OSMOPHORES,FLORAL FEATURES,AND SYSTEMATICS OF STANHOPEA (ORCHIDACEAE)

The floral fragrance glands (osmophores) of 18 species of Stanhopea and Sievekingia were examined through a series of developmental studies at light and electron microscope levels including late bud stages through postanthesis. Various characters were identified to be of potential systematic value and were recorded for each species. These characters included: texture of the osmophore surface, number of distinct cell layers comprising the osmophore, nature of lipid inclusions in osmophore cells, and presence or absence of plastoglobuli in osmophore amyloplasts. These characters were combined with traditional features of floral lip morphology for cladistic analysis. Sievekingia was the postulated outgroup. Stanhopea ecornuta showed the largest number of plesiomorphic characters. Stanhopea pulla, S. annulata, and S. Candida were only slightly more derived. Stanhopea anfracta, S. gibbosa, S. martiana, S. oculata, S. radiosa, S. ruckeri, S. saccata, S. shuttleworthii, S. tigrina, S. vasquezii, and S. wardii form a monophyletic group that can be recognized by a labellum with an articulated epichile and a bicornuate mesochile (or hypochile). Stanhopea tricornis may be a hybrid between a species of Sievekingia and Stanhopea.     

ULTRASTRUCTURAL AND HISTOCHEMICAL CHARACTERISTICS OF THE STIGMA OF CICER ARIETINUM

The stigma of Cicer arietinum L. cv. UC-5, a self-compatible legume, is comprised of a small central region of papillate cells which exhibit a localized surface secretion at the white bud stage of development, and of surrounding peripheral cells which lack surface secretion at the white bud stage and at anthesis. The cuticle of cells of the central region is thin and smooth and is displaced from subtending cells and fragmented as a result of secretory production. The cuticle of peripheral cells is thick and rugose. Although it is also displaced by secreted material, it is not disrupted during the white bud stage of development or at anthesis. The contents of central and peripheral papillate cells are similar. Cells are densely cytoplasmic, often with starch-containing plastids. Mitochondria, Golgi bodies, and associated vesicles are abundant, along with strands of smooth and rough endoplasmic reticulum. The limited stigma surface area covered by the secretion may restrict pollen capture and retention. This limited area may partly account for the notably unsuccessful hybridization attempts to broaden the genetic base and to develop improved cultivars of Cicer.     

Ultrastructural Development of Plastids in the Epidermis and Starch Layer of Glossy Ranunculus Petals

The differentiation of chromoplasts and amyloplasts has beenfollowed in developing petals of Ranunculus acris, R. ficariaand R. repens from small bud stages through anthesis. Theseare typical of Ranunculus species with glossy yellow petals.The plastids in the adaxial epidermis of the glossy part developmany globules which enlarge and coalesce with the eventual completebreakdown of plastid structure. At anthesis only a few cytoplasmicremnants remain in the dispersed pigment in these cells whichpartially collapse with folding of the anticlinal walls. Inthe non-glossy proximal part of the petal the adaxial epidermalcells have more convex outer walls and the chromoplast developmentdoes not progress beyond a stage found in the glossy regionjust before the petal tips emerge from the bud: they have largeperipheral globules with irregular tubular lamellae betweenthem and in the central stroma. In the abaxial epidermis theplastids produce small globules and retain some grana; somehave small starch grains and differ little from the plastidsin the mesophyll. The starch layer beneath the adaxial epidermisin the glossy region is formed from a single embryonic celllayer. Amyloplasts differentiate rapidly in these cells andall plastid structure has disappeared before the flower budopens leaving the sloping palisade cells packed with starchgrains. Chromoplast, amyloplast, petal, ultrastructure, development, Ranunculus, buttercup, lesser celandine     

Microtubule organization in the differentiating transfer cells of the placenta inLilium spp.

Summary Placental cells in the ovarian transmitting tissue ofLilium spp. are organized as transfer cells with inbuddings facing the ovarian locule. A detailed analysis of microtubule (MT) organization during development of these polarized cells is reported here. Formation of wall projections occurs at the apical part of the cell starting on the day of anthesis, and a fully mature secretion zone is found four days after anthesis. MTs are organized into distinct cortical and central arrays. The cortical array undergoes a unique transition at anthesis. MTs in the basal half of the cell remain in longitudinal bundles while in the apical half of the cell their longitudinal orientation is replaced by a transverse alignment. One day after anthesis, these transverse bundles become a meshwork of short, randomly organized MTs, while MTs in the basal half of the cell retain their longitudinal alignment. The realignment of MTs in the apical half of the cell coincides with the deposition of the secondary cell wall. The central array is composed of short, randomly arranged strands of MTs in the cytoplasm between the nucleus and the apical and basal periclinal walls of the cell. This array first appears as solitary strands in the apical part of the cell one day before anthesis. The central array extends during development and is eventually seen in the basal half of the cell. We propose that MTs in the cortical region near the apical wall act as templates for the deposition of cellulose microfibrils in the secondary cell wall. MTs in the central array in these transfer cells may be involved in the trafficking of vesicles and/or positioning of organelles near the secretion zone.Abbreviations MT microtubule - daa day after anthesis - dba day before anthesis     

Distribution of vimentin in the developing chick taste bud during the perihatching period.

The tissue environment within which taste bud cells develop has not been wholly elaborated. Previous studies of taste bud development in vertebrates, including the avian chick, have suggested that taste bud cells could arise from one, or several tissue sources (e.g. crest-mesenchyme, local ectoderm or endoderm). Thus, molecular markers which are present in gemmal as well as interfacing (peribud epithelium; mesenchyme-epithelium) regions, and their degree of expression during stages of taste bud development, are of special interest. The intermediate filament protein, vimentin, occurs in mesenchymal and mesodermally-derived (e.g. endothelial, fibroblast) cells as well as highly proliferating epithelium (e.g. tumors). The present study in chick gustatory tissue utilized antibodies against vimentin and the avidin-biotin-peroxidase technique to evaluate vimentin immunoreactivity (IR) within a timeframe which includes: 1) early stages of the taste bud primordium [embryonic days (E)17-E18)]; 2) the beginning of an accelerated bud cell proliferation at the time of initial, taste bud pore opening [around E19]; 3) attaining the adult complement of taste buds [around posthatch (H) day 1], and 4) completed organogenesis (H 17). During this time span, vimentin-IR was characterized in a region including and sometimes bridging taste bud and subepithelial connective tissue, whereas non-gustatory surrounding epithelium and salivary glands were vimentin-immuno-negative. Intragemmally, the proportion of vimentin-IR cells as related to total taste bud cells peaked at E19. These results indicate that vimentin expression, in part, is related to the onset of taste bud cell proliferation and suggest that mesenchyme could be one source of taste bud cells. Secondly, fibronectin, an extracellular matrix component of the epithelial basement membrane interface with mesenchyme, was expressed at or near the apical surfaces of taste bud cells projecting into the bud lumen, and in the basal gemmal region suggesting the possible role of fibronectin as a chemotactic anchor for differentiating and migrating taste bud receptor cells. Lastly, neuron-specific enolase-IR indicates that axonal varicosities are already present intragemmally at E17-E18, that is, during the incipient period of identifiable taste bud primordia.     

Characterization of three male-sterile mutants of Arabidopsis thaliana exhibiting alterations in meiosis

Male-sterile mutants are being studied to deepen our understanding of the complex processes of microsporogenesis and microgametogenesis. Due to difficulties associated with isolating the mutated gene, there is currently very little molecular information on the defects responsible for male sterility. As a first step in utilizing male-sterile mutants to better understand the bio-chemical and molecular processes that control pollen development, we have characterized a number of Arabidopsis thaliana lines that were generated by seed transformation and exhibit male sterility. We report here the identification and characterization of three male-sterile A. thaliana lines, all of which are tagged with T-DNA and show aberrant meiosis. A detailed cytochemical study was conducted on these lines to better understand the timing and nature of each mutation and to investigate how these mutations affect subsequent steps of pollen development. All three mutants undergo apparently normal morphogenesis until the onset of meiosis. In one line (6492) the mutation is most notable at the tetrad stage when up to eight microspores can be seen in each callose-encased tetrad. The resulting mutant microspores are of variable sizes and contain different amounts of DNA. Two other mutants (7219 and 7593) possess many common features, including variable developmental pathways, failure to produce callose, production of vacuolate, coenocytic (multi-nucleate) cells that are surrounded by persistent microsporocyte walls, and asynchronous patterns of development. Unlike the situation in wild-type plants, where developmental stages are correlated with bud length, such correlations are almost impossible with these two mutants. The sporogenous tissue within all three of these mutant lines collapses prior to anthesis.     

INITIATION AND DEVELOPMENT OF SHOOT-BUDS FROM PROTONEMATA IN THE MOSS PHYSCOMITRIUM TURBINATUM

Moss protonemata of Physcomitrium turbinatum were grown on mineral nutrient agar in culture tubes under various controlled conditions. By use of the described system individual cells of the protonema were discernible in situ and buds could be detected at the one-cell stage (initiation) and observed throughout their development. Buds normally arose by differentiation of a lateral filament near the apex of a growing caulonemal (heterotrichous) strand. Other modes of origin were erratic. From various other observations we conclude that the most pertinent morphological assays in studies of bud differentiation are growth of single caulonemal strands and the time they require to initiate a bud. A time course for bud development from the one-cell stage through the stage of leaf expansion is presented. At 26 C, 2 days elapse between these stages. From the time course, the time of bud initiation could be estimated with a probable accuracy of ±2 hr with only daily observations.     

Osmophore structure and phylogeny of Cirrhaea (Orchidaceae,Stanhopeinae)

Phylogenetic relationships and osmophore evolution of six Cirrhaea spp. were studied. Floral morphology was analysed using fresh flowers, and osmophore anatomy was determined on the basis of fixed flowers. Phylogenetic relationships of Cirrhaea were inferred on the basis of internal transcribed spacer (ITS), matK and trnL‐F regions using maximum parsimony and Bayesian analyses. Floral morphology and osmophore structure vary among species. All Cirrhaea osmophores have a secretory epidermis without papillae. Cirrhaea is monophyletic and includes three subclades: (1) C. dependens/C. nasuta, with a secretory cylindrical protuberance at the base of the labellar midlobe; (2) C. fuscolutea/C. longiracemosa, with a secretory tissue at the base of the shell‐shaped midlobe; and (3) C. loddigesii/C. seidelii with secretory tissue on the inner surface of the lateral lobes. The features of the flowers and osmophores in Cirrhaea spp. extend our knowledge of the diversity of secretory structures in Stanhopeinae, and demonstrate that floral morphology reflects phylogenetic relationships in Cirrhaea. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 369–383.     

ORIGIN AND EARLY MORPHOGENESIS OF LATERAL BUDS IN THE FERN DAVALLIA

The general organography, vascular organization, and leaf and bud development in Davallia solida and D. trichomanoides are described. These epiphytic species have creeping shoots with dorsally-borne leaves in a distichous phyllotaxis and the buds occur near each leaf base. Roots are borne on the ventral and flanking surfaces of the rhizome, but only at bud positions. The vascular pattern of these species is a perforated solenostele. Leaf and bud traces have distinctly different origins. While the proximity of buds to leaves has suggested that bud origin is axillary, observations show that the origin of buds is cauline and that their position is extra-axillary from inception. The stages of structural morphogenesis in Davallia buds differ significantly from the scheme proposed by Wardlaw. The principal difference is the absence of a resting period occurring between the origin and continued development of buds in Davallia. The elongated internodes which separate leaf-bud pairs from one another, the topographically distinct and predictable positions of leaves and buds, the structural equivalence of unexpanded buds, and vascular differences in leaves and buds make Davallia an useful species for physiological studies of differential bud expansion.     

Cytokinin translocation: Changes in zeatin and zeatin-riboside levels in the root exudate of tomato plants during their development

Summary The zeatin and zeatin riboside content of tomato (Lycopersicon esculentum Mill.) root exudates were determined at different stages of development. Zeatin riboside was found to be the major translocational form of cytokinin in the xylem during early vegetative growth. During flower bud formation this cytokinin decreased markedly in concentration so that, at anthesis, there was no appreciable difference in the zeatin and zeatin riboside concentration in the root exudate.     

STUDIES ON SARGASSUM. I. A LIGHT MICROSCOPIC EXAMINATION OF THE WOUND REGENERATION PROCESS IN MATURE STIPES OF S. FILIPENDULA

Regrowth from wounded stipe explants of Sargassum can be divided into four stages based on cytological changes. The first stage involves changes associated with the wound reactions and the formation of a wound epidermis. The second stage includes the formation of a well defined medullary pit with meristematically active cells around its periphery. Several “bud primordia” are also formed which begin to grow by cell division towards the wound surface. The third stage involves a period of internal tissue differentiation in the “bud primordia” such that mitotic activity is localized in the bud tip and the basal cells grow by cell elongation. The fourth stage marks a major change in the morphology of the regeneration branch from a tubular structure to that of a flattened blade. This change in morphology is preceded by the formation of an apical pit around which the flattened growth appears to be organized.     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

Adaptations for insect‐trapping in brood‐site pollinated Colocasia (Araceae)

The Araceae include both taxa with rewarding and deceptive trap pollination systems. Here we report on a genus in which rewarding and imprisonment of the pollinators co‐occur. We studied the pollination of four species of Colocasia in Southwest China and investigated the morpho‐anatomical adaptations of the spathe related to the attraction and capture of pollinators. All four species were pollinated by drosophilid flies of the genus Colocasiomyia. The flies are temporally arrested within the inflorescence and departure is only possible after pollen release. Trapping of the flies is accomplished by the closure of the spathe during anthesis. Moreover, in two species the spathe is covered with papillate epidermal cells known to form slippery surfaces in deceptive traps of Araceae. However, in Colocasia the papillae proved not slippery for the flies. The morpho‐anatomical properties of the spathe epidermis indicate that it is an elaborate osmophore and serves for the emission of odours only. Despite its similarity to deceptive traps of other aroids, Colocasia and Colocasiomyia have a close symbiotic relationship, as the attracted flies use the inflorescence as a site for mating and breeding. The trap mechanism has presumably evolved independently in Colocasia and is supposed to facilitate more efficient pollen export.     

Ultrastructural Differentiation of the Ovarian Transmitting Tissue in Lilium regale

The cells of the ovarian transmitting tissue of Lilium regaleare papilla shaped and form and epithelium on the placenta.Their ultrastructural organization and differentiation from1 d before to 7 d after anthesis is presented. These placentacells are typical transfer cells with a prominent secretionzone similar to that known from stylar canal cells. After anthesisthe secretion zone continues to grow by addition of vesiclefrom the numerous dictyosomes. Maximum depth of this zone isreached by day 4 after anthesis. The outer surface of the cellwall is distinctly rugged on cell maturation and the outermostlayer is corroded. The ER system undergoes transition from asmooth to a granular condition. Before anthesis there is a centralvacuole which at anthesis is reduced to a system of small vauoles.These are supplemented by autophagic vacuoles formed from theER. Such vacuoles are found near the secretion zone and mayalso fuse with the plasmalemma. The cuticle is sloughed andsecretion commences before anthesis. Accumulations of vesiclesfound in the nucleus and occasional connections between suchvesicles and the inner membrane of the nuclear envelope indicatethe presence of a nuclear network. Protein crystals are presentin the cytoplasm and the nucleus. The starch grains in the plastidsare digested after anthesis, but new ones are formed by days6 and 7.Copyright 1995, 1999 Academic Press Lilium regale, transmitting tissue, placenta, secretion, nuclear reticulum, transfer cells     

Petaline nectaries in Swietenia macrophylla (Meliaceae): Distribution and structural aspects

There are few anatomical studies of the reproductive organs of Swietenia macrophylla, despite its economic importance. This study aims to describe the structural and ultrastructural organization of the petaline nectaries in mahogany flowers. Flower buds and flowers at anthesis were collected, fixed, and processed for studies under light and electron microscopy. Nectaries occur in the median region of the petal, on the abaxial surface. Nectar is produced at all stages, from the very young buds until anthesis. The nectary presents a uniseriate epidermis, without stomata; intercellular spaces among the epidermal cells are frequent and contiguous to the subcuticular space. The secretory tissue consists of two to five layers of cells, which are rich in organelles. The nectaries lack vasculature, and the secretory tissue is isolated from the petaline mesophyll by an endodermoid layer. In the staminate flowers, the number of nectaries is less than that observed in pistillate ones.     

EFFECT OF FLORAL AGING ON THE GROWTH OF COMPATIBLE AND INCOMPATIBLE POLLEN TUBES IN LILIUM LONGIFLORUM

Compatible and incompatible pollen tube growth in detached styles of three Lilium longiflorum cultivare varies with the physiological age of the style. Before anthesis both compatible and incompatible pollen tubes grow, in 48 hr, only a fraction of the distance compatible tubes grow after anthesis. Incompatible pollen tubes are restricted to about half the distance of compatible tubes in the four days postanthesis, but thereafter increase up to or three-fourths or more the length of compatible tubes at the time of floral senescence. About 10 days after anthesis, growth of both types of pollen tubes decreases. The detached style method of pollen-tube cultivation is validated in the cultivar ‘Ace’ by seed set obtained following self-pollination in the 6- to 9-day interval and failure of seed set after either self- or cross-pollination after 9 days following anthesis. Also, in agreement with detached style data, self-pollination fails to produce seeds when attempted in bud stages or the five days following anthesis. Cross-pollinations are successful in this period. This material and technique appear well suited for study of the nature of the self-incompatibility reaction.     

Bud formation in the scyphozoan Cassiopea andromeda: epithelial dynamics and fate map

Cassiopea andromeda scyphistomae reproduce asexually by forming spindle shaped buds which, after detachment, metamorphose into polyps. Parent polyps appear to contribute to the buds' ecto- and endodermal epithelial cells, septal muscle cells, nematocytes and some zooxanthellae. Herein we describe bud morphogenesis, define 5 bud stages, and investigate the recruitment of bud ectoderm. India ink vital marking experiments reveal permanent apicobasal displacement of ectoderm. Labelled polyp cells are displaced towards and incorporated into the emerging bud. Ectoderm is recruited from all angular positions and cells labelled at increasing distances from the bud center are traced at increasingly more proximal positions on the buds. Unlike in Hydra attenuata, the recruitment area appears to be asymmetric since the zone contributing ectoderm from below is smaller than the zones above and lateral to the buds.     

ULTRASTRUCTURAL EVIDENCE FOR SECRETORY PHASES IN THE LIFE HISTORY OF STIGMATIC HAIRS OF COTTON: A DRY TYPE STIGMA

Stigmatic hairs of the cotton flower were studied through their developmental stages up to anthesis. Stigmatic hairs invariably develop from a densely straining band of epidermal cells opposite the transmitting tissue cells. At anthesis, these are single cell structures measuring up to 300 μm long. At the 5-mm stage of stylar length (7–10 days before anthesis), some stigmatic hair cells begin to accumulate an osmiophilic substance between the plasmalemma and the cell wall, possibly synthesized in the endoplasmic reticulum. This material is apparently never secreted outside the cell wall. Immediately following this secretory phase in some stigmatic hair cells a second secretory phase starts. A dense osmiophilic substance, different in appearance from the previous phase, accumulates in the vacuoles of each hair cell. Concomitantly, dimorphism develops in the cytoplasmic densities of stigmatic hair. Some stigmatic hair cytoplasm appears very dense and shows signs of degeneration while other cytoplasm appears normal. A third secretory phase, which begins at anthesis, occurs in the normal hair cells. This phase is characterized by enhanced activity in the cytoplasm of the endoplasmic reticulum and Golgi apparatus. Large vesicles containing granular material are seen fusing with the plasmalemma. Coincident with this activity there is dissolution of the middle layers of the cell wall and the cuticle is ruptured at various points. The dense osmiophilic substance that had accumulated in the vacuole breaks down into fine granular material. Significance of these changes is discussed in relation to the pollen germination mechanism on the dry type stigma of cotton.     

Isolation and characterization of a fruit-specific cDNA and the corresponding genomic clone from tomato

Differential screening of a cDNA bank constructed from ripe tomato fruit mRNA allowed the isolation of cDNA clone 2A11 which is entirely fruit-specific, is expressed at steadily increasing levels from anthesis to breaker, and accounts for approximately 1% of the messenger RNA in mature tomato fruit. A genomic clone corresponding to the 2A11 cDNA was isolated from a tomato genomic library. Sequence comparison of the cDNA clone with the genomic clone shows they are identical over the shared region with the genomic clone possessing a single large intron near the 5 end of the message.The open reading frame of 2A11 would encode a sulfur-rich polypeptide 96 amino acids in length. The identity of the putative protein is unknown. In situ hybridization shows that the 2A11 message is found throughout the pericarp cells in a tomato fruit. In contrast, in situ hybridization of early ripening stages with a polygalacturonase probe shows higher mRNA levels in cells of the outer pericarp and cells surrounding the vascular regions of the pericarp.