bluuebunny/crossref_metadata_2025 huggingface dataset:
CYTOKININ‐ AND GIBBERELLIC ACID‐INDUCED EFFECTS ON THE DETERMINATION AND MORPHOGENESIS OF LEAF PRIMORDIA IN OPUNTIA POLYACANTHA (CACTACEAE)
Authors: Mauseth James D.
Published: January 2018

Cytokinins and gibberellins are able to strongly influence the development of “leaf” primordia in the cactus Opuntia polyacantha. Under the influence of cytokinin, the primordia produced by cultured axillary bud apical meristems develop as normal, photosynthetic leaves, being composed of regular epidermal cells, guard cells, mesophyll and mucilage cells as well as vascular tissue. Under the influence of gibberellic acid (GA), the primordia develop as cactus spines, composed of thick‐walled epidermal and fiber cells. Guard cells, vascular tissue and parenchyma do not occur. Thus GA is able to redirect leaf morphogenesis in O. polyacantha far more completely than has been reported for other plants. The mitotic activity of the primordia that will develop into spines is significantly higher (at the 5 % level) than the mitotic activity of the primordia that will develop into leaves. This is interpreted to indicate that the primordia are either leaf primordia or spine primordia from a very early age, and possibly are never uncommitted or undetermined primordia, as has been suggested for fern leaf primordia.
THE FLAVONOIDS OF THE DECIDUOUS RHODODENDRON OF NORTH AMERICA (ERICACEAE)
Authors: King Bruce L.
Published: January 2018

The native Azaleas of North America (Rhododendron: subgenus Pentanthera) produce 58 flavonoids in five aglycone classes: flavonols, dihydroflavonols, flavanones, dihydrochalcones and chalcones. A comparison of the flavonoids of selected samples of these species indicated that the compounds generally occur as species specific ensembles. Species were grouped into “alliances” based on common flavonoid constituents and a phylogenetic treatment of the group was developed. Evolutionary trends of flavonoids within subgenus Pentanthera are not well‐defined but appear to be associated with a loss of the ability to synthesize some compounds and a decrease in diversity of glycosides and methoxylated flavonoids. Intraspecific variation in flavonoids was found in Rhododendron canescens, R. alabamense and R. austrinum when these were sampled on a population basis.
THE SYNANGIATE NATURE OF DOLEROTHECA
Authors: Stidd Benton M.
Published: January 2018

Transverse sections through the distal region of a Dolerotheca specimen in a coal ball from the Calhoun coal of Illinois show the double rows of sporangia where they are free from one another. This leads to the conclusion that the sporangial rows should be regarded as extending inward from the campanulum cover rather than radiating outward from the center. This observation suggests that Dolerotheca is a synangium composed of many sporangial units of different lengths.
REGULATION OF CHAMISE SHOOT GROWTH
Authors: Adams D. R. , Radosevich S. R.
Published: January 2018

Nutritional, hormonal, and environmental control of chamise (Adenostoma fasciculatum H. & A.) shoot growth was investigated. In vitro culture of shoot tips demonstrated that 0.18 M sucrose was required for optimum apical growth. Cytokinin (benzyladenine) promoted shoot growth at otherwise growth‐limiting sucrose concentrations and induced uptake of sucrose from the basal medium. Abscisic acid inhibited growth of cultured shoot tips induced by high sucrose concentration or cytokinin. In the field, inhibition of shoot growth was a function of water stress. These studies indicate that the effects of water stress on chamise shoot growth may be mediated by changes in carbohydrate, cytokinin, or growth inhibitor levels at the shoot apex.
AN INVESTIGATION OF THE PHYLOGENETIC AND ONTOGENETIC VARIABILITY OF SHOOT APICAL MERISTEMS IN THE CACTACEAE
Authors: Mauseth James D.
Published: January 2018

The sizes, shapes and zonations of the shoot apical meristems of 22 species of cacti were examined. This family was chosen because of its great diversity of habits; the more primitive members are nonsucculent. leafy trees and more advanced members are highly specialized “leaf‐less” stem‐succulents. By combining these measurements with those already in the literature, a sample of almost 70 species was obtained. Apical meristems range in size from only 80 μm in diam in some species to as much as 1.500 μm in diam in others. The shape ranges from being flat to almost hemispherical. Despite the great range in size and shape of the apical meristems, or the range in the morphologies of the leaves and stems which are produced by the meristems. all apices had the usual zonation: tunica, central mother cells, peripheral zone, and pith‐rib meristem. The sizes of each of the zones. expressed either as the number of cells per zone or expressed as a percentage of the whole apex. were highly variable. The variation in apical dimensions and zone sizes occurred both phylogenetically and ontogenetically. and this has been interpreted to indicate that the morphogenetic mechanisms which control apical size and zonation are easily modified, both during the development of individual plants and during the evolution of new species.
GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. V. ETHYLENE AND THE EARLY EVENTS OF SPORE GERMINATION
Authors: Fisher Robert W. , Miller John H.
Published: January 2018

Early events during the germination of spores of the fern Onoclea sensibilis were studied to determine the time during germination when ethylene had its greatest inhibiting effect. Water imbibition by dry spores was rapid and did not appear to be inhibited by ethylene. During normal germination DNA synthesis occurred about four hours before the nucleus moved from a central position to the spore periphery. Following nuclear movement, mitosis and cell division occurred, partitioning the spore into a small rhizoid cell and a large protonemal cell. Cell division was complete approximately six hours after nuclear movement. Ethylene treatment of the spores blocked DNA synthesis, nuclear movement, and cell division. The earliest DNA replication in uninhibited spores was observed after 14 hours of germination, and the maximal rate of spore labeling with 3H‐thymidine was between 16 and 20 hours. Spores were most sensitive to ethylene, however, during the stages of germination prior to DNA synthesis, and it was concluded that ethylene did not directly inhibit DNA replication but blocked germination at some earlier fundamental step. The effects of ethylene were reversible. since complete recovery from inhibition of germination was possible if ethylene was released and the spores were kept in light. Recovery was much slower in darkness. It was hypothesized that light acted photosynthetically to overcome the ethylene inhibition of germination. Consistent with this, it was shown that spores exhibit net photosynthesis after only two hours of germination.
ALLELOPATHIC EFFECTS OF DECAYING LITTER OF DOMINANT TREES AND THEIR ASSOCIATED SOIL IN A LOWLAND FOREST COMMUNITY
Authors: Lodhi M. A. K.
Published: January 2018

Phytotoxins released by the dominant species in a lowland forest showed highest accumulations in their respective stands. The accumulation of such phytotoxins corresponded with the amount of litter produced and its decaying rate. The release of phytotoxins and their activity depended on whether they were free or bound, and on their solubility. Therefore, the phytotoxins in soils were highly variable in amounts from one species stand to another species stand, during the same and different times of the year. The persistent accumulation of phytotoxins from all dominant tree species continues to influence the soil properties around the trees. Fourteen phytotoxins were isolated from the leaf litter and the soil. Seven persistent toxins were quantified in soils under different tree stands at various times of the year. The cycle of release of bound and free phenolics is discussed.
A NOMARSKI INTERFERENCE STUDY OF MEGASPOROGENESIS AND MEGAGAMETOGENESIS IN SMELOWSKIA CALYCINA (CRUCIFERAE)
Authors: Greene Craig W.
Published: January 2018

Ovule development, megasporogenesis and megagametogenesis in an aneuploid population of the arctic‐alpine crucifer, Smelowskia calycina, were examined to test for the possibility of apomictic seed production. Whole mounts of ovules cleared in Herr's “4½” clearing fluid were examined using Nomarski differential interference microscopy. The campylotropous ovule was bitegmic, with a micropyle formed by both integuments. The single archesporial cell of a crassinucellar nucellus functioned directly as a megasporocyte, dividing to form a linear tetrad of megaspores. The chalazal megaspore divided to form an 8‐nucleate, 7‐celled gametophyte of the Polygonum type, having hooked synergids with a well‐developed filiform apparatus and polar nuclei that fused prior to fertilization. In the absence of any anomalous development indicative of agamospermy, seed production was assumed to be sexual.
THE AVAILABILITY OF TRANSPIRATIONALLY SUPPLIED SUCROSE FOR METABOLIC PROCESSES IN THE POD AND SEEDS OF PHASEOLUS VULGARIS
Authors: Oliker M. , Mayer A. M. , Poljakoff‐Mayber A.
Published: January 2018

Radioactive sucrose supplied to growing bean pods via the transpiration stream is metabolically available and appears in various cell fractions including proteins and cell wall material. Sucrose distribution between pod and seed tissue depended on the stage of fruit development.
SPERMATOGENESIS IN LYCOPODIUM: THE MATURE SPERMATOZOID
Authors: Robbins Robert R. , Carothers Zane B.
Published: January 2018

The mature spermatozoid of Lycopodium cernuum is a blunt ended, fusiform cell, 8–10 μm long by 4–5 μm wide. A multilayered structure (MLS) and a subtending anterior mitochondrion are located at the anterior of the cell. The MLS is coiled through 1–1.5 gyres in a shallow sinistral helix around the periphery of the cell. The MLS would be triangular in outline if unwound and laid flat, about 1.4 μm wide, 7.5–8 μm long, and 80 nm thick. The MLS comprises four layers, S1–S4. The S1 forms the spline, a supportive sheet of microtubules; the S2, lamellate in younger stages, is an homogeneous, darkly staining layer in the mature sperm; the S3 and S4 retain their lamellate appearance and are delimited by lateral connections. Approximately 200 S1 microtubules extend posteriorly from the MLS at about 45° to the MLS long axis and form a partial sheath around the nucleus. The two basal bodies are located on opposite sides of the cell external to the MLS. Each is tangential to the curve of the MLS and surrounded by a globular matrix. At their attachment, the axonemes are oriented laterally and are antiparallel to each other. Distally, the flagella, each about 38 μm long, trail behind the cell as it swims. The nucleus is roughly ovoid, about 4 μm diam, and centrally or sometimes laterally located. The greater volume of the nucleus is occupied by condensed, amorphic chromatin. Cavities within the chromatin are often seen to contain spheroidal inclusions that have two differently staining regions. The inclusions are also located at the periphery of the chromatin. The posterior of the cell is occupied by several small mitochondria and an amyloplast, about 2 μm diam containing numerous starch grains.
BOSTONIA PERPLEXA GEN. ET SP. NOV., A CALAMOPITYAN AXIS FROM THE NEW ALBANY SHALE OF KENTUCKY
Authors: Stein William E. , Beck Charles B.
Published: January 2018

Bostonia perplexa, gen. et sp. nov., was collected from the Lower Mississippian Falling Run member of the Sanderson Formation. The single short segment of an axis, preserved as a petrifaction, contains at least three vascular columns, each with both primary and secondary tissues. Primary xylem is two or three ribbed, and contains several mesarch protoxylem strands. Gymnospermous secondary xylem is characterized by both uniseriate and multiseriate rays. The ground tissue is parenchymatous except for a few clusters of sclerotic cells. In its apparent polystelic nature, the specimen superficially resembles members of the Pennsylvanian to Permian Medullosaceae. All evidence currently available, however, leads to the conclusion that this species should be placed in the Upper Devonian to Lower Mississippian Calamopityaceae. It has not been determined with certainty whether the species is polystelic (in the sense of the Medullosaceae), or whether the apparent polystely is the result of stelar branching proximal to the level of branch divergence.
VARIATION IN NUTLET MORPHOLOGY OF LIMNANTHES
Authors: Hauptli Holly , Webster Barbara D. , Jain Subodh
Published: January 2018

Morphological features of nutlets of all members of the genus Limnanthes were examined by light and scanning electron microscopy (SEM). Eight distinct nutlet types are recognized on the basis of presence or absence, size, shape, density, and color of tubercles and associated filamentous or globular background structures. Some taxa (e.g., L. macounii, L. bakeri) display only one nutlet type, some (e.g., L. floccosa floccosa) have different types in different populations, and others (e.g., L. alba, L. striata) have two or more types within populations. Four classes of nutlets are designated as subtypes on the basis of their forms varying between the eight types recognized. The relationships among various taxa on the basis of nutlet types are schematically diagrammed and compared with other classification schemes. Results suggest that the proposed details of nutlet morphology should be considered in an identification key. Preliminary evidence indicates that certain highly sculptured (tuberculate) nutlet types with large surface areas occur more often in wetter habitats and that variation in this trait in different Limnanthes species might be adaptively associated with geographical distribution patterns.
THE ULTRASTRUCTURE OF THE STALK AND BASE OF THE ANTHERIDIUM OF POLYTRICHUM
Authors: Hausmann M. K. , Paolillo D. J.
Published: January 2018

The fluorescent boundary across the stalk of an antheridium of Polytrichum appears as a distinctive, secondary wall layer in electron micrographs. Lamellations of electron‐dense and ‐lucent materials cause this layer to resemble the “suberized lamellae” of root endodermis and leaf bundle sheaths in grasses. The cells of the stalk below the boundary are especially rich in lipid droplets, whereas those in the base of the antheridium, above the boundary, have markedly fewer and smaller lipid droplets and abundant rough endoplasmic reticulum often in loosely parallel arrays. Cytological differences develop before the boundary appears, so that the distinctive wall layer is secreted by protoplasts that are already specialized morphologically. During maturation of an antheridium there is a secretion of a fluid into a space that forms at the bottom of the sperm chamber. However, the cells surrounding this fluid show no special morphological adaptations that would seem to relate to secretion.
GENETICAL AND CYTOLOGICAL EVIDENCE FOR CHROMOSOMAL ELIMINATION IN A TRUE SLIME MOLD, DIDYMIUM IRIDIS
Authors: Collins O'Neil R. , Therrien C. D. , Betterley Donald A.
Published: January 2018

In crosses involving a polyploid myxamoebal clone. CR 2‐25*, F1 plasmodia and myxamoebae display a variety of unexpected ploidy levels as indicated by nuclear DNA measurements. Genetic analyses of the F1 generations reveal either complete elimination of certain genetic markers or greatly skewed segregation ratios. On the basis of these two kinds of evidence, it is assumed that chromosome elimination occurs at some stage (or stages) following karyogamy between parental nuclei. The possible significance of polyploidy in relation to myxomycete speciation and evolution is discussed.
LEAF‐OPPOSED BUDS IN MUSA: THEIR DEVELOPMENT AND A COMPARISON WITH ALLIED MONOCOTYLEDONS
Authors: Fisher Jack B.
Published: January 2018

A single, lateral, vegetative bud which is positioned 180° from the axil of a leaf is a generic feature of Musa (Musaceae). Such leaf‐opposed buds occur in all ten species and five cultivars examined, representing all four sections of the genus and all groups of cultivated bananas and plantains. The bud arises relatively late and is first visible as a vascular‐free “clear zone” in the axis directly below the future bud meristem site. It is first associated with the fifth or sixth leaf primordium from the apex. A defined superficial meristem develops on the stem directly above the insertion of the leaf margins one or more plastochrons later. Normal, basically axillary, vegetative buds occur in the closely related genera: Orchidantha (Lowiaceae), Heliconia (Heliconiaceae), Strelitzia, and Ravenala (Strelitziaceae). These buds arise in the axil of the first to the third leaf primordium in a manner similar to most other monocotyledons. Axillary vegetative buds also occur in the remaining families of the Zingiberales: Cannaceae, Costaceae, Marantaceae, and Zingiberaceae.
MOISTURE AND TEMPERATURE IN RELATION TO SEED STRUCTURE AND GERMINATION OF SUGAR PINE (PINUS LAMBERTIANA DOUGL.)
Authors: Baron Frank J.
Published: January 2018

The typical, irregular, delayed germination of sugar pine seeds was studied under different conditions of environment and seed dissection. Individual seeds showed a 3‐phase pattern of water uptake which was obscured when average values for groups of seeds were used. Stratification at 5 C slowed the rate of imbibition as well as the growth rate, but when followed after 3 months by return to 20 C, germination was uniformly rapid. Complete removal of the seed coats yielded prompt germination without stratification. The thin layer of the inner coat was a critical factor. Slitting this layer indicated less significance for gas exchange or mechanical restraint than for a restriction upon the rate of water uptake. Regardless of the method of seed treatment, the visible stages of germination consistently occurred within well‐defined levels of water uptake. The delicate balance between water entry and use as well as the internal distribution of water within seed components should be evaluated, rather than a mere expression of the total amount of water in a seed.
TRACHEID LENGTH AS AN ECOTYPIC CHARACTER IN ACER NEGUNDO L.
Authors: Winstead Joe E.
Published: January 2018

Laboratory germinated seedlings of Acer negundo grown under controlled environmental conditions showed patterns of decreasing cell length (tracheids) with decrease in length of growing season of parental tree's habitat. Populations tested represented a range in latitude of 15 degrees (Texas to Canada) and the results indicate populational response to shorter growing seasons being reflected in xylem development.
CHLOROPLAST DEVELOPMENT DURING SPOROGENESIS IN SIX SPECIES OF MOSSES
Authors: Jensen Kenneth G. , Hulbary Robert L.
Published: January 2018

Chloroplast development during sporogenesis in Mnium cuspidatum, M. medium, M. rostratum, Aulacomnium heterostichum, Bartramia pomiformis, and Timmia megapolitana is as follows: During the early mitotic divisions in the sporogenous area of the capsule the number of plastids is reduced from many to one cup‐shaped plastid per sporogenous cell. This single plastid divides during the early spore‐mother‐cell stage. A second division of plastids produces four plastids within each spore‐mother‐cell. A massive accumulation of starch occurs within each of the four plastids. Following meiosis, the single plastid allocated to each spore produces distinct lobes that are “blebbed” off as proplastids. A photosynthetic membrane system is established within the many proplastids as each spore matures.
NITROGEN FIXATION BY LEGUMES AND BLUE‐GREEN ALGAL‐LICHEN CRUSTS IN A COLORADO DESERT ENVIRONMENT
Authors: Eskew D. L. , Ting I. P.
Published: January 2018

Potential sources of fixed nitrogen in a Colorado desert environment were examined by the acetylene reduction method at the Deep Canyon Desert Research Center, near Palm Desert, California. In field and greenhouse studies all members of the genera Astragalus, Dalea, Lotus, Lupinus, Melilotus, and Prosopis examined formed active nodules (acetylene reduction) with indigenous soil bacteria. No evidence of nodulation was found for Acacia greggii, Cercidium floridum, or Hoffmannseggia microphylla. Lotus tomentellus was estimated to fix 0.1 kg N ha−1 by the time of flowering under field conditions. Several members of the genus Dalea showed substantial rates of acetylene reduction in the greenhouse: D. emoryi, 16.1 + 3.5, D. mollissima, 11.4 + 3.7, D. schottii 2.9 + 1.7, D. spinosa 2.5 + 0.4 μmoles ethylene plant−1 hr−1. In greenhouse assays where water was supplied continuously, blue‐green algal‐lichen crusts reduced acetylene at an average rate of 11.0 + 5.7 nmoles ethylene cm−2 hr−1 with a maximum of 57.1. But when in situ assays were done following irrigation of a field plot with 2.3 cm of water, much lower activities were observed with a maximum activity of only 6.4 nmoles cm−2 hr−1.
LEAF ISOZYMES AS GENETIC MARKERS IN CITRUS
Authors: Torres Andrew M. , Soost Robert K. , Diedenhofen Ulrike
Published: January 2018

The genetic control of isozymes from Citrus and its near relatives was determined for three gene/enzyme systems: glutamate oxaloacetate transaminase, phosphoglucose isomerase and phosphoglucose mutase. These enzymes are controlled by four genes having 19 codominant alleles, 12 of which occur in Citrus subg Citrus. Formal genetic studies were carried out with F, biotypes and F1 populations of known origin. When biotypes were grouped into traditionally recognized species to examine genetic affinities within and between species, a remarkable pattern of uniformity of genotype combinations was found within a species, and every species had an unique combination. Because many economically important cultivars produce asexual(nucellar) as well as sexual(zygotic) embryos, a central problem of the breeder is to distinguish these when plants are young, long before fruiting. Isozyme markers can be used with varying degrees of efficiency, depending on the genotypes of the particular parents, to distinguish nucellar seedlings from those of zygotic origin.
VEGETATIVE AND FLORAL RELATIONSHIPS AMONG WESTERN NORTH AMERICAN POPULATIONS OF COLLOMIA LINEARIS NUTTALL (POLEMONIACEAE)
Authors: Wilken Dieter H.
Published: January 2018

Thirty‐seven characters were measured on greenhouse grown progenies of twenty‐three populations representing, for Collomia linearis, a broad geographical and ecological distribution in western North America. Twelve vegetative and seventeen floral characters showed significant among‐population/within‐population variance ratios (F‐statistics). Overall, floral characters showed higher F‐statistics than did vegetative characters. The F‐statistics and character means were used to construct phenograms based on weighted similarity measures and single‐linkage clustering. With the exception of a homogeneous cluster comprising northern Rocky Mountain OTUs, relationships based on floral characters were geographically random. No clearly defined morphological trends toward increased autogamy were observed in association with geographical or ecological distribution. Several clustering relationships, based on vegetative characters, were interpreted as representing geographically unrelated genotypes convergent with respect to ecotypic differentiation. The most distinctive clusters of OTUs in the vegetative phenogram were associated with subalpine and wet meadow sites, habitats considered as ecologically marginal for the species. Comparison of the two phenograms revealed considerable disparity between relationships based on floral characters and those based on vegetative characters. This disparity lends support to the hypothesis that floral and vegetative character combinations are subject to independent selective processes. The absence of polyploidy or mitotically detectable chromosomal rearrangements indicates that the observed variation among widely separated populations represents either divergence or convergence via genetic differentiation at the diploid level.
ROGERSIOMYCES, A NEW GENUS IN THE FILOBASIDIACEAE (HOMOBASIDIOMYCETES) FROM AN AQUATIC HABITAT
Authors: Crane J. L. , Schoknecht J. D.
Published: January 2018

Rogersiomyces okefenokeensis gen. et sp. n. is a Homobasidiomycete described in the Filobas‐idiaceae. It is characterized by gymnocarpous basidiocarps composed of fasciculate or loose synnematous holobasidia. The basidia are characteristically obclavate with prominent, truncate sterigmata and function as apobasidia. The basidiospores are borne symmetrically, are nonapiculate, and germinate directly to form mycelium or occasionally by repetition. Some examples are presented to illustrate an apparent correlation of apobasidia with an adaptation to aquatic habitats.
ANGIOSPERM PALEOBIOCHEMISTRY OF THE SUCCOR CREEK FLORA (MIOCENE) OREGON, USA
Authors: Niklas Karl J. , Giannasi David E.
Published: January 2018

The organic chemical profiles of fossil Acer and Quercus leaf tissues are presented and correlated with those of previously described fossil Celtis, Ulmus and Zelkova and interpreted in conjunction with referable extant genera. Intrageneric comparisons among fossil and extant taxa indicate that relatively minor phytochemical differences exist suggesting that little flavonoid and steroid evolution since post‐Miocene times has occurred. Biosystematic relationships between living North American and Asian genera indicate that in some cases (Quercus, Zelkova) a greater affinity exists between living Asiatic species and elements of the Succor Creek Flora. The chemical data are proposed as an independent parameter in assessing angiosperm biogeography and proposed migration patterns of the Fagaceae and Ulmaceae. The high chemical fidelity seen between some living and fossil genera preserved in ash‐fall deposits is ascribed to the reaction of membrane bound lipids with various organic acids and to subsequent rapid dehydration.
CHLOROPHYLL AND CAROTENOID ACCUMULATION IN THREE CHLOROPHYLLOUS CALLUS PHENOTYPES OF GLYCINE MAX
Authors: Hemphill John K. , Venketeswaran S.
Published: January 2018

Effects of exogenous carbohydrates and various medium supplements on chlorophyll and carotenoid accumulation in three chlorophyllous callus phenotypes of Glycine max (L.) Merrill were studied. Glucose (filtered), at 3%, supported the highest level of chlorophyll and carotenoids in the NG and Y phenotypes, while only moderate levels of chlorophyll accumulated in the LG phenotype. Sucrose (filtered and autoclaved), at 3%, supported phenotypical levels of chlorophyll and carotenoids for all phenotypes. Ascorbic acid, at 75 mg/l, stimulated chlorophyll‐carotenoid accumulation for all phenotypes, while δ‐aminolevulinic acid was slightly toxic for pigment biosynthesis in the NG and LG phenotypes. In contrast, δ‐aminolevulinic acid supported chlorophyll‐carotenoid accumulation in the Y phenotype. A negative correlation (rXY) was evident between chlorophyll formation and callus growth for all phenotypes. Light intensity of 3,000 lux suppressed chlorophyll accumulation in the Y callus phenotype while an increase in pigment formation occurred in the NG and LG callus phenotypes. In comparison, light intensity of 700 lux supported chlorophyll accumulation in the Y callus phenotype. Carotenoid accumulation appeared to be coupled with chlorophyll formation in all callus phenotypes except for the Y callus phenotype when grown under the higher light intensity. All phenotypes accumulated chlorophylls a and b, α‐ and β‐carotene, lutein plus zeaxanthin, violaxanthin and neoxanthin as indicated by their respective absorption maxima. Under cultural conditions, the genetic mutation (yll) in these soybean callus phenotypes appeared to regulate carotenoid formation which in turn influenced chlorophyll stability.
COMPARATIVE INHIBITION OF NITRIFIERS AND NITRIFICATION IN A FOREST COMMUNITY AS A RESULT OF THE ALLELOPATHIC NATURE OF VARIOUS TREE SPECIES
Authors: Lodhi M. A. K.
Published: January 2018

Inhibition of nitrification and nitrifiers was significantly variable under different tree species in the same forest ecosystem. Nitrate nitrogen was always lower than ammonium nitrogen when compared under each species. On the other hand, low numbers of Nitrosomonas and Nitrobacter showed an inverse relationship with large amounts of ammonium in most samples. Aforementioned variation is due to the variable tree litter under different species, which in turn produces inhibitors of nitrification and nitrifiers. Inhibition of nitrification in natural ecosystems increases the amounts of ammonium nitrogen thus resulting in a conservation of energy, if plants utilize such nitrogen directly.
PROBLEMS IN THE IDENTITY AND ORIGIN OF THE APPALACHIAN VITTARIA GAMETOPHYTE, A SPOROPHYTELESS FERN OF THE EASTERN UNITED STATES
Authors: Farrar Donald R.
Published: January 2018

Populations of a fern gametophyte presumed to be of the genus Vittaria occur commonly in the uplands of the southeastern United States. The gametophytes occur on non‐calcareous rock outcrops of various composition in areas which provide continuous moisture and protection from temperature extremes. Gametophytes in these habitats are robust and long lived, frequently forming the dominant vegetation in areas covering several square feet. Reproduction is exclusively vegetative by production of gemmae. Although sex organs are present in most populations, viable sporophytes are never produced. The gametophytes have previously been considered most likely to be V. lineata, which occurs in Florida, but morphological and physiological comparisons do not support that conclusion. Significant differences between Appalachian and Florida gametophytes occur in growth form, growth rate, cold hardiness, sporophyte production, and patterns of gemma production. The distribution of the Appalachian gametophytes correlates with old, unglaciated land masses suggesting antiquity rather than recent introduction. Present evidence favors the interpretation that the Appalachian Vittaria gametophytes either belong to a tropical American species from which they have long been separated, or that they represent a distinct species of which the sporophyte no longer exists.
OBSERVATIONS ON THE CHARACTERISTICS OF THE LEMMA AND PALEA OF THE LATE CENOZOIC GRASS PANICUM ELEGANS
Authors: Thomasson Joseph R.
Published: January 2018

Scanning electron microscopy (SEM) was used to study the surface features of the anthoecia (fertile lemma and palea) of Panicum elegans Elias from the Late Cenozoic deposits in Ellis County, Kansas. Examination of the lemma revealed a well developed germination lid, irregularly arranged, simple, rounded papillae and a crescent‐shaped scar of attachment. The presence of a germination lid indicates that this structure has been present in some members of the Gramineae since at least the Late Miocene‐Early Pliocene. Evidence is presented which contradicts current ideas regarding the distribution of the germination lid in extant Gramineae. The surface of the palea is characterized by simple, rounded papillae spaced in regular rows. The arrangement and form of these papillae are like that present in some modern Dichanthelium. Both the epidermises of the lemma and palea are composed entirely of long cells with strongly sinuous, interlocking cell walls. The pattern of cells on the lemma indicates that the systematic placement of Panicum elegans is correct.
IS THE PREDOMINANT PERIOD OF CELL ARREST AND PRESENCE OF ENDOREDUPLICATED CELLS COINCIDENT WITH PRODUCTION OF SECONDARY VASCULAR TISSUES IN INTACT AND CULTURED ROOTS OF RAPHANUS SATIVUS L.?
Authors: Evans Lance S. , Verville Kathleen M.
Published: January 2018

Experimental results show that predominant cell arrest in G2 and the presence of endoreduplicated cells are coincident with presence of secondary vascular tissues while preponderant cell arrest in G1 and absence of polyploid cells are coincident with an absence of secondary vascular tissues in mature root tissues of intact and cultured roots of Raphanus sativus L. In mature tissues of intact seedling roots, most cells arrest in G2, and both polyploid cells and secondary vascular tissues are present. If excised roots are grown on simple medium, most mature cells arrest in G1, none undergo endoreduplication, and only primary vascular tissues are present. When bases of these excised roots are later placed in a medium with auxin, cytokinin, and myo‐inositol that produces secondary vascular tissues in vitro, preponderant cell arrest occurred in G2 with some polyploid cells. The general relationship of predominant period of cell arrest, presence of polyploid cells, and presence of secondary vascular tissues in mature roots among plants of various taxa is surveyed.
THE ROLE OF ENDOMYCORRHIZAE IN REVEGETATION PRACTICES IN THE SEMI‐ARID WEST. II. A BIOASSAY TO DETERMINE THE EFFECT OF LAND DISTURBANCE ON ENDOMYCORRHIZAL POPULATIONS
Authors: Moorman Thomas , Reeves F. Brent
Published: January 2018

Populations of the endomycorrhizal fungus Glomus fasciculatus were significantly reduced following land disturbance in western Colorado soil. A bioassay was developed to measure changes in the endomycorrhizal population. In the bioassay, inoculum levels were measured by comparing the percentage infection in corn (Zea mays) root systems thirty days after planting in undisturbed or disturbed soils. The percentage infection was 2% in the disturbed soil compared to 77% in the adjacent undisturbed soil. Glomus fasciculatus was identified as the endophyte in both soils. Considering the importance and function of endomycorrhizal fungi to their plant hosts the reduction of active inoculum in the disturbed soil may be an important ecological factor in subsequent succession.
ONTOGENY IN MONOCOTYLEDONS AS REVEALED BY STUDIES OF THE DEVELOPMENTAL ANATOMY OF PERICLINAL CHLOROPLAST CHIMERAS
Authors: Stewart R. N. , Dermen Haig
Published: January 2018

The developmental anatomy of apically stable periclinal chloroplast chimeras was studied in a number of monocotyledonous genera. Their ontogeny is basically similar to that of dicotyledons. In both there are three independent apical layers (L‐I, L‐II, and L‐III) whose derivatives can be traced in stem, leaf and flower. The bulk of the stem tissue is derived from L‐III with only the epidermis and one or two hypodermal cell layers from L‐I and L‐II. All three layers participate in formation of the leaf with great flexibility in the amount of tissue from each. There is more instability in growth of most monocotyledonous leaves than in dicotyledonous leaves. As a result there is relatively more tissue derived from L‐I and L‐II and less from L‐III. The same is true in floral development so that a significant number of gametes are of L‐I origin. As in dicotyledons, there is variation in direction, timing, and frequency of cell division. However, an overriding genetic control results in normal size, shape, and structure. The evidence from genetic and cytochimeras in both monocotyledons and dicotyledons has provided direct experimental proof of the functional reality of the apical layers described by Hanstein and Schmidt.
PATTERNS OF RESOURCE ALLOCATION IN WILDFLOWER POPULATIONS OF FIELDS AND WOODS
Authors: Abrahamson Warren G.
Published: January 2018

Fifty‐two populations of fifty species of wildflowers characteristic of either field or deciduous forest were analyzed to determine pattens of biomass allocation to component organs. These populations' allocation patterns were used to determine generalized allocation patterns of the herb component of earlier (field) and later (deciduous forest) secondary successional communities. The following patterns were determined: (1) The proportion of dry matter allocated to seed reproductive organs was greater in field populations than in woods populations; (2) The herbs of woodland habitats allocated a greater proportion of their resources to leaves and belowground organs than field habitat herbs; (3) The field annuals allocated a greater proportion of their resources to reproduction than field perennials; (4) Introduced species showed a higher reproductive allocation than native species of fields; (5) Regression analysis showed strong correlations of component organ biomass to total biomass and belowground biomass to shoot biomass.
THE ORIGIN AND EVOLUTIONARY RELATIONSHIPS OF ‘HUAUZONTLE’ (CHENOPODIUM NUTTALLIAE SAFFORD), DOMESTICATED CHENOPOD OF MEXICO
Authors: Wilson Hugh D. , Heiser Charles B.
Published: January 2018

A New World assemblage of tetraploid Chenopodium species (section Chenopodium, subsection Cellulata) includes two domesticates, C. quinoa of Andean South America and C. nuttalliae of Mexico. Both have been combined into a single species and the Mexican form has been considered as a possible derivative of C. quinoa. The domesticates and related, sympatric weed forms, C. berlandieri of North America and C. hircinum of the Andes, were examined for variation in morphological and biochemical characteristics and also were included in a program of artificial hybridization. Results indicate that the domesticated forms are more closely related to their sympatric weeds than to each other. The Mexican cultigen is placed as a subspecies of C. berlandieri, the taxon from which it most likely evolved under human selection in North America. Possible origins for the Andean weed‐crop complex are considered. Southward migration of a North American tetraploid appears to be more likely than independent allotetraploidy in South America. Of the North American tetraploids examined, C. berlandieri var. zschackei of the western U.S. shows closest affinities to the Andean complex.
ONTOGENY OF THE INFLORESCENCE OF SAURURUS CERNUUS (SAURURACEAE)
Authors: Tucker Shirley C.
Published: January 2018

The spicate inflorescence of Saururus cernuus L. (Saururaceae) results from the activity of an inflorescence apical meristem which produces 200–300 primordia in acropetal succession. The inflorescence apex arises by conversion of the terminal vegetative apex. During transition the apical meristem increases greatly in height and width and changes its cellular configuration from one of tunica‐corpus to one of mantle (with two tunica layers) and core. Primordia are initiated by periclinal divisions in the subsurface layer. These are “common” primordia, each of which subsequently divides to produce a floral apex above and a bract primordium below. The bract later elongates so that the flower appears borne on the bract. All common primordia are formed by the time the inflorescence is about 4.4 mm long; the apical meristem ceases activity at this stage. As cessation approaches, cell divisions become rare in the apical meristem, and height and width of the meristem above the primordia diminish, as primordia continue to be initiated on the flanks. Cell differentiation proceeds acropetally into the apical meristem and reaches the summital tunica layers last of all. Solitary bracts are initiated just before apical cessation, but no imperfect or ebracteate flowers are produced in Saururus. The final event of meristem activity is hair formation by individual cells of the tunica at the summit, a feature not previously reported for apical meristems.
ALLOZYME VARIATION IN SEVERAL CLOSELY RELATED DIPLOID SPECIES OF CHENOPODIUM OF THE WESTERN UNITED STATES
Authors: Crawford Daniel J. , Wilson Hugh D.
Published: January 2018

Twelve allozyme loci were examined in a complex of closely related diploid (2n = 18) members of the genus Chenopodium occurring in the western United States. These plants are generally treated taxonomically as belonging to C. atrovirens, C. desiccatum, C. hians, C. leptophyllum, and C. pratericola. Also included were populations referable to C. incognitum. The enzymes examined and the allelic designations are given as follows: leucine aminopeptidase, Lap; phosphoglucoisomerase, Pgi‐1, Pgi‐2; glutamate‐oxaloacetate transaminase, Got‐1, Got‐2, Got‐3; glutamate dehydrogenase, Gdh; phosphoglucomutase, Pgm‐1, Pgm‐2; malate dehydrogenase, Mdh‐1, Mdh‐2; and malic enzyme, Me. All populations were fixed for the same allele at Gdh, Pgi‐2, and Mdh‐1. Chenopodium hians was fixed for a unique allele at Got‐3 and contained two alleles at the Lap locus and two at Pgi‐1 which were not detected elsewhere. Chenopodium leptophyllum likewise has unique alleles at Lap and Pgi‐1. The other three taxa, C. atrovirens, C. desiccatum and C. pratericola, have alleles at Lap and Pgi‐1 which were not found in C. hians or C. leptophyllum. The former three species have the same alleles in highest frequency at all polymorphic loci except Me, where C. desiccatum is consistently separable from C. atrovirens and C. pratericola. Allozyme data are concordant with information from morphology, flavonoid chemistry and seed protein profiles in suggesting that: (1) Chenopodium hians and C. leptophyllum are best regarded as distinct species; (2) C. atrovirens and C. pratericola are very similar and perhaps should not be recognized at the specific level; (3) C. desiccatum appears most closely allied to C. pratericola; (4) plants referable to C. incognitum represent two biological entities, one the same as C. atrovirens, and the other conspecific with C. hians; (5) little genetic variation is detectable in any taxon of these weedy annuals; (6) interspecific hybridization is not a cause of taxonomic difficulties in these plants.
ARCHAEOBOTANICAL STUDIES OF ELEUSINE CORACANA SSP. CORACANA (FINGER MILLET)
Authors: Hilu K. W. , de Wet J. M. J. , Harlan J. R.
Published: January 2018

Two controversial archaeological specimens of finger millet, Eleusine coracana ssp. coracana (L.) Gaertn., were examined by light and scanning electron microscopy. Identification of the material was based on morphological and anatomical comparison with laboratory carbonized grains of modern Eleusine. Seed morphology of the Indian archaeological collection did not conform with those of domesticated or wild species of Eleusine. The other archaeological collection examined is from Ethiopia. It is estimated to date back to the third millennium B.C. These well preserved inflorescence fragments were positively identified as finger millet. If the suggested date is correct, they represent the oldest archaeological record for the crop, as well as the oldest agricultural record for Africa south of the Sahara. These findings support biosystematic evidence for an East African origin of finger millet which leaves India as a secondary center of diversity.
LECLERCQIA COMPLEXA: EARLIEST LIGULATE LYCOPOD (MIDDLE DEVONIAN)
Authors: Grierson James D. , Bonamo Patricia M.
Published: January 2018

Our discovery of a ligule on Leclercqia complexa Banks, Bonamo and Grierson 1972 is the earliest occurrence of a ligulate lycopod in the fossil record. The ligule 1) occurs on a homosporous lycopod, differing with current concepts that the ligule is linked with the heterosporous condition; 2) is located on the leaf far distant from the attachment of leaf to stem, thus differing in position from any known ligulate lycopod, extinct or extant; 3) is comparable in morphology to ligules of extant lycopods, therefore providing no clues as to any earlier specialized function. These findings extend the enigma of the function of the ligule back in time, but necessitate a re‐evaluation of the spatial relationship of the leaf and the ligule and of the link between heterospory and the ligule.
RELATIONSHIPS BETWEEN SHOOT GROWTH AND CHANGING PHYLLOTAXY OF RANUNCULUS
Authors: Meicenheimer Roger D.
Published: January 2018

Growth of Ranunculus shoots through ontogeny is quantified by techniques utilizing scanning electron microscopy and studies on living plant material. The order of the contact parastichy phyllotaxy in the apical system is related to the relative plastochron rates of growth of the shoot. There is a change in the (2, 3) contact parastichy pattern of vegetative phyllotaxy to a transitional (3, 5) contact pattern which is maintained through sepal production. Formation of a 5(1, 1) whorl of petal primordia establishes a (5, 8) contact pattern with the sepal primordia. Subsequent initiation of stamen primordia, in spiral sequence, results in (5, 8, 13) triple contacts between petal and stamen primordia. The stamen primordia and carpel primordia arrangement is characterized by a (8, 13) contact parastichy pattern of phyllotaxy. Through ontogeny the volume of the shoot apex progressively increases but the shape of the apex, described by a second degree polynomial, remains constant. The plastochron and the relative plastochron rates of radial and vertical displacement of primordia progressively decrease during transition but there is no alteration of the chronological rate of apical expansion. The change in contact parastichy phyllotaxy through ontogeny is interpreted as a change in the relative positions of primordia insertion on the apex resulting from an increase in apical volume and an increased rate of primordia initiation.
HETEROSTYLY IN LITHOSPERMUM COBRENSE (BORAGINACEAE)
Authors: Ganders Fred R.
Published: January 2018

Lithospermum cobrense Greene exhibits the floral dimorphisms and strong self‐incompatibility system typical of most distylous plants. Flowers of the long styled (pin) form produce smaller pollen grains but more pollen per flower than flowers of the short styled (thrum) form. Corollas of pins and thrums are equal in size. The breeding system of L. cobrense is less specialized than, and probably ancestral to, that of L. caroliniense.
HYDROXYPROLINE‐INDUCED CHANGES IN FORM, APICAL DEVELOPMENT, AND CELL WALL PROTEIN IN THE LIVERWORT PLAGIOCHILA ARCTICA
Authors: Basile Dominick V. , Lehman Herbert H.
Published: January 2018

Hydroxy‐L‐proline induces phenovariation in Plagiochila arctica Bryhn & Kaal. (Plagiochilaceae) similar to that previously induced by this compound in representatives of three other families of leafy liverworts (i.e., Cephaloziaceae, Jungermanniaceae and Scapaniaceae). Because the pattern of phenovariation in P. arctica was uniform and persistent over relatively long incubation periods, adequate material for chemical analysis and reliable material for histological analysis could be obtained for the first time. These analyses revealed interesting correlations between form, cellular “behavior,” and wall chemistry in normal and phenovariant plants. The correlations interpreted in the context of available information suggest, as a working hypothesis, that hydroxyproline‐proteins regulate several aspects of morphogenesis in leafy liverworts by suppressing growth and development at critical times in highly localized areas.
DIFFERENTIATION IN RESPONSE TO CHILLING TEMPERATURES AMONG POPULATIONS OF THREE MARINE SPERMATOPHYTES, THALASSIA TESTUDINUM, SYRINGODIUM FILIFORME AND HALODULE WRIGHTII
Authors: McMillan Calvin
Published: January 2018

Upon exposure to chilling conditions, the seagrass populations of Thalassia testudinum Banks ex König, Syringodium filiforme Kütz., and Halodule wrightii Aschers. showed various amounts of leaf and plant damage that correlated with their origin in the Gulf of Mexico‐Caribbean. Populations of more tropical origin in the southern Gulf and Caribbean showed the most chill damage and those of the northern Gulf showed the least injury from the exposure to low temperatures. Of the three seagrasses, Halodule showed greatest chill tolerance, Syringodium showed the least tolerance and Thalassia was intermediate. The uptake of 14C by leaves following exposure to chilling temperatures showed quantitative differences that correlated with the amount of leaf damage in the various populations. No significant changes in the fatty acids in total lipid extracts were noted in the Texas seagrasses after chilling and, therefore, their resistance to low temperature damage did not relate to changes in saturation of fatty acids. Although the growing conditions slightly altered the severity of the chilling effects, the differentiation of response to chilling among the seagrass populations is based on inherited properties.