Trichome forms in Ardisia (Myrsinaceae) in relation to the bacterial leaf nodule symbiosis

Symbiotic leaf-nodule bacteria in nodulated members of Rubiaceae live in mucilage secreted by colleters located on stipules within buds. These differ from colleters on most nodule-free species. This study was undertaken to examine buds of Ardisia and the related monotypic Amblyanthus of Myrsinaceae to see if nodulated species had secretory structures dissimilar from those of nodule-free species. Buds removed from herbarium specimens (61 species) and live plants (3 species) were paraffin-sectioned. Diverse trichome forms occur, including dimorphism between adaxial and abaxial trichomes in some species. Species within each subgenus were arranged according to trichome form: peltate scale, irregularly capitate, capitate, sessile capitate, bicellular capitate, and uniseriate. Only seven Ardisia species (all in subgenus Crispardisia, widely assumed to have bacteria in marginal leaf nodules of all 30 species) have short-lived trichomes bearing one or more elongate, swollen, distal cells that appear to be secretory cells. These trichomes are analogous to the dendroid or brushlike colleters of nodulated Rubiaceae. Druses occur in most subgenera and this appears to be by far the most predominant crystal type m Ardisia.     

SCANNING ELECTRON MICROSCOPY OF CORALLINA AND HALIPTILON (CORALLINACEAE,RHODOPHYTA): SURFACE FEATURES AND THEIR TAXONOMIC IMPLICATIONS1

Scanning electron microscopy of intergenicula in members of the subfamily Corallinoideae reveals two distinctive surface morphologies: a Corallina-type (C-type) with round to irregular cell outlines and round trichocyte bases, and a Jania-type (J-type) with elongate, polygonal cell outlines and elongate trichocyte bases with excentric pores. The surface results from the calcified lateral walls of the epithallial cells projecting up from around collapsed protoplasts. Since J-type surfaces and trichocytes only occur in unequivocal members of the tribe Janieae—especially the genera Jania and Haliptilon, the presence of J-type surfaces in questionable members of Corallina reveals that they in fact belong to Haliptilon. Thus the two surface types clarify previously difficult taxonomic distinctions between Haliptilon and Corallina and allow identification to genus from purely vegetative material. Seventeen new combinations in Haliptilon are proposed. These results have considerable biogeographic implications with tropical species found to belong to Haliptilon, and Corallina sensu stricto being recognized primarily as a temperate and cold water genus.     

TYPES OF LATICIFERS AND CRYSTALS IN JATROPHA AND THEIR TAXONOMIC IMPLICATIONS

Anatomical examination of 37 species of Jatropha (Euphorbiaceae) has revealed the occurrence of two distinct types of laticifers—articulated, and nonarticulated—in addition to idioblasts that are irregularly shaped individual cells. With the notable exception of J. augustii Pax & K. Hoffm. (section Peltatae (Pax) Dehgan & Webster), these idioblasts occur in the two most advanced sections of the subgenus Curcas (Adans.) Pax, namely Loureira (Cav.) Muell. Arg. ex Pax and Mozinna (Ortega) Pax. The presence of two laticifer types and “idioblastic laticifers” in the genus, in association with the morphological reduction series found with evolutionary advancement are, therefore, significant in the delimitation of sections and subsections. Further evidence is presented by the occurrence of “chambered crystalliferous cells” in subgenus Curcas, but not in subgenus Jatropha (=Adenorhopium Griseb.). Reexamination of laticifers in other genera of the Euphorbiaceae is suggested as a possible means of alleviating the long-standing taxonomic dilemma of this large and morphologically diverse family.     

HYBRIDIZATION AND CYTOTAXONOMY OF DICENTRA

Biosystematic relationships among species assigned to three subgenera of the genus Dicentra were investigated with respect to hybridization and chromosomal constitution and fertility of the hybrids. Four species of subgenus Dicentra, D. formosa, D. eximia, D. nevadensis, and D. peregrina, were intercrossed in various ways to form diploid, triploid, and tetraploid hybrids. Hybrids at the tetraploid level in this subgenus invariably were highly fertile. Triploid hybrids, as expected, were mostly very sterile. Diploid hybrids varied in this respect, but none was highly fertile. Crosses with two of the remaining four species of subgenus Dicentra produced no hybrids, but abundant seed was obtained in one instance. The two species of the subgenus Chrysocapnos, D. chrysaniha and D. ochroleuca, cross to produce a partially fertile tetraploid hybrid, but cross-pollinations involving these species with those of other subgenera failed. The single species of subgenus Hedycapnos, D. spectablis (diploid) produced no hybrids when cross-pollinated with members of the other two sections. These results are fully concordant with presumed affinities based on morphological similarity In addition, preliminary results of hybridization between the monocotyledonous D. peregrina and a number of dicotyledonous species of Dicentra are reported.     

TAXONOMIC REVISION OF SARGASSUM SPECIES (FUCALES,PHAEOPHYCEAE) FROM NEW CALEDONIA BASED ON MORPHOLOGICAL AND MOLECULAR ANALYSES1

Sargassum C. Agardh (1820) is a taxonomically difficult genus distributed worldwide and reported as the most species‐rich genus of the Fucales. It is especially abundant in the Pacific where decreasing species richness is reported to occur from west to east. New Caledonia has been recognized as one of the hotspots of Sargassum diversity; however, species lists available for this region are old and incomplete and have not yet been updated with regard to the latest taxonomic revisions published. This study aimed at revising Sargassum diversity in New Caledonia and to assess its geographic affinities with neighboring Pacific regions. We used combined morphological and DNA analyses on new collections and examined numerous type specimens. Although 45 taxa have been listed in the literature, most of them have been either transferred to synonymy since or misidentified, and in this study, only 12 taxa were recognized as occurring in New Caledonia. They belong to the subgenus Sargassum sect. Binderianae (Grunow) Mattio et Payri (2), sect. Ilicifoliae (J. Agardh) Mattio et Payri (2), sect. Polycystae Mattio et Payri. (1), sect. Sargassum (4), sect. Zygocarpicae (J. Agardh) Setch. (2), and subgenus Phyllotrichia (Aresh.) J. Agardh (1). New Caledonian Sargassum flora appeared as the second richest in the region after the Pacific coast of Australia, with which it has shown high similarity, and shared species with all neighboring regions. One species, S. turbinarioides Grunow, is considered as endemic to New Caledonia. The low genetic diversity detected among several polymorphic species belonging to sect. Sargassum is also discussed.     

Drought acclimation among tropical forest shrubs (Psychotria,Rubiaceae)

Summary Mechanisms of dry-season drought resistance were evaluated for five evergreen shrubs (Psychotria, Rubiaceae) which occur syntopically in tropical moist forest in central Panama. Rooting depths, leaf conductance, tissue osmotic potentials and elasticity, and the timing of leaf production were evaluated. From wet to dry season, tissue osmotic potentials declined and moduli of elasticity increased in four and five species, respectively. Irrigation only affected osmotic adjustment by P. furcata. The other seasonal changes in leaf tissue properties represented ontogenetic change. Nevertheless, they made an important contribution to dry-season turgor maintenance. Small between-year differences in dry season rainfall had large effects on plant water status. In 1986, 51 mm of rain fell between 1 January and 31 March, and pre-dawn turgor potentials averaged <0.1 MPa for all five Psychotria species in March (Wright 1991). In 1989, 111 mm of rain fell in the same period, pre-dawn turgor potentials averaged from 0.75 to 1.0 MPa for three of the species in April, and only P. chagrensis lost turgor. The relation between leaf production and drought differed among species. P. limonensis was buffered against drought by the lowest dry-season conductances and the deepest roots (averaging 244% deeper than its congeners) and was the only species to produce large numbers of leaves in the dry season. P. chagrensis was most susceptible to drought, and leaf production ceased as turgor loss developed. For the other species, water stress during severe dry seasons may select against dry-season leaf production.     

Chemical Constituents of Plants from the Genus Psychotria

Psychotria is a genus of ca. 1500 species in the family Rubiaceae. Up to now, 41 species of the Psychotria genus have been chemically investigated, and 159 compounds, including alkaloids of indole, quinoline and benzoquinolizidine type, terpenoids, steroids, phenolics and aliphatic compounds have been isolated. These compounds show potent bioactivities, such as antimicrobial, antiviral, and antiparasitic activities.     

ANATOMICAL STUDIES OF CYATHEA AND TRICHIPTERIS (CYATHEACEAE)

Comparative anatomical studies of the mature stems of two species each of Trichipteris and Cyathea (Cyatheaceae) are described. The outermost boundary of the stem is typically a two-layered hypodermis. Mucilage-sac cells are randomly distributed in all parenchymatous areas of the stem and form articulated laticifer systems. Localized areas of sclerenchyma tissue occur in the cortex of both T. microphylla and C. suprastrigosa. All species studied possess medullary bundles, whereas cortical bundles are found only in T. trichiata. Accessory bundles occasionally are associated with indentations in the internal stelar sheath of T. trichiata. The stelar pattern in each genus is a dictyostele and consists of individual meristeles. Distinctive cubical cells typically occur wherever sclerenchymatous fibers and parenchyma cells abut one another. Tangential cells occur within the primary phloem of each meristele, and occasionally within the larger accessory bundles. The primary xylem of the adventitious roots is typically diarch, although triarch and tetrarch xylem may occur. Leaf traces and petiole strands are similar anatomically to the accessory bundles. Based upon this study Trichipteris and Cyathea show striking anatomical similarities, and appear to be closely-related taxa.     

Application of epidermal morphology to taxonomic delimitations in the genus Jatropha L. (Euphorbiaceae)*

SEM examination of the epidermis of mature leaves of 37 species in the ten sections of Jatropha (Euphoi-biaceae) has provided information consistent with an earlier revision of the genuS. All species examined show basic paracyic stomata, excluding J.fremontioides which has anisocytic stomata. Subgenera are well demarcated by presence of true paracytic stomata in subgenus Curcas and hrachyparacytic stomata in subgenus Jatropha. The two subgenera can also be distinguished by the presence of smooth hairs in subgenusJatropha and verrucose hairs in subgenus Curcas (except in section Curcas).Uniseriate, inulticellular hairs occur only in the three most advanced.closely related.sections (Jatropha, Collenucia and Spinosae) in subgenus Jatropha.Similarities and dissimilarities of cuticular ornamentations, shape of the epidermal and vein cells and direction of anticlinal walls can be used as distinguishing characters, usually significant at the species level.     

OCCURRENCE OF INTERCALARY AND UNINTERRUPTED MERISTEMS IN EQUISETUM

Quantitative data on cell length and mitotic index in elongating internodes of seven species of Equisetum are presented as evidence for the occurrence of two patterns of internode development in rhizomes of different species. In rhizomes of three species of subgenus Equisetum (E. arvense, E. diffusum, E. telmateia) uninterrupted meristems are present, characterized by acropetal internode maturation. In rhizomes of four species of subgenus Hippochaetae (E. hyemale, E. variegatum, E. scripoides, and E. laevigatum) intercalary meristems are present. The number and locations of intercalary meristems are described for an aerial shoot of E. diffusum. The absence or diminution of intercalary meristems from rhizomes of a variety of vascular plants with intercalary meristems in aerial shoots is discussed from the standpoint of adaptive significance.     

A CHLOROPLAST-DNA PHYLOGENY OF THE WILD PERENNIAL RELATIVES OF SOYBEAN (GLYCINE SUBGENUS GLYCINE): CONGRUENCE WITH MORPHOLOGICAL AND CROSSING GROUPS

Hypotheses of evolutionary relationships among the Australian wild perennial relatives of soybean (Glycine subgenus Glycine) are based largely on patterns of meiotic pairing in intra- and interspecific experimental hybrids. This evidence has indicated a number of genome groupings within the subgenus but has not resolved most phylogenetic relationships. Restriction-endonuclease site variation of chloroplast DNA (cpDNA) within the perennial subgenus is reported here, representing a sampling of approximately 3% of the approximately 150-kilobase plastome. Seven hundred twenty-one unique restriction sites were compared within Glycine using 29 restriction endonucleases; 157 sites varied within the genus. Distance and parsimony methods using these data yielded congruent results, recognizing the existence of three major groups within subgenus Glycine: the species-rich and geographically diverse A clade consisting of G. canescens and related taxa; the B clade, which includes the stoloniferous species; and the C group, containing two species with distinctive curved pods. These results are in general agreement with hypotheses based on genome analysis; inconsistencies involve the inclusion of genetically divergent taxa such as G. falcata in well-supported plastome clades comprised of otherwise interfertile species. Such findings are not unexpected if crossing barriers are considered to be unique features of such anomalous species, paralleling their often numerous morphological and cpDNA autapomorphies. Consideration of cpDNA divergence within the three major clades of subgenus Glycine indicates that the rate of plastome evolution is uncoupled from rates of morphological or ecological diversification.     

Absence of CeCl3-detectable peroxisomal glycolate-oxidase activity in developing raphide crystal idioblasts in leaves of Psychotria punctata Vatke and roots of Yucca torreyi L.

Three peroxisomal enzymes, glycolate oxidase, urate oxidase and catalase were localized cytochemically in Psychotria punctata (Rubiaceae) leaves and Yucca torreyi (Agavaceae) seedling root tips, both of which contain developing and mature calcium-oxalate raphide crystal idioblasts. Glycolate-oxidase (EC 1.1.3.1) and catalase (EC 1.11.1.6) activities were present within leaftype peroxisomes in nonidioblastic mesophyll cells in Psychotria leaves, while urate-oxidase (EC 1.7.3.3) activity could not be conclusively demonstrated in these organelles. Unspecialized peroxisomes in cortical parenchyma of Yucca roots exhibited activities of all three enzymes. Reactionproduct deposits attributable to glycolate-oxidase activity were never observed in peroxisomes of any developing or mature crystal idioblasts of Psychotria or Yucca. Catalase localization indicates that idioblast microbodies are functional peroxisomes. The apparent absence of glycolate oxidase in crystal idioblasts of Psychotria and Yucca casts serious doubt that pathways involving this enzyme are operational in the synthesis of the oxalic acid precipitated as calcium-oxalate crystals in these cells.Abbreviations AMPD 2-amino-2-methyl-1,3-propandiol - CTEM conventional transmission electron microscopy - DAB 3,3-diaminobenzidine tetrahydrochloride - HVEM high-voltage electron microscopy     

OCCURRENCE,TYPE, AND LOCATION OF CALCIUM OXALATE CRYSTALS IN LEAVES AND STEMS OF 16 SPECIES OF POISONOUS PLANTS

Crystals in 16 species of poisonous plants growing naturally in Saudi Arabia were studied with light microscopy. Three types of crystals were observed: druses, prismatics, and crystal sand. Raphides and styloids were not observed in any of the species studied. Druses occur more frequently in the leaf midrib and in the cortex and pith of the stem. In contrast, crystal sand and prismatic crystals are rare and occur in the leaf, intercostal lamina, and in the vascular tissues. The preliminary results show the absence of the three types of calcium oxalate crystals in the stem and leaf of seven species: Ammi majus L., Anagallis arvensis L., Calotropis procera Ait., Citrullus colocynthis (L.) Schard, Euphorbia peplis L., Hyoscyamus muticus L., and Solarium nigrum L., and the presence of druses, prismatic crystals, and crystal sand either in the leaf and stem or in the leaves or stems of nine species: Anabasis articulata (Forssk.) Moq. in DC., Chenopodium album L., Convolvulus arvensis L., Datura stramonium L., Nerium oleander L., Ricinus communis L., Rumex nervosus Vahl., Pergularia tomentosa L., and Withania somnifera (L.) Dun. in DC. These observations indicate that there is no apparent relationship between the distribution of calcium oxalate crystals and the toxic organs of the plants, and supports the view that the presence of calcium oxalate crystals may not be related to plant toxicity.     

Colleter morphology in Pavetta, Neorosea and Tricalysia (Rubiaceae) and its relationship to the bacterial leaf nodule symbiosis

Buds removed from herbarium specimens were processed for light microscopic examination of colleter form and anatomy. Most Pavetta species have dendroid colleters and bacterial leaf nodules, a correlation also found in an earlier study of Psychotria. Colleters of Neorosea , another genus with leaf-nodulated species, are more like the standard rubiaceous type that predominates in the family except that they have irregular, bulging epidermal cells. Tricalysia , a nodule-free genus closely related to Neorosea , shows a range of colleter form from standard to dendroid, and some species have the Neorosea type of colleter. Such morphological correlation between the bacterial leaf nodule symbiosis in Pavetta and Psychotria and dendroid colleters may indicate a chemical change in colleter secretion. Apart from their involvement with the bacterial symbiosis, rubiaceous colleters have now been shown to vary sufficiently in certain taxa to be considered as additional useful taxonomic characters.     

THE FLAVONOIDS OF THE DECIDUOUS RHODODENDRON OF NORTH AMERICA (ERICACEAE)

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

CYTOGEOGRAPHY AND PHYLOGENY OF THE NORTH AMERICAN SPECIES OF VERBENA

Lewis , Walter H., and Royce L. Oliver . (Stephen F. Austin State Coll., Nacogdoches, Texas.) Cytogeography and phylogeny of the North American species of Verbena. Amer. Jour. Bot. 48(7): 638–643. Illus. 1961.—Chromosome numbers of 26 Verbena species in North America, separable into 2 series, are reported. The x = 5 series has no diploid representative, few tetraploids, and numerous widespread hexaploid species, while the x = 7 series has many pandemic diploid species and few tetraploid and hexaploid taxa. When compared with the data available for the South American verbenas, these frequencies and distributions were found to be almost opposite. The origin of the 2 groups from an x = 6 prototype followed by ascending and descending aneuploidy is suggested. Migration via tropical land bridges is proposed to explain the occurrence of both groups in the 2 continents. The following taxa are proposed: subgenus Verbenaca (Schauer) Lewis, and subgenus Glandularia (Gmelin) Lewis.     

STUDIES OF PALEOZOIC MARATTIALEANS: THE MORPHOLOGY AND PHYLOGENETIC POSITION OF EOANGIOPTERIS GOODII SP. N.

Eoangiopteris goodii sp. n. is described from Upper Pennsylvanian coal balls from Ohio (Shade locality) containing isolated pecopterid pinnules approx. 7 × 9 mm that bear up to 20 linear synangia on the lower surface. The synangia extend at right angles from the midrib to the downturned pinnule margins and measure 2.0–3.5 mm in length. Individual synangia are compact and are composed of 10–19 sporangia that have their bases embedded in an elongate parenchymatous pad. In longitudinal section sporangia measure 0.4 × 2.0 mm and have acute elongate, curved apices. Spores average 70 μm in diam and are most similar to the dispersed spore genus Verrucosisporites. Eoangiopteris goodii differs from the generitype E. andrewsii Mamay in its greater size, pinnule histology, and spore type. Sporangium wall complexity and spore type of the two presently known species of Eoangiopteris are considered to be at about the same evolutionary level as the more primitive species of Scolecopteris. Construction of the synangia in Eoangiopteris is different from that of Scolecopteris and indicates that at least two evolutionary lines are recognizable within the Pennsylvanian Marattiales.     

SPONTANEOUS PARTIAL ROTATION AND OSCILLATION OF THE PROTOPLASM IN COLEOCHAETE AND OTHER CHLOROPHYCEAE

Geitler , Lothar . (Botanisches Institut, Universität, Wien, Austria.) Spontaneous partial rotation and oscillation of the protoplasm in Coleochaete and other Chlorophyceae. Amer. Jour. Bot. 48(8): 738–741. 1961.—In certain differentiated cells, such as the hairs, zoosporangia, oogonia, but also in the unicellular germlings, of species of Coleochaete, Chaetotheke, and Chaetosphaeridium, there occurs regularly a spontaneous movement of the protoplasm, which expresses itself strikingly in rapid rotation or oscillation of the chromatophore. The movement occurs partially and localized in certain parts of the cell. It is comparable to no type of protoplasmic streaming known up to the present. Rotation and oscillation occur as regular, cell-specific attributes, but rotation may be converted experimentally and transiently into oscillation. Oscillation is an intermittent rotation with periodic change of direction. Exploratory researches concerning osmotic values and permeability do not yet reveal definite relationships between the several types of movement in various specialized cells and their physiological condition. However, only the hair cells of Coleochaete and Chaetotheke with rotation show selective vital-staining with neutral red; the similarly constructed ones of Chaetosphaeridium with oscillation do not.     

CAESALPINIA SUBGENUS MEZONEURON (LEGUMINOSAE,CAESALPINIOIDEAE) FROM THE TERTIARY OF NORTH AMERICA

Legume fruits from the Eocene of Tennessee and Wyoming and the Miocene of Idaho are described and assigned to Caesalpinia subgenus Mezoneuron (Caesalpinioideae), an extant Paleotropical taxon that does not occur in North or South America today. Morphological and anatomical details of the fruits are used in evaluating their systematic relationships. The features of the fossil fruits are accommodated only within this extant subgenus. These fossils represent the only reliable known occurrence of C. subgenus Mezoneuron in the paleobotanical record. These fossils suggest that subgenus Mezoneuron was distinct from subgenus Caesalpinia by the Middle Eocene. Further, they document the widespread occurrence of this currently Paleotropical group for at least 30 million years in North America.     

Identification,origin, and evolution of leaf nodulating symbionts of <Emphasis Type="Italic">Sericanthe</Emphasis> (Rubiaceae)

Bacterial leaf symbiosis is an intimate association between bacteria and plants in which endosymbionts are housed within leaf nodules. This phenomenon has been reported in three genera of Rubiaceae (Pavetta, Psychotria, and Sericanthe), but the bacterial partner has only been identified in Psychotria and Pavetta. Here we report the identification of symbiotic bacteria in two leaf nodulating Sericanthe species. Using 16S rRNA data and common housekeeping genetic markers (recA and gyrB) we studied the phylogenetic relationships of bacterial endosymbionts in Rubiaceae. Endosymbionts of leaf nodulating Rubiaceae were found to be closely related and were placed as a monophyletic group within the genus Burkholderia (β-Proteobacteria). The phylogenetic analyses revealed a pattern of strict host specificity and placed the two investigated endosymbionts at two distinct positions in the topology of the tree, suggesting at least two different evolutionary origins. The degree of sequence divergence between the Sericanthe endosymbionts and their relatives was large enough to propose the Sericanthe endosymbionts as new species (‘Candidatus Burkholderia andongensis’ and ‘Candidatus Burkholderia petitii’). In a second part of this study, the pylogenetic relationships among nodulating and non-nodulating Sericanthe species were investigated using sequence data from six chloroplast regions (rps16, trnG, trnL-trnF, petD, petA-psbJ, and atpI-atpH). Overall, genetic variation among the plastid markers was insufficient to enable phylogenetic estimation. However, our results could not rule out the possibility that bacterial leaf symbiosis originated once in a common ancestor of the Sericanthe species.