bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT AND MORPHOLOGY OF STELAR COMPONENTS IN THE STEMS OF SOME MEMBERS OF THE LEGUMINOSAE AND ROSACEAE
Authors: Devadas Crispin , Beck Charles B.
Published: January 2018

Two species of Leguminosae and five species of Rosaceae have been studied in an attempt to determine the relationship between the development of primary vascular bundles and their morphology, and the variation in morphology among vascular bundles of different types in the stem. A residual meristem occurs in all species. The direction of differentiation of provascular tissue and primary phloem is acropetal and continuous, but differentiation of primary xylem is usually basipetal in the stem. Rare acropetal differentiation of primary xylem was observed in two species only, and in these it is restricted to axial bundles. In order to identify the different types of vascular bundles and to understand their relationship to each other and to the organs they supply, the architecture of the primary vascular system was determined. The several types of vascular bundles are highly variable in size and tracheary cell content. Of all the vascular bundles, the leaf traces are the largest and contain the greatest number of files of tracheary elements. Whereas leaf traces gradually increase in size from the levels of their divergence from axial bundles to the levels at which they enter leaf bases, axial bundles maintain a size in approximate proportion to the diameter of the vascular cylinder. Branch traces decrease in size acropetally. In axial bundles there are usually only one or two files of tracheary elements in contrast to as many as nine files in the median leaf traces of some species. In apical regions where the axial bundles are the sole means of continuous longitudinal transport in the stem, effective water and mineral conduction occur through a relatively small number of tracheary elements. In leaf traces, the much larger number of tracheary elements may have, among other functions, adaptive value in compartmentalization of transport.
STUDIES ON THE ANOMALOUS CAMBIAL ACTIVITY IN DOXANTHA UNGUIS‐CATI (BIGNONIACEAE). II. A CASE OF DIFFERENTIAL PRODUCTION OF SECONDARY TISSUES
Authors: Dobbins David R.
Published: January 2018

The peculiar secondary growth in Doxantha unguis‐cati provides several developmental problems concerning cambial activity. One of the most interesting of these problems is the presence of both unidirectional and bidirectional arcs of cambium within the same stem. This investigation reports the ontogenetic development of these two kinds of cambial arcs. The first cambial divisions are observed in the fascicular regions of the 11th to 16th internodes from the shoot tip. This event is initiated after internode elongation is completed. In the initial stages, secondary tissues have a cylindrical configuration, but subsequently four grooves become apparent. These grooves signify the first evidence of unidirectional cambial activity. The four unidirectional arcs occur near the four major vascular strands to which all of the leaf traces connect. As secondary growth continues, the bidirectional and unidirectional arcs of cambium become separated and radial fissues can be seen between the furrows of phloem and the lobes of secondary xylem. Additional furrows originate either as sets of four between the original set of four or as single furrows to either or both sides of an existing furrow. All furrows are bordered by multiseriate rays. The initials of the bidirectional and unidirectional cambial arcs are non‐stratified and are similar in size and appearance. The phloem produced within the furrow differs in several respects from that produced by the bidirectional arcs. The two types of cambial activity and the precise locations of the unidirectional cambial arcs in the stem (i.e. near the four major strands) suggests that transported products from the leaves are involved in the control of unidirectional cambial activity.
A NEW CLEARING‐SQUASH TECHNIQUE FOR THE STUDY OF OVULE DEVELOPMENT IN ANGIOSPERMS
Authors: Herr J. M.
Published: January 2018

The simple, efficient method described here for the study of ovule and megagametophyte development in angiosperms provides for the extension of investigation beyond the limits imposed by the traditional but arduous section technique. Excised pistils previously fixed in FPA50 and stored in 70 % ethanol are placed in a clearing fluid composed of lactic acid (85 %), chloral hydrate, phenol, clove oil, and xylene (2:2:2:2:1, by weight). After 24 hr, ovules dissected from the ovularies are transferred with some of the fluid to a slide, covered so that the cover glass is supported laterally by two permanently affixed covers, and examined with phase contrast optics. The unique action of the clearing fluid permits the study of cellular structure with the phase oil objective focused at any focal plane within the ovule. Downward focusing thus reveals a series of optical sections in the sagittal, frontal, or transverse plane depending on the orientation of the ovule. Orientation can be altered by a slight shifting of the cover glass on the lateral support mounts. The ovules become quite fragile in the clearing fluid. Pressure applied to the cover glass gradually breaks the ovule apart without disrupting the structural integrity of individual cells. This squash procedure provides for extending observations to cytological features of megasporocytes, megaspores, and megagametophytes previously identified in intact ovules. The new method is applied here to the study of ovule development in two unrelated species, Cassia abbreviata Oliver var. granitica Bak. f. (Leguminosae) and Ludwigia uruguayensis (Camb.) Hara. (Onagraceae). For best results, the ovules of Ludwigia must be pretreated in lactic acid (85 %) for 24 hr prior to application of the clearing fluid. Other methods for pretreatment likely will be required as the technique is applied to a wider range of flowering plant species.
PHYTOCHEMICAL STUDIES IN THE FAMILY MALVACEAE. I. COMPARISON OF ESSENTIAL OILS OF SIX SPECIES BY GAS‐LIQUID CHROMATOGRAPHY
Authors: Thompson A. C. , Hanny Barbara W. , Hedin P. A. , Gueldner R. C.
Published: January 2018

When the chemical constitution of the essential oils of six species within three genera of the family Malvaceae were investigated, the essential oils of Gossypium hirsutum L. and Cienfuegosia rosei Fryxell were found to contain 67.0 % and 58.2 % hydrocarbons, respectively. Those of Hibiscus lasiocarpus (Cav.) and Callirhoe involucrata (Nutt.) Gray contained equal percentages of hydrocarbons (14 %), but that of Cienfuegosia drummondii (A. Gray) Lewt. contained only 2.9 % hydrocarbons. Beta‐bisabolol was the major oxygenated component in G. hirsutum (13.7 %), Hibiscus militaris (Cav.) (55.0 %), and Hibiscus lasiocarpus (32.6 %), but the major constituents in the essential oil of C. involucrata were myrtenal (32.0 %) and trans‐2‐cis‐6‐nonadienal (12.0 %), and the major oxygenated component in C. rosei was an unknown sesquiterpene alcohol (17.4 %) with chemical and physical properties resembling those of beta‐bisabolol. The concentration of total oil was 150.0 ppm in G. hirsutum; 50.0 ppm in H. militaris; 46.3 ppm in C. rosei; 41.0 ppm in H. lasiocarpus; 25. 4 ppm in C. drummondii; and 10.0 ppm in C. involucrata, all based on wet weight.
HOST‐PARASITE RELATIONSHIPS IN SOOTY BLOTCH DISEASE OF WHITE CLOVER
Authors: Camp R. R. , Whittingham W. F.
Published: January 2018

Leaflets of Trifolium repens L. parasitized by Cymadothea trifolii (Pers.) Wolf were examined by light and electron microscopy to ascertain cellular aberrations induced by the fungus. The lamellar organization of the chloroplasts became disrupted, with a concomitant increase in the amount of osmophilic material. Many of the cells in diseased tissues exhibited tubule‐like aggregations, which often were arranged in a highly ordered pattern. Curious extracytoplasmic, dumbbell‐shaped structures extending between host cells and contiguous hyphae were also observed in diseased tissue.
MORPHOGENESIS OF THE STAMENLESS‐2 MUTANT IN TOMATO. I. COMPARATIVE DESCRIPTION OF THE FLOWERS AND ONTOGENY OF STAMENS IN THE NORMAL AND MUTANT PLANTS
Authors: Sawhney Vipen K. , Greyson Richard I.
Published: January 2018

The single gene recessive mutant stamenless‐2 (sl2/sl2) differs phenotypically from the normal (+/+) only in the stamen structure. Stamens of the mutant plants were laterally free, twisted, shorter, paler in color, possessed abnormal pollen, and bore naked external ovules (E.O.) on the adaxial surface near the junction of anther and filament. Mutant plants grown in the field during summer produced flowers in which a number of carpel‐like organs (‘carpelloid stamens‘) with few or no E.O. replaced the stamens. On the other hand, plants grown in the greenhouse during winter possessed flowers with greater number of yellow and pubescent stamens and many E.O. Study of stamen ontogeny revealed that at initiation (up to 100 μ in length) stamen primordia of normal and mutant plants resembled each other. Thereafter the development of stamens in the two genotypes could be distinguished.
WOOD FORMATION IN PROSOPIS: EFFECT OF 2,4‐D, 2,4,5‐T, AND TIBA
Authors: Robnett William E. , Morey Philip R.
Published: January 2018

Treatment of erect stems of Prosopis with near phytotoxic levels of 2,4‐D or 2,4,5‐T causes the formation of an unusual wood with narrow, thick‐walled vessels and axial parenchyma in which cell wall thickening is inhibited. Although reduced in diameter, the vessels formed during 2,4‐D and 2,4,5‐T treatment are so numerous that there is no significant difference between phenoxyacetic acid and control seedling groups with regard to total area of xylem occupied by vessels. The preferential maturation of xylem vessels over parenchyma and the transformation of fusiform initials into septate parenchyma strands in phenoxyacetic acid‐treated Prosopis resemble the structural changes reported to occur after girdling in the cambial tissue of other arborescent angiosperms. Bending experiments indicate that tension‐wood fibers of Prosopis differentiate in response to an auxin deficiency. However, xylogenesis in erect stems treated with TIBA is affected such that a significantly higher proportion of the cambial cell population becomes axial xylem parenchyma.
EFFECT OF FLUOROPHENYLALANINE ON L‐PHENYLALANINE AMMONIA‐LYASE ACTIVITY IN AVENA COLEOPTILES
Authors: Orkwiszewski Joseph A. J. , Hopkins William G.
Published: January 2018

Treatment of etiolated A vena coleoptile apices with several concentrations of DL‐p‐fluorophenylalanine, previously reported to stimulate coleoptile elongation, caused marked reductions in chlorogenic acid content. Levels of this analogue which had no growth effect caused no detectable alteration of chlorogenic acid accumulation. Evidence is presented which indicates that chlorogenic acid levels may reflect extractable L‐phenylalanine ammonia‐lyase activity in this tissue. Incubation of coleoptiles with 5 mm DL‐p‐fluorophenylalanine resulted in significantly lowered extractable ammonia‐lyase activity compared to controls. Similar treatment of tissues with the ortho isomer also caused a reduction of enzyme activity but to a lesser extent. Treatment with the meta isomer had no effect on extractable enzyme activity. These findings provide further evidence for the hypothesis that DL‐p‐fluorophenylalanine stimulates coleoptile elongation by lowering L‐phenylalanine ammonia‐lyase activity and the subsequent biosynthesis of potentially inhibitory low molecular weight phenols.
A MODE OF ENTRY OF BLUE‐GREEN ALGAE INTO THE APOGEOTROPIC ROOTS OF MACROZAMIA COMMUNIS
Authors: Nathanielsz Charmian P. , Staff Ian A.
Published: January 2018

The entry of blue‐green algae into an aerial root of Macrozamia communis via a break in the dermal layers and leading through a continuous cortical channel into the algal zone is reported. Penetration of the algae appears to be mainly in the form of filaments. Intercellular migration of the algae is found to occur after dissolution of host cell middle lamellae, but host cortical cells are also destroyed near some of the algae. Intracellular migration is also suggested to be a likely pathway for the algae as they proceed to the algal zone.
THE INFLUENCE OF PHOTOPERIOD AND EXOGENOUS NITROGEN‐CONTAINING COMPOUNDS ON THE REPRODUCTIVE CYCLES OF THE LIVERWORT CEPHALOZIA MEDIA
Authors: Lockwood Linda G.
Published: January 2018

The effects of photoperiod and a number of metabolites (inorganic nitrogenous compounds, amino acids, and growth substances) on reproductive differentiation in the leafy liverwort Cephalozia media Lindb. were studied under axenic conditions. The increase or decrease in the number of branches bearing localized reproductive structures was used to determine the influence of the experimental variables on the regulation of both asexual and sexual phases of reproductivity (production of gemmae and gametangia). Within the context of photoperiodic control, the magnitude of the normal reproductive response was significantly stimulated or inhibited by low concentrations of certain amino acids or kinetin. Certain metabolites (10‐6M concentrations of arginine, cysteine, tryptophan plus kinetin) were able to overcome photoperiodic control of the reproductive response. Generally, organic compounds which stimulated asexual reproductivity under short photoperiod inhibited sexual reproductivity under long photoperiod. Exogenous inorganic nitrogen did not significantly affect the asexual or sexual reproductive response.
THE CYTOGENETICS OF XANTHISMA TEXANUM DC. (ASTERACEAE) AND ITS B‐CHROMOSOMES
Authors: Semple John C.
Published: January 2018

The karyotype of A‐set and B‐chromosomes of Xanthisma texanum DC. are described in detail and measurements are given. The distribution of B‐chromosomes in stem tissue is described and the loss of B‐chromosomes from primary roots confirmed. The number of B‐chromosomes in pollen mother cells was constant within single inflorescence buds and in all buds throughout the flowering period. The behavior of one and two B‐chromosomes during meiosis is described in detail. During meiosis, B1's divided in 71% of the cases during anaphase II and in 29% of the cases during anaphase I. First anaphase division resulted in some lagging and elimination of B‐chromatids during second division. During anaphase I, B11's divided into chromosomes and in anaphase II these divided into chromatids in 95% of the cases. In the other 5 % non‐disjunction of the B‐chromosomes or chromatids and A‐set chromosome abnormalities occurred. Post meiotic preferential distribution during pollen mitosis resulting in a doubling of the number of B‐chromosomes passed to progeny via pollen occurred, but no doubling occurred in the female line. Crosses involving plants with two B‐chromosomes each yielded fewer plants with three B‐chromosomes than expected. Polyploidy is extremely rare in the species. The evolutionary significance of B‐chromosome behavior is discussed in relation to its origin and survival.
LIGHT‐MEDIATED INHIBITION OF IN VITRO DEVELOPMENT OF RUDIMENTARY EMBRYOS OF ILEX OPACA
Authors: Hu Ching‐yeh
Published: January 2018

The mature seeds of Ilex opaca Ait. contain rudimentary heart‐shaped embryos. When excised embryos of cv. Farage were grown in vitro with a 16‐hr photoperiod, only 20 % reached germination size after 13‐day incubation, while 75% of the embryos reached the same stage when incubated in darkness. This light inhibitory effect increased with the length of daily light exposure as the daily photoperiod reached 4 hr. Nearly 50% growth reduction resulted as the cultures were preincubated in light continuously for 2 days before a 10‐day dark incubation. After 4 days of light incubation the inhibitory effect could no longer be reversed by the subsequent dark incubation. Once the heart‐shaped embryos started to grow in darkness they become progressively insensitive to subsequent light inhibition. After a 6‐day initial dark incubation the embryos become immune from the inhibitory effect of light. This light inhibitory effect on in vitro embryo growth was universal in all 11 tested cultivars.
SUBMERGENCE EXPERIMENTS ON NINE SPECIES OF SEMI‐AQUATIC POLYGONUM
Authors: Mitchell Richard S.
Published: January 2018

Cloning experiments were carried out in growth chambers to determine responses of members of the genus Polygonum (sect. Persicaria) to aquatic submergence. By using both external morphology and anatomical modifications, comparisons were made among 23 populations with respect to their preadaptations after a rise in water level. Varieties of P. amphibium L. responded quite differently to submergence, offering more evidence to the theory that there is a cline of phenotypic plasticity in the species which corresponds roughly with the gradient in morphology. Other than P. amphibium, the species most well adapted to aquatic conditions was P. densiflorum Meisn., a member of the P. punctatum Ell. complex. Populations of P. hydropiperoides Michx. showed a dichotomy of response which appeared to correlate with the habitats in which they were collected. A few species of Polygonum did not survive well after inundation, but most were capable of underwater growth, and were at least half as well adapted to aquatic conditions as was the most plastic variety, P. amphibium var. stipulaceum Colem.
FURTHER CYTOLOGICAL STUDIES OF A PERIODIC ACID‐SCHIFF'S SUBSTANCE IN THE OVULES OF PASPALUM ORBICULARE AND P. LONGIFOLIUM
Authors: Chao Chuan‐ying
Published: January 2018

A periodic acid‐Schiff's substance present in the micropylar end of the ovules of Paspalum orbiculare and P. longifolium was further studied by light and electron microscopy of glutaraldehyde‐osmium‐fixed and freeze‐substituted, osmium‐fixed tissues. The PAS substance is water soluble and is found in intercellular spaces between the nucellus and inner integument, the inner and outer integuments, the outer integument and ovary wall, and in the micropyle. Structurally the substance consists of fibrils embedded in a dense, amorphous matrix and may be associated with membranous structures in special layers between the plasmalemma and the cell wall in nucellar and integumentary cells. Part of the water soluble substance is believed to be secreted from the nucellar and integumentary cells. A large amount of this substance may be formed as a result of the dissolution of about one third of the distal micopylar portion of the outer integument prior to anthesis. Many of the electron‐dense fibrils seem to be fibrillar intercellular substances and others appear to originate from the cell walls, including the cuticle. Both the matrix and the fibrils may be chemically heterogeneous and together form a mucilagenous substance which may facilitate the final growth of pollen tubes in these two species.
THE PRIMARY ROOT EPIDERMIS OF PANICUM VIRGATUM L. II. FINE STRUCTURAL EVIDENCE SUGGESTIVE OF A PLANT‐BACTERIUM‐VIRUS SYMBIOSIS
Authors: Lewis Robert F. , Crotty William J.
Published: January 2018

Roots of P. virgatum seedlings have been found to be associated invariably with a symbiotic bacterial species. These bacteria were found both on the surface of, and buried in, the outer walls of the more basal elongating epidermal cells. Often the morphology of the wall‐associated bacteria suggested that they were infected with a virulent phage. Other observations included the sudden appearance of virus‐like particles in the cytoplasm of these basal elongating epidermal cells. Since the appearance of phage‐infected bacteria was found to coincide with the appearance of the cytoplasmic virus‐like particles, and since these two events also coincided with the culmination of the ontogeny of large epidermal cytoplasmic inclusions (ECI) in these cells, it has been suggested that these three events may be related.
IDIOSPERMUM AUSTRALIENSE (IDIOSPERMACEAE)—ASPECTS OF VEGETATIVE ANATOMY
Authors: Wilson Carl L.
Published: January 2018

Vegetative structural features of Idiospermum, a monotypic ranalean genus rediscovered in 1972, are described and contrasted with comparable features of Calycanthus and Chimonanthus (Calycanthaceae) to note resemblances and differences. The leaf trace pattern and nodal anatomy of Calycanthaceae and Idiospermaceae (one‐trace and unilacunar) are very similar. The nodal anatomy of certain highly reduced leaves (scale leaves) of Idiospermum is, however, two‐trace and unilacunar. The microscopic wood anatomy of Idiospermum is distinctively different in a number of respects from that of the Calycanthaceae. Although there are similarities, it is suggested that the floral anatomy and vegetative features of Idiospermum set it apart sufficiently from the Calycanthaceae to justify family rank as the Idiospermaceae.
THE PHOTOBIOLOGY OF FERN GAMETOPHYTES. II. THE PHOTOCONTROL OF FILAMENTOUS GROWTH AND ITS IMPLICATIONS FOR THE PHOTOCONTROL OF THE TRANSITION TO TWO‐DIMENSIONAL GROWTH
Authors: Cooke Todd J. , Paolillo Dominick J.
Published: January 2018

Current descriptions of the photocontrol of the filamentous growth of fern gametophytes contain several apparent photobiological anomalies. These anomalies are the result of the fundamental assumption that the rate of filament elongation is the growth parameter under direct photocontrol. This paper constructs and tests a model for the photocontrol of filamentous growth: k = A(dl/dt), where k, A, and (dl/dt) represent a constant rate of volume increase, the cross‐sectional area of the filament tip, and the rate of filament elongation, respectively. This model predicts that the photocontrol of filamentous growth could involve the direct regulation of the cross‐sectional area. Because this alternative perspective resolves the apparent photobiological anomalies, the photoresponse of the cross‐sectional area should represent the correct measure of the photocontrol over filamentous growth. It follows from the experimental results that the photocontrol of filamentous growth does not antagonize but rather preconditions the transition to two‐dimensional growth. Therefore, the original grounds for postulating that the transition in growth form involves the photoinduction of specific genes for two‐dimensional growth are no longer valid.
REGULATORY ROLE OF INDOLE‐3‐ACETIC ACID AND GIBBERELLIC ACID IN VEGETATIVE DEVELOPMENT OF XANTHIUM PENNSYLVANICUM
Authors: Orkwiszewski Joseph A. J. , Maksymowych Roman , Maksymowych Andrew B.
Published: January 2018

A single application of gibberellic acid to young internodes significantly accelerated the rate of internode growth and the rate of leaf production in shoots of Xanthium pennsylvanicum Wallr. The average duration of one plastochron in treated plants was reduced to 43% of control levels. Gibberellic acid also had a pronounced morphogenetic effect on leaves so that the area and leaf length of treated plants were both significantly reduced. Depending upon concentration, auxin had both inhibitory and promotive effects on Xanthium shoots. Indole‐3‐acetic acid markedly altered the response of the gibberellic acid‐treated internodes and those located above and below the site of application. In addition, high auxin concentrations induced the formation of adventitious roots in treated internodes. Auxin also brought about significant reductions in the length and area of leaves developed under the influence of this hormone.
A COMPARATIVE STUDY OF OVULE AND MEGAGAMETOPHYTE DEVELOPMENT IN FIELD‐GROWN AND GREENHOUSE‐GROWN PLANTS OF GLYCINE MAX AND PHASEOLUS AUREUS (PAPILIONACEAE)
Authors: George Glenda P. , George Ralph A. , Herr J. M.
Published: January 2018

A study of ovule and megagametophyte development in field‐ and greenhouse‐grown plants of Glycine max (L.) Merrill and Phaseolus aureus Roxb. reveals several consistent features for both species. These features include: a multiple archesporium, enlargement of a primary sporogenous cell directly into a megasporocyte, production of unequal dyad cells, a functional chalazal megaspore, Polygonum‐type development, and a hypostase. A filiform apparatus was not observed in either species. Several marked differences in development also occur. Phaseolus usually produces one sporogenous cell per ovule; Glycine produces 2–3 sporogenous cells per ovule. Meiosis II is synchronous in Phaseolus but nonsynchronous in Glycine. Linear tetrads are produced in Phaseolus, whereas linear and T‐shaped tetrads are found in Glycine. Starch grains accumulate in the mature megagametophyte of Glycine but are absent at that stage in Phaseolus. The usefulness of the modified clearing fluid, benzyl benzoate‐4½, for the study of ovule and megagametophyte development in Glycine max and Phaseolus aureus is here demonstrated. In addition, the study indicates for both species that megagametophyte development in plants grown under field conditions is markedly similar to development in plants grown in the more uniform conditions of the greenhouse. Accordingly, these findings suggest generally that embryological data collected from plants grown under greenhouse conditions will reflect those from plants found in nature.
OBSERVATIONS ON PLASTID FINE‐STRUCTURE IN THE HOLOPARASITIC ANGIOSPERM EPIFAGUS VIRGINIANA
Authors: Walsh Michael A. , Rechel Eric A. , Popovich Thomas M.
Published: January 2018

The ultrastructure of plastids in cortex and phloem parenchyma cells of Epifagus virginiana (L.) Bart. is described. Based upon morphology and content, several distinct plastid types appear to exist. “Tubular” complexes, lipid globules and electron dense inclusions in different arrangements appear to account for the degree of plastid variability. When results obtained with Epifagus are compared with those obtained by others for a closely related genus, a striking parallel is shown to exist.
SEED‐COAT MORPHOLOGY AND ANATOMY IN COLLOMIA (POLEMONIACEAE)
Authors: Hsiao Yi‐Chun , Chuang T. I.
Published: January 2018

Seed‐coat morphology of 14 species of Collomia (Polemoniaceae) was examined with light microscopy and scanning electron microscopy. Two seed types were observed based on surface sulpturing: Type 1—hexagonal epidermal cells forming a shallow reticulum with well‐defined cell boundaries; Type 2—longitudinally ridged and irregularly arranged crater‐like depressions with inconspicuous cell boundaries. Only two species, C. debilis and C. larsenii of sect. Collomiastrum have seed‐coat Type 1. Seed‐coat Type 2 is characteristic of all species of sect. Collomia, sect. Courtoisia, and C. mazama, C. rawsoniana of sect. Collomiastrum. The present investigation reveals a fairly homogeneous seed‐coat pattern in the genus and does not offer significant information for realignment of infrageneric classification. Anatomical studies with light microscopy show that a mucilaginous seed coat develops from the outermost layer of integument in which each epidermal cell develops spiral secondary wall thickenings. Mucilaginous seeds of most Collomia species probably provide adaptive significance in that adherence of seeds to ground prohibits further dispersal to unfavorable habitats, or epizoochoric dispersal.
REPRODUCTIVE DEVELOPMENT IN LOBLOLLY PINE. II. THE EFFECT OF AGE, GIBBERELLIN PLUS WATER STRESS AND OUT‐OF‐PHASE DORMANCY ON LONG SHOOT GROWTH BEHAVIOR
Authors: Greenwood Michael S.
Published: January 2018

The effects of age from seed, out‐of‐phase dormancy, and gibberellin treatment with water stress on the reproductive and vegetative development of the long shoot terminal bud were observed. Scions of different ages were grafted onto 1‐yr‐old rootstocks, and the younger scions grew more and produced fewer strobili than older ones. Out‐of‐phase dormancy promoted both male and female flowering at all ages, but the older scions responded better. Gibberellin4/7 plus water stress promoted development of female strobili only. Treatments that promote flowering also increase the size of the resting bud. It is proposed that treatment effects promoting flowering appear to fall into two categories: 1) Those which promote the formation of a resting bud, and 2) those which affect the subsequent development of resting buds which have the potential to develop strobili.
SOME RECENT ADVANCES IN THE CHEMICAL STUDIES OF CHINESE HERBAL MEDICINE
Authors: Sheng‐din Fang , Ren‐sheng Xu , Yi‐sheng Gao
Published: January 2018

Selection of target herbs in China for investigation is based upon their clinical history in traditional medicine and use in folk medicine. Crude drugs having anti‐schistosomal activity, ascaricidal action, sedative value, ameliorative effects on viral hepatitis, or of use as abortificients or in treatment of coronary disease, or as asthma palliatives are described. The active principles are identified and discussed.
STUDIES OF VEGETATIVE COMPATIBILITY‐INCOMPATIBILITY IN HIGHER PLANTS. I. A STRUCTURAL STUDY OF A COMPATIBLE AUTOGRAFT IN SEDUM TELEPHOIDES (CRASSULACEAE)
Authors: Moore Randy , Walker Dan B.
Published: January 2018

Initial adherence of the cut surfaces occurred by 24 hr after grafting and was correlated both with a pronounced dictyosome activity along the graft interface and with callus proliferation in both the stock and scion. A necrotic layer of one or two collapsed cells in thickness initially extended as a continuous barrier between the stock and scion, but the layer was fragmented by 2–3 days after grafting as the callus proliferation continued. Graft incision also induced a mild senescence in cells at the graft interface characterized by a reduced staining intensity of the cytoplasm, replacement of the large primary vacuole by numerous smaller vacuoles, and the occurrence of flocculent material throughout the cytoplasm. Starch accumulated during the first day after grafting but disappeared by 2–3 days after grafting. The cellular senescence never proceeded beyond an early, nonlethal stage, and cells along the graft interface completely recovered by 3 wk after grafting. Procambial differentiation occurred across the callus bridge by 10 days after grafting, and mature vascular continuity was established by 14 days. The results of this study are discussed relative to cellular recognition phenomena and to proposed mechanisms for plant graft compatibility‐incompatibility.
STUDIES OF VEGETATIVE COMPATIBILITY‐INCOMPATIBILITY IN HIGHER PLANTS. II. A STRUCTURAL STUDY OF AN INCOMPATIBLE HETEROGRAFT BETWEEN SEDUM TELEPHOIDES (CRASSULACEAE) AND SOLANUM PENNELLII (SOLANACEAE)
Authors: Moore Randy , Walker Dan B.
Published: January 2018

An ontogenetic study of a shoot heterograft between Sedum telephoides and Solanum pennellii was performed in order to characterize the cellular events that occur during an incompatible graft union. Adhesion of stock and scion occurred by 21 hr after grafting and was correlated with an accumulation of dictyosomes in cells at the graft interface. The graft incision triggered a wound response in cells of both partners along the graft interface that was characterized by: 1) a reorientation of cytoplasm in cells adjacent to the cut surfaces; 2) deposition of cell wall; 3) starch accumulation; 4) a reduced staining intensity of the cytoplasm, and 5) callus proliferation. While Solanum cells recovered from the effects of wounding at an early and nonlethal stage, Sedum cells bordering the graft interface underwent a lethal cellular senescence characterized by: 1) cell wall suberization; 2) vesiculation of the cytoplasm; 3) degeneration of cellular organelles; 4) loss of membrane integrity, and finally 5) death and collapse of the cell. Thus, cellular necrosis in the Sedum partner characterized the incompatibility response between Sedum and Solanum and resulted in formation of a necrotic layer of collapsed cells and cytoplasmic remnants at the graft interface. This necrotic layer was never ruptured by callus proliferation and consisted of up to 8–10 collapsed cells by 10–14 days after grafting. Vascular redifferentiation did not occur in the callus masses at the graft interface. Sedum abscission occurred by 3–5 wk after grafting, presumably due to desiccation of tissues. Both Sedum and Solanum stocks grafted to wooden applicator sticks in the same manner they grafted to a living scion, indicating that initial adhesion of the graft partners did not involve a recognition event between opposing living cells. The possible roles of toxins that may elicit the incompatibility response and of a direct cellular interaction that may contribute to procambial redifferentiation are discussed.
ORIENTATION, PAR INTERCEPTION, AND NOCTURNAL ACIDITY INCREASES FOR TERMINAL CLADODES OF A WIDELY CULTIVATED CACTUS, OPUNTIA FICUS‐INDICA
Authors: Nobel Park S.
Published: January 2018

Terminal vertical cladodes (flattened stems) of Opuntia ficus‐indica growing in widely separated locations were nonrandomly oriented. On plantations at 33°S latitude in Chile individual cladodes tended to orient in the same direction as the planted cladodes on which they developed. However, after 2 years unshaded new cladodes tended to face east‐west. Terminal cladodes also tended to face east‐west for irrigated O. ficus‐indica in California (at 34°N) and in Israel (32 to 33°N), but cladodes developing in the winter tended to face north‐south. Except for the residual effect of initial planting direction, the observed patterns tended to maximize the interception of photosynthetically active radiation (PAR). Specifically, east‐west cladode orientation would maximize PAR interception, except for cladodes developing near the winter solstice at latitudes more than 27° from the equator. Nocturnal acidity increases and hence productivity would generally be light‐limited, since the nocturnal increase in acidity was 90% saturated for a total daytime PAR of 24 mol m–2 day–1 and the PAR received on vertical surfaces is usually less than this. Topographical features can modify the orientation patterns, since at a site where PAR was considerably blocked by surrounding mountains the maximal nocturnal acidity increases and peak in cladode orientation occurred 20° from facing east–west. Laboratory studies showed that developing cladodes oriented toward a horizontal light and were rotated an average of 16° in a direction that increased PAR interception compared to the cladodes on which they developed. Such phototropic responses, the higher productivity of favorably oriented cladodes, and the tendency to orient similarly to the underlying cladode presumably accounts for the overall orientation patterns observed, where up to four times more cladodes may face in a particular direction than at right angles to it.
SHOOTLESSNESS, VELAMENTOUS ROOTS, AND THE PRE‐EMINENCE OF ORCHIDACEAE IN THE EPIPHYTIC BIOTOPE
Authors: Benzing D. H. , Friedman W. E. , Peterson G. , Renfrow A.
Published: January 2018

Roots of representative epiphytic orchids were examined for anatomical detail, desiccation resistance and evidence of CAM activity. Those “shootless” taxa examined (Campylocentrum pachyrrhizum (Reichenb. f.) Rolfe, Harrisella porrecta Reichenb. f.) Fawc. & Rendle, and Polyradicion lindenii (Lindl.) Cogn. ex Urban) and a semi‐shootless type (Kingidium taeniale (Lindl.) P. F. Hunt) bear thinner or eroded velamina and greater volumes of cortical intercellular space than do those of the leafy forms tested (Campylocentrum sellowii (Reichenb. f.) Rolfe, Encyclia tampensis (Lindl.) Small, Epidendrum radicans Pavon ex Lindl., Phalaenopsis amabilis (L.) Blume, Rangaeris amaniensis (Krzl.) Summerhayes and Vanda parishii (Reichenb. f.)). Shootless species also bear a more elaborate aeration apparatus at the velamen‐cortex interface. Structurally distinct cortical cells located in this region may regulate gas exchange across the exodermis. Velamen thickness varies greatly among the ten species, as does the development of outer tangential walls of U cells in the underlying exodermis. Desiccation resistance under laboratory conditions was more closely related to root surface‐to‐volume ratio (S/V) than to any other measured anatomical parameter, including velamen development. Modes of carbon gain and the possible pathway for movement of fungus‐borne carbon into an orchid's pool of assimilates are described, as is the possible significance of these processes to survival in forest canopy habitats.
CIBOTIUM OREGONENSE: AN EOCENE TREE‐FERN STEM AND PETIOLES WITH INTERNAL STRUCTURE
Authors: Barrington David S.
Published: January 2018

Cibotium oregonense sp. nov. is described from the Upper Eocene of Medford, Oregon. The fossil comprises petiole bases and stem periphery of a large fern preserved via permineralization. A stele devoid of sclerenchymatous sheathing and a petiole vascularized with a large number of leaf traces in a cyatheacean pattern characterize the fossil. A distinctive U‐shaped interior series of leaf traces allows assignment to the genus Cibotium. This fossil provides evidence that the genus Cibotium was represented by an arborescent species with large leaves in the Early Tertiary of western North America.
RELATIONSHIP BETWEEN MALE AND FEMALE GAMETOPHYTE DEVELOPMENT IN RYE
Authors: Xiang‐Yuan Xi , DeMason Darleen A.
Published: January 2018

The development of male gametophyte and female gametophyte within a floret of rye (Secale cereale L.) was examined. Generally, meiosis in microsporocytes and in megasporocytes occurs simultaneously in most florets, but the period from zygotene to tetrad meiosis in the megasporocyte progresses more slowly than that in the microsporocyte. When the female gametophyte has one nucleus and no vacuoles, the male gametophyte has a single, eccentric nucleus. By the time the female gametophyte develops to the vacuolated one‐, two‐, four‐, and eight‐nucleate stages and to the growth and differentiation of the egg apparatus stage, the male gametophyte reaches the two‐celled pollen stage. As the female gametophyte matures, the male gametophyte also reaches maturity. The duration of male gametophyte development from microspore mother cell and the duration of female gametophyte development from megaspore mother cell are the same in most florets. The relationship between sexual development of cross‐pollinated rye is similar to that of self‐pollinated wheat (Triticum aestivum L.). It seems that the relationship is not related to the breeding system.
POLLEN LONGEVITY AND STIGMA PRE‐EMPTION IN CLARKIA
Authors: Smith‐Huerta Nancy L. , Vasek Frank C.
Published: January 2018

The ability of pollen to effect seed set decreases with age when stored at room temperature or on the plant, but not when stored at 5 C. Seed set declines rapidly with pollen stored 10 days or more at room temperature. Seed set declines rapidly with pollen stored 4 days or more on the plant. The degree of pollen germination on the stigma and the number of pollen tubes in the style correlate positively with seed set. Pollen germination on the stigma and pollen tube growth in the style are strongly correlated with seed set for pollen stored at room temperature, but not, or only weakly, correlated for pollen stored at 5 C. In the latter case, seed sets are lower than expected, indicating a possible viability reduction associated with a post‐pollination function. Inviable pollen grains temporarily interfere with normal pollen germination on the stigma. Essentially no seeds are produced when in viable pollen, immediately followed by viable pollen, is placed on a fresh stigma. However 27 to 65 seeds are produced when in viable pollen, followed in 1 to 6 days by viable pollen, is placed on fresh stigmas. New stigma surface is exposed at the center as expanding stigma surfaces carry the interfering inviable pollen toward the edge of the stigma.
POST‐FIRE RECOVERY OF FLORIDA LAKE WALES RIDGE VEGETATION
Authors: Abrahamson Warren G.
Published: January 2018

Community responses to fire of five major vegetation associations of the Lake Wales Ridge were investigated during a 5‐yr post‐fire period. Vegetation of southern ridge sandhills, sand pine scrub, scrubby flatwoods, flatwoods, and swales was sampled using permanent line transects and quadrats in both burned and unburned (control) areas. Fire passed through the mosaic of vegetation leaving a pattern of unburned and lightly to severely burned areas. There was little change in soil chemistry (pH, K, P, Mg) with the exception of a short‐lived increase in Ca. Vegetation recovery rates, measured by percentage cover and Horn's Index, were rapid. Typically, less than 2 yr was needed for recovery of poorly drained flatwoods and swale associations and 1 to 4 years for better drained scrubby flatwoods and southern ridge sandhills. Species diversity (H′) increased significantly following fire at poorly drained sites due to increased evenness, but was largely unchanged at better drained sites. There was virtually no change in vascular plant species composition for the sprouting associations. Fire is not a succession‐initiating disturbance in the Clementsian sense. The species present prior to burning either resprout soon after fire or resist fire, thus rapidly restoring the preburn conditions. Limited data suggest fire in the associations dominated by seeding species likewise does not initiate a relay type succession. The ridge vegetation exhibits marked resiliency to fire as a result of an evolutionary history of a stressful environment including winter droughts, acidic, nutrient‐poor sand substrates, and frequent lightning‐caused low intensity burns.
CYTOGEOGRAPHIC STUDIES ON NORTH AMERICAN ASTERS. I. RANGE SURVEYS OF VIRGULUS ADNATUS, V. CONCOLOR, V. GEORGIANUS, V. GRANDIFLORUS, V. NOVAE‐ANGLIAE, V. OBLONGIFOLIUS, V. PATENS, AND V. WALTERI
Authors: Semple John C.
Published: January 2018

Chromosome number determinations from 118 populations of eight species of the aster genus Virgulus are reported for the first time. Based on these counts and literature reports the geographic distributions of diploids and tetraploids in V. concolor, V. novae‐angliae, V. oblongifolius, and V. patens have been determined. In the first three species, diploids were widely distributed, while tetraploids were more restricted. In V. patens, diploids were restricted to the southwestern portion of the species’ range, while tetraploids were found throughout the range. Both V. adnatus and V. walteri were found only at the tetraploid level throughout their ranges. Two other species with restricted distributions were consistently found to be high level polyploids: V. georgianus with 2n = 50, V. grandiflorus with 2n = 60. The following new combinations are listed: Virgulus georgianus (Alexander ex Small) Semple; Virgulus subsect. Brachyphylli (Torr. & Gray) Semple; and Virgulus sect. Polyliguli (Semple & Brouillet) Semple.
VARIATION IN CELL‐CYCLE TIME AND NUCLEAR DNA CONTENT IN THE APICAL MERISTEM OF HELIANTHUS ANNUUS L. DURING THE TRANSITION TO FLOWERING
Authors: Marc Jan , Palmer John H.
Published: January 2018

The mitotic cycle in the apical meristem of Helianthus annuus L. has been investigated during the transition to flowering. Towards the end of the strictly vegetative phase 8 days after sowing the average cell‐cycle time, measured by colchicine‐induced metaphase accumulation, was 37 hr in the peripheral zone, 83 hr in the central zone and 118 hr in the rib meristem. By Day 12 the cycle had shortened in all zones. By the time of floral initiation on Day 16 the cycle time had returned to its original value in the peripheral zone and the rib meristem, while in the central zone it continued to shorten to 33 hr, approaching the cycle time of the peripheral zone. Cytophotometric measurements of nuclear DNA showed that mitotic activation of the central zone was not associated with any reduction in the proportion of nuclei with a 4 C DNA content. It was calculated that the spatial and temporal variation in cell‐cycle time was mainly a function of the length of the G1/G0 phase which lasted about 19 hr in the peripheral zone, 82 hr in the rib meristem, and declined from 55 to 21 hr in the central zone.
FINE‐STRUCTURAL STUDY ON THE FORMATION OF THE GENERATIVE CELL WALL AND INTINE‐3 LAYER IN A GROWING POLLEN GRAIN OF LILIUM LONGIFLORUM
Authors: Nakamura Sumio , Miki‐Hirosige Hisako
Published: January 2018

At the end of mitosis in the lily pollen microspore, the fan‐shaped cell plate gives rise to a cell wall delineating a hemispherical cell. At first, the cell wall of the newly formed generative cell and the intine‐3 layer of the pollen grain wall are inseparable. Gradually, the wall of the generative cell near the pollen grain wall becomes thicker and wall segments are formed between the thickened zones, and these make a network system by which the generative cell becomes suspended and separated from the pollen grain wall. After the separation, the intine‐3 layer is formed inside the intine 2. The generative cell wall and the intine‐3 layer are formed by coated vesicles, polysaccharide particles and rough ER.
INBREEDING AND THE RATE OF SELF‐FERTILIZATION IN A GRAPE FERN, BOTRYCHIUM DISSECTUM
Authors: McCauley David E. , Whittier Dean P. , Reilly Linda M.
Published: January 2018

Botrychium dissectum is a homosporous fern with bisexual, subterranean gametophytes. Because of these features, B. dissectum would be suspected of displaying a very high frequency of self‐fertilization. Sporophytes collected from three populations of this species were assayed for heterozygosity by determining the electrophoretic mobility patterns displayed by two polymorphic enzymes. Extreme deviations from Hardy‐Weinberg expectations were observed in each population and analyzed by means of F‐statistics. The average inbreeding coefficient was found to be 0.951. A population genetic model is derived that demonstrates that the rate of intragametophytic self‐fertilization in homosporous ferns is equal to the inbreeding coefficient calculated from deviations from Hardy‐Weinberg expectations. It is therefore concluded that B. dissectum outcrosses about 5% of the time.
STUDIES IN CRATAEGUS (ROSACEAE: MALOIDEAE) XIV. THE BREEDING SYSTEM OF CRATAEGUS CRUS‐GALLI SENSU LATO IN ONTARIO
Authors: Dickinson T. A. , Phipps J. B.
Published: January 2018

Crataegus crus‐galli L. sensu lato in southern Ontario is a complex of taxa, two of which appear to consist exclusively of both triploid and tetraploid individuals. While pollen fertility is reduced in triploids, both ploidy levels are characterized by production of eight nucleate aposporous embryo‐sacs and hence remain seed‐fertile; in addition, single, apparently sexual, embryo‐sacs are found in the ovules of tetraploids. Agamospermy is shown experimentally to be pseudogamous. Polyploidy in C. crus‐galli s.l. is accompanied by self‐compatibility, in contrast to the self‐incompatibility of diploid Crataegus species such as C. punctata, with which comparison is made. The weediness of the component taxa of C. crus‐galli s.l., in general, and their tendency toward uniparental reproduction, in particular, may explain the homogeneity of their topodemes, and the way in which these topodemes may be markedly differentiated from one another even within a single taxon.