bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF CO2 ENRICHMENT ON ROOT NODULE DEVELOPMENT AND SYMBIOTIC N2 REDUCTION IN PISUM SATIVUM L.
Authors: Phillips Donald A. , Newell Keith D. , Hassell Shirley A. , Felling Charles E.
Published: January 2018

A very significant increase in N2(C2H2) reduction by Visum sativum L. infected with Rhizobium leguminosarum occurred when plants were grown in the light with 6 hr of CO2 enrichment (0.00120 atm). Plants grown for 4 wk under 0.00120 atm CO2 showed significant increases over control plants at 0.00032 atm CO2 in plant dry weight, N content, root nodule mass, number of nodules, and mean nodule dry weight. Acetylene‐reduction assays, however, revealed no reproducible increase in nitrogenase activity/mg nodule in plants subjected to long‐term CO2 enrichment. Both control and CO2‐enriched plants optimized the sink/source ratio between the mass of nodules and the extranodular plant mass. The optimum ratio for N2 reduction by 4‐week‐old peas was 0.05. Long‐term CO2 enrichment did not promote root nodule formation to a greater degree than total plant development, and increases in N content were directly proportional to increases in nodule mass. Morphological data revealed significantly greater deposits of starch in root nodules of plants grown under CO2‐enriched conditions. The results are interpreted as showing that short‐term increases in CO2 levels promote N2 reduction by affecting root nodule functioning, whereas long‐term CO2 enrichment promotes N2 reduction by increasing total plant and root nodule development.
GROWTH AND GRAVITATIONAL RESPONSE IN THE DEVELOPMENT OF LEAF BLADE HYPONASTY
Authors: Hayes Alice B. , Lippincott James A.
Published: January 2018

Rapid (4 hr) auxin‐induced hyponastic curvature of primary leaves of Phaseolus vulgaris is shown to depend on a positive increase in growth of the lower portion of the blade. The curvature involves laminar growth as well as vein growth and is not due to simple turgor changes. The response is sensitive to gravitational orientation, as inversion and horizontal rotation reduce the auxin‐induced curvature. The ethylene‐generating compound, 2‐chloroethylphosphonic acid, had no hyponastic effect on the leaves when applied to either the upper or lower surface and it inhibited auxin‐induced hyponasty. This inhibition was additive to that of inversion. Long‐term (24–48 hr) effects of 1 mM auxin depend on the surface of the leaf treated. Application to the upper surface results in epinasty, lower surface application in hyponasty, although the initial response in each case is a hyponastic curvature. A dorsi‐ventral auxin transport system and differential auxin sensitivity of upper and lower portions of the leaf blade are postulated to account for these responses.
GAMETOPHYTES AND YOUNG SPOROPHYTES OF OPHIOGLOSSUM CROTALOPHOROIDES WALT.
Authors: Mesler Michael R.
Published: January 2018

The lens‐shaped, dorsiventral gametophytes of Ophioglossum crotalophoroides are superficially different from the cylindrical gametophytes of other species of Ophioglossum. However, they have the same features as other Ophioglossum gametophytes (fundamentally axial organization, radially symmetrical apical meristem, radial distribution of gametangia) except that the cylindrical axis is reduced in length. Young sporophyte development is unique in the genus: all primary organs clearly arise from the embryo and develop simultaneously. The length of the life cycle of O. crotalophoroicles is considerably shorter than that of some other species in the Ophioglossaceae. A timetable for gametophyte and young sporophyte development is postulated. Spores germinate soon after they are released in the spring, and mature gametophytes develop by the next growing season. Fertilization occurs approximately one year after spore dispersal, and after two years, the photosynthetic first leaf of the young sporophyte emerges.
SPORE MORPHOLOGY IN THE CYATHEACEAE. II. THE GENERA LOPHOSORIA, METAXYA, SPHAEROPTERIS, ALSOPHILA, AND NEPHELEA
Authors: Gastony Gerald J. , Tryon Rolla M.
Published: January 2018

Scanning electron microscopy and transmitted light microscopy are used in a palynological study of Lophosoria, Metaxya, Sphaeropteris, Alsophila, and Nephelea of the tree fern family Cyatheaceae. The monotypic American genera Lophosoria and Metaxya each have a unique spore morphology which reinforces the taxonomic distinctness of these genera as indicated by their other characters. All investigated paleotropical species of Sphaeropteris develop a single type of perine characterized by coarse, pointed projections. In the neotropics, the Sphaeropteris horrida group shares this perine type, whereas all other neotropical Sphaeropteris species appear to have a different kind of perine with fine hair‐like processes. The exine in paleotropical Sphaeropteris appears uniformly unsculptured, whereas in the neotropics several exine morphologies are found. In Alsophila all investigated neotropical species and the vast majority of the paleotropical species are characterized by a basically ridged perine morphology and an unsculptured exine. In several paleotropical Alsophila species, however, a perine with hair‐like processes similar to those in neotropical Sphaeropteris is found, and the exine in several species is variously pitted. In at least one paleotropical Alsophila species, the porate exine morphology is indistinguishable from that in the neotropical genus Cnemidaria. The spores of the American genus Nephelea are similar to those of the majority of Alsophila species in ridged perine morphology and unsculptured exine. Several new instances of atypical spore numbers per sporangium are reported in Sphaeropteris and Alsophila. These and the palynological data are discussed in a taxonomic framework. The spore morphology in these genera is consistent with Tryon's recent generic revision of the family.
MORPHOLOGICAL STUDIES IN PODOSPORA ANSERINA
Authors: Mai Shing H.
Published: January 2018

Perithecium development in Podospora anserina begins with the formation of a coiled ascogonial initial that arises as a lateral branch from a vegetative hypha. Hyphae grow up around the initial, forming an envelope that will become the ascocarp wall. As the ascocarp increases in size, several layers of thin‐walled pseudoparenchyma cells form inside the wall, especially at the apex of the ascocarp. Paraphyses arise both from the base of the ascocarp and from the innermost layer of pseudoparenchyma cells and grow inward and upward, completely filling the centrum with tightly packed filaments. During development of the ascocarp the ascogonium proliferates to form ascogenous hyphae along the base of the centrum. Asci arise from the ascogenous hyphae and grow up among the paraphyses. Meristematic growth at the ascocarp apex results in the formation of an ostiole lined with periphyses. Centrum structure in P. anserina could be interpreted as intermediate between the Xylaria and Diaporthe types.
THE ULTRASTRUCTURE OF SCHOPFIPOLLENITES: ORBICULES AND TAPETAL MEMBRANES
Authors: Taylor Thomas N.
Published: January 2018

Electron microscopy of in situ fossil (Pennsylvanian) pollen assignable to the taxon Schopfipollenites indicates the presence of orbicules and tapetal membranes similar to those associated with the secretory tapetum of extant plants. Orbicules are spheroidal, hollow and associated with a complex tapetal membrane system. Each membrane is three‐parted, consisting of two thin layers attached by beads of electron‐dense material. A thicker, outer layer is suggestive of the orbicule reticulum described in some angiosperm families. A comparison between the fossil orbicules and membrane systems and those of extant plants is presented.
ADVENTITIOUS ROOT DEVELOPMENT FROM THE COLEOPTILAR NODE IN ZEA MAYS L.
Authors: Martin Elizabeth M. , Harris William M.
Published: January 2018

Department of Botany and Bacteriology, University of Arkansas, Fayetteville, Arkansas 72701

Zea mays L. root development from the coleoptilar node was observed by light and electron microscopy. Roots developed opposite collateral vascular bundles in the coleoptilar nodal region. Three distinct histogens (stelar, cortical‐protoderm, and root cap) became evident in early development. In median sections of the young roots, root cap and cortical regions formed a “hat” configuration over the stelar region. As the root matured, this “hat” developed centripetally to encapsulate the stelar region. Central core cells of the root cap were characterized by having numerous dictyosomes, amyloplasts, vacuoles, and thin cell walls. As these cells matured into outer or peripheral cap cells, the Golgi vesicles became hypertrophied. These hypertrophied vesicles contained a granular PAS‐positive material which accumulated between the plasma membrane and the cell wall and formed a thick layer. As the PAS‐positive material passed through the cell wall, it changed to a fibrillar texture. A PAS‐positive material similar to that in the outer root cap cells was found adjacent to the outer walls of the protodermal cells. In median sections, PAS‐positive material was not present in the promeristem region. Root cap cells as well as parent cortical cells were crushed as the young root forced its way through the parent tissue.
GIBBERELLIC ACID‐INDUCED GERMINATION OF SPORES OF ANEMIA PHYLLITIDIS: NUCLEIC ACID AND PROTEIN SYNTHESIS DURING GERMINATION
Authors: Raghavan V.
Published: January 2018

The distribution and synthesis of nucleic acids and proteins during gibberellic acid‐induced germination of spores of Anemia phyllitidis were studied in order to relate biochemical activity with morphogenetic aspects of germination. Germination is accompanied by the hydrolysis of storage protein granules and the localized appearance of cytoplasmic RNA, protein, and insoluble carbohydrates in a small area adjoining the spore wall and surrounding the nucleus. The protoplast of the spore enlarges in this region, the spore wall breaks and a protonemal cell is formed which contains many chloroplasts. A second division in the spore at right angles to the first yields a rhizoid cell. Autoradiography of 3H‐thymidine incorporation has shown that DNA is synthesized both in the nucleus and in the immediately surrounding cytoplasm of the germinating spore until some time after the first division, although a strictly nuclear DNA synthesis is observed later. Synthesis of RNA and proteins is limited to the presumptive regions of the germinating spore which become the protonema and rhizoid, shifting to specific sites in these cells as germination proceeds. The nucleus of the spore continues to be biosynthetically active long after it ceases to divide.
LONG‐TERM DEVELOPMENTAL CHANGES IN XANTHIUM INDUCED BY GIBBERELLIC ACID
Authors: Maksymowych Roman , Cordero Robert E. , Erickson Ralph O.
Published: January 2018

One application of gibberellic acid (GA3) to Xanthium shoots resulted in an initial large stimulation, followed by inhibition, of internode elongation. After presumed translocation of the hormone from the locus of its application to the stem apex several morphological changes were observed. There was a significant increase in number of mitotic figures in the apical meristem and a twofold increase in volume of the apical dome. With time, the rate of leaf production was accelerated about 1.8 times. The phyllotaxis of leaf primordia initiated under the influence of GA:, changed from a (2, 3) contact parastichy pattern in control shoot to a (3, 5) pattern. Final petiole length was smaller than the control, and the absolute rate of lamina expansion decreased under prolonged treatment. Gibberellic acid had a pronounced effect on leaf morphology. GAa induced the development of lanceolate leaves instead of typical deltoid leaves. The reduction in leaf area coincided with a 32% reduction in the average area of epidermal cells. Plastochron changes were correlated with anatomical and morphological changes during the course of leaf development.
STUDIES OF PALEOZOIC SEED FERNS: ANATOMY AND MORPHOLOGY OF MICROSPERMOPTERIS APHYLLUM
Authors: Taylor Thomas N. , Stockey Ruth A.
Published: January 2018

The discovery of numerous specimens of the monostelic pteridosperm genus Microspermopteris in Pennsylvanian coal ball petrifactions from the Lewis Creek and What Cheer localities provides additional information about the anatomical and morphological variability within the genus. Specimens are now known up to 1.1 cm in diam that bear epidermal appendages in the form of variously‐shaped trichomes. The external surface of the stem is further ornamented by longitudinal flaps of cortical tissue. Petioles exhibiting a single C‐shaped vascular strand with abaxial protoxylem are produced in a 2/5 phyllotaxy. Large petiole bases that clasp the stem produce primary pinnae alternately. The presence of axillary branching appears similar to that reported in Callistopliyton and Lyginopteris. Triarch to polyarch adventitious roots, some with secondary tissues, are produced at both nodal and internodal regions. Of the currently recognized monostelic seed fern genera, Microspermopteris is most similar to Heterangium. Information is presented that supports current ideas regarding the evolution of the gymnospermic eustele from protostelic Devonian ancestors.
HENRICKSONIA (ASTERACEAE‐COREOPSIDINAE), A NEWLY DISCOVERED GENUS WITH A PALEACEOUS PAPPUS FROM NORTH‐CENTRAL MEXICO
Authors: Turner B. L.
Published: January 2018

A new genus, Henricksonia, containing the single species H. mexicana, has been described from a locality in north‐central Mexico. It is unique among the genera of the subtribe Coreopsidinae in possessing a pappus of well‐developed scales such as frequently occurs in other subtribes of the Heliantheae. The discovery of four, previously uncollected, monotypic genera among several tribes of the Asteraceae from this region over the past several years suggests that the area is a primary center of diversification for this large family.
ON THE RELEASE OF SPERMS IN ATRICHUM
Authors: Paolillo D. J.
Published: January 2018

An antheridium of Atrichum contracts when it opens. This contraction rapidly ejects much of the mass of sperms because a fluid present in the base of the antheridial chamber acts as an hydraulic ram. The residue of sperms is slowly extruded as the same fluid takes up water. Photographs allow the construction of time courses that directly demonstrate the existence of two phases (rapid vs. slow) in sperm release. Antheridia open as quickly in 1 m sucrose as they do in water. Molar sucrose allows only the rapid phase of sperm release, caused by the contraction of the jacket, and the antheridia remain only partly emptied. This behavior in sucrose solution provides a convenient test for similarities among antheridia. The mechanism of sperm release that occurs in Atrichum occurs in Polytrichum and Mnium as well.
FOLIAR PENETRATION OF NAPHTHALENEACETIC ACID: ENHANCEMENT BY LIGHT AND ROLE OF STOMATA
Authors: Greene Duane W. , Bukovac Martin J.
Published: January 2018

Light enhanced the penetration of naphthaleneacetic‐1‐14C acid (NAA) into the stomatous lower surface of pear (Pyrus communis L. cv. Bartlett) leaf discs. The light effect was rapidly lost on transfer to the dark and was diminished by pretreatment of leaf discs with a Hill reaction inhibitor (2‐chloro‐4‐ethylamino‐6‐isopropyl‐amino‐s‐triazine). The effect of light on NAA penetration was isolated from its effect on stomatal opening. A similar stimulation of NAA penetration was obtained with stomata opened and closed, providing evidence that penetration did not take place by mass movement into the substomatal chamber.
ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE ANTHOCEROTALES. I. THE BLEPHAROPLAST AND ANTERIOR MITOCHONDRION IN PHAEOCEROS LAEVIS: EARLY DEVELOPMENT
Authors: Moser John W. , Duckett Jeffrey G. , Carothers Zane B.
Published: January 2018

Electron microscopic examination of thin sections showed that the blepharoplast of a young spermatid of Phaeoceros consists of two side‐by‐side centrioles and an accumulation of osmiophilic, granular matrix at their proximal ends. Lying between these nearly parallel organelles is a dark‐staining body that will later disappear at the onset of flagellogenesis. For a brief period the centrioles are oriented perpendicular to the nuclear surface so that the granular matrix at their proximal ends is confluent with the nuclear envelope; furthermore, the nucleoplasm immediately in front of the centrioles becomes densely staining. The multilayered structure (MLS) develops directly under the centrioles. It comprises a band of 12 microtubules (the S1 stratum) and three lower strata (S2–4) whose constitutent lamellae are oriented at an oblique angle to the S1 axis. While the S1 tubules grow rearward over the nucleus which forms a beak adjacent to the posterior end of the lamellar strata, the centrioles are transformed into basal bodies with the distal growth of the axonemes and the proximal growth of the central cartwheels and lowermost triplets. The proximal ends of the basal bodies and the S1 tubules overlying the lamellar strata are invested with osmiophilic matrix that extends down to the S2 layer and may temporarily occlude the lamellar plates. At the onset of nuclear elongation an anterior mitochondrion becomes situated close beneath the lamellar strata which extend laterally beyond the S1 tubules.
KARYOLOGY DURING CONIDIOGENESIS IN GLIOMASTIX MURORUM: LIGHT MICROSCOPY
Authors: Hammill Terrence M.
Published: January 2018

Light microscopic observations of nuclear behavior (karyology) during conidiogenesis in the long, narrow phialides of Gliomastix murorum (Corda) Hughes are presented and discussed. Nuclei were observed mostly in a submedian position in phialides. The onset of mitosis was signalled by an increase in the size of nuclei and by the appearance of numerous chromatinic granules (chromosomes?). The number of chromatinic granules appeared to decrease, while the chromatin was arranged in the characteristic “double track” associated with somatic nuclear divisions in hyphomycetes. Transverse separation of the “double track” arrangement produced two daughter chromatinic masses which stained intensely, were small, and moved apart. Separation of daughter chromatinic masses (nuclei) appeared to be largely a function of migration of distal daughter nuclei several micrometers toward phialidic apices; the submedian position of proximal daughter nuclei was maintained. Upon movement of migrating distal daughter nuclei into conidial initials, conidia were delimited septally. Conidial nuclei remained condensed, while daughter nuclei remaining in phialides decondensed (i.e., enlarged and stained less intensely), thereby entering interphase. Repeated, single nuclear divisions and migrations were correlated with repeated conidial development. Karyological events described herein were compared with other published studies of both phialidic and non‐phialidic species, and a “phialidic pattern” of nuclear behavior was suggested as a possibility. But, apparently a non‐phialidic pattern cannot yet be suggested.
STRUCTURE OF GRAVITY‐SENSITIVE SHEATH AND INTERNODAL PULVINI IN GRASS SHOOTS
Authors: Dayanandan P. , Hebard Frederick V. , Baldwin Van D. , Kaufman Peter B.
Published: January 2018

The location and some morphological, anatomical, and functional aspects of the gravity‐sensitive pulvini of a selected number of grass shoots are examined. There are two distinct gravity‐sensitive regions near the nodal regions of Gramineae. One, the leaf sheath pulvinus, is located at the base of the sheathing leaf bases, and is characteristic of the subfamily Festucoideae. The other, the internodal pulvinus, is located at the base of the internode, a little above the nodal joint. Most members of the Panicoideae possess internodal pulvini, in addition to more or less developed leaf sheath pulvini. Three members of the Oryzoideae examined possess leaf sheath pulvini only, while Phragmites australis (Arundinoideae) possesses both leaf sheath and internodal pulvini. Leaf sheath pulvini of some grasses develop hairs, cork‐silica cell pairs or stomatal apparatuses over the epidermis while many others are devoid of any such idioblasts. Both the leaf sheath and internodal pulvini of all grasses examined preferentially exclude, or accumulate very little silica, whereas the regions of the shoot immediately above and below the pulvini in these same grasses accumulate large quantities of silica. Pulvini remain unsilicified or poorly silicified throughout their life and even after several days following geotropic bending. Pulvini are also distinguished from the regions above and below them by the lack of lignin in the bundle cap cells. Lignin is found only in the xylem vascular tissue, and this consists of annular and helical vessel elements only. The bundle cap cells are rich in pectin and are described as collenchymatous. All pulvini possess specialized zones of cells containing starch statoliths. In response to horizontal displacement of the shoots, the lower side of the pulvini grows by cell elongation only. The collenchymatous cells stretch in a manner that results in alternately thin and thick regions of cell wall.
MORPHOLOGICAL ABERRATIONS IN TYPHA POPULATIONS IN A POST‐THERMAL AQUATIC HABITAT
Authors: Suda Janet R. , Sharitz Rebecca R. , Straney Donald O.
Published: January 2018

Morphological aberrations in Typha populations inhabiting a once thermally stressed aquatic system on the Savannah River Plant in South Carolina were investigated by using both morphological and enzymatic procedures. No evidence of hybridization or introgression between T. latifolia and T. domingensis was found. Exposures of these populations to postthermal conditions and low levels of radiocesium were judged insignificant in contributing to the morphological differences observed. Both genotypic flexibility and plasticity appear to be critical factors in the adaptation of Typha to varied environments.
INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: A MIMOSOID INFLORESCENCE
Authors: Crepet W. L. , Dilcher D. L.
Published: January 2018

Six examples of a spicate inflorescence from the Middle Eocene Claiborne Formation in western Tennessee have been investigated. Individual flowers are small, alternately arranged, nearly sessile, and perfect. The style protrudes 2 mm beyond the floral envelope and terminates in a slightly swollen, rounded stigma. Both the style and the stigma are hairy. Ten stamens are exserted and extend 5 mm beyond the floral envelope. Anthers are small, versatile, and dehisce longitudinally. Pollen grains are tricolporate, tectate, and are in permanent tetrahedral tetrads 32 μm in diameter. Comparison of the fossil inflorescences with those of extant families having multiple pollen grain configurations suggests that the fossil inflorescences are most closely allied to the subfamily Mimosoideae of the Leguminosae. These are the first structurally documented remains of the Mimosoideae from the Middle Eocene.
PINUS TRIPHYLLA AND PINUS QUINQUEFOLIA FROM THE UPPER CRETACEOUS OF MASSACHUSETTS
Authors: Robison Coleman R.
Published: January 2018

Dwarf shoots and needle leaves of Pinus triphylla Hollick and Jeffrey and P. quinquefolia Hollick and Jeffrey have been discovered recently in a Late Cretaceous age clay deposit on Martha's Vineyard Island, Massachusetts. Detailed study of these fossils provides further information on the internal construction of the two taxa. This new information permits both species to be compared easily with similar fossil forms from the Upper Cretaceous of Japan as well as with dwarf shoots and needles of modern species of Pinus. As a result, the relationships between Cretaceous pines and the extinct genus Prepinus are found to be less than previously believed. Moreover, the dwarf shoots and needles of Cretaceous members of the genus Pinus appear to be most like those of present‐day species included in the subgenus Pinus.
AXILLARY BUD DEVELOPMENT IN POPULUS DELTOIDES. I. ORIGIN AND EARLY ONTOGENY
Authors: Larson Philip R. , Pizzolato Thompson D.
Published: January 2018

Origin and early development of axillary buds on the apical shoot of a young Populus deltoides plant were investigated. The ontogenetic sequence of axillary buds extended from LPI –1 (Leaf Plastochron Index) near the apical bud base to LPI –11, the fifth primordium below the bud apex. Two original bud traces diverged from the central (C) trace of the axillant leaf and developed acropetally. During their acropetal traverse the original bud traces gave rise to three pairs of scale traces. All subsequent scale traces, and later the foliar traces, were derived by divergencies from the first two pairs of scale traces. Just before the bud vascular system separated from that of the main axis, a third pair of traces diverged from the original bud traces to vascularize the adaxial scale. Concomitantly, the original bud traces were inflected toward the main vascular cylinder where they developed acropetally and eventually merged with the left lateral trace of the leaf primordium situated three nodes above the axillant leaf; they did not participate in further vascularization of the bud. During early ontogeny a shell zone formed concurrent with initiation of the original bud traces and lay interjacent to them. The shell zone defined the position of the cleavage plane that formed between the axillary bud and the main axis. The axillary bud apex first appeared in the region bounded laterally by the original bud traces and adaxially by the shell zone. Following divergence of the main prophyll traces from the original bud traces, the apex assumed a new position intermediate to the prophyll traces. Ontogenetic development suggested that the axillary bud apex may have been initiated by the acropetally developing original bud traces under the influence of stimuli arising in more mature vegetative organs below.
WELWITSCHIA MIRABILIS AND NEOTENY
Authors: Martens P.
Published: January 2018

The adult Welwitschia is generally considered to be “a persistent seedling” and a classical example of neoteny. In the author's opinion, and after twenty years study of the plant, the neotenic interpretation appears inadequate. The question is to inquire if authentic juvenile characters persist in the adult stage; when closely considered, the answer is, they do not. Welwitschia is not a neotenic, but a “handicapped” plant. In a proper sense, it has “lost its head” at an early stage. Hundreds, or even a thousand years later, it still produces new roots, new buds, new branches, and new bracteal leaves, i.e., vegetative productions. Without invoking any intervention of neotenic agents, the history of the plant may be reduced to seven events, each one with its ineluctable morphogenetic consequence. Starting with these views, it is possible to imagine several experimental approaches, designed to throw some light on the phyletic problem.
MORPHOLOGICAL AND PHYSIOLOGICAL CHARACTERISTICS OF AN ACHLOROPHYLLOUS MUTANT SOYBEAN VARIETY SUSTAINED TO MATURATION VIA GRAFTING
Authors: Noble R. D. , Czarnota C. D. , Cappy J. J.
Published: January 2018

An achlorophyllous lethal‐yellow (LY) soybean mutant was demonstrated to be capable of survival when provided with a suitable carbon source. In this study the carbon source was a normally pigmented soybean plant to which the LY was grafted. When grafted to a green plant the LY grew to maturity and produced viable seeds. Under moderate to high light intensities the LY leaves possessed virtually no chlorophyll; however, under low levels of continuous illumination the chlorophyll content of LY leaves increased greatly and these leaves were then capable of limited photosynthetic activity. Under the low‐light conditions, LY plants could survive, independent of grafting, for several weeks. A major genetic difference in the LY when compared to its chlorophyllous counterparts appears to be a tendency for rapid chlorophyll degradation rather than inability to synthesize it.
POLLEN OF KLOTZSCHIA (UMBELLIFERAE): A POSSIBLE LINK TO ARALIACEAE
Authors: Shoup Jane R. , Tseng Charles C.
Published: January 2018

The sexine stratification of the pollen of Klotzschia (Umbelliferae) is strikingly similar to that of many Araliaceae, forming a possible link between the putative ancestral araliaceous type and more specialized umbelliferous types. Among the three species of Klotzschia, the tectal surface sculpture of K. rhizophylla appears to be intermediate between that of K. glaziovii and K. brasiliensis.
THE DEVELOPMENT OF ISOLATED ROOTS OF COMPTONIA PEREGRINA (MYRICACEAE) IN CULTURE
Authors: Goforth Patricia L. , Torrey John G.
Published: January 2018

Seedling roots of the sweet fern Comptonia peregrina (L.) Coult. were excised aseptically and cultured in a modified Bonner‐Devirian liquid nutrient medium. Root elongation was very slow in the basic medium which contained inorganic salts, B‐vitamins, trace elements and 4 % sucrose. The addition of plant hormones including gibberellic acid, indoleacetic acid, and zeatin, alone or in combinations, had little effect on growth. Myoinositol at 10 or 100 ppm doubled the rate of elongation. The effect of this sugar alcohol could not be replaced by scyllitol, D‐sorbitol, D‐mannitol or by increasing the sucrose concentration. Subcultured root tips showed progressively less elongation in successive transfers. Secondary thickening of the roots, especially in the basal half, occurred in initial passages and in subcultured roots without added hormones. Root buds also occurred spontaneously especially in the basal portions of cultured roots, both in first and in successive passages. An anatomical analysis showed that these buds were endogenous, arising from a secondary cortex of pericyclic origin.
VARIATION IN SEED SIZE WITHIN A CROP OF A COSTA RICAN MUCUNA ANDREANA (LEGUMINOSAE)
Authors: Janzen Daniel H.
Published: January 2018

The mature viable seeds within the seed crop of one individual of Costa Rican Mucuna andreana varied in fresh weight from 2.6 to 9.4 g (average of 6.81 g, s.d. = 1.09 g, n = 282). The seed coats weighed 14 to 17 percent of the fresh seed weight and variation in their weight was not the cause of the variation in seed weight. There was no significant difference in average seed weight of seeds from pods with 1 to 5 filled seeds. The great range of seed weights within one plant's seed crop is interpreted as possibly of adaptive significance in generating a more homogeneous seed shadow than would be the case with a narrow range of seed weights.
ULTRASTRUCTURAL DEVELOPMENT OF CAPITATE GLANDULAR HAIRS OF CANNABIS SATIVA L. (CANNABACEAE)
Authors: Hammond Charles T. , Mahlberg Paul G.
Published: January 2018

The capitate‐sessile and capitate‐stalked glands of the glandular secretory system in Cannabis, which are interpreted as lipophilic type glandular hairs, were studied from floral bracts of pistillate plants. These glands develop a flattened multicellular disc of secretory cells, which with the extruded secretory product forms the gland head and the auxiliary cells which support the gland head. The secretory product accumulates beneath a sheath derived from separation of the outer wall surface of the cellular disc. The ultrastructure of secretory cells in pre‐secretory stages is characterized by a dense ground plasm, transitory lipid bodies and fibrillar material, and well developed endoplasmic reticulum. Dictyosomes and dictyosome‐derived secretory vesicles are present, but never abundant. Secretory stages of gland development are characterized by abundant mitochondria and leucoplasts and by a large vacuolar system. Production of the secretory product is associated with plastids which increase in number and structural complexity. The plastids develop a paracrystalline body which nearly fills the mature plastid. Material interpreted as a secretion appears at the surface of plastids, migrates, and accumulates along the cell surface adjoining the secretory cavity. Extrusion of the material into the secretory cavity occurs directly through the plasma membrane‐cell wall barrier.
INFLORESCENCE DEVELOPMENT IN BRASSICA CAMPESTRIS L.
Authors: Orr Alan R.
Published: January 2018

Vegetative seedlings of the Ceres strain Brassica campestris L., a quantitative, long‐day plant, were induced to flower by exposure to a 16‐hr, long‐day cycle. Cytohistological and cytohistochemical changes associated with inflorescence development were examined. Developing shoot apices were classified in vegetative, transitional, and reproductive stages. The vegetative apex possessed a biseriate tunica, central zone, peripheral zone and pith‐rib meristem. The transitional stage at 48 hr was marked by an increase in size and by a stratification of the upper cell layers of the shoot apex with a concurrent decrease of apical cytohistochemical zonation. The reproductive stage was initiated at 58 hr by periclinal cell divisions in the 3rd and 4th cell layers of the flank region. Cytohistochemical zonation in the vegetative apical meristem was restored in the floral apex. An “intermediate developmental” phase was not observed between the vegetative and reproductive stage.
SPECIAL PAPER: PLANT GROWTH CHAMBERS ON SPACELAB: A CALL FOR SCIENTIFIC INPUT
Authors: Sweet Haven C. , Tremor John W.
Published: January 2018

Various members of the scientific community have proposed that plant experiments be performed on board the space shuttle. To permit the proper execution of most tests, the craft must contain a plant‐growth chamber which controls those environmental factors which can influence a plant's physiology and morphology. In this paper, the various needs of, and environmental factors affecting plants in such a space chamber, have been identified. A set of design, construction, and performance limits which are compatible with both physiological requirements and constraints imposed by the space shuttle have been proposed. These specifications are presented in the hope of stimulating input from the scientific community so that the final chamber design selected by NASA will be representative of botanists' needs.
LEAF DEVELOPMENT OF RUMEX PATIENTIA L. (POLYGONACEAE) EXPOSED TO UV IRRADIATION (280‐320 NM)
Authors: Dickson Judith G. , Caldwell Martyn M.
Published: January 2018

Two factors which affect leaf ontogeny and ultimate leaf size: (1) the rate and duration of cell expansion, and (2) the rate and duration of cell division, were examined for their role in the slower early leaf growth rate and the smaller size of fully expanded leaves of plants exposed to ultraviolet‐it (UV‐B 280‐320 nm) radiation. Rumex patientia L. was grown in controlled environment chambers under enhanced UV‐B radiation (equivalent to daily solar UV‐B irradiation at 40°N latitude in mid‐May with an atmospheric ozone concentration of 0.20 atm‐cm) and control treatments. The pattern of growth as expressed in changes of mean cell size in two distinct cell types, tissue cell density, and length of the entire leaf blades are consistent with the hypothesis that the radiation primarily affects cell division rather than cell expansion. Furthermore, it appears that the radiation probably alters the rate rather than the duration of the cell division phase. An understanding of the mechanism of radiation damage should facilitate prediction of how this stress may interact with other stresses to which plants are normally subjected. Species with normally prolonged periods of cell division during leaf expansion may be particularly impacted if solar UV radiation were intensified as a result of atmospheric ozone reduction.
ULTRASTRUCTURE OF THE CUTICLE OF OHELO (VACCINIUM RETICULATUM)
Authors: Singh Adya P. , Hemmes Don E.
Published: January 2018

When viewed by electron microscopy of thin sections, the inner two‐thirds of the petiolar cuticle of Vaccinium reticulatum appears dense and is penetrated by a channel‐like reticulum which emanates from the primary cell wall. The outer one‐third of the cuticle stains lightly and is homogeneous. This arrangement is compared with the ultrastructure of cuticle previously reported for other plant species.
POLLEN TUBE‐SYNERGID INTERACTIONS IN PROBOSCIDEA LOUISIANICA (MARTINEACEAE)
Authors: Mogensen H. Lloyd
Published: January 2018

The ultrastructure of the synergids of Proboscidea louisianica was investigated from just before fertilization until 48 hr after pollination. It was found that the cytoplasm of one synergid consistently begins to degenerate before arrival of the pollen tube at the embryo sac, and that it is always this synergid which receives the pollen tube tip and its discharge. The other synergid (persistent synergid) remained unchanged throughout the study period. Polysaccharide vesicles of pollen tube origin were observed fusing with the pollen tube wall as well as contributing to cell wall formation of the degenerate synergid. In one ovule (48 hr after pollination) two pollen tubes had entered and grown the length of the micropyle, but only the first tube penetrated the degenerate synergid and discharged normally. The second pollen tube was abutting against the persistent synergid, but had not entered or discharged. In another exceptional case (18 hr after pollination), a pollen tube had grown the length of the micropyle, but did not discharge, or enter either synergid. Both synergids of this ovule were observed to be completely intact. It is concluded that synergid and pollen tube cytoplasmic degeneration is the result of a very specific interaction between these two cells and that this degeneration is probably a prerequisite for normal pollen tube entrance and discharge into the embryo sac, and for male gamete transfer to the egg and central cell.
CELL WALL CHEMISTRY AND FINE STRUCTURE IN LEPTOIDS OF DENDROLIGOTRICHUM (BRYOPHYTA): THE END WALL
Authors: Scheirer Daniel C.
Published: January 2018

Leptoids (sieve elements) of Dendroligotrichum are characterized by a highly oblique end wall which is composed of cellulose (birefringent; IKI‐H2SO4‐positive), polyuronides (toluidine blue‐positive), pectins (hydroxylamine‐positive) and natural aldehydes (silver hexamine and silver proteinate‐positive). Cytochemically the end wall appears identical to the unevenly thickened lateral wall. Electron cytochemical localization of aldehydes with silver proteinate reveals two distinct wall layers in comparison to the 3‐layered lateral wall. Plasmodesmata are present in the end wall with a frequency of 15‐20 per μm2. A characteristic feature of end wall plasmodesmata is an expanded median cavity which is 0.12‐0.15 μm in diameter. Frequently an electron‐dense substance, whose chemical nature and origin are unknown, occludes the plasmodesmata.
CAUSES OF DECREASES IN PRODUCTIVITY IN UNDISTURBED TALL GRASS PRAIRIE
Authors: Rice Elroy L. , Parenti Robert L.
Published: January 2018

There is abundant evidence that protection of the tall grass prairie from grazing, mowing, or burning for even a few years results in accumulation of much litter and reduced productivity. This reduced productivity has been attributed primarily to either the insulating effect of the litter, a lowered rate of mineral recycling, or a presence of toxins in the litter. Considerable evidence exists in the literature concerning the first suggestion, but no studies have been reported concerning the last two in grasslands. A comprehensive project was conducted during the growing season of 1977 in a tall grass prairie in Oklahoma to investigate the three suggestions. It was clear from our data that increased productivity as a result of mowing and burning was not due to the elimination of toxins nor to an increased rate of turnover of organic matter. Soil moisture stress was greater in the mowed and burned plots than in the controls. Thus, the single factor examined which was consistently different, and likely to explain the increased productivity, was the higher soil temperature in the burned and mowed plots early in the growing season. The four dominant grasses in the study plots are non‐Festucoid species which are known to have high optimum temperatures for growth.
DISTRIBUTION ECOLOGY OF HAPLOPAPPUS AND CHRYSOTHAMNUS IN THE MOJAVE DESERT. I. NICHE POSITION AND NICHE SHIFTS ON NORTH‐FACING GRANITIC SLOPES
Authors: Cody Martin L.
Published: January 2018

The close systematic affinities between the composite genera Haplopappus and Chrysothamnus, including different points of contact with “intergeneric” hybrids, are reviewed. The Mohave Desert has several shrubby representatives of each genus, and at census sites from the east‐central New York Mountains to buttes at the extreme western end of the desert, north‐facing granitic slopes at the foothills of mountain ranges support four Haplopappus species (H. cuneatus. H. laricifolius, H. linearifolias and H. cooperi) and one Chrysothamnus (C. teretifolius). These five species occupy “distributional niches” represented as ranges and areas of dominance on the habitat plane of slope angle and proportion of rocks in the substrate. Central desert sites have four species (excluding C. teretifolius); peripheral desert sites always include C. teretifolius rather than H. laricifolius and support two to four species depending on the size and isolation of the suitable habitat area. Species may occupy different positions on the habitat gradient depending on species number at the site, moisture availability, and in particular competition from other species. C. teretifolius appears to be favored when population turnover rates are high, either in disturbed sites or on natural islands of habitat.
ULTRASTRUCTURE OF NON‐ARTICULATED LATICIFERS IN MATURE EMBRYOS AND SEEDLINGS OF ASCLEPIAS SYRIACA L. (ASCLEPIADACEAE)
Authors: Wilson Kathryn J. , Mahlberg Paul G.
Published: January 2018

The protoplast of the non‐articulated branched laticifer in the embryo and seedling of Asclepias syriaca L. was studied at the ultrastructural level and was found to differ from that of adjacent cell types. Embryonal laticifers possess numerous vesicles with electron‐dense contents, but lack a large organized central vacuole. Plastids have few lamellae, possess phytoferritin, and accumulate small amounts of starch. Other organelles and membrane systems are similar to those in other cells. After germination, laticifers develop numerous elongated vacuoles by dilation of endoplasmic reticulum. Nuclei in laticifers within the hypocotyl of seedlings are highly lobed and possess dilated perinuclear spaces. Plastids and other organelles are similar to those observed in the protoplast of laticifers in the embryo. The latex or rubber component of the laticifer is not apparent in mature embryos of 72‐hr seedlings.
EMBRYOGENIC DETERMINATION AND RIBONUCLEIC ACID SYNTHESIS IN POLLEN GRAINS OF HYOSCYAMUS NIGER (HENBANE)
Authors: Raghavan V.
Published: January 2018

3H‐uridine administered as a one‐ or two‐hour pulse to embryogenic pollen grains of freshly excised anthers of Hyoscyamus niger (henbane) was autoradiographically localized in embryoids formed during a subsequent chase. Although continuous incubation of anthers in actinomycin D inhibited embryogenesis, a small percentage of potentially embryogenic pollen escaped inhibition if anthers were grown for at least one hour in the basal medium before actinomycin treatment. The results imply that certain pollen grains become embryogenically determined immediately after culture of the anther and that this is accompanied by the synthesis of ribonucleic acid.
ORGANELLE SIZE AND NUMBER IN FERTILE AND T‐CYTOPLASMIC MALE‐STERILE CORN
Authors: Lee Sheu‐Ling Janet , Warmke H. E.
Published: January 2018

Anthers of inbred F44 fertile (N) and cytoplasmic male‐sterile (T) corn plants (Zea mays L.) were compared cytologically. No differences between fertile and sterile anthers were observed in size and number of mitochondria or plastids until after the start of anther degeneration. A rapid division of mitochondria was observed, however, in the tapetum and sporogenous cells of both fertile and sterile anthers during early growth stages. This rapid increase in mitochondrial numbers per cell (some 20‐to 40‐fold) preceded tapetal breakdown in sterile anthers and did not occur in other anther cells or in plastids. Limited observations on the megagametophyte and nucellus revealed that mitochondria in ovules remain relatively constant in size and number during gametogenesis and do not undergo degeneration.
CYTOLOGICAL PROOF OF APOMIXIS IN CRATAEGUS (ROSACEAE)
Authors: Muniyamma M. , Phipps J. B.
Published: January 2018

An abundance of circumstantial evidence has led earlier workers to believe that apomixis was a common phenomenon in North American Crataegus. However, direct proof was lacking. In this paper, working with accessions of Crataegus pruinosa (Wendl.) K. Koch, sens. lat., a common and rather variable species of eastern North America, we present cytological proof of apomixis. This paper demonstrates the existence of apospory and documents the development of the aposporous embryo sac. Pseudogamy is inferred.
ROLE OF CELLULASE IN AERENCHYMA DEVELOPMENT IN SUNFLOWER
Authors: Kawase Makoto
Published: January 2018

A hypothesis that ethylene causes aerenchyma development in waterlogged plants through increased cellulase activity was tested with sunflower, Helianthus annuus L. Treatment with commercial cellulase induced aerenchyma development in sunflower stem sections. Some of the cellulase‐treated cortical cells enlarged radially and some disintegrated, leading to intercellular space. Cell disintegration started with progressive plasmolysis and severe plasmolysis was associated with or was apparently followed by cell wall breakdown. Localized stem treatment of an intact sunflower with ethylene increased cellulase activity in that part of the stem. Localized stem treatment of an intact sunflower with a water jacket increased cellulase activity in that part of the stem. When the lower part of the sunflower was waterlogged, the cellulase activity in the waterlogged stem increased. Present and earlier results suggest that aerenchyma development is a plant adaptation to waterlogging conditions. The deficiency of oxygen in a waterlogged plant triggers the anaerobic stimulation of ethylene production, which causes an increase in cellulase activity leading to aerenchyma development and enhancing the transport of oxygen to the roots. It is proposed that there is competition between neighboring cortical cells for water after an increase in cell wall plasticity by the action of cellulase. The competition causes progressive plasmolysis and eventual disintegration of weaker cells.
HISTOCHEMISTRY OF THE PRIMARY THICKENING MERISTEM IN THE VEGETATIVE STEM OF ALLIUM CEPA L.
Authors: DeMason Darleen A.
Published: January 2018

Stems of Allium cepa L., 1, 2, 5, and 6 months old respond similarly when stained for protein and RNA. The primary thickening meristem (PTM) stains more intensely than surrounding stem tissues. The acropetal region of the PTM is a broadly staining band which narrows basipetally to the level of the initiation of shoot‐borne roots in the stem and disappears more basipetally. These staining patterns are consistent with the hypothesis that the PTM functions in stem thickening and root production, and also indicate that the meristem functions before histological evidence of the cambial‐like zone exists in the onion stem. Histochemical staining may be an accurate method of locating the PTM.
THE OCCURRENCE AND BEHAVIOR OF B‐CHROMOSOMES IN ASTRANTHIUM INTEGRIFOLIUM (COMPOSITAE)
Authors: Chinnappa C. C. , Morton J. K.
Published: January 2018

Plants of Astranthium integrifolium (Michx.) Nutt. from Oklahoma proved to have a large B‐chromosome which was morphologically similar to the smaller A‐chromosomes. It was eliminated from some of the progeny of selfed plants. Structural modifications in the B‐chromosome were observed. These observations are compared with ones obtained by previous workers, both for this species and in other genera.