bluuebunny/crossref_metadata_2025 huggingface dataset:
EXPERIMENTAL STUDIES OF THE SHOOT APICAL MERISTEM OF SEED PLANTS. II. MORPHOLOGICAL AND CYTOCHEMICAL EFFECTS OF KINETIN APPLIED TO THE EXPOSED MERISTEM OF PINUS ELLIOTTII
Authors: Varnell R. J. , Vasil I. K.
Published: January 2018

Treating shoot apical meristems of Pinus elliottii seedlings with 1.5 μg kinetin results in bud scale formation and the onset of dormancy. IAA and GA produce no morphogenetic effects. According to cytochemical analyses, levels of ribonucleic acid (RNA) in kinetin‐treated meristems exceed controls through the sixth day following treatment, during which time unsaturated lipids fall sharply below control values. Rapid declines in RNA by day eight, when cytoplasmic protein may also be at a relatively low concentration, coincide with the first appearance of bud scales, signaling the onset of dormancy in kinetin‐treated meristems. Changes in concentration of RNA and lipid (and possibly protein) suggest that kinetin may effect nucleus‐based events and/or membranes in the cytoplasm in the apical meristem. These effects may be related to the subsequent development of bud scales in the subapical region and to the onset of dormancy throughout the shoot tip. The central mother cell zone is not metabolically quiescent in the vegetative shoot apical meristem of Pinus seedlings.
POSTGENITAL CARPEL FUSION IN CATHARANTHUS ROSEUS (APOCYNACEAE) IV. SIGNIFICANCE OF THE FUSION
Authors: Walker Dan B.
Published: January 2018

The ontogenetic and phylogenetic significances of the postgenital carpel fusion in Catharanthus roseus were investigated experimentally. When one of the two carpel primordia was surgically destroyed prior to carpel fusion, the remaining carpel differentiated nevertheless; however, the tissue development on the adaxial (normally fused) carpel face appeared aberrant. Possible reasons for this modified ontogeny are discussed. The suggestion that syncarpy is phylogenetically significant because any pollen tube can potentially reach any ovule was verified in C. roseus by monitoring pollen tube growth following spatially controlled pollinations. The suture formed by the postgenital fusion was no barrier to pollen tube growth, and the pollen tubes rapidly became distributed throughout the stigmatic tissue.
BOTRYOPTERIS PINNULES WITH ABAXIAL SPORANGIA
Authors: Good Charles W.
Published: January 2018

Small sporangia borne abaxially on pinnules attached to Botryopteris foliar members are described from coal ball petrifactions of Early Pennsylvanian age. This is the first report of laminar sporangia in this genus. Sporangia are stalked and borne singly near lateral veins on Sphenopteris‐like pinnules. Individual sporangia are of the leptosporangiate type, with a lateral annulus and a dehiscence zone of thin‐walled cells immediately adjacent to the annulus. Spores are small, trilete, triangular in outline, typically have blunt spines covering the exine, and correspond to the dispersed spore genera Acanthotriletes, Leiotriletes, or Lophotriletes. These sporangia and their spores are unlike previously described globose Botryopteris fructifications from the Middle and Upper Pennsylvanian, but are similar to sporangia produced by modern members of the Osmundaceae.
LEAF DEVELOPMENT IN SENECIO ROWLEYANUS (COMPOSITAE)
Authors: Hillson Charles J.
Published: January 2018

Prolonged apical growth of the leaf primordium and the presence of distinct marginal meristems do not occur in Senecio rowleyanus. Intercalary cell divisions accompanied by radial expansion of derivatives from an adaxial meristem account for the spherical shape of the leaf. The “window” in the lamina marks the position of the adaxial meristem and precludes interpretation of the leaf as being unifacial. Stomata are mesoperigenous and anomocytic in type. Schizogenous secretory canals occur in both the leaf and the stem, and their association with vascular bundles is discussed. The anatomy of the leaf is interpreted in terms of xeromorphy.
ABSORPTION OF ANIMAL TISSUE BREAKDOWN PRODUCTS INTO A PLANT STEM—THE FEEDING OF A PLANT BY ANTS
Authors: Rickson Fred R.
Published: January 2018

Cohabiting ants place animal remains in stem cavities of Hydnophytum formicarum Jack (Rubiaceae). Insect larvae were made radioactive, introduced into the plant, and pieces of stem tissue were subsequently analyzed for radioactivity. Breakdown products of the insects had moved into the stem tissue and were also translocated up the stem. The conclusion is that the ants “feed” the plant a portion of their catch, thereby maintaining the fecundity of the host plant, and ultimately insuring a supply of homesites.
ON SOME PECULIARITIES IN THE LIFE HISTORY OF PENNATE DIATOMS HITHERTO OVERLOOKED
Authors: Geitler Lothar
Published: January 2018

In this paper, as a sequel of my survey appeared in 1969 in this Journal, supplements are given to the topics “Pairing,” “Gametogenesis,” “Haploid Parthenogenesis,” “Hybrids,” “Automixis,” and “Some Cytological Details” in pennate diatoms. The various kinds of peculiarities are facts—their interpretation in terms of physiology and biochemistry, indeed, rest completely open for future research.
A NEW MODE OF LIFE HISTORY IN THE FRESHWATER RED ALGAL GENUS BATRACHOSPERMUM
Authors: von Stosch H. A. , Theil Gisela
Published: January 2018

In a new type of Batrachospermum life history, the Batrachospermum phase does not originate from the erect filaments of a Pseudochantransia but directly from a prostrate crustose growth, the prothalle of Sirodot. It is probable that the few lowermost segments of those Batrachospermum cladomes are diploid, the remainder due to an interposed “somatic” meiosis are haploid.
GAMETOPHYTE ONTOGENY, SEX EXPRESSION, AND GENETIC LOAD AS MEASURES OF POPULATION DIVERGENCE IN BLECHNUM SPICANT
Authors: Cousens Michael I.
Published: January 2018

Early gametophyte ontogeny was quantitatively distinct for Olympic Peninsula, Alaskan, and disjunct Idaho populations of the homosporous fern Blechnum spicant (L.) J. Sm. Although variable, gametophyte sex expression was shown to have a genetic component. Statistically different patterns of sex expression characterize each population. The Olympic Peninsula populations were distinct from each other but consistent in having a predominantly unisexual pattern. The disjunct Idaho population was predominantly bisexual at the time when comparable field collected gametophytes bear sporophytes. Preliminary experiments suggest that an antheridogen operates in this species. Increased sowing density favors maleness, and an extract from soil cultures of gametophytes shifts cultures to an exclusively male pattern after a dramatic suppression of growth. Mating experiments revealed that all populations are interfertile, although fertility was highest when the test Idaho population underwent intergametophytic‐selfing. The Idaho population evidenced a low level of genetic load consistent with predictions based on its sex expression. Although Olympic Peninsula populations evidenced apparent high genetic load in some experiments, failure to produce abundant sporophytes in other experiments suggested that additional cultural factors operated to reduce sporophyte formation. Moderate density mating experiments produced single sporophytes that were comparable to field collections. Isolated gametophytes underwent polyembryony after a time delay and gametophyte proliferation. Cultural conditions which allow sporophyte formation on isolated gametophytes without this delay or proliferation must be sought before further genetic analysis is undertaken.
THE MORPHOLOGY OF THE EXINE IN NIGELLA (RANUNCULACEAE)
Authors: Skvarla John J. , Nowicke Joan W.
Published: January 2018

The pollen morphology of eight species of Nigella (Ranunculaceae) was examined by scanning and transmission electron microscopy. The exomorphology of all species was identical: 3‐colpate, spinulose, and punctate, but thin sections revealed two structural patterns. The ektexine structure of Nigella integrifolia, consisting of thickened foot layer, columellae, and thin tectum, is typical for the family as well as the order Ranunculales in general. In contrast, the remaining seven species, N. arvensis, N. damascena, N. elata, N. hispanica, N. sativa, N. segetalis, and N. stellaris, have an ektexine with an additional unit, a horizontal layer with shorter columellae, placed between the foot layer and tectum. Of all genera examined in the Ranunculaceae, only Nigella had this unusual stratification. This difference in the exine structure would add support to the treatment of N. integrifolia as a monotypic genus, Komaroffia integrifolia (Regel) Lemos Pereira.
3H‐URIDINE INCORPORATION IN THE PREMITOTIC STAGE OF RHIZOID CELL DIFFERENTIATION IN PTERIS VITTATA L.
Authors: Cohen David , Crotty William J.
Published: January 2018

The premitotic rhizoid stage (corona stage) of P. vittata gametophytes was pulsed in radioactive uridine for 5, 15, or 30 min and the data analyzed quantitatively by autoradiography. After 5 min, only the nucleoplasmic compartment is labelled significantly, suggesting that this short pulse is insufficient time for labelled precursor to be fixed in the nucleolus or to be transported from the nucleus to the cytoplasm. Since after 15 and 30 min, all compartments are labelled, with the greatest proportional increase over the nucleolus, it is concluded that cytoplasmic labelling is nuclear in origin and that nucleolar RNA activity is relatively high in this stage.
DICTYOSTELIUM AUREO‐STIPES AND DICTYOSTELIUM TENUE: NEW SPECIES OF THE DICTYOSTELIACEAE
Authors: Cavender James C. , Raper Kenneth B. , Norberg Ann M.
Published: January 2018

Three new cellular slime molds, Dictyostelium aureo‐stipes sp. n., D. aureo‐stipes var. helvetium var. n. and D. tenue sp. n., are described which possess characteristics heretofore unrecorded in the Dictyosteliaceae. The two species are unlike in dimensions and complexity of form, yet show a number of features in common, and may in fact be closely related. D. aureo‐stipes var. helvetium is relatively large and robust, forming multiple‐branched fruiting bodies without the regularity of form found in Polysphondylium, yet tending toward symmetry when well‐developed. The golden‐yellow stipe is a distinguishing feature of D. aureo‐stipes and is even more pronounced in var. helvetium. D. tenue is smaller and simpler in form. The degree of branching is much reduced, and oftentimes a solitary sorus terminates a delicate stipe composed of a single tier of cells. Both species are quite sensitive to environmental conditions, particularly temperature, for optimum development occurs within relatively narrow ranges.
PLASTIDS IN LATICIFERS OF PAPAVER. I. DEVELOPMENT AND CYTOCHEMISTRY OF LATICIFER PLASTIDS IN P. SOMNIFERUM L. (PAPAVERACEAE)
Authors: Nessler Craig L. , Mahlberg Paul G.
Published: January 2018

Plastids were observed in all stages of laticifer differentiation in Papaver somniferum L. Plastids in laticifer initials were present as proplastids that later developed electron‐dense inclusions, but never possessed the thylakoids or starch grains that characterize chloroplasts in other cells. Electron‐dense inclusions in laticifer plastids were membrane‐bound and appeared to arise from the accumulation of material within an invagination of the inner plastid membrane. Cytochemical studies of these plastid inclusions indicated that their matrix was not composed of crystalline protein, α‐amylose, amylopectin or polysaccharide. The results suggest that the electron‐dense, membrane‐bound inclusions in laticifer plastids may be composed of lipoprotein.
14C UPTAKE BY THE MARINE ANGIOSPERM PHYLLOSPADIX SCOULERP
Authors: Barbour Michael G. , Radosevich Steven R.
Published: January 2018

Rhizomes and attached leaves of Phyllospadix scouleri Hook, were collected in the intertidal zone along the central California coast and exposed to a solution of NaH14CO3 in seawater under controlled laboratory conditions. Over a 90‐min period roots and rhizomes absorbed very little 14C compared to leaves. Translocation during that time was minor. Plants pretreated with the photosynthetic inhibitor DCMU showed no 14C uptake, indicating that under normal circumstances the carbon which is absorbed by leaves is fixed and accumulates as photosynthate. The rate of gross photosynthesis was about 13 mg CO2 g dry wt−1 hr−1. Gross photosynthesis of wet leaves exposed to 14CO2 in air was significantly less than leaves exposed to NaH14CO3. The effect of a leaf‐grazing limpet (Notoacmea paleacea) on leaf anatomy and 14C uptake is discussed.
EVALUATION OF PROLINE ACCUMULATION IN THE ADAPTATION OF DIVERSE SPECIES OF MARSH HALOPHYTES TO THE SALINE ENVIRONMENT
Authors: Cavalieri Anthony J. , Huang Anthony H. C.
Published: January 2018

Proline accumulation by eight major species of salt marsh halophytes was examined under growth chamber and field conditions. When the plants were exposed to increasing salinities in the growth chamber, they accumulated proline after a threshold salinity had been reached. Three general patterns were apparent. Limonium carolinianum (Walt.) Britt. and Junius roemerianus Scheele began to accumulate proline at 0.25 m NaCl with accumulations up to 63.6 μmoles per gram fresh weight at higher salinities. The C4 grasses, Spartina alterniflora Loisel., Spartina patens (Aiton) Muhl., and Distichlis spicata (L.) Greene, had threshold salinity levels around 0.5 m NaCl and accumulated proline to 27.4 μmoles per gram fresh weight. The succulents, Salicornia bigelovii Torr., Salicornia virginica L., and Borrichia frutescens (L.) DC, did not accumulate proline until very high salinities (0.7 m) were reached. Water stress imposed by polyethylene glycol instead of NaCl caused similar proline accumulation in the species studied, but to different extents. Field measurements of proline content and soil salinities correlated well with the findings from growth chamber experiments. Rates of proline accumulation and breakdown in L. carolinianum were sufficient for osmotic adjustment by the plant to the changes in interstitial salinity in the marsh. The significance of proline accumulation as an adaptation to the salt marsh environment was species specific. We suggest that proline accumulation is of considerable importance in L. carolinianum and J. roemerianus, important to the C4 grasses at certain times and in certain locations in the marsh, and of little importance in the succulents.
ECOLOGICAL DIFFERENTIATION IN PERENNIAL, OCTOPLOID SPECIES OF FRAGARIA
Authors: Hancock J. F. , Bringhurst R. S.
Published: January 2018

Plants of octoploid Fragaria (2n = 56) were collected from 19 natural sites supporting strawberry colonies in California, grown in a common greenhouse and analyzed for 25 quantitative traits and 2 enzyme systems. Inter‐populational variation was measured by using analysis of variance and genetic identity techniques. Micro‐ and macro‐environmental measurements were made at each site. Stepwise multiple regressions were completed on the morphological‐environmental variations and the allozyme frequency‐environmental variations. Clonal propagules were compared under three controlled environmental conditions. Octoploid Fragaria appears to have undergone considerable ecological differentiation. Significant amounts of inter‐populational variation were observed in a number of polygenic and monogenic traits. Numerous significant correlations were found between environmental and character variations, and in many cases, only a few environmental variables were necessary to “explain” significant amounts of that variation. Inter‐populational differences were also found in the abilities of plants to accumulate biomass and survive under salt, nutrient and shade stress. It has been suggested that ecological differentiation plays a minor role in determining the eco‐geographical range of allopolyploids due to the effects of polyploidy on the generation of mutational and recombinational variability. Clearly, this has not been the case in Fragaria.
OLIGOTROPHIC TILLANDSIA CIRCINNATA SCHLECHT (BROMELIACEAE): AN ASSESSMENT OF ITS PATTERNS OF MINERAL ALLOCATION AND REPRODUCTION
Authors: Benzing D. H. , Davidson E. A.
Published: January 2018

Analyses ofTillandsia circinnataSchlecht specimens from nutrient‐stressed and more fertile habitats in southern Florida confirmed earlier findings that its vegetative and reproductive vigor are enhanced as shoot tissue concentrations of P, K and Mg increase. Demands by this perennial herb for N, P and K are more pronounced than for B, Ca, Cu, Fe, Mg, Mn, Mo and Zn, primarily because N, P and K must be maintained at relatively high concentrations in vegetative tissues and are heavily expended during seed production. When most or all of this epiphyte's self‐fertile flowers set fruit— a fairly common occurrence in most of the populations examined—asexual propagation by offshoot is subordinated to the sexual effort, especially if the specimen is growing in an unusually sterile habitat and has very limited mineral resources. Predictions implicit inr‐Kselection and related life history theory are consistent with the notion presented here thatT. circinnatais following a pattern of nutrient use for reproductive purposes that represents a highly adaptive way to expend slowly accumulated mineral resources in stressful habitats represented by small, scattered, short‐lived microsites. Specifically, it expends scarce mineral resources during the reproductive effort in a way that greatly enhances fecundity and vagility while minimizing the rate at which new microsites and reproducing individuals must be recruited. Reproduction and mineral use byT. circinnatais compared with that ofT. utriculata, a semelparous epiphyte that shares many of the same forest habitats in southern Florida.
COMPARATIVE LEAF STRUCTURE OF SEVERAL SPECIES OF HOMOSPOROUS LEPTOSPORANGIATE FERNS
Authors: Warmbrodt Robert D. , Evert Ray F.
Published: January 2018

The structure of the mature leaves of 13 species from 9 families of homosporous leptosporangiate ferns was examined by light and electron microscopy. In 11 species (Adiantum pedatum L., Athyrium angustum Roth., Cyathea dregei Sm., Lygodium palmatum Sw., Mohria caffrorum (L.) Desv., Oleandra distenta Kuntae, Pellaea calomelanos (Sw.) Link, Pityrogramma calomelanos (L.) Link var. austro‐americana (Domn.) Farw., Trichomanes melanotrichum Schlechtend., Vittaria guineensis Desv., and Woodwardia orientalis Sw.) the lamina veins are collateral; in two (Phlebodium aureum and Platycerium bifurcatum), bicollateral as well as collateral veins are present. The vascular bundles in the midribs of C. dregei and those in the petioles and midribs of Phlebodium and Platycerium are concentric. All of the vascular bundles in the homosporous leptosporangiate ferns studied are delimited by a tightly arranged cylinder of endodermal cells with Casparian strips. Within the veins without parenchymatic xylem sheaths, some sieve elements commonly abut tracheary elements with hydrolyzed primary walls. The majority of vascular parenchyma cells contact both sieve elements and tracheary elements, although some parenchyma cells are associated with only one type of conducting cell. Transfer cells (parenchyma cells with wall ingrowths) occur in the veins of 6 species examined. Most of the vascular parenchyma cells, however, have no distinctive structural characteristics. The sieve elements of the homosporous leptosporangiate ferns are very similar structurally and each consists of a plasmalemma, a parietal, anastomosing network of smooth endoplasmic reticulum (ER), and variable numbers of refractive spherules, plastids and mitochondria. The sieve elements of L. palmatum also contain plasmalemma tubules. The parenchymatic cells of the leaf (mesophyll, endodermal and vascular parenchyma cells) are united by desmotubule‐containing plasmodesmata. The sieve elements are connected to each other by sieve pores and to parenchymatic cells by pore‐plasmodesma connections. The sieve‐area pores contain variable amounts of membranous material, apparently ER membranes, but do not occlude them. These membranes commonly are found in continuity with the parietal ER of the lumen. Based upon the relative frequencies of cytoplasmic connections between cell types, the photosynthates may move from the mesophyll to the site of phloem loading via somewhat different pathways in different species of homosporous leptosporangiate ferns.
CYTOKININ‐ELICITED FORMATION OF THE PITH‐RIB MERISTEM AND OTHER EFFECTS OF GROWTH REGULATORS ON THE MORPHOGENESIS OF ECHINOCEREUS (CACTACEAE) SEEDLING SHOOT APICAL MERISTEMS
Authors: Mauseth James D.
Published: January 2018

Shoot apical meristems of Echinocereus engelmannii have only a tunica‐corpus organization at germination, but the corpus rapidly develops central mother cells, a peripheral zone and a pith‐rib meristem. The manner in which nutrition, darkness and various growth regulators at several concentrations and in several combinations affect the development of zonation was examined by growing derooted seedlings on agar which contained the nutrients or growth regulators. Benzylaminopurine was able to elicit the formation of the pith‐rib meristem in an otherwise non‐zonate corpus. Also, the rate of leaf initiation was greatly increased. Gibberellic acid severely inhibited the formation of corpus zones but had little effect on leaf initiation. Indoleacetic acid had no effects other than mild inhibition of zonation and a slight retardation of leaf initiation. Abscisic acid was strongly inhibitory. Sucrose only slightly increased the rate of leaf formation and did not affect apex size or zonation. To more closely examine the cytokinin‐induced effects on the apical meristem, several growth regulators were applied in combination with the most effective concentration of cytokinin. Certain combinations were able to interfere with several of the cytokinin‐induced responses, while other cytokinin‐induced responses occurred even in the presence of high concentrations of these other growth regulators. Leaf initiation and meristem morphogenesis appeared to be remarkably stable and insensitive to the presence of most hormones except cytokinin and gibberellin.
PHYSIOLOGY AND MICROCLIMATE IN A HEMIPARASITE CASTILLEJA CHROMOSA (SCROPHULARIACEAE)
Authors: Hansen David H.
Published: January 2018

The hypothesis, that through use of a host, a hemiparasitic angiosperm will be able to “uncouple” physiological functions from microenvironmental variations, was tested by field measurements of water and carbohydrate balance between Castilleja chromosa and host Artemisia tridentata in three different microhabitats in the White Mountains of California. Movement of reducing sugars from host to parasite correlated with the water potential gradient from host to parasite, and the gradient occurred when water potentials of the host‐parasite system exceeded 15 bars. Changes in carbohydrate and water balance in Castilleja were unaffected by microclimatic differences, whereas these same functions in the host were tightly coupled with differences in microhabitat.
CELL DIVISION KINETICS IN THE SHOOT APICAL MERISTEM OF CERATOPTERIS THALICTROIDES BRONG. WITH SPECIAL REFERENCE TO THE APICAL CELL
Authors: Polito Vito S.
Published: January 2018

The duration of mitosis and the cell cycle were determined for defined cell populations of the shoot apical meristem of Ceratopteris thalictroides Brong. by using the colchicine‐induced metaphase accumulation technique. The results indicate that the apical cell is mitotically active and cycles at an apparently greater frequency than the cells of subjacent populations. Duration of mitosis was similar for all cells of the meristem. These results are correlated with mitotic indices of control apices, the geometry of the apex, and the mean number of cells in the meristem. Shoot apices from adult plants were examined to determine mitotic indices within the meristem; mitotic activity was again noted for the apical cell. These results contradict recent proposals that the pteridophyte apical cell serves as a unicellular quiescent center which lacks histogenic potential and offer experimental support for the classical concept of apical cell function in those fern shoot meristems which terminate in a single apical cell.
ROOT CONTRACTION IN FREESIA (IRIDACEAE)
Authors: Ruzin Steven E.
Published: January 2018

The contractile roots of the horticultural variety Freesia hybrida Bailey (Iridaceae) were determined to contract via a growth/collapse mechanism. Contraction is initiated by a radial growth of middle and outer cortical parenchyma cells which is morphologically evident by an expanded diameter of the root. No concomitant decrease in length of the actively growing cells was observed. Shortening of the root is caused by axial tension produced by the radial growth of cells contiguous with nonexpanded cells distally. Centripetal collapse of expanded cells, coupled with passive shortening of inner cortical parenchyma and stelar tissues, releases axial tension slowly, returning the shortened root to equilibrium. Inner cortical parenchyma cells shorten in an accordion‐like manner facilitated by partial dissolution of middle lamellar material.
THE FUNCTION OF EXTRAFLORAL NECTARIES IN OPUNTIA ACANTHOCARPA (CACTACEAE)
Authors: Pickett Charles H. , Clark W. Dennis
Published: January 2018

Opuntia acanthocarpa (Cactaceae) possesses extrafloral nectaries embedded in the areoles of new reproductive and vegetative growth. The nectar secreted by these glands attracts ants and is a nutritional food source. Members of one attracted ant species, Crematogaster opuntiae (Myrmicinae), are aggressive and efficient defenders of the plants against cactus‐feeding insects. The results of our study are consistent with the ant‐guard hypothesis for the role of extrafloral nectaries in O. acanthocarpa. Additionally, individuals of O. acanthocarpa are well protected in comparison with those of O. phaeacantha. The latter generally possess ephemeral extrafloral nectaries and consistently maintain fewer ants.
CLEISTOGAMY IN SALPIGLOSSIS SINUATA
Authors: Lee Chi Won , Erickson Homer T. , Janick Jules
Published: January 2018

Cleistogamy in Salpiglossis sinuata L. (Solanaceae) involves a series of developmental events that includes germination of pollen tetrads en masse inside the anther, penetration of pollen tubes through the anther wall toward the stigma which is in contact with the anther, growth of pollen tubes down the style, and, finally, fertilization. This occurs within 6 days from the first appearance of the flower as compared to 10–12 days for normal anthesis of chasmogamous flowers. Coincident with these events in cleistogamous flowers are lack of corolla development and reduced size of androecium and gynoecium.
BRANCH GEOMETRY AND EFFECTIVE LEAF AREA: A STUDY OF TERMINALIA‐BRANCHING PATTERN. 2. SURVEY OF REAL TREES
Authors: Fisher Jack B. , Honda Hisao
Published: January 2018

Branching angles, the angles between branch units of lateral branch complexes, were measured for 32 species of tropical trees with Terminalia‐branching pattern, representing seven dicotyledonous families. Angles of many but not all species are similar to the theoretical optimal values determined by computer simulations based on Terminalia catappa. These theoretical values maximize the effective leaf area of the branch complex. Real branching angles tend to remain relatively constant within a lateral branch complex, although a difference between sapling and adult branches was noted in T. muelleri. The pattern of mirror image symmetry of complexes within one branch tier appears to be random. The coefficient of variation is greater for the separate branching angles of a bifurcation than for the bifurcation angle as a whole. We conclude that observed branching angles optimize effective area in many species (as predicted by the T. catappa model). Large differences between the real and theoretical values for some species may be due to their dissimilarity to the T. catappa simulation.
THE EFFECT OF AERATION ON THE GROWTH OF SPARTINA ALTERNIFLORA LOISEL.
Authors: Linthurst Rick A.
Published: January 2018

A greenhouse experiment was designed to investigate the correlations between waterlogging and aeration, and associated changes in pH, redox potentials and sulfide concentrations, on the growth of Spartina alterniflora Loisel. Elemental concentrations of the aerial and root material were determined and used for correlations with growth response. Redox potentials adjusted to pH 7 (Eh 7) ranged from −184 mv to 5 mv and were highly correlated (r) with aerial and root dry weight biomass (.97 and .97, respectively) and plant height (1.0). The range of soil pH at the conclusion of the study was 6.07 to 6.74 and was negatively correlated with aerial and root dry weight biomass. Sulfide concentrations ranged from 10–2 to 10–7 m and vorrelations with aerial and root dry weights and height were −.85, −.85 and −.87, respectively. High negative correlations were found between sodium and sulfur concentrations and S. alterniflora growth. Positive correlations between potassium, phosphorus, manganese, zinc, copper, iron and growth response were also observed. Correlations of elemental concentrations of the plants with redox potentials and/or pH suggest that these two physical variables may be responsible in part for the regulation of 5. alterniflora growth in nature by regulating availability of nutritional elements.
AN INTERPRETATION OF THE HYDRODYNAMICS OF POLLEN
Authors: Heslop‐Harrison J.
Published: January 2018

The pollen grains of angiosperms are usually desiccated to some extent at the time of dispersal. Rehydration is an essential prelude to germination, and this takes place by uptake of water from the stigma after capture, water entering from the cells of the stigma surface following a water potential gradient. The passage of water into the pollen grain is regulated by the cuticle of the stigma papilla in the vicinity of the contact face, and also by the apertural mechanisms of the pollen grain exine, which act by varying the degree of exposure of the underlying pectocellulosic intine according to the degree of hydration of the grain. The sequence of events during rehydration suggests that at first the vegetative cell of the male gametophyte is without a normal plasmalemma, so that the initial dilation of the grain is followed by an interval of exudation. Thereafter, with the re‐establishment of the cell membranes, the vegetative cell behaves in the manner of a normal plant cell through the period of germination.
AN AUTORADIOGRAPHIC STUDY OF RNA SYNTHESIS DURING POLLEN EMBRYOGENESIS IN HYOSCYAMUS NIGER (HENBANE)
Authors: Raghavan V.
Published: January 2018

RNA synthesis during pollen embryogenesis in cultured anther segments of Hyoscyamus niger (henbane) has been followed by autoradiography of 3H‐uridine incorporation. Embryogenic divisions were initiated in binucleate pollen grains in which the generative nucleus or both generative and vegetative nuclei synthesized RNA. When the first haploid mitosis in culture resulted in pollen grains with two nearly identical nuclei, those in which both nuclei synthesized RNA became embryogenic. Binucleate pollen grains in which 3H‐uridine incorporation was confined exclusively to the vegetative nucleus gradually became starch‐filled and nonembryogenic. Based on the degree of involvement of the vegetative nucleus in embryoid formation, some differences were noted between the counts of autoradiographic silver grains over cells cut off by the generative and vegetative nuclei during progressive embryogenesis. The possible significance of RNA synthesis in the nuclei of binucleate pollen grains in determining the pathway of embryogenic divisions is discussed.
GENOME RELATIONSHIPS OF INTRA‐ AND INTERSECTIONAL SPECIES HYBRIDS OF ONCIDIUM TRIQUETRUM
Authors: Phang V. P. E. , Charanasri U. , Kamemoto H.
Published: January 2018

Chromosome numbers and meiotic behavior of six interspecific hybrids of Oncidium triquetrum were investigated. The somatic chromosome number of O. triquetrum (section Oncidium) x O. variegatum (section Oncidium) was 2n = 42. O. triquetrum x O. splendidum (section Plurituberculata) and O. triquetrum x O. cebolleta (section Cebolletae) were 2n = 39 and O. triquetrum x O. floridanum (section Planilabra), O. triquetrum x O. flexuosum (section Synsepala) and O. triquetrum x O. onustum, (section Onusta) were 2n = 49. The intersectional species hybrid, O. triquetrum x O. variegatum, showed fairly regular meiosis with a mean of 20.4 bivalents, indicating strong homology of parental genomes. In contrast, highly irregular meiosis with poor chromosome pairing was observed in all intersectional hybrids. The mean number of bivalents ranged from 1.8 to 9.5. On the basis of chromosomal affinity at metaphase I, O. triquetrum showed a close relationship to O. variegatum in the same section, but more distant relationships to O. splendidum, O. cebolleta, O. floridanum, O. flexuosum and O. onustum belonging to different sections.
FORMATION OF THE HILAR APPENDIX IN BASIDIOSPORES OF BOLETUS RUBINELLUS
Authors: Yoon Kwon S. , McLaughlin David J.
Published: January 2018

The hilar appendix body is reported in the basidiospore primordium of Boletus rubinellus as well as the subsequent development of the hilar appendix through spore maturation. The hilar appendix body is similar in its morphology and pattern of development to that in Coprinus spp. The evolutionary implications of the results are discussed.
ANOMALOUS SECONDARY THICKENING IN PHYTOLACCA AMERICANA L. (PHYTOLACCACEAE)
Authors: Mikesell Jan E.
Published: January 2018

Differentiation of the primary thickening meristem (PTM) was investigated in seedlings and older plants of Phytolacca americana L. Initiation of the PTM occurs in pericycle or inner cortex at the hypocotyl‐primary root junction of young plants. Differentiation of the PTM in stems occurs acropetally in a cylinder of randomly dividing cells termed the diffuse lateral meristem (DLM). The PTM produces secondary tissue to the inside (internal conjunctive tissue) and to the outside (external conjunctive tissue). Patches of xylem and phloem differentiate, opposite each other, in recently produced internal and external conjunctive tissue, respectively. The resulting strands (desmogen strands) of xylem and phloem are secondary in origin, and are peripheral to primary vascular tissues. Phloem of desmogen strands usually differentiates first. Xylem of desmogen strands is composed of both tracheids and vessel elements; the latter sometimes becoming occluded with tyloses and unidentified substances. As root and hypocotyl increase in diameter, cylinders of PTMs differentiate successively and centrifugally in external conjunctive tissue. Even though the first PTM differentiates in pericycle or inner cortex and later PTMs differentiate in external conjunctive tissue, all are referred to as PTMs because of their similar activity. Multiple rings of desmogen strands can be observed in transections of lateral roots, primary roots and hypocotyls. Throughout the length of the stem, only one ring of desmogen strands is present. Fewer rings of desmogen strands are present in the top of the hypocotyl and cotylendonary node, as compared to the subjacent hypocotyl, due to anastomoses of centrifugally differentiating desmogen strands.
TEMPORAL COMPARTMENTATION IN LEMNA PAUCICOSTATA: PHOTOPERIODISM, RESPIRATION, NITROGEN NUTRITION AND HETEROTROPHIC GROWTH OF DIFFERENT STRAINS
Authors: Hillman William S.
Published: January 2018

In previous work with strain 6746 of Lemna paucicostata Hegelm. in heterotrophic culture, changes in the light schedule affected certain features of the daily respiratory pattern, on some but not all nitrogen sources, in a manner parallelling their effects on timing in the photoperiodic flowering response. Seeking further guidance on which metabolic processes should be investigated to understand this relationship, twelve additional strains were compared with 6746 in regard to 1) heterotrophic flowering under short‐day skeleton photoperiods, and 2) daily respiratory patterns under 0.25 hr daily of dim red light. Heterotrophic flowering occurred in eight strains; among these, several differed sharply from 6746 in the character of their respiratory patterns and the probable relation of those patterns to photoperiodic timing. For example, in 6746, the second daily peak on NO3, NH4 and probably on glutamine reflects photoperiodic timing; the patterns on N‐deficient, aspartate and glutamate media do not. In strains 6609 and 381, in contrast, glutamate also elicits a second peak probably reflective of photoperiodic timing; in strain 421, neither the NO3 nor NH4 patterns resemble those reflecting photoperiodic timing in 6746. Other strain differences in flowering, respiratory patterns and heterotrophic growth provide useful material for studying phytochrome action, N assimilation and respiration, and they confirm the view that strain identity may be crucial in biochemical investigations on Lemnaceae. These results also reinforce the concept that the “temporal compartmentation” of systems entrained to light/dark cycles can provide important insights, and should be more widely used, in work on regulation of plant metabolism.
INFLORESCENCE ARCHITECTURE AND FLOWER SEX RATIOS IN SAGITTARIA BREVIROSTRA (ALISMATACEAE)
Authors: Kaul Robert B.
Published: January 2018

Two populations of Sagittaria brevirostra from the same lake were sampled 10 years apart and yielded similar data on inflorescence structure and on numbers and ratios of male and female flowers. Larger inflorescences have relatively more male than female flowers than do smaller inflorescences. Pollination success is unrelated to inflorescence size or sex ratio within an inflorescence.
MILLAYA GEN. N., AN UPPER PALEOZOIC GENUS OF MARATTIALEAN SYNANGIA
Authors: Mapes Gene , Schabilion J. T.
Published: January 2018

Anatomically preserved fertile marattialean pinnules from the Lower Permian (Wolfcampian) Bursum Formation in Tularosa, New Mexico, and isolated synangia from the Upper Pennsylvanian (Missourian) Stanton Formation near Tyro, Kansas, are described. The sessile synangia are partially sunken into the pinnule lamina and arranged abaxially in a single row on each side of the midrib. Comparisons are made with other fossil and modern marattialeans and the evolutionary significance considered.
WHAT ARE THE CHROMIDIA OF POLYPHAGUS EUGLENAE?
Authors: Powell Martha J.
Published: January 2018

Zoospores, prosporangia, and asexual sporangia were studied with electron microscopy to determine the ultrastructural identification of “chromidia,” granular masses surrounding nuclei that classical mycologists believed to be extruded chromatin used for lipid synthesis. In the zoospore the nucleus was enclosed by an aggregation of ribosomes. In other developmental stages the behavior of microbodies was identical to that described for “chromidia.” A microbody network with interspersed ER surrounded nuclei in young prosporangia. As the prosporangium matured, lipid globules became associated with the microbodies. When the single, large nucleus migrated into the elongate asexual sporangium, microbodies still surrounded the nucleus; but after the nucleus divided and a multinucleate sporangium formed, microbodies were scattered throughout the cytoplasm. When incubated in the diaminobenzidine medium for the cytochemical detection of catalase, reaction product was found in these microbodylike structures, confirming that “chromidia” described in prosporangia and asexual sporangia by classical mycologists are really microbodies. Rather than giving rise to lipid, these microbodies are probably involved in the metabolism of the lipid globules with which they are associated. The “chromidia” in zoospores are not extruded chromatin as suggested earlier, but correspond in their location around the nucleus to an aggregation of ribosomes.
ULTRASTRUCTURE OF CEPHALEUROS VIRESCENS (CHROOLEPIDACEAE; CHLOROPHYTA). II. GAMETES
Authors: Chapman Russell L.
Published: January 2018

Transmission electron microscopic examination ofCephaleuros virescensKunze growing on leaves ofCamelliasp. indicates that gametes are similar to those ofTrentepohlia aurea. The gametes bear two, smooth isokont “keeled” flagella containing typical “9 + 2” axonemes and lacking scales. Flagellar insertion is apical and the parallel basal bodies overlap laterally. Each basal body is associated with a separate multilayered structure and component microtubular spline. The latter extends posteriorly beneath the plasmalemma. A nucleus, mitochondria, chloroplasts, and cytoplasmic haematochrome droplets are present. Pyrenoids and eyespots are absent. The subcellular components ofC. virescensgametes are comparable to those found in gametes ofT. aurea; however, the arrangement of basal bodies and multilayered structures differs slightly from that inT. aurea. Comparison of the fine structure of gametes fromCephaleuros, Phycopeltis, andTrentepohliaclearly indicates that the (1) mode of flagellar insertion, (2) morphology, number, and arrangement of multilayered structures, and (3) keeled flagella are common to these three genera and, thus far, unique among the green algae. Although flagellar insertion is apical, it is not bilaterally symmetrical (sensu stricto), nor is it asymmetrical (cf.CharaandNitellasperms). The arrangement may be termed “reversed bilateral symmetry” and standardization of the terminology is recommended.
ONTOGENY OF MAJOR VEINS IN THE LAMINA OF POPULUS DELTOIDES BARTR
Authors: Isebrands J. G. , Larson Philip R.
Published: January 2018

The ontogeny of the major venation in the lamina of Populus deltoides Bartr. leaves was investigated in relation to the development of original procambial bundles, subsidiary bundles, and their derivatives. Serial sections and clearings were used to show that the midrib region is a composite structure consisting of several independent vascular bundles, each of which eventually diverges into the lamina to become a secondary vein. The sequence of events in the ontogeny of major secondary veins is: (1) an original procambial strand develops acropetally and becomes the precursor of the first vascular bundle of the midrib region of the lamina, (2) ground tissue at the forefront of acropetally developing subsidiary procambial bundles differentiates in a wavelike continuum; meristematic regions precede the acropetally developing procambial bundles, (3) discrete subsidiary bundles differentiate in the meristematic regions as they advance acropetally, (4) subsidiary bundles diverge obliquely in the lamina margin giving rise to the secondary veins in a basipetal fashion, and (5) subsequent differentiation and maturation of the secondary veins occurs within the lamina. The original procambial bundles and first‐formed subsidiary bundles become the secondary veins of the uppermost portions of the lamina, the next‐formed subsidiary bundles become the secondary veins of the middle portions of the lamina, and the last‐formed subsidiary bundles become the secondary veins of the lowermost portion of the lamina.
ANOMALOUS GROWTH AND VEGETATIVE ANATOMY OF SIMMONDSIA CHINENSIS
Authors: Bailey Douglas C.
Published: January 2018

The anatomy of the stem, root, and leaf of Simmondsia chinensis (Link) Schneider was investigated, as well as the mode of tissue formation in the stem. Perivascular tissue is present as part of the primary body; outermost cell layers of this tissue mature as a fibrous sheath. The first short‐lived extrafascicular cambium is generated within the remaining parenchymatous perivascular tissue. Successive independent extrafascicular cambia, organized as complete rings or large arcs, arise within peripheral conjunctive parenchyma produced by previous cambia. Extrafascicular cambia produce secondary xylem centripetally and conjunctive tissue bands and strands of secondary phloem centrifugally. Conjunctive tissue initials produce raylike structures of conjunctive tissue; true vascular rays are absent. The phellogen is actually a region of transition where the peripheral conjunctive parenchyma of previous extrafascicular cambia undergoes further cellular subdivision; a true phellogen is lacking. Xylem bands do not represent annual or seasonal growth increments, and secondary growth in Simmondsia is an unequivocal example of the “concentric” anomaly.
A MORPHOMETRIC STUDY OF THE ULTRASTRUCTURE OF ECHINOCEREUS ENGELMANNII (CACTACEAE). I. SHOOT APICAL MERISTEMS AT GERMINATION
Authors: Mauseth James D.
Published: January 2018

At germination the shoot apical meristems of Echinocereus engelmannii were discs with a volume of 666,000 μm3 and were composed of a unistratose tunica (volume: 260,000 μm3) and a corpus which was two cell‐layers thick (volume: 406,000 μm3). Four days after germination the nucleus constituted 28.9% of the volume of the cell, and the vacuole constituted 24.5%. The mitochondria were 13.3% of the volume of the tunica cytoplasm, the chloroplasts 9.4%, and the dictyosomes only 1.2%. The endoplasmic reticulum was too sparse to be accurately measured. The organelles of the corpus were identical in size and shape to those of the tunica, but there were statistically significant differences in their cellular and cytoplasmic densities: the more distal corpus layer (C1) was less vacuolate (16.6% of the cell volume), and both corpus layers contained more chloroplasts, 12.0% of the cytoplasmic volume in C1 and 14.3% in the more proximal corpus layer (C2). During the first four days after germination there was a dramatic increase in the size of the central vacuole (e.g., from 15.4% to 24.5% in the tunica), and the mitochondria increased in density from 10.2% of the cytoplasmic volume to 13.3%. Chloroplast density also increased in all meristem layers, but the dictyosome density decreased, as much as a 30% loss in C2. There was also a highly significant reduction in the number of cisternae per dictyosome, from 5.47 to 4.77. Surprisingly, there was no change in heterochromatin: ca. 27% of the volume of the nuclei of all layers was heterochromatic at all stages studied. Thus, the organellar structure of corpus cells is distinctly different from that of tunica cells, and as the apical meristem becomes active after germination, the changes which occur are not uniform in the meristem but rather are zone‐specific.
MORPHOLOGICAL STUDIES OF THE NYMPHAEACEAE. XI. THE FLORAL BIOLOGY OF NELUMBO PENTAPETALA
Authors: Schneider Edward L. , Buchanan John D.
Published: January 2018

The floral biology of Nelumbo pentapetala (Walter) Fernald, the American lotus, native to Texas, was investigated. Anthesis occurs over three consecutive days with flowers opening each morning and closing around noon. First‐day flowers are protogynous with the perianth parts partially expanded so that pollen‐covered insects which are attracted by floral color and the intense “fruity” odor (diffused with the aid of increased floral temperature) are directed on to the flattened receptacle (= carpellary receptacle) from which the receptive stigmas protrude, thus accomplishing pollination. During the second morning anther dehiscence begins and insects which visit and forage within the flower become covered with pollen and typically crawl over the still receptive stigmas achieving “facilitated” self‐pollination (indirect autogamy). By mid‐morning of the second day the stigmas dry and become non‐receptive to pollen. During the third day of anthesis perianth and staminal parts quickly abscise and over the period of a few weeks the receptacle and enclosed fruits mature. In most populations studied, Hymenoptera (e.g., Lusioglossum spp., and Apis mellifera) were the most abundant and effective pollinators. In some populations, however, Coleoptera (e.g., Chauliognathus) were also numerous and effective pollinators. It is suggested that the overall floral structure (e.g., large numbers of stamens, masses of pollen, staminal appendages) are adaptations which facilitate the pollination of Nelumbo by beetles.