was no indication that ants protect the vetches from seed predators, but fruit set was substantially lower in plants with excised nectaries. Analysis of sugar and amino acid composition of extrafloral nectar served as a basis for feeding tests with Argentine ants by using artificial nectar solutions. Ants preferred sucrose and glucose solutions over fructose. They showed no preference for any one sugar mixture over another, nor did they exhibit differential recruitment to artificial nectar solutions containing only sugars or sugars and amino acids.
BIOSYSTEMATICS OF THE GENUS HYDROPHYLLUM L. (HYDROPHYLLACEAE)
Authors: Beckmann Robert L.
Published: January 2018

Hydrophyllum is a group of mesophytic herbs occurring in two disjunct groups in North America. The genus is a natural taxonomic entity with the constituent species showing low levels of variability. Morphological similarities of the disjunct species suggest a close affinity between H. tenuipes and H. virginianum and a lesser, yet distinct, affinity between H. occidentale and H. macrophyllum. Biosystematic studies that included herbarium comparisons, field descriptions, artificial hybridizations, chromatographic studies, and electrophoretic analyses characterize the interrelationships of the various species.
APOGAMY AND SOMATIC RESTITUTION IN THE FERN CERATOPTERIS
Authors: Hickok Leslie G.
Published: January 2018

A mutant stock of the fern Ceratopteris has been derived from an inbreeding study following an interspecific hybridization between two diploid species. The mutant is characterized by gametophytes that produce non‐functional spermatozoids and are incapable of selfing. Sporophytes develop apogamously from the mutant gametophytes and, although they are initially haploid and sterile, portions of the fronds later become doubled somatically and behave like tissues of sexually derived homozygous sporophytes. The mutant segregates from sporophytes in a 1:1 ratio when crosses are made with wild type gametophytes. Certain aspects of the behavior are similar to those seen in some naturally occurring apomictic ferns.
INFREQUENT ESTABLISHMENT OF SEEDLINGS OF AGAVE DESERTI (AGAVACEAE) IN THE NORTHWESTERN SONORAN DESERT
Authors: Jordan Peter W. , Nobel Park S.
Published: January 2018

Survival of seedlings of the common desert succulent, Agave deserti, required unusually wet years and the protection afforded by nurse plants or other shelters. The characteristics of seed germination and of seedlings showed that water stress in the seedling stage may be the most important factor affecting establishment. Leaves wilted irreversibly at an osmotic potential of −1.6 MPa (–16 bars). Survival of seedlings required the generation of enough biomass during the first wet season to survive drought periods when the water potential of the soil was below −1.6 MPa. Lengths of individual growing seasons and subsequent droughts were obtained from rainfall records for 1961 through 1978 for a site in the western Colorado desert. The length of the first major drought following germination apparently limited establishment of Agave deserti to only one year in the last 17. The favorable year, 1967, was consistent with the estimated year of germination of the six smallest Agave deserti observed in 1,500 m2 at the field site.
DEVELOPMENT OF POWDERY MILDEW (ERYSIPHE POLYGONI) ON SUSCEPTIBLE AND RESISTANT RACES OF OENOTHERA BIENNIS
Authors: Dickey Jean L. , Levy Morris
Published: January 2018

Races of Oenothera biennis (evening primrose) resistant and susceptible to Erysiphe polygoni (a powdery mildew fungus) were artificially inoculated with E. polygoni and the time course and mode of disease development recorded. This study was the initial stage in investigating the host's resistance mechanism(s). On leaves of susceptible and resistant races, spores germinated within 5 hr, appressoria were formed in 8‐12 hr, and penetration had been effected and haustoria initiated by 20 hr. There was no further development on resistant plants. On susceptible hosts, secondary penetration occurred by 26 hr after inoculation, secondary haustoria were formed, and sporulating colonies were seen in 4 days. It was concluded that the fungus is unable to establish a feeding relationship with the epidermal cells of resistant Oe. biennis, marking the period between 20 and 26 hr after inoculation as the time frame for the manifestation of the resistance mechanism(s).
ANALYSIS OF STARCH ACCUMULATION AND GERMINATION IN ONOCLEA SPORES
Authors: Towill Leslie R.
Published: January 2018

Previous studies have shown that low fluences of light accelerate starch accumulation and enhance germination of Onoclea spores. Fluence response curves for induction of starch accumulation were compared with fluence response curves for enhancement of germination in order to determine if the two photoresponses in Onoclea spores have a common photoreceptor. Fluence response curves indicate that both responses were proportional to the log of the fluence and that the relative fluence efficiencies of the four wavelength regions tested were similar for induction of both germination and starch accumulation. Red (600–720 nm) irradiation was the most efficient, while green (500–600 nm), blue (400–520 nm), and far‐red (720–900 nm) irradiations showed a decreasing order of efficiency for induction of the responses. A correlation coefficient between the amount of starch accumulated as a result of red irradiation and the final percent germination was calculated to be 0.964. These results support the hypothesis that a common photoreceptor mediates both photoinduced germination and starch accumulation. 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) inhibits photosynthesis by blocking the flow of electrons from Photosystem II to Photosystem I. At 0.1 mM DCMU failed to inhibit both photoinduced starch acumulation and germination. This result and the greater efficiency of red than blue light, the low fluence functional for induction, and the fluence dependency argue against the participation of photosynthesis in photoinduced starch accumulation. A similar conclusion has been previously drawn for photoenhancement of Onoclea spore germination. Additionally, the effects 0.01–1.0 mm cycloheximide and 100 μl/l ethylene on photoinduced starch accumulation were investigated. Neither agent inhibited starch accumulation, whereas both substances inhibited germination 70–90% when applied at a time coincidental with the period of rapid starch accumulation. These results indicate that the photoinduction of starch accumulation does not have an ethylene sensitive stage nor does it require protein synthesis as does photoenhancement of germination of Onoclea spores.
POLLEN ENERGETICS AND POLLINATION MODES
Authors: Colin Larry J. , Jones C. Eugene
Published: January 2018

The caloric content of pollen for several different species was determined by using a semimicro oxygen bomb calorimeter. The species studied were divided into subsets for statistical comparisons. The subsets considered were wind‐pollinated dicots, monocots and gymnosperms; insect‐pollinated dicots; and taxonomic subclasses of the wind‐pollinated angiosperms (Asteridae, Hamamelidae, Caryophyllidae and Commelinidae). The results indicated a statistically significant caloric content difference (0.05 or higher) between wind‐pollinated dicots vs. monocots and gymnosperms. There was no statistical difference between wind‐pollinated dicots and insect‐pollinated dicots. All subclasses were significantly different from one another. A statistically significant difference was found between two tribes in the Asteraceae which have shifted from insect to wind pollination, providing additional evidence for an independent evolution of the two. The need for future research in this area is discussed.
SEASONAL ALTERATION OF PHOTOSYNTHETIC UNIT SIZES IN THREE HERB LAYER COMPONENTS OF A DECIDUOUS FOREST COMMUNITY
Authors: Harvey Geoffrey W.
Published: January 2018

The pigment content and photosynthetic unit size of three herbs on the floor of a mature yellow oak (Quercus meuhlenbergii) forest were measured during most of the growing season. Two species, dutchman's breeches (Dicentra cucullaria) and Virginia bluebell (Mertensia virginica) are spring ephemerals, while Hepatica acutiloba has a semi‐evergreen habit. Although pigment composition changed in Dicentra, photosynthetic unit size only varied slightly. Mertensia was nearly invariant in pigment composition, but unit size was modified as the growing season progressed. The semi‐evergreen herb, Hepatica, underwent a remarkable alteration in pigment content, photosynthetic unit size, and number following overstory leaf expansion. The results indicate that an alteration of photosynthetic unit size is possible in fully expanded leaves of two forest floor herbs.
CYTOLOGICAL AND BIOCHEMICAL ASPECTS OF CYTOKININ‐ENHANCED GROWTH OF RADISH (RAPHANUS SATIVUS) COTYLEDONS
Authors: Thomas Jerry , Kugrens Paul , Ross Cleon W.
Published: January 2018

Light and electron microscopy revealed no stimulation of oleosome disappearance or chloroplast development associated with zeatin‐enhanced growth of excised radish cotyledons. Accelerated protein body breakdown was the only detectable effect of zeatin treatment. Isocitrate lyase activity, disappearance of total lipids, and appearance of galactolipids, phospholipids, and chlorophyll were unaffected by zeatin. Results indicate that cytokinins do not accelerate conversion of radish cotyledons from storage to photosynthetic organs.
AMMONIUM ION‐INDUCED CHANGES IN FORM AND HYDROXYPROLINE CONTENT OF WALL PROTEIN IN THE LIVERWORT, GYMNOCOLEA INFLATA
Authors: Basile Dominick V. , Basile Margaret R.
Published: January 2018

Ammonium ion induces phenovariation in Gymnocolea inflata (Huds.) Dum. (Lophoziaceae) similar in nature to that induced in representatives of four other families of leafy liverworts by antagonists of hydroxyproline‐protein metabolism. That is, in the presence of ammonium ion, ventral leaves developed and the lateral leaf morphology and the branching pattern of the plants changed. These changes, which reflect altered patterns of morphogenesis, were correlated with statistically significant (P ≥ 0.01) differences in peptidyl‐hydroxyproline between normal and NH4+‐induced phenovariant plants. The results support the hypothesis that cell wall‐associated hydroxyproline‐protein plays a morphoregulatory role and that any of a number of factors, genetic, epigenetic or environmental, that could alter the synthesis/distribution of this moiety could cause changes in form.
INTRA‐INFLORESCENCE VARIABILITY IN POLLEN/OVULE RATIOS IN THE CLEISTOGAMOUS SPECIES LAMIUM AMPLEXICAULE (LABIATAE)
Authors: Lord Elizabeth M.
Published: January 2018

A comparative study was made of the various floral forms in the main shoot inflorescence of the cleistogamous species Lamium amplexicaule L. (Labiatae). This study revealed significant differences in pollen/ovule (P/O) ratios between successively produced flowers. The variation in P/O ratio is due to a change in pollen count/flower and not in ovule number. The study included two plant populations, one grown in November when only closed flowers are produced, and the other grown in April when open flower production occurs at the upper nodes. The intra‐inflorescence variation in P/O ratio among the spring population showed a correlation between P/O ratio and breeding system. The cleistogamous flowers had low P/O ratios of about 200 while the chasmogamous flowers had higher P/O ratios of about 600.
STRUCTURE AND FUNCTION OF THE STROPHIOLAR PLUG IN SEEDS OF ALBIZIA LOPHANTHA
Authors: Dell B.
Published: January 2018

Entry of water into the testa of hard seeds of Albizia lophantha (Willd.) Benth. is controlled by a small strophiolar plug (0.3 × 0.25 mm), adjacent to the hilum, which is lost by eruption after heating. Movement of water through the testa is facilitated by the vascular bundle which arches close to the strophiole. Each seed imbibes 90 to 110 μl of water. This water enters the testa with an average flux of 165 μl/mm2/hr. Development of the testa is described with particular relevance to the strophiolar plug and associated tissues.
RECONSTRUCTIONS OF THE GRANA‐FRETWORK SYSTEM OF A CHLOROPLAST
Authors: Paolillo Dominick J. , Rubin Gail
Published: January 2018

The grana‐fretwork system was reconstructed from serial sections representing 0.5 μm slice, in profile view, from the midregion of a chloroplast of Nicotiana tabacum. Reconstructions show grana in multiple strata. The fretwork integrates the grana in all three dimensions. Large grana are visualized as complex structures consisting of two or more eccentrically stacked solids that vary in height and diameter. The close spacing and overlapping positions of grana in the plastid explain why phase microscopy cannot be used to demonstrate adequately the numerous strata of grana within a chloroplast. The grana are not far enough apart to allow for successful optical sectioning of a plastid in face view. In profile view no distinct grana can be resolved because the grana‐fretwork system has the aspect of a “honeycomb.” Thus, observations with a light microscope are not adequate to determine the arrangement of grana in a chloroplast, and the recently‐proposed model showing all grana of a plastid to be arranged in a single spiral ribbon must be rejected as incompatible with properties of real plastids.
MITOSIS IN THE AQUATIC FUNGUS RHIZOPHYDIUM SPHEROTHECA (CHYTRIDIALES)
Authors: Powell Martha J.
Published: January 2018

The structure of centric, intranuclear mitosis and of organelles associated with nuclei are described in developing zoosporangia of the chytrid Rhizophydium spherotheca. Frequently dictyosomes partially encompass the sides of diplosomes (paired centrioles). A single, incomplete layer of endoplasmic reticulum with tubular connections to the nuclear envelope is found around dividing nuclei. The nuclear envelope remains intact during mitosis except for polar fenestrae which appear during spindle incursion. During prophase, when diplosomes first define the nuclear poles, secondary centrioles occur adjacent and at right angles to the sides of primary centrioles. By late metaphase the centrioles in a diplosome are positioned at a 40° angle to each other and are joined by an electron‐dense band; by telophase the centrioles lie almost parallel to each other. Astral microtubules radiate into the cytoplasm from centrioles during interphase, but by metaphase few cytoplasmic microtubules are found. Cytoplasmic microtubules increase during late anaphase and telophase as spindle microtubules gradually disappear. The mitotic spindle, which contains chromosomal and interzonal microtubules, converges at the base of the primary centriole. Throughout mitosis the semipersistent nucleolus is adjacent to the nuclear envelope and remains in the interzonal region of the nucleus as chromosomes separate and the nucleus elongates. During telophase the nuclear envelope constricts around the chromosomal mass, and the daughter nuclei separate from each end of the interzonal region of the nucleus. The envelope of the interzonal region is relatively intact and encircles the nucleolus, but later the membranes of the interzonal region scatter and the nucleolus disperses. The structure of the mitotic apparatus is similar to that of the chytrid Phlyctochytrium irregulare.
A GROWTH COMPARISON OF SPARTINA ALTERNIFLORA LOISEL. ECOPHENES UNDER AEROBIC AND ANAEROBIC CONDITIONS
Authors: Linthurst Rick A.
Published: January 2018

Spartina alterniflora Loisel. culms were collected from tall (creekbank), short (highmarsh) and dieback sites in a North Carolina salt marsh and grown in aerobic and anaerobic simulated marsh systems in the greenhouse. There were no significant differences between density, aerial live biomass, height, leaf width or root biomass and sprig source. All variables were significantly different between aeration treatments. Aerated systems had an average of 6.3 times more biomass than the unaerated treatments. There was a significant interaction between sprig source and aeration treatments based on a multivariate analysis of variance representing overall plant performance. These results demonstrated that pioneer sprigs from the dieback sites had an advantage over the other sprigs when exposed to unaerated systems. Tall plants performed better than plants from short or dieback zones in the aerobic systems.
SEED MORPHOLOGY OF MONOTROPA UNIFLORA L. (ERICACEAE)
Authors: Olson A. Randall
Published: January 2018

Mature seeds of Monotropa uniflora L., an achlorophyllous mycotrophic perennial, underwent imbibition and were processed for study using modern histological and histochemical techniques. The seeds ranged from 0.6‐0.8 mm in length and 0.12‐0.15 mm in width and exhibited integumentary winglike structures at either end. As in other members of the Ericaceae, seeds are unitegmic, tenuinucellate, albuminous, and form both micropylar and chalazal endosperm haustoria. A two‐celled reduced embryo was observed in all seeds, except one where the embryo was three‐celled. Protein granules in the thick walled endosperm were found to contain an aniline blue‐fluorescent material that may be a calloselike carbohydrate. The limited amount of seed food reserves and the retardation of embryo differentiation may reflect specialized germination requirements.
CONE COLOR POLYMORPHISM ASSOCIATED WITH ELEVATION IN WHITE FIR, ABIES CONCOLOR, IN SOUTHERN COLORADO
Authors: Sturgeon Kareen B. , Mitton Jeffry B.
Published: January 2018

Morphological variation in color of female cones in white fir, Abies concolor, is postulated to have adaptive value. The purple variant is only found in one part of the range of white fir where it grows at high elevations. In addition, the frequency of purple cones increases with increasing elevation, suggesting a thermoregulatory function for the purple variant in the cold habitats found at high elevations. Temperature measurements support this hypothesis: purple cones attain higher internal temperatures than do green cones of comparable size. Cone diameter may, in fact, be correlated with cone color but definitive evidence is lacking. Alternative hypotheses are offered which may also be important in maintaining the presence of the purple variant at high elevations. It is suggested that other characters associated with purple cones may place them at a competitive disadvantage at lower elevations.
STUDIES IN THE FLORAL ANATOMY OF CLAYTONIA (PORTULACACEAE)
Authors: Milby T. H.
Published: January 2018

Claytonia virginica has a regular flower with two sepals, five petals with an equal number of stamens in positions opposite the petals and a many‐seeded tricarpellate gynoecium with basal placentation. The flower has been interpreted as uniseriate, the putative sepals as bracts and the corolla as modified calyx lobes. Anatomical and developmental studies were undertaken to find evidence for the existence of vestigial or rudimentary parts whose existence would illuminate the true nature of the flower. Vascular and epidermal anatomy of sepals are both similar to that of leaves. Corolla and androecium develop basipetally and petals and stamens share common vascular traces in the lower part of the receptacle. Thus, in terms of both anatomy and development, evidence supports the conclusion that the perianth is essentially biseriate. Vestigial or rudimentary parts are not present which would alter the manifest design of the mature flower.
TRACE METAL CYCLING IN TROPICAL‐SUBTROPICAL ESTUARIES DOMINATED BY THE SEAGRASS THALASSIA TESTUDINUM
Authors: Schroeder Peter B. , Thorhaug Anitra
Published: January 2018

The present study was designed to determine the uptake and release rates of various trace metal cations by turtle grass and its community in order to provide the coefficients of our previously described computer model intended to simulate trace metal cycling in subtropical and tropical estuaries. The site of uptake in Thalassia was also examined.
PINUS BUCHANANII, A NEW SPECIES BASED ON A PETRIFIED CONE FROM THE OLIGOCENE OF WASHINGTON
Authors: Underwood James C. , Miller Charles N.
Published: January 2018

A silicified seed cone of Oligocene age from the Olympic Peninsula of Washington represents a new species of Pinus. The cone was about 8 cm long and 3 cm at its widest diameter in the living condition. Its scale apices are thickened and each has a dorsal umbo. Internal cone construction confirms the assignment of the new species to Pinus and suggests affinity with the subsections Australes and Ponderosae of the section Pinus, subgenus Pinus. The cone is peculiar in having a stout bract trace that is slightly concave on its adaxial side and in having resin canals that diverge from the axial secretory system toward the bract but constrict markedly and terminate before entering the bract.
THE QUANTITATIVE ULTRASTRUCTURE OF THE MERISTEMATIC CELLS OF XANTHIUM STRUMARIUM DURING THE TRANSITION TO FLOWERING
Authors: Havelange A.
Published: January 2018

Ultrastructural changes occurring in the central part of the apical meristem of the SDP Xanthium strumarium, induced to flower by a single 16‐hr long night, were quantitatively investigated using stereological methods and compared to the changes previously reported in other species, particularly the LDP Sinapis alba. Changes detected in Xanthium, which are also found in other species, included: increase in cellular, cytoplasmic, cytoplasmic matrix and nucleolar sizes, change in nucleolar structure; increase in mitochondrial number and chondriome size, increase in dictyosome number. These changes are believed to be essential for floral evocation because of their universality. Other changes were specific to Xanthium and not detected in Sinapis. Accordingly, they were thought to be accompanying nonessential events of floral evocation in Xanthium. These changes included an increase in the number of plastid profiles and in plastidome size. The size of the nucleus, chromatin and vacuolar apparatus, as well as the number of vacuolar profiles, did not change in Xanthium, contrary to what was observed in other plants.
COMPARISON OF ISOZYMES AMONG TYPHA SPECIES IN THE EASTERN UNITED STATES
Authors: Sharitz Rebecca R. , Wineriter Susan A. , Smith Michael H. , Liu Edwin H.
Published: January 2018

Biochemical phenotsypes of four taxa ofTyphafrom the eastern United States were determined by starch gel electrophoresis. The isozyme banding patterns ofT. latifolia, T. angustifoliaandT. domingensisare distinct and allow unambiguous species identification when morphological characters are inadequate or unsuitable. The fourth form,T. glauca, is not an F1hybrid, but it does appear to be intermediate betweenT. latifoliaandT. angustifolia. The status ofT. glaucaand evolutionary relationships among the four forms may now be clarified by additional sampling because of the distinct and relatively invariant isozyme banding patterns which are described.
POLLEN MORPHOLOGY OF HAPLOPAPPUS AND RELATED GENERA (COMPOSITAE—ASTEREAE)
Authors: Clark W. Dennis , Brown Gregory K. , Mayes Richard A.
Published: January 2018

Pollen grains of Haplopappus and related genera in the subtribe Solidaginae from North and South America were examined by light and scanning electron microscopy. The grains are consistently tricolporate and echinate. Some genera can be distinguished by pollen size, spine length, and number of spine rows between colpi. Based on these characters, the divergence of Benitoa from other members of the subtribe, as indicated by its morphology and secondary chemistry, is supported. Additionally, the recently suggested absence of a close relationship between Pyrrocoma and Oonopsis is indicated by their contrasting pollen types. This study demonstrates the potential of pollen studies in distinguishing some taxonomic groups in the Astereae.
REGULATION OF NaCl IN JAUMEA CARNOSA (ASTERACEAE), A SALT MARSH SPECIES, AND ITS EFFECT ON LEAF SUCCULENCE
Authors: Omer Lucy St. , Schlesinger William H.
Published: January 2018

A salt marsh species, Jaumea carnosa, was used in hydroponic experiments to test the effects of increasing NaCl concentrations on leaf succulence and plant accumulations of K, Ca, Mg, Na and Cl. A nested experimental design was used with four salinity levels. Plants were grown in full Hoagland's solution plus different amounts of NaCl (0.0–1.2 osmoles). Leaf succulence was measured as percent water content as well as vertical elongation of mesophyll cells. There were no corresponding increases in leaf succulence with increasing concentrations of NaCl in the root zone. Plants receiving aerosol spray (40 mg/dm2/day) did not show significant increases in leaf succulence. Leaf succulence was significantly increased when the plants were removed from the NaCl solutions and placed in non‐salinized Hoagland's solution. Osmotic concentrations of cell sap in leaf tissues showed significant increases as NaCl concentrations increased in the root zone. The concentrations of K, Ca and Mg were higher in plants grown without NaCl than in those grown with NaCl. The accumulations of K in the root tissues were always higher than those of the shoot tissues. Although there was a two‐fold difference in NaCl concentrations at the highest levels, the concentrations of Na in the shoot tissues were relatively similar. The results of the Cl analyses of shoot tissues showed a similar pattern of regulation of uptake. This regulation of salt uptake may be important in preventing injury by limiting accumulations of salt in plant tissues when growing in soils of high osmotic potentials.
MECHANICAL STRESS AND CELL WALL ORIENTATION IN PLANTS. I. PHOTOELASTIC DERIVATION OF PRINCIPAL STRESSES. WITH A DISCUSSION OF THE CONCEPT OF AXILLARITY AND THE SIGNIFICANCE OF THE “ARCUATE SHELL ZONE”
Authors: Lintilhac Philip M. , Vesecky Thompson B.
Published: January 2018

This study describes a further investigation into the meaning of patterns of cell wall orientation in plants and outlines a modified method for the generation of patterns of principal stresses in a two‐dimensional model. Evidence from simple photoelastic models is presented which supports the concept that the initial location of a presumptive axillary bud primordium may be controlled by mechanical stress in the region of the leaf axil.
MITOTIC ACTIVITY IN THE ROOT APICAL MERISTEM OF AZOLLA FILICULOIDES LAM., WITH SPECIAL REFERENCE TO THE APICAL CELL
Authors: Nitayangkura iporn , Gifford Ernest M. , Rost Thomas L.
Published: January 2018

The meristematic activity of the apical cell and its derivatives (merophytes) in the unbranched, determinate roots of Azolla filiculoides Lam. was investigated. The plane of division of the apical cell indicates that it is the initial of each merophyte. The division plane of each newly formed merophyte is strictly periclinal to the root surface and provides confirmation that the immediate derivatives of the apical cell cannot be the ultimate root initials. The frequency of cell division as determined by the mitotic index, and by the duration of the cell cycle as determined by the colchicine method, confirmed the meristematic activity of the apical cell. As roots increase in length, the duration of the cell cycle in the total meristem increases, with the apical cell possessing the longest cell cycle, whereas the immediate derivatives maintain approximately the same cycle duration as in shorter roots. In determinate Azolla roots, cell division appears to play a major role up to a certain root length, then increase in length is produced mainly by cell elongation.