bluuebunny/crossref_metadata_2025 huggingface dataset:
ULTRASTRUCTURE OF AUXIN‐INDUCED TUMORS OF THE COLEORHIZA‐EPIBLAST OF WHEAT
Authors: Walne Patricia L. , Haber Alan H. , Triplett L. L.
Published: January 2018

When wheat is germinated in high concentrations of certain auxins, the coleorhiza‐epiblast grows in an excessive and disorganized manner and resembles a callus. Wheat was germinated in 10−3M indoleacetic acid or in water. There was greater net synthesis of DNA, RNA, and protein in the tumor tissue than in control tissue. Control and tumor tissue was fixed for electron microscopy 1, 2, 3, and 4 days after sowing. In contrast to the controls, many more lipoidal bodies appeared in 1‐day‐old, auxin‐treated tissue and thereafter diminished in number. In 2‐ and 3‐day‐old tumor tissue, small membraneous fragments were prominent but disappeared in older tissue. With time, the following changes became progressively more pronounced: cytoplasmic vacuolation, appearance of myelin figures, polyribosome configurations and extensive profiles of rough endoplasmic reticulum, and sloughing of cytoplasmic contents into and accumulation of electron‐dense material in vacuoles. Possible factors in susceptibility of certain tissues to tumor formation are discussed.
OVULE ABORTION IN QUERCUS (FAGACEAE)
Authors: Mogensen H. Lloyd
Published: January 2018

This study deals with the occurrence and relative abundance of four different types of abortive ovules in three species of Quercus. It was found that, contrary to previous literature, fertilization does not always occur in the abortive ovules. The most common type of abortive ovule is the one in which a normal embryo sac develops, yet fertilization does not occur. The absence of embryo sacs and the occurrence of empty embryo sacs account for abortion in other ovules. All types of abortive ovules can occur in the same ovary. It is proposed that all of the ovules that develop a normal embryo sac are potential seeds, but the first one to be fertilized suppresses the normal development of the others.
GENETICS OF SORDARIA FIMICOLA. IX. LINKAGE GROUP II
Authors: El‐Ani Arif S. , Olive L. S.
Published: January 2018

Ten mutant sites have been located in linkage group II of Sordaria fimicola, nine of them affecting fertility. Two different regions of the chromosome are marked with allelic mutations or mutant sites in closely linked loci involved in sexual reproduction. Mutants of one of these two regions also have an arginine deficiency. Crosses between the self‐sterile mutants of each region yield hybrid perithecia containing asci with four spores of each parental genotype and few or no asci with recombinant spores. The bearing that these findings have upon the evolution of heterothallism is discussed.
CARPELLARY VASCULATURE AND THE OVULAR VASCULAR SUPPLY IN DRIMYS
Authors: Tucker Shirley C.
Published: January 2018

The ovules in Drimys winteri var. chilensis and D. lanceolata are consistently vascularized entirely by the ventral bundles, without contribution from the dorsal bundle(s) as generally assumed. The ovules are initiated in two rows, without any in “median” position. Post‐initiatory differential growth of the carpel wall brings the lowermost ovules into apparently median position at maturity. The anomalous vascular supply to the lowermost ovules is thought to be related to concurrence of delayed initiation and development of these ovules with delayed differentiation of the vascular supply.
ARIADNAESPORITES AND GLOMERISPORITES IN THE LATE CRETACEOUS: ANCESTRAL SALVINIACEAE
Authors: Hall John W.
Published: January 2018

GlomerisporitesandAriadnaesporitesare two genera based on megaspores and microspores from the late Cretaceous. Each has megaspores with characteristics shared with other late Cretaceous Salviniaceae, including numerous floats, an acrolamella, and a complex perispore. Microspores are borne singly, however, not in characteristic salviniaceous massulae. Microspores ofGlomerisporiteshave a pseudovacuolate basal region and a single spore in an apical neck. Microspores ofAriadnaesporitesare structurally like the megaspores but of smaller size.Ariadnaesporites variusoccurs in the Cenomanian Stage (early late Cretaceous) and is the oldest presumed member of the Salviniaceae.
PHOTORESPONSES OF PHYCOMYCES BLAKESLEEANUS: INITIATION AND DEVELOPMENT OF SPORANGIOPHORE PRIMORDIA
Authors: Thornton Robert M.
Published: January 2018

Phycomyces blakesleeanus (Burgeff) produces both giant and dwarf sporangiophores from superficial and submerged hyphae. The morphogenesis of submerged primordia has been studied in cultures grown in petri dishes on a defined nitrogen‐poor medium at low temperature under varied conditions of illumination. The primordia of dwarf and giant sporangiophores differed markedly in size, morphology, tropistic behavior, developmental plasticity, photosensitivity, and conditions required for initiation. Dwarf primordia, abundant only in dark‐grown cultures, began as hyphal thickenings that later developed characteristic ramifications not seen in giant primordia. The formation of dwarf primordia was correlated spatially and temporally with termination of mycelial expansion near the rim of the dish and in local regions elsewhere. Illumination strongly suppressed the ramification process in existing primordia but did not prevent the maturation of dwarf sporangiophores that had already emerged from the nutrient surface. Giant primordia were prominent only in illuminated cultures. With continuous light from the time of inoculation, giant sporangiophores and giant primordia were found chiefly in midregions of the dish. If illumination was delayed until dwarfs had begun to form near the rim of the dish, the giant primordia were also concentrated near the rim. In that case about half of the giants were formed by conversion of a small fraction of the existing dwarf primordia and the rest were formed de novo from vegetative hyphae.
HISTOLOGICAL COMPARISON OF SINGLE AND ADDITIVE O3 AND SO2 INJURIES TO ELONGATING PONDEROSA PINE NEEDLES
Authors: Evans Lance S. , Miller Paul R.
Published: January 2018

Visual symptoms and histological effects of SO2, O3, and a combination of SO2 and O3 were compared in rapidly elongating needles of sensitive clonal selections of Pinus ponderosa Laws. Both pollutants were administered separately or in combination at 0.45 ppm for 9 hr/day. Visual and histological injury appeared in distal needle portions after exposure to SO2 or SO2 plus O3; but damage was predominately due to SO2. Ozone caused an aggregation of cytoplasm and cellular organelles into peripheral areas of plicate parenchyma cells. Ozone injury, which became evident several days after SO2 damage, prevailed mostly on needle sections 10–15 mm from the distal tip. Sulfur dioxide caused dissolution of cellular components in virtually all needle cell types (parenchyma, epidermis, hypodermis, resin duct epithelium, and vascular tissues). Injury from SO2 and O3 is compared with that produced by other abiotic agents in pine in order to outline histological techniques for diagnostic purposes.
POSTGENITAL CARPEL FUSION IN CATHARANTHUS ROSEUS (APOCYNACEAE). I. LIGHT AND SCANNING ELECTRON MICROSCOPIC STUDY OF GYNOECIAL ONTOGENY
Authors: Walker Dan B.
Published: January 2018

The detailed ontogeny of postgenital fusions within the gynoecium of Catharanthus roseus was investigated. The basal margins of the young carpel primordia infold and fuse together to seal shut the loculi. Independently, the opposing distal tips of the two carpels also unite, with the fusion region subsequently developing into the stigma, style, and a small distal region of the compound ovary. The basal ovary regions of the two opposing carpels remain unfused, thus leaving the tip fusion spatially restricted. In the region of contact, cells with distinctively epidermal features progressively lose their epidermal character after their participation in the fusion. In the fused stigma these former epidermal cells redifferentiate into transmitting and secretory tissues; in the fused style these cells undergo a tremendous expansion in length while forming stylar transmitting tissue; but in the compound ovary region corresponding cells experience little expansion or redifferentiation. It is concluded that the loss of epidermal features or the occurrence of periclinal cell divisions in the epidermis is a definitive indication that cells have fused postgenitally. However, studies with the transmission electron microscope are necessary to detect the first indications of a postgenital fusion. The compound ovary region within the gynoecium of C. roseus is a tissue appropriate for a high resolution ultrastructural study of the cytological events accompanying postgential tissue fusion because the fusion occurs quickly and little subsequent cell expansion takes place within this region.
FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. III. KIRENGESHOMOIDEAE, HYDRANGEOIDEAE AND ESCALLONIOIDEAE
Authors: Bensel Carolyn R. , Palser Barbara F.
Published: January 2018

The floral morphology and anatomy of the one species in the monotypic Kirengeshomoideae, eight species in the Hydrangeoideae, and six in the Escallonioideae are described and compared. Similarities in floral structure and vascularization between Kirengeshoma palmata and members of the Philadelpheae strongly support the placement of this genus in the same subfamily as the tribe—the Hydrangeoideae. While the anatomy and morphology of flowers in the Hydrangeoideae do not clearly exclude the subfamily from a family that also includes the Saxifragoideae, certain commonly appearing floral characteristics probably do. These include relatively extensive polyandry, the frequent occurrence of highly vascularized isomerous gynoecia, petals with lateral bundles originating from traces in the sepal planes, no suggestion of a floral cup continuing beyond the divergence of the floral organs from the carpel walls in epigynous flowers, and essentially no independence among carpels in the ovary region of the gynoecium. In addition, a fascicled stamen arrangement characterizes the polyandrous members (Philadelpheae mostly). Although floral anatomy of too few members of the Escallonioideae has been investigated, the floral characteristics of this subfamily appear to be very diverse and not particularly distinctive when compared with the Saxifragoideae. Some diagnostic trends may be recognized, however: Escallonioids generally have fewer ovules per carpel (except Escallonia), less commonly show independence between carpels, and have epidermal hairs that are quite different from the complex trichomes of the flowers in Saxifragoideae. In addition, the ventral carpel bundles in two species studied in the subfamily terminate at the top of the ovary and do not enter the style.
FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. IV. BAUEROIDEAE AND CONCLUSIONS
Authors: Bensel Carolyn R. , Palser Barbara F.
Published: January 2018

This paper presents a description of the floral anatomy and morphology of Bauera rubioides and a general discussion of how the patterns of variation in floral characters among the subfamilies of the Saxifragaceae sensu lato described in this and previous papers correlate with the patterns of variation in other types of characters (i.e., embryology, biochemistry, etc.). Major conclusions are: (1) The Saxifragoideae, including Ribes, forms a rather homogeneous taxon with regard to floral and other characters. (2) Since the high degree of similarity in floral structure between Itea (Iteoideae) and members of the Saxifragoideae is not correlated with similarities in a number of other characteristics, the affinity between the two probably is not as strong as floral characters suggested. (3) The differences in floral structure between Parnassia (Parnassioideae) and the Saxifragoideae are correlated with differences in other characteristics, and on this basis the taxon should be excluded from the family. (4) Brexia and Ixerba (Brexioideae) are strikingly dissimilar in floral structure and therefore probably do not belong in the same subfamily. Tentatively, Ixerba may find a place in the Escallonioideae, but the relationships of Brexia remain problematical. (5) Bauera (Baueroideae), which has a floral structure quite distinct from that of the Saxifragoideae, shares a number of similarities in embryology, pollen morphology, vegetative anatomy, and biochemistry with the Cunoniaceae and is probably better placed in that family than in the Saxifragaceae. (6) Kirengeshoma palmata (Kirengeshomoideae) should be transferred to the Hydrangeoideae and the whole removed from the Saxifragaceae, since certain floral characters which isolate the group from the Saxifragoideae are correlated with differences in embryology, pollen morphology, leaf and nodal anatomy, and cytology. (7) The Escallonioideae remains a major taxonomic problem because so little information is available on the members of this taxon.
HORMONAL CONTROL OF ORGANOGENESIS IN OPUNTIA POLYACANTHA (CACTACEAE)
Authors: Mauseth James D. , Halperin Walter
Published: January 2018

An axillary bud (areole) of Opuntia polyacantha is composed of an extremely short axis which bears highly modified leaves (spines). After producing the spines, the bud apical meristem becomes quiescent. When the axillary bud is excised and cultured with benzylaminopurine (BAP), the apical meristem increases in complexity and produces leaves on an elongated axis. Gibberellic acid (GA) induces spine production with no elongation of the axis. Naphthaleneacetic acid (NAA) causes no structural change in the meristem but induces root formation in adjacent tissue. The initiation of roots, spines, or leaves is visible within three days. Explants on medium lacking hormones show no structural change, but by the tenth day are insensitive to BAP or NAA. These aged explants can be made to respond to BAP or NAA by merely rewounding them at the time of hormone application. With concentrations previously found to be optimal for single hormone responses, NAA in combination with BAP prevents shoot formation, or in combination with GA prevents spine production. When all three hormones are combined, spines are produced, indicating that GA is active morphologically while BAP and NAA counteract each other. If the level of NAA is decreased, BAP counteracts the NAA and also overrides the GA and leafy shoots are produced. By varying the proportions of BAP and GA, in the absence of NAA, four types of lateral appendage can be produced: leaves, mildly altered leaves, leaf‐spine transition forms, and spines.
STEM AND LEAF GAS EXCHANGE OF TWO ARID LAND SHRUBS
Authors: DePuit Edward J. , Caldwell Martyn M.
Published: January 2018

Gas exchange studies were conducted on two shrub species found in cool shrub‐steppe communities of the American West, big sagebrush (Artemisia tridentata subsp. tridentata Nutt.) and broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. and Rusby), with a goal of evaluating characteristics and relative contributions of green stem and leaf material to total shoot CO2 exchange at different temperatures. Variations in tissue temperature exerted a pronounced effect on CO2 exchange—net photosynthesis and dark respiration—of green stems and leaves of both species. Definite temperature optima of net photosynthesis were noted, and dark respiration rates consistently increased with increases in temperature. Green stems of both species exhibited sizable dark respiration rates, although stem rates at all temperatures were lower than corresponding leaf rates. Artemisia tridentata did not exhibit sizeable green stem net photosynthesis even under conditions of optimal temperature and water availability, and leaf net photosynthesis rates were much lower than those of G. sarothrae. However, A. tridentata in general possessed a greater leaf biomass than G. sarothrae. Green stems of G. sarothrae exhibited considerable rates of net photosynthesis under both optimal and sub‐optimal temperature and water availability conditions. A higher optimum temperature of net photosynthesis was noted for stems than for leaves of G. sarothrae. The adaptive significance of these interspecific differences in CO2 exchange characteristics is discussed.
THE GAMETOPHYTES OF OPHIOGLOSSUM PALMATUM L.
Authors: Mesler Michael R.
Published: January 2018

Gametophytes of the epiphytic species Ophioglossum palmatum L. are described for the first time, bringing the number of Ophioglossum species with known gametophytes to 11. Although somewhat unusual in terms of (a) degree of branching, (b) the marked expansion of the basically cylindrical axis in some cases, and (c) production of stout, papilla‐like rhizoids, the gametophytes of O. palmatum are more similar to other Ophioglossum gametophytes than they are to the gametophytes of Botrychium or Helminthostachys. Gametophyte characters do not provide strong evidence for placing O. palmatum into a separate genus, viz., Cheiroglossa. The gametophytes of O. palmatum most closely resemble those of the other epiphytic species in the genus, O. pendulum. This similarity suggests a need for a revaluation of modern taxonomies which, in general, treat the two species as only distantly related.
FLORAL DEVELOPMENT IN SAURURUS CERNUUS (SAURURACEAE): 1. FLORAL INITIATION AND STAMEN DEVELOPMENT
Authors: Tucker Shirley C.
Published: January 2018

The inflorescence of Saururus cernuus L. produces lateral “common” primordia in acropetal succession on the flanks of the inflorescence meristem; curiously, the “subtending” bract is initiated upon the lateral primordium rather than subtending it. On the basis of mature floral structure, flowers of S. cernuus have previously been described as having spiral initiation of parts. The current ontogenetic investigation contradicts this interpretation. Stamens arise in three successive pairs; the carpels also are initiated in pairs. Floral symmetry is shown to be bilateral from the onset of organ initiation, a rare feature among primitive angiosperms. On the basis of symmetry and paired initiation of organs, the possibility of close relationships between Saururaceae and Magnolialian or Ranalian lines appears remote.
STUDIES ON THE PHYSIOLOGY OF ABSCISSION: EFFECT OF TREATMENTS WITH GIBBERELLIC ACID
Authors: Medeghini‐Bonatti P. , Laudi G. , Fricano G.
Published: January 2018

Abscission of debladed petioles of Coleus was observed following spray applications of gibberellic acid (GA) to the foliage. Sprays were applied to some branches which were left intact (inducing branches), or to adjacent branches whose leaves were later debladed (induced branches). In all experiments three applications of GA were made after which the induced branches were debladed, but in one series deblading was delayed for a week after the last spray application. All treatments resulted in accelerated petiole abscission relative to the controls. Differences between the results of these experiments and the results of similar, earlier experiments with indoleacetic acid (IAA) are discussed. The evidence suggests that GA accelerates abscission by a different mechanism than does IAA.
CONDUPLICATE AND SPECIALIZED CARPELS IN THE ALISMATALES
Authors: Kaul Robert B.
Published: January 2018

Carpel closure and stigmatic localization in the Alismatales have accompanied decreases in carpel size and numbers of ovules per carpel and increases in carpel numbers per flower. The most specialized carpels are uniovulate and indehiscent and occur acyclically in great numbers in each flower, with strong trends toward monoecism and even dioecism. The least specialized carpels in the order are open, multiovulate, and conduplicate, with poor differentiation of style and stigma. The Alismatales show a broad range from primitive to specialized gynoecial features.
ORIGIN AND EARLY MORPHOGENESIS OF LATERAL BUDS IN THE FERN DAVALLIA
Authors: Croxdale Judith G.
Published: January 2018

The general organography, vascular organization, and leaf and bud development in Davallia solida and D. trichomanoides are described. These epiphytic species have creeping shoots with dorsally‐borne leaves in a distichous phyllotaxis and the buds occur near each leaf base. Roots are borne on the ventral and flanking surfaces of the rhizome, but only at bud positions. The vascular pattern of these species is a perforated solenostele. Leaf and bud traces have distinctly different origins. While the proximity of buds to leaves has suggested that bud origin is axillary, observations show that the origin of buds is cauline and that their position is extra‐axillary from inception. The stages of structural morphogenesis in Davallia buds differ significantly from the scheme proposed by Wardlaw. The principal difference is the absence of a resting period occurring between the origin and continued development of buds in Davallia. The elongated internodes which separate leaf‐bud pairs from one another, the topographically distinct and predictable positions of leaves and buds, the structural equivalence of unexpanded buds, and vascular differences in leaves and buds make Davallia an useful species for physiological studies of differential bud expansion.
ORGANELLE DISTRIBUTION AND APPORTIONMENT DURING MEIOSIS IN THE MICROSPOROCYTE OF GINKGO BILOBA L.
Authors: Wolniak Stephen M.
Published: January 2018

Microsporocytes of Ginkgo biloba were observed in stages of meiosis with both the light and electron microscopes. After telophase I, all of the plastids and mitochondria were located in the equatorial region of the cell and this non‐random pattern of distribution was maintained until nuclear division had ceased. The ensuing apportionment of organelles among tetrad members was approximately equal, and was coincident with centripetal formation of the partitioning walls. Although no mechanisms for the initial equatorial positioning or later dispersal of the organelles could be ascertained, membrane proliferations were prevalent and may have played a role in maintaining the pattern of organelle distribution through the duration of the second division. Microtubules, which permeate the central region of the cell may have also functioned to maintain the non‐random pattern of organelle distribution.
FLORAL DEVELOPMENT IN SAURURUS CERNUUS (SAURURACEAE). 2. CARPEL INITIATION AND FLORAL VASCULATURE
Authors: Tucker Shirley C.
Published: January 2018

Paired initiation of stamens and carpels on the apical meristem and bilateral symmetry of the flower are shown to prevail in Saururus cernuus. The carpels are initiated in two successive pairs of two members each, in a decussate arrangement. The floral apex shows plastochronic expansion in area between initiation of the last stamens and the first carpels, and also a less marked expansion between the two pairs of carpels. Vascularization appears to be whorled, with all carpels being supplied at once and at the same level. The vasculature of the flower is basically four‐stranded, such that each strand supplies a carpel and one, two, or three stamens. Carpels of a flower become unequal in size and level of attachment through post‐initiatory changes; these changes obscure the paired, decussate sequence of initiation. Phylogenetic conclusions about Saururus based on its supposedly spiral initiation of parts are in need of reexamination; Saururus exhibits a highly specialized pattern of paired organ initiation which is bilaterally organized, rather than radial and helical as in most primitive angiosperms. Vasculature of the flower involves divergence of appendage traces at approximately the same time for all stamens, and simultaneously for all carpels, contrary to previous reports that divergence is helical or spiral in succession. All carpel bundles diverge from sympodia which supply at least one stamen, also contrary to previous descriptions.
ULTRASTRUCTURAL CHARACTERISTICS OF SPORE GERMINATION IN THE MOSS DAWSONIA SUPERBA
Authors: Stetler D. A. , DeMaggio A. E.
Published: January 2018

The spore wall of Dawsonia superba has characteristics that, in many respects, are similar to those of other mosses except for the exine, which is layered in Dawsonia. Imbibed spores have a well‐developed endoplasmic reticulum with dilated cisternae that are associated with vesicles at the periphery of the cell. Ribosomes on the surface of the vesicles suggest that many vesicles originate from the endoplasmic reticulum. Two types of protein storage bodies are observed: membrane bound protein bodies with a homogeneous matrix which gradually becomes vesicular, and densely stained and non‐membrane bound bodies consisting of crystalline arrays of fibrils. As in spores of higher plants, the protein reserves disappear during germination and may be converted to starch and other materials needed for development of the gametophyte.
ULTRASTRUCTURE AND DIFFERENTIATION IN CLADOPHORA GLOMERATA. I. CELL DIVISION
Authors: McDonald Kent L. , Pickett‐Heaps Jeremy D.
Published: January 2018

Cladophora glomerata is a coenocytic, fresh‐water green alga in which mitosis and cytokinesis occur independently. The mitotic spindle is centric, closed, and develops from two half‐spindles which form from amorphous but well‐defined MTOCs at each pole. The nucleolus is only partially dispersed during mitosis and structured kinetochores are evident on the chromosomes. Anaphase separation of chromosomes is asynchronous and results from spindle elongation plus shortening of the chromosome‐to‐pole distance. Neither a phycoplast nor a phragmoplast is present during cytokinesis. Microtubules are associated with the septum but whether they participate actively in its ingrowth is not clear. Two types of vesicles are associated with the growing septum. The membrane at its leading edge is thicker and more densely stained than elsewhere. The ultrastructure of nuclear and cell division in C. glomerata is sufficiently different from the data on other green algae that conclusions about phylogeny must await further study, especially of other coenocytic green algae.
ULTRASTRUCTURAL STUDIES OF ABSCISSION IN PHASEOLUS: LOCALIZATION OF PEROXIDASE
Authors: Webster Barbara D. , Dunlap Tania W. , Craig Mary E.
Published: January 2018

Segments of leaf abscission zone tissue of Phaseolus vulgaris L. cv. Red Kidney were fixed in glutaraldehyde, incubated to demonstrate peroxidase activity in medium containing 3,3'‐diaminobenzidine (DAB) and postfixed in osmium tetroxide. Electron microscopic observation of treated tissue revealed pronounced deposition of highly electron‐opaque material in the form of granules or globules in cell walls, on mitochondrial membranes, associated with rough endoplasmic reticulum and along the plasmalemma and tonoplast. This distribution pattern was typical of both non‐treated and ethephon‐treated tissue. Ethephon‐treated material also contained these granules within cytoplasmic vacuoles. It is suggested that pH of the incubation medium may affect localization sites and that exposure of tissue to light during incubation may modify localization patterns. Differing patterns of distribution of the reaction product in treated and non‐treated tissue may reflect changes in membrane permeability and microfibrillar modifications related to ethephon treatment.
BIOSYSTEMATICS OF RUELLIA TUBEROSA L. (ACANTHACEAE)
Authors: Long Robert W.
Published: January 2018

Ruellia tuberosa is a wide‐ranging tropical, perennial herb that has been designated the type species for the large genus Ruellia. To clarify interspecific relationships, the R. tuberosa species complex, including R. nudiflora, R. malacosperma, and R. lorentziana, and R. tuberosa, has been proposed as the redefined and restricted genus Ruellia. All other Ruellia species would be transferred to segregate genera. Biosystematic investigations that included artificial hybridization experiments, herbarium comparisons, chromatographic analyses, and cytological studies demonstrated that R. tuberosa is genetically related to a number of North American temperate taxa and to certain other tropical species. The narrow definition of Ruellia cannot be supported from the biosystematic evidence at hand. Morphological comparisons suggest that R. tuberosa may be a primitive component in a broadened generic concept.
THE ABSORPTIVE CAPACITIES OF BROMELIAD TRICHOMES
Authors: Benzing David H. , Henderson Karen , Kessel Bruce , Sulak JoAnne
Published: January 2018

Tritiated glycine and leucine and microautoradiographic techniques were employed to determine whether various bromeliad species produce foliar trichomes capable of absorbing these two solutes from solutions placed on intact leaf surfaces. All trichomes borne by members of subfamily Tillandsioideae, whether on the leaf blade or sheath, accumulated both amino acids in substantial quantities. Trichomes located on the leaf sheaths of tank‐forming members of Bromelioideae absorbed much smaller quantities while trichomes located on the blades of the same tank‐producing bromelioids, as well as those of nontank‐forming members of Pitcairnioideae and Bromelioideae, took up little or none at all. The evolution of the bromeliad trichome is considered in the light of these results.
PROMOTION OF PLASTID PIGMENT ACCUMULATION IN WATER STRESSED WHEAT LEAF SECTIONS BY HORMONE TREATMENT
Authors: Duysen M. E. , Freeman T. P.
Published: January 2018

Chlorophyll (Chl) and carotenoid accumulations are markedly reduced in detached wheat leaves after 20‐hr exposure to light when subjected to mild (‐7 bar) osmotic stress prior to illumination. The treatment of N6‐benzyladenine (BA) in combination with gibberellic acid (GA) stimulated the recovery of plastid pigment accumulations in mildy stressed detached leaves. The combination treatment of BA plus IAA increased pigment accumulations only to the level stimulated by BA treatment alone. Mild water deficits increased the Chl a/b ratio and reduced the Chl/carotenoid ratio in wheat sections. Growth promoting hormones generally lowered the Chl a/b ratio and increased the Chl/carotenoid ratio in mildly stressed detached leaves. Abscisic acid (ABA) reduced plastid pigment concentrations in greening tissue and increased the Chl a/b ratio while decreasing the Chl/carotenoid ratio. In detached leaves stressed to ‐14 bars, BA in combination with GA stimulated only partial recovery of the plastid pigment accumulations and improved slightly the Chl a/b and Chl/carotenoid ratios.
THE POLLINATION BIOLOGY OF TILIA
Authors: Anderson G. J.
Published: January 2018

An anthecological study ofTiliain the Great Plains and New England was undertaken for both native and introduced species. The floral bracts are postulated as being at least as important in pollinator attraction as they are in fruit dispersal. A characteristic sweet odor is always present, but becomes stronger at dusk. Flowers are protandrous with anthers opening for the first time late in the afternoon and releasing pollen abundantly for about 24 hr. Initial nectar production coincides with stigma receptivity which begins late in the afternoon, but on the second day a flower is open. Sixty‐six species of insects in 29 families were collected. Bees and flies are the most common diurnal visitors and moths are the primary nocturnal visitors. Samples of pollen taken from the insects indicate a relatively high constancy. Experimental tests show thatTiliais not apomictic or self compatible. Anemophily plays a secondary role to entomophily in pollination. Nocturnal pollinators are slighly less effective than diurnal pollinators in effecting fruit set. Although nocturnal pollinators are favored by the syndrome of floral characteristics, it is concluded thatTiliais a generalist in regard to pollination. It is proposed that the lack of clear morphological differences betweenTiliaspecies leads to pollinator inconstancy and thus hybridization.
ANATOMICAL DEVELOPMENT OF THE LEAF TRICHILIUM AND MÜLLERIAN BODIES OF CECROPIA PELTATA L.
Authors: Rickson Fred R.
Published: January 2018

The anatomical development of trichilia and Müllerian bodies of Cecropia peltata was investigated at the light microscope level. The petiole base is initiated in a normal manner and the abaxial surface becomes keel‐shaped during later stages of development. At maturity the trichilium is well supplied with vascular tissue but no transfer cells were observed. Before Müllerian body development, trichilium epidermal cells become modified into two types of trichomes. Müllerian bodies are initiated in sub‐epidermal tissue and by continued cell division and expansion reach a size of 1 mm wide X 3 mm in length. There is no storage polysaccharide present during early stages of Müllerian body development. Glycogen production and storage begins as the food body reaches three‐fourths final size and continues after cell division ceases. The mature Müllerian body is mutlicellular and rich in lipid and glycogen.
PROCAMBIUM VS. CAMBIUM AND PROTOXYLEM VS. METAXYLEM IN POPULUS DELTOIDES SEEDLINGS
Authors: Larson Philip R.
Published: January 2018

The concept of a procambium‐cambium continuum was examined in Populus deltoides by following its development in serially sectioned bud and stem tissues. As in other species, the term cambium is used to refer to that part of the continuum associated with the formation of secondary vascular tissues; i.e., with secondary growth. However, that part of the continuum associated with the formation of primary vascular tissues is subdivided to facilitate interpretation of the consecutive stages of primary xylem differentiation. Thus, the procambium as envisioned by other authors is subdivided into procambium, initiating layer, and metacambium, all of which develop acropetally and in complete continuity. The procambium is derived from the residual meristem in the form of acropetally developing strands and traces. The initiating layer is represented by the first, tangentially separated, periclinal divisions that delineate the position of the prospective cambium. The metacambium is a later stage during which additional periclinally dividing cells unite the initiating layer into a tangentially continuous meristem within a trace bundle. After establishment of the initiating layer, the procambial trace is completely phloem dominated. Protoxylem differentiation begins in an originating center at the base of the leaf primordium and it progresses basipetally to form the protoxylem pole. Cells of the initiating layer do not contribute to the formation of either protoxylem or protophloem. However, those cells of the initiating layer directly opposite the protoxylem pole divide precociously and later differentiate to metaxylem, thus forming a radial file of protoxylem‐metaxylem elements. Protoxylem elements of lateral traces are longitudinally continuous with the protoxylem of their parent traces, whereas those of a central trace are longitudinally continuous with the metaxylem of its parent trace. Metaxylem is formed later than protoxylem and it is derived from the metacambium. Metaxylem does not form a continuous system with protoxylem of the same trace because of the different temporal and spatial origins of the two kinds of xylem. Rather, metaxylem is longitudinally continuous with secondary xylem of older traces below. An attempt was made to determine the functional significance of the pattern of protoxylem and metaxylem differentiation in relation to primary and secondary plant development.
A NEW FOSSIL ALGA FROM THE SILURIAN OF MICHIGAN
Authors: Taggart Ralph E. , Parker Lee R.
Published: January 2018

The record of Paleozoic algal diversity is strongly biased toward calcareous and stromatolitic types due to the general paucity of well preserved compression fossils of other taxa. A new genus, Thalassocystis (type species T. striata) is described on the basis of compression fossils in middle Silurian dolomite from the northern peninsula of Michigan. The plant is characterized by a short branched thallus, each branch terminated by an enlarged bladder‐like structure. The plants were deposited in a tropical, shallow water marine environment but whether they were benthic, adventive to the pelagic zone, or completely pelagic cannot be determined from the evidence available.
ORGANIZATION AND ONTOGENY OF THE VASCULAR SYSTEM IN THE PETIOLE OF EASTERN COTTONWOOD
Authors: Isebrands J. G. , Larson Philip R.
Published: January 2018

The topologic arrangement of petiolar bundles varies within the length of the cottonwood petiole. Each petiolar bundle is formed by the subdivision and aggregation of acropetally differentiating subsidiary bundles in a predictable pattern. The subsidiary bundles provide vascular continuity between the stem and specific portions of the leaf lamina. Spot‐labeling of individual veins with 14CO2, freeze substitution, and microautoradiography were used to establish the relation between the secondary veins of the lamina and the vasculature of the petiole. Within the petiole vasculature each subsidiary bundle was continuous with a specific portion of the lamina and seemed to have a separate function. Subsidiary bundles continuous with the central leaf trace were closely related functionally to the tip region of the lamina, while the subsidiary bundles continuous with the lateral leaf traces were functionally related to the middle and basal portions of the lamina.
DEVELOPMENT AND CYTOCHEMISTRY OF THE THYLAKOIDAL BODY IN TOBACCO CHLOROPLASTS
Authors: Hurkman W. J. , Kennedy G. S.
Published: January 2018

Developing plastids in young tobacco leaves contain thylakoidal bodies, inclusions bound by a single membrane continuous with stroma lamellae. Both the thylakoidal body and its attached lamellae contain an enzyme that catalyzes an oxidation reaction with 3,3'‐diaminobenzidine (DAB). DAB staining of the thylakoidal body and lamellae is not the result of photo‐oxidation and is inhibited by potassium cyanide. The thylakoidal body disappears as plastids develop into chloroplasts and, further, the lamellar systems of the mature chloroplasts do not stain with DAB. In developing chloroplasts, it is suggested that the thylakoidal body forms by accumulation of protein which stains with DAB within primary lamellae derived from the inner plastid membrane. The ultrastructural and cytochemical evidence suggests that the thylakoidal body stores protein used later in lamellar formation.
FEATURES OF DICHOTOMIZING APICES IN FLAGELLARIA INDICA (MONOCOTYLEDONES)
Authors: Tomlinson P. B. , Posluszny Usher
Published: January 2018

During vegetative growth aerial shoots of Flagellaria indica bifurcate regularly at intervals even though axillary meristems are absent. Dichotomy involves no change in the cytohistological organization of the apical meristem; the shoot apex simply enlarges in the plane of distichy, a median furrow appears, and two new equal centers of meristematic activity are constituted in a process of continuous growth. Dichotomy can occur at any stage in the plastochron, and the morphology of the leaf immediately below the fork may be modified under the influence of the two new meristematic centers. The first leaf on each of the new apices is always on the same side, so there is no mirror image symmetry. The suggestion that dichotomy is the result of precocious axillary branching is discussed but rejected.
INTROGRESSION IN TRICHOMANES
Authors: Bierhorst David W.
Published: January 2018

Anderson's graphic method of population analysis applied to a number of specimens of Trichomanes sect. Selenodesmium points to introgressive hybridization between T. polystromaticum and T. dentatum. The two species, one of which grows in a xeric habitat and the other in a very protected mesic one, tend to maintain their specific integrities in their extreme habitats. Intermediate forms which tend to grow in intermediate habitats give indication of genetic imbalance in the form of diad spore production. Peculiarities of the fern and in particular of the hymenophyllaceous life cycle are discussed in the context of hybridization.
THE PRIMARY VASCULATURE OF CORDAIANTHUS CONCINNUS
Authors: Rothwell Gar W.
Published: January 2018

The pollen strobilus Cordaianthus concinnus is examined as a possible indicator of the basic pattern of vascular architecture in stems of the Cordaitales. Bract traces arise from two points in the stele of the bilateral primary axis and diverge to the regularly arranged, four‐ranked bracts. Tracheids to the axillary secondary shoots arise as two traces that flank the position of bract trace emission. Distally, the secondary shoot traces unite to form a stele that becomes increasingly dissected at successively higher levels. Although radially aligned, these tracheids show thickening patterns on all walls and are not separated by vascular rays; they are therefore interpreted as primary xylem. The traces form sympodia that are similar to those of typical eustelic gymnosperms. Scale traces from the secondary shoots arise by the tangential division of an individual axial bundle and occur in arrangements that range from a ½ to a % spiral. The vascular architecture of these secondary axes is interpreted as the equivalent of that in the stems of extant conifers with spiral phyllotaxis.
GERMINATION ECOLOGY OF SEDUM PULCHELLUM MICHX. (CRASSULACEAE)
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

Factors controlling the timing of seed germination were investigated in the small succulent winter annual Sedum pulchellum Michx. (Crassulaceae) in its natural habitat on unshaded limestone outcrops in northcentral Kentucky. At maturity in early July the dormant seeds are not dispersed but are retained in the fruits on the standing dead plants until September and October. Many, but not all, of the seeds afterripen in the fruits during summer, and at the time of dispersal some of them are dormant and some are nondormant. Germination and annual population establishment occur in September and October from seed reserves that have been in the soil for one or more years and from seeds produced in the current year. Germination of nondormant seeds may be prevented in autumn by lack of the appropriate combination of environmental factors including light, temperature and soil moisture in the seed's microsite. The effect of low winter temperatures on ungerminated seeds in the population is to induce nondormant seeds into secondary dormancy and to prevent afterripening of dormant seeds. Thus, in spring all the seeds in the population's seed reserve are dormant. During spring and summer some of these seeds afterripen, and they germinate in autumn when, and if, germination requirements are fulfilled.
GLYCOLATE DEHYDROGENASE IN PRIMITIVE GREEN ALGAE
Authors: Floyd Gary L. , Salisbury Jeffrey L.
Published: January 2018

Glycolate dehydrogenase occurs in nine species of the Prasinophyceae. The occurrence of glycolate dehydrogenase in these unicellular flagellated organisms does not correspond to the lines of evolution suggested for the green algae based on glycolate enzymology and the nature of the spindle at telophase of mitosis. It is proposed that the evolutionary divergence of the glycolate enzyme came after the evolutionary divergence of the spindle features in the green algae.
TAXONOMIC IMPLICATIONS OF EXTERNAL POLLEN MORPHOLOGY TO VERNONIA (COMPOSITAE) IN THE WEST INDIES
Authors: Keeley Sterling C. , Jones Samuel B.
Published: January 2018

External pollen morphology of 39 species of West Indian Vernonias was examined by light and scanning electron microscopy in conjunction with a systematic revision of these species. There were three distinct types of pollen: Type A: subechinolophate, tricolporate grains with prominent spines; Type B: echinolophate, tricolporate with expanded germinal furrows and coincident polar muri; Type C: echinolophate, tricolporate grains with prominent polar lacunae. Pollen grains intermediate between the major types were found in several species. These same species had very distinct and atypical megamorphologies. In general, pollen types were found to correlate well with classification based on megamorphological characters, particularly at the infrageneric level, and to provide confirmation of subsectional assignments in the genus.
PROGRESSIVE LOSS OF ANT‐RELATED TRAITS OF CECROPIA PELTATA ON SELECTED CARIBBEAN ISLANDS
Authors: Rickson Fred R.
Published: January 2018

Cecropia of South and Central America, and Trinidad and Tobago, maintain a symbiotic relationship with Azteca ants. The plant provides a domicile and food supply and in return the ants defend the plant from insect attack and/or vine overgrowth. Cecropia is present on certain Caribbean islands, north of Trinidad and Tobago, but does not maintain a relationship with ants. The Cecropia on Puerto Rico have lost all structures normally associated with the production of the ant food. On the islands between Trinidad and Puerto Rico, stages in the loss of traits related to the ant symbiosis are present.
ULTRASTRUCTURAL AND ENZYMATIC EVIDENCE FOR THE PRESENCE OF MICROBODIES IN THE FUNGUS ACHLYA
Authors: Choinski John S. , Mullins J. T.
Published: January 2018

Ultrastructural evidence for structures resembling microbodies is presented for the fungus Achlya ambisexualis Raper. These structures are DAB positive and thus presumably contain the enzyme catalase. Activities from mycelial homogenates for. the following enzymes are given: catalase, glycolate oxidase, uricase, isocitrate lyase, malate dehydrogenase, citrate synthetase, malate synthetase and glutamate: oxaloacetate transaminase. These results suggest that Achlya contains microbodies and that they may be of the glyoxysome type. The specific activity of catalase increases substantially following initiation of antheridial hyphae by the hormone antheridiol.
THE SHOOT APICAL ONTOGENY OF THE PICEA ABIES SEEDLING. IV. PROTOXYLEM INITIATION AND AGE OF INTERNODES
Authors: Gregory Robert A. , Romberger J. A.
Published: January 2018

In Picea abies seedlings the distance below the base of the shoot apical dome to the first protoxylem (px) to be differentiated in the internodes beneath is a linear function of apical dome basal diameter. By using mathematical relations derived in earlier papers of this series, we computed the morphogenic age in plastochrons and the chronometric age in days of the internode in which px is first differentiated (npx). As the seedlings age from 30 to 140 days, the distance from the base of the apical dome to px increases from 186 to 295 μm, the n of npx increases from 16 to 53, but the chronometric age of npx remains within the range of 10 to 12 days. Protoxylem differentiation in young internodes is, therefore, more closely related to chronometrie age than it is to morphogenic age or to distance from the base of the shoot apical dome.
CHARACTERIZATION OF VACUOLAR BODIES IN SPARTINA ALTERNIFLORA: I. FORMATION, DEVELOPMENT, MORPHOLOGY, AND ULTRASTRUCTURE
Authors: Akers Stuart W. , Anderson Charles E. , Blum Udo
Published: January 2018

Spherical, golden bodies, 0.5 to 25 μm in diameter, were noted in outer bundle sheath and mesophyll of cells of fresh sections of Spartina alterniflora leaves. Attempts to further characterize these structures with light and electron microscope (EM) techniques after dehydration failed initially because these bodies were soluble in organic solvents such as alcohol. Subsequently, it was found that certain heavy metals would stabilize the structure so that dehydration techniques could be used. The resultant stabilized bodies as viewed with EM were found to reside in the cell vacuole. Two major structural components were recognized: (1) a granular matrix and (2) a non‐electron dense internal vesicle. Internal vesicles were not always present. No membranes were visible with this technique. These vacuolar bodies also were found to occur in parenchyma cells of roots, peduncles, glumes, and rhizomes of S. alterniflora. The material which forms the vacuolar body matrix is probably produced in the cytoplasm and gradually accumulates in the vacuole, forming larger and more numerous vacuolar bodies during the growing season. The matrix material remains in the leaf cells following their senescence.