Comparative wood anatomy ofCoriaria

Wood anatomy ofCoriaria was surveyed to clarify generic features on the basis of 14 species collected from various regions of the World to cover the whole range of geographic distribution and habitual variation. Wood anatomy ofcoriaria is considerably uniform, and the species share a combination of the following features: 1) pores are thin-walled, polygonal in outline and mostly in multiples; 2) vessel elements and libriform fibers are very short; 3) perforation plates are exclusively simple; 4) intervessel pits are alternate; 5) vascular tracheids are present; 6) wood parenchyma is vasicentric and sometimes confluent; 7) rays are heterogeneous and large. Its species differ in several characters, such as distinctness of growth rings, pore size, pore patterns, type and abundance of wood parenchyma, and distinctness of storied structure. Comparisons among species indicate that the species of the Northern Hemisphere show a tendency toward having semi-ring porosity, while those of the Southern and Western Hemisphere have diffuse porosity. The other infrageneric variations appear to be related to different habits of the species rather than to geographic distribution. Small trees mostly have confluent and vasicentric parenchyma composed of fusiform cells and distinctly storied tissues, while shrubs and herbs have less abundant parenchyma which is vasicentric and comprises strands of two to four cells and indistinctly storied tissues.     

Secondary root growth in Rhynchosia edulis Griseb. (Leguminosae): Origin of cambia and their products

This study focuses on the development of a secondary root structure in Rhynchosia edulis Griseb. (Leguminosae). Its principal objectives are (i) to study the origin of cambia and the nature of their products; (ii) to correlate root structure to habitat; and (iii) to compare this anatomy with that of other Leguminosae species growing in the same environment. Serial transverse cuts of the main root show that the secondary root structure in this species results from several phenomena, namely (1) a cambium arising from procambial and pericycle cells; (2) a lateral meristem producing cell layers from the periphery towards the inner part of the root and from which vascular bundles, whose cambia fuse forming a continuous ring, originate; and (3) the formation of “elliptical cambia” in the mid portion of the root giving rise to vascular bundles in reverse orientation. The comparison of secondary root growth in R. edulis with other root structures in Leguminosae species growing in hilly areas shows different structural patterns. Nonetheless, these different patterns have the same objective: to enlarge storage parenchyma tissue enabling survival within an environment having limited water availability.     

Systematic root anatomy of Asparagales and other monocotyledons

Root anatomy of several taxa of Asparagales and some taxa formerly included in Asparagales is described in a systematic context together with a literature review. The presence of a dimorphic outer layer with long and short cells is widespread in monocotyledons, indicating that it originated early in the monocot lineage, but whereas this layer is rhizodermal in most monocotyledons, in Asparagales and Araceae it is usually hypodermal. There may be a correlation between the presence of a velamen or a persistent rhizodermis in many Asparagales and Araceae and the presence of a dimorphic hypodermal layer. Many other root anatomical characters, such as the presence of vascular bundles in the central pith and a multi-layered sclerenchymatous cylinder, are probably xeromorphic and developed convergently.     

Control of wheat root growth. The effects of excision on growth,wall rheology and root anatomy

Excision and subsequent incubation of the apices (1 cm) of wheat (Triticum aestivum L.) seedling roots in simple media severely reduced elongation from 28 mm·(24 h)^-1 in intact roots to a maximum of 2 mm·(24 h)^-1 in excised roots. The reduction in growth was accompanied by a loss of cell turgor in the growing zone but was correlated with a hardening of the cell walls in this region. Rheological properties were measured as percent extensibility (both plastic and elastic) using a tensiometer, and as instantaneous volumetric elastic modulus ( _i) using the pressure probe. Excision decreased plastic and elastic properties with a half-time of some 60 min. Plastic extension was reduced from 2.5% to 0.9% and elastic from 4.8% to 2.6% for an 8-g load. By contrast, _i was increased by excision. The observed reduction in root elongation rate was accompained by a reduction in mature cell length from 240 m to 40 m and a shortening of the zone of cell expansion.Symbol _i instantaneous volumetric elastic modulus     

RRNA and dnaK relationships of Bradyrhizobium sp. nodule bacteria from four papilionoid legume trees in Costa Rica

Enzyme electrophoresis and sequencing of rRNA and dnaK genes revealed high genetic diversity among root nodule bacteria from the Costa Rican trees Andira inermis, Dalbergia retusa, Platymiscium pinnatum (Papilionoideae tribe Dalbergieae) and Lonchocarpus atropurpureus (Papilionoideae tribe Millettieae). A total of 21 distinct multilocus genotypes [ETs (electrophoretic types)] was found among the 36 isolates analyzed, and no ETs were shared in common by isolates from different legume hosts. However, three of the ETs from D. retusa were identical to Bradyrhizobium sp. isolates detected in prior studies of several other legume genera in both Costa Rica and Panama. Nearly full-length 16S rRNA sequences and partial 23S rRNA sequences confirmed that two isolates from D. retusa were highly similar or identical to Bradyrhizobium strains isolated from the legumes Erythrina and Clitoria (Papilionoideae tribe Phaseoleae) in Panama. rRNA sequences for five isolates from L. atropurpureus, P. pinnatum and A. inermis were not closely related to any currently known strains from Central America or elsewhere, but had affinities to the reference strains Bradyrhizobium japonicum USDA 110 (three isolates) or to B. elkanii USDA 76 (two isolates). A phylogenetic tree for 21 Bradyrhizobium strains based on 603 bp of the dnaK gene showed several significant conflicts with the rRNA tree, suggesting that genealogical relationships may have been altered by lateral gene transfer events.     

<Emphasis Type=Italic>Galactia dimorphophylla</Emphasis> (Leguminosae: Phaseoleae), a new species from southeastern South America

Galactia dimorphophylla, a new species from northeastern Argentina and northern Uruguay, is described and illustrated. This new species is assigned to sect. Odonia. A table distinguishing it from similar species in Southern South America is presented, and its relationships and distinguishing characters including karyological features are discussed.     

Comparative floral anatomy and ontogeny in Magnoliaceae

Floral anatomy and ontogeny are described in six species of Magnoliaceae, representing the two subfamilies Liriodendroideae (Liriodendron chinese and L. tulipifera) and Magnolioideae, including species with terminal flowers (Magnolia championi, M. delavayi, M. grandiflora, M. paenetalauma) and axillary flowers (Michelia crassipes). The sequence of initiation of floral organs is from proximal to distal. The three distinct outermost organs are initiated in sequence, but ultimately form a single whorl; thus their ontogeny is consistent with a tepal interpretation. Tepals are initiated in whorls, and the stamens and carpels are spirally arranged, though the androecium shows some intermediacy between a spiral and whorled arrangement. Carpels are entirely free from each other both at primordial stages and maturity. Ventral closure of the style ranges from open in Magnolia species examined to partially closed in Michelia crassipes and completely closed in Liriodendron, resulting in a reduced stigma surface. Thick-walled cells and tannins are present in all species except Michelia crassipes. Oil cells are normally present. Floral structure is relatively homogeneous in this family, although Liriodendron differs from other Magnoliaceae in that the carpels are entirely closed at maturity, resulting in a relatively small stigma, in contrast to the elongate stigma of most species of Magnolia. The flower of Magnolia does not terminate in an organ or organ whorl but achieves determinacy by gradual diminution.     

Endogenous and exogenous auxin in the control of root growth

The endogenous indol-3yl-acetic acid (IAA) of detipped apical segments from roots of maize (cv ORLA) was greatly reduced by an exodiffusion technique which depended upon the preferential acropetal transport of the phytohormone into buffered agar. When IAA was applied to the basal cut ends of freshly prepared root segments only growth inhibitions were demonstrable but after the endogenous auxin concentration had been reduced by the exodiffusion technique it became possible to stimulate growth by IAA application. The implications of the interaction between exogenous and endogenous IAA in the control of root segment growth are discussed with special reference to the role of endogenous IAA in the regulation of root growth and geotropism.Abbreviations IAA indol-3yl-acetic acid - GC-MS gas chromatography-mass spectrometry     

Developmental anatomy of vascular cambium and periderm ofBotrypus virginianus and its bearing on the systematic position of ophioglossaceae

The developmental anatomy of the vascular cambium and periderm ofBotrypus virginianus was studied, and its bearing on the systematic position of Ophioglossacease is discussed. The cambial zone including cambium is initiated in a procambial ring of the stem before primary vascular tissue is well differentiated. The presumed cambium is composed of fusiform and ray initials. The cambium is extremely unequally bifacial, producing secondary xylem centripetally, and quite a small number of parenchymatous cells but no secondary phloem centrifugally. The cambial activity persists long, although it is very low in the mature part of the stem. It seems that the circumferential increase of the cambium is accommodated by an increase in the number of cambial initials. Secondary xylem is nonstoried and composed of tracheids with circular-bordered pits with evenly thick pit membranes, and uniseriate or partly biseriate radial rays. It makes up the bulk of the stem xylem. Periderm is formed almost entirely around the stem, simultaneous with its increment due to the secondary xylem. The combination of these anatomical features of secondary tissue supports the idea that Ophioglossaceae are living progymnosperms.     

Rapid,localized light effect on root growth in maize

A method using optical microfibers permitted localized exposure of the cap or the elongating part of growing maize (Zea mays L.) roots to white light. When the cap was illuminated, a strong and very rapid inhibition of the elongation rate of the roots was found. When the light microbeam was directed at the elongating region, the roots continued to grow at the same rate as before the illumination.     

Comparative floral anatomy of Strobilanthinae (Acanthaceae), with particular reference to internal partitioning of the flower

This paper provides the first comparative survey of structural variation in inflorescence architecture and flower structure of Hemigraphis and other members of the subtribe Strobilanthinae (Acanthaceae). Several discrete structural characters are identified which may provide support for phylogenetic relationships within the group. These include (1) the presence or absence of an accessory bud, (2) the presence or absence of a hollow style, (3) the presence or absence of an abscission layer, (4) the number of stamens comprising the androecium, and (5) the pattern of filament detachment. The structure of the filament curtain, a complex structure that partitions the flower, is also investigated. A more precise term for this structure stapetal curtain is suggested since it is a result of close synorganisation between the filaments and corolla tube. This structure appears to have a wide distribution throughout Acanthaceae and is not confined to Ruellieae s.l., as previously described. The earlier characterisation of four discrete types of filament curtain is unsatisfactory, since many of the features used to distinguish them are continuous and not unique features of particular species.We acknowledge Richard Bateman, Mark Carine, Peter Endress, Colin Hughes, Toby Pennington and an anonymous reviewer for comments on this paper. ECM gratefully acknowledges Chrissie Prychid, Peter Gasson, and the late Tim Lawrence of the Micromorphology section, Royal Botanic Gardens, Kew for their assistance and encouragement and Jesus Cordero-Salvado for help with the figures. This work was supported by the Druce Fund from the University of Oxford.     

Intracellular magnetophoresis of amyloplasts and induction of root curvature

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, (H²/2), was about 10⁹ Oe² · cm^–1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.Abbreviations HGMF high-gradient magnetic field - emu electromagnetic units - Oe Oersted We thank Dr. John Kiss, Miami University, Ohio for providing the Arabidopsis seeds. This work was supported by NASA grant NAGW-3656     

Importance of the cap in maize root growth

A large population of primary roots of Zea mays (cv. LG 11) was selected for uniform length at zero time. Their individual growth rates were measured over an 8-h period in the vertical position (in humid air, darkness). Three groups of these roots with significantly different growth rates were then chosen and their cap length was measured. It was found that slowly growing roots had long caps whereas rapidly growing roots had short caps. The production by the cap cells of basipetally transported growth inhibitors was tested (biologically by the curvature of half-decapped roots) and found to be significantly higher for longer root caps than that for shorter ones.     

Distribution of quinolizidine alkaloid types in nine Ormosia species (Leguminosae-Papilionoideae)

Quinolizidine alkaloids were surveyed in 22 plant samples, representing nineOrmosia species and up to five different plant parts per species, using combined gas chromatography and mass spectroscopy. The detected alkaloids were classified into 40 structural types. There was a remarkable degree of dissimilarity of alkaloid-type profiles between any two plant samples, including those obtained from the same species and even from a single tree. The similarity of alkaloid-type profiles among the studied samples varied between 0% and 79% (Jaccard similarity coefficient). Of chemotaxonomic interest was the finding of acosmine inO. isthmensis, which previously had been reported only from the related genusAcosmium. Furthermore, the alkaloid-type profile ofO. panamensis seeds was distinct from that of all other samples, supporting the hypothesis that this species is only distantly related to the other Latin AmericanOrmosia species.     

Developmental anatomy of the fifth shoot-borne root in young sporophytes of<Emphasis Type="Italic"> Ceratopteris richardii</Emphasis>

Young sporophytes of the homosporous fern Ceratopteris richardii produce a single shoot-borne root below each leaf. The developmental anatomy of the fifth sporophyte root is described using scanning electron microscopy and histological techniques. Three merophyte orthostichies in the body of the root originate from three proximal division faces of a tetrahedral root apical cell. Eight or nine divisions occur in a relatively regular sequence within each merophyte and produce a characteristic radial anatomical pattern in the root. The exact number of early divisions within a merophyte depends on the merophytes position within the root as a whole. Predictable inter-merophyte differences arise because a 2-fold (diarch) anatomical symmetry that is characteristic of mature roots is superimposed on a 3-fold radial symmetry that originates behind the apical cell. Before early formative divisions within a merophyte are completed, additional proliferative divisions begin to increase the number of cells within previously established tissue zones. The cellular parameters of early fifth root development in C. richardii are relatively invariant, and are reminiscent of patterns previously described for the heterosporous fern Azolla. Young sporophytes of C. richardii provide a useful model to further investigate the genetic regulation of root development in a non-seed plant, where the anatomy of meristem organization differs from that seen in flowering plant species.Abbreviations SEM Scanning electron microscopy - RAC Root apical cell     

The taxonomy of some Swartzieae (Leguminosae, subfam. Papilionoideae) from southeastern brazil

Three new species of Swartzieae are described and illustrated:Swartzia alternifoliolata, S. capixabensis, andZollernia cowanii. Swartzia apetala var.blanchetii and var.subcordata are considered to be synonyms ofS. apetala var.apetala, andS. grazielana a synonym ofS. macrostachya var.macrostachya. Keys to southeastern Brazil members ofSwartzia andZollernia are provided.     

Structure and identification of root bark of Quercus robur L.

The root bark structure of Quercus robur L. was analysed at different stages of root development and compared to the structure of stem bark. Root bark thickness varied considerably between different roots. Sclereid quantity decreased with increasing distance from the stem, which means it increased with age. Visible growth increments diminished with increasing distance from the stem. In lateral roots crystal quantity decreased with increasing distance from the stem. In lateral roots secondary phloem fibre length, sieve tube member length, and sieve tube diameter showed no regular trend. There were only a few basic structural differences between root and stem bark. The zone of cell differentiation (cell expansion, lignification) was wider in root bark; sieve tube collapse was delayed. In lateral root bark fewer sclereids were formed. The first-formed periderm often originated from deeper cell layers. Thus, primary elements were lacking after periderm formation. In root bark the phellem cell walls were of equal thickness. Thus, phellem lacked visible growth increments. Root bark phellem cells were slightly larger. The root phelloderm was more distinct. The secondary phloem fibres were slightly shorter than those in stem bark. Sieve tube members of stem and root bark were of similar length and diameter. The qualitative bark anatomical characters of oak root bark are suitable for root identifications. Due to minor structural differences between root and stem bark the characters must be used with care.     

Wood anatomy ofTrimeniaceae

Four collections of three species ofTrimenia and one collection ofPiptocalyx were studied; early-formed and later-formed wood was analyzed for oneTrimenia. Liquid-preserved material permitted analysis of mucilage and starch storage in wood ofT. neocaledonica andP. moorei. BecausePiptocalyx is scandent whereasTrimenia is arborescent, wood differences relative to evolution of a climbing habit could be examined.Piptocalyx contrasts withTrimenia in having wider vessels, more numerous per mm², resulting in a conductive area five times greater per unit area than that of theTrimenia woods averaged.Piptocalyx has appreciably fewer bars per perforation plate and thus much greater conductive area per perforation plate than have the species ofTrimenia. Rays inPiptocalyx are much taller and wider than those ofTrimenia. Wood ofTrimeniaceae is highly primitive in its scalariform perforation plates, scalariform lateral wall pitting on vessels, relatively long vessels elements, and heterocellular rays. Imperforate tracheary elements are septate nucleate fibertracheids (or even libriform fibers) rather than tracheids, but loss of borders on pits (and thus lowered conductive function of the imperforate tracheary elements) can be explained by the development of these elements into starchstoring cells. Some fiber-tracheids inT. neocaledonica are enlarged mucilagecontaining cells. Details of vessel structure inTrimeniaceae are similar to those ofMonimiaceae (s. s.), but similarity to some other lauralean (annonalean) families may be found: in mucilage presence,Trimeniaceae resembleLauraceae rather thanMonimiaceae. Wood ofTrimeniaceae may be regarded as highly mesomorphic, corresponding to the moist habitats in which all of the species occur.