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INFLORESCENCE AND FLOWER DEVELOPMENT IN THE PIPERACEAE. I. PEPEROMIA
Abstract
Flowers of Peperomia species are the simplest structurally of any of the members of the Piperaceae. The spicate inflorescences form terminally and in axillary position; in each, the apex first is zonate in configuration with a two-layered tunica while 3-4 leaves are initiated. Later, when the inflorescence apical meristem begins bract initiation, the biseriate tunica persists, but zonal distinctions diminish and the apex can be described in terms of a simple tunicacorpus configuration. The inflorescence apex aborts after producing 30-40 bracts in acropetal succession an abscission layer forms across the base of the apex, and the meristem dries and drops off. Bracts are produced by periclinal divisions in T2 (and occasionally also in the third layer as well); the later-formed floral apices arise by periclinal divisions in T2 and the third layer. Each floral apex is at first a long transverse ridge in the axil, perpendicular to the long axis of the inflorescence. This establishes bilateral symmetry in the flower, which persists throughout subsequent growth. The floral meristem becomes saddle-shaped, and two stamen primordia are delimited, one at either end and lower than the central floral apex. A solitary carpel is initiated abaxially, and soon forms a circular rim which heightens as a tube with an apical pore. Within the open carpel, a solitary ovule is initiated from the entire remains of the floral apical meristem; it, hence, is terminal in the flower, and its placentation is basal. Carpellary closure in P. metallica results from accelerated growth of the abaxial lip, and the two margins become appressed. Species differ greatly as to whether the abaxial or the adaxial lobe predominates in late stages of carpel development. In P. metallica, the receptive portion of the stigma forms from the shorter lobe which is overtopped. Stigmatoid tissue forms internal to the receptive stigma. The prevailing bilateral floral symmetry, absence of a perianth, and the spicate inflorescence are features which distinguish Peperomia (and Piperaceae) from the magnolialian line of angiosperms.
... Peperomia is distinct from the other genera of Piperaceae Giseke mainly because its flowers have only two stamens and one pistil (with a unilocular ovary and harboring only one ovule). Its flowers are achlamydeous, arranged in a spadix (Mathieu et al., 2008) that develop in the axils of the leaves, opposite to or at the apex of the plant (terminal), being solitary or grouped (Tucker, 1980;Wanke et al., 2006;Frenzke et al., 2015). ...
... Suissa and Sundue (2020) emphasize that topographical differences (more homogeneous) may be responsible for the manifestation of this pattern, since areas with greater topographical heterogeneity (as in the Atlantic Forest) present greater availability of habitats, favoring biological diversity (Freitas et al., 2016). In addition, the genus Peperomia is mostly composed of epiphytic species (Tucker, 1980;Wanke et al., 2006;Frenzke et al., 2015), and data for other areas in the Neotropical region show that vascular epiphytes have higher richness in mountainous ranges (Krömer et al., 2005;Marcusso et al., 2022), a different condition from that found in the Brazilian Amazon. Still, it is possible to perceive through our results that extensive areas in the Amazon region do not have any occupied grid cells, while the cells with the highest values of records and richness are in locations close to large botanical collections (or areas where their researchers collect), suggesting the possible existence of the sampling bias known as the 'museum effect' (Ponder et al., 2002;Gasper et al., 2020). ...
Among one of the largest genera of angiosperms, Peperomia has a Pantropical distribution. However, studies that analyze the chorological details and conservation status of its species still are scarce. Brazil is home to 169 species of Peperomia and approximately two thirds (111 spp.) are considered endemic in the Flora of Brazil. Due to this, the present study aims to answer: (1) Are the Peperomia cited in Flora do Brasil 2020 as endemic really endemic? (2) How are these species distributed? (3) What is the extinction risk of the Peperomia species endemic to Brazil? In order to extract and clean the occurrence data, we used records available in open databases then applied a workflow method developed by CNCFlora (National Center for the Conservation of Flora). Based on our data, at current 100 species can be considered endemic to Brazil. We found that almost half of the endemic species are threatened on some level and that the phytogeographical domain with the greatest richness and highest number of records is the Atlantic Forest.
... Morphological interpretation and origin of the gynoecium of Peperomia (Piperaceae) are of considerable interest. This closed tubular structure either has no lobes on the edge or has two poorly developed lobes that emerge at late developmental stages; a single basal orthotropous ovule is located in the center of the gynoecium [97,98]. Phylogenetic data clearly demonstrate that this gynoecium is derived from a mixomerous gynoecium with a single basal ovule and several stigmas [99]. ...
... Phylogenetic data clearly demonstrate that this gynoecium is derived from a mixomerous gynoecium with a single basal ovule and several stigmas [99]. The reduction of the number of carpels to one is usually believed to have occurred upon the emergence of Peperomia gynoecium (which is thus monomerous), but the hypothesis of the origin of this gynoecium upon a complete loss of carpel individuality similar to that observed in Primulaceae is as valid as the former one (for a review of the hypotheses, see [97]). ...
The presence of a gynoecium composed of carpels is a key feature of angiosperms. The carpel is often regarded as a homologue of the gymnosperm megasporophyll (that is, an ovule-bearing leaf), but higher complexity of the morphological nature of carpel cannot be ruled out. Angiosperm carpels can fuse to form a syncarpous gynoecium. A syncarpous gynoecium usually includes a well-developed compitum, an area where the pollen tube transmitting tracts of individual carpels unite to enable the transition of pollen tubes from one carpel to another. This phenomenon is a precondition to the emergence of carpel dimorphism manifested as the absence of a functional stigma or fertile ovules in part of the carpels. Pseudomonomery, which is characterized by the presence of a fertile ovule (or ovules) in one carpel only, is a specific case of carpel dimorphism. A pseudomonomerous gynoecium usually has a single plane of symmetry and is likely to share certain features of the regulation of morphogenesis with the monosymmetric perianth and androecium. A genuine monomerous gynoecium consists of a single carpel. Syncarpous gynoecia can be abruptly transformed into monomerous gynoecia in the course of evolution or undergo sterilization and gradual reduction of some carpels. Partial or nearly complete loss of carpel individuality that precludes the assignment of an ovule (or ovules) to an individual carpel is observed in a specific group of gynoecia. We termed this phenomenon mixomery, since it should be distinguished from pseudomonomery.
... Представляют интерес морфологическая интерпретация и происхождение гинецея Peperomia (Piperaceae). Это замкнутая трубчатая структура без лопастей по краю или с двумя слабо выраженными и поздно возникающими лопастями, имеющая в центре одну базальную ортотропную семяпочку [97,98]. Филогенетические данные чётко указывают на происхождение этого гинецея из миксомерного с одной базальной семяпочкой и несколькими рыльцами [99]. ...
... Обычно гинецей Peperomia считают возникшим в результате редукции числа плодолистиков до одного (мономерным), но не менее правдоподобна гипотеза о его происхождении путём полной утраты индивидуальности плодолистиков, подобной тому, что мы наблюдаем у Primulaceae (см. обзор гипотез в работе Ш. Такер [97]). ...
The presence of a gynoecium composed by carpels is a key feature of angiosperms. The carpel is often viewed as homologous to megasporophyll of gymnosperms (i.e., a leaf bearing ovules), but it is possible that its morphological nature is more complex. Carpels of angiosperms can unite to form a syncarpous gynoecium. Most syncarpous gynoecia possess a compitum, which is a region where pollen tube transmitting tracts of individual carpels unite in a way that pollen tubes can grow from one carpel to another. The presence of a compitum is a precondition for evolution of carpel dimorphism, where some carpels do not possess functional stigma or fertile ovules. Pseudomonomery is a kind of carpel dimorphism where only one carpel has a fertile ovule (or ovules). Pseudomonomerous gynoecium usually has a single symmetry plane and it is likely that regulation of its development is similar to those of monosymmetric perianth and androecium. Monomerous gynoecium consists of a single carpel. In course of evolution, syncarpous gynoecia can jump abruptly to monomerous gynoecia or undergo sterilization and gradual reduction of some carpels. There is a peculiar group of gynoecia with partial or complete loss of carpel individuality, so that it is impossible to assign an ovule (or ovules) to particular carpel. A term mixomery is proposed for this phenomenon, which is not identical to pseudomonomery.
... O número de carpelos, em Peperomia, é motivo de controvérsias (Tucker, 1980). Wettstein (1935), por exemplo, registra dois carpelos em Peperomia, baseado na evidência de dois lobos estigmáticos no gineceu. ...
... Wettstein (1935), por exemplo, registra dois carpelos em Peperomia, baseado na evidência de dois lobos estigmáticos no gineceu. Por outro lado, Lei e Liang (1999) e Tucker (1980) consideram o gineceu de Peperomia monocarpelar, com base em estudos de desenvolvimento; o aspecto bilobado do estigma não é evidência de gineceu bicarpelar, já que é explicado como lobos adaxial e abaxial de uma estrutura ascidial. Para Judd et al. (2002), Peperomia é um gênero derivado dentro da família Piperaceae e apresenta apenas um carpelo. ...
Peperomia parnassifolia Miq. is a herbaceous species that occurs in forest remnants in Maringá, Brazil, among other places. The stem and reproductive organs of this species are the objects of the present study. Samples of botanical material (fresh or fixed in FAA 50/FPA 50) were cut using a rotation microtome, in accordance with usual practice. The spike axis features a polystelic structure. Bracts are peltate with a homogeneous mesophyll. The gynoecium is monocarpous, has a stigma with two lobes, solid style, ovary with simple structure and an atropous, crassinucellate and unitegmic ovule. The anther wall consists of epidermis, endothecium, one middle layer and a uninucleate secretory tapetum. The fruit is a berry and its seed is perispermic. This plant reproduces vegetatively by stolon.
... O número de carpelos, em Peperomia, é motivo de controvérsias (Tucker, 1980). Wettstein (1935), por exemplo, registra dois carpelos em Peperomia, baseado na evidência de dois lobos estigmáticos no gineceu. ...
... Wettstein (1935), por exemplo, registra dois carpelos em Peperomia, baseado na evidência de dois lobos estigmáticos no gineceu. Por outro lado, Lei e Liang (1999) e Tucker (1980) consideram o gineceu de Peperomia monocarpelar, com base em estudos de desenvolvimento; o aspecto bilobado do estigma não é evidência de gineceu bicarpelar, já que é explicado como lobos adaxial e abaxial de uma estrutura ascidial. Para Judd et al. (2002), Peperomia é um gênero derivado dentro da família Piperaceae e apresenta apenas um carpelo. ...
Peperomia parnassifolia Miq. is a herbaceous species that occurs in forest remnants in Maringá, Brazil, among other places. The stem and reproductive organs of this species are the objects of the present study. Samples of botanical material (fresh or fixed in FAA 50/FPA 50) were cut using a rotation microtome, in accordance with usual practice. The spike axis features a polystelic structure. Bracts are peltate with a homogeneous mesophyll. The gynoecium is monocarpous, has a stigma with two lobes, solid style, ovary with simple structure and an atropous, crassinucellate and unitegmic ovule. The anther wall consists of epidermis, endothecium, one middle layer and a uninucleate secretory tapetum. The fruit is a berry and its seed is perispermic. This plant reproduces vegetatively by stolon.
... The flowers of Peperomia are greatly reduced and have no perianth. Each flower comprises two stamens, asingle stigma and a fleshy floral bract that subtends the single ovary (Tucker 1980). These morphological features are thought to represent primitiveness and although members of the genus are usually considered di-cotyledons (e.g. ...
... In angiosperms the most superficially similar conditions to those in Gnetales occur in Piperaceae (Tucker 1980(Tucker , 1982 or some Araceae (Bogner 1972). The basal orthotropous bitegmic or unitegmic ovule is surrounded by a saclike gynoecium wall. ...
The female structures in Gnetales share the presence of an integument with a long, open micropylar tube that takes up the pollen grains via nucellar secretion presented at the micropylar apex. The micropylar tube is sheathed by one or two united pairs of outer envelopes that resemble the inflorescence bracts. Developmentally, Gnetales and angiosperms have in common a circular (inner) integument and its initiation at the rime when the sporogenous cells become apparent, whereas the integument is two-lobed and its initiation Precedes the differentiation of sporogenous cells in other gymnosperms. However, Gnetales differ from angiosperms in having an acropetal (and not basipetal) initiation sequence for the two inner envelopes, including the integument. The attachment of the two envelopes of the nucellus is at about the same level in most angiosperms, whereas the outer is much lower than the inner in Gnetales. The second or third envelope as counted from the nucellus (the carpel) is the receptive one in angiosperms, while it is always the innermost one (the integument) in Gnetales. In all three genera of the Gnetales bisexual organ complexes occur in various combinations but always with the female organs more apical than the male ones, in Ephedra at inflorescence (rarely flower) level, in Gnetum at partial inflorescence level, and in Welwitschia at flower level. The female organs in these bisexual complexes are often sterile but seem to be regularly functional by secreting a sweet pollination drop that serves as nectar for pollinating insects. In some species of Ephedra and Gnetum that lack female flowers, in the male inflorescences nectar may also be secreted by other parts of the inflorescence. Homologies of the female organ complexes with those of angiosperms are uncertain apart from the nucellus and the (inner) integument. The floral bracts (outer envelopes) may be apomorphic in Gnetales without direct correspondence in angiosperm flowers. The basipetal development of the bisexual complexes in Gnetum is compared with the basipetal development of the ovules in Bennettitales and a similar topology in conifers with several ovules on a seed scale.
... In Piperales the extreme gynoecium forms are those in Saururus (Saururaceae) on one end and those of Peperomia (Piperaceae) on the other. If the almost apocarpous gynoecium of Saururus is interpreted as plesiomorphic in Piperales (Tucker, Douglas & Liang, 1993), the unicarpellate gynoecium of Peperomia, constituting a completely ascidiate carpel (Tucker, 1980), would be derived from a syncarpous (paracarpous) gynoecium by reduction of carpel number. Another interpretation suggested by Endress, (1990) would be that a single ascidiate carpel with a single ovule is plesiomorphic. ...
Gynoecium and ovule structure was compared in representatives of all families of the paleoherbs, including Nymphaeales (Cabombaceae, Nymphaeaceae), Piperales (Saururaceae, Piperaceae), Aristolochiales (Lactoridaceae, Aristolochiaceae), Rafflesiales (Hydnoraceae, Rafflesiaceae) and, in addition, Ceratophyllaceae and Nelumbonaceae, both of which were earlier included in Nymphaeales, but then segregated and with an unestablished position. In all representatives studied, the carpels are closed at anthesis. Carpel closure is attained in three different ways: (1) postgenital fusion of inner surfaces (Piperales, Aristolochiales); (2) occlusion by secretion or mutual appression of inner surfaces without postgenital fusion (Cabombaceae, Ceratophyllaceae, Nelumbonaceae (?) or (3) strong secretion combined with postgenital fusion at the periphery of the carpel (Nymphaeaceae). In Cytinus (Rafflesiaceae), after an earlier developmental stage with apparent postgenital fusion there is strong internal secretion (within the cell walls). Stigma shape tends to be double-crested in the basal taxa of each order: Cabombaceae (Brasenia), Saururaceae, and Lactoridaceae. In some Aristolochiaceae and Cytinus (Rafflesiaceae) they have two lobes in the transverse symmetry plane (i. e. at right angles to the median plane) or, if the carpels are united, the stigmatic lobes are commissural, accordingly. Stigmas are unicellular papillate and secretory in most taxa, but the papillae are uniseriate-pluricellular in some (not basal) Nymphaeaceae, Asaroideae (Aristolochiaceae) and Cytinus (Rafflesiaceae). Ceratophyllaceae have smooth stigmas. Intrusive oil cells in the carpel epidermis were found in Piperales and Aristolochiaceae. Mature ovules vary in length between 0. 2 mm and 2. 5 mm. Mature nucelli vary in breadth between 0. 03 mm and 1. 6 mm. These differences are larger than in the other major magnoliid groups. The outer integument is fully annular (not semiannular) in all taxa with orthotropous ovules (all Piperales and Barclaya of Nymphaeaceae) and also in some with anatropous ovules (some Nymphaeaceae, some Aristolochiaceae). The integuments are variously lobed or unlobed; both integuments tend to exhibit the same behaviour within a family, either both lobed or both unlobed. The results strongly support three pairs of families in sister group relationships, as suggested by studies based on other characters: Cabombaceae-Nymphaeaceae, Saururaceae-Piperaceae, and Lactoridaceae-Aristolochiaceae, and Hydnoraceae-Rafflesiaceae to some extent. Piperales and Aristolochiales are closer to each other than either is to Nymphaeales. Nelumbonaceae is isolated, as is Ceratophyllaceae, but the status of the latter is more difficult to interpret owing to apparent reduction in morphological, anatomical and histological traits.
... Etymology-The specific epithet ''tuckerae'' is proposed in honor of Dr. Shirley Tucker, University of California-Santa Barbara, for her work on furthering our understanding of floral structure and ontogeny in Saururaceae. Sources: Raju, 1961;Tucker, 1975Tucker, , 1976Tucker, , 1979Tucker, , 1980Tucker, , 1981Tucker, , 1982Tucker, , 1985Xi, 1980;Omori, 1982;Liang, 1992;Kubitzki, 1993;Huber, 1993;Tebbs, 1993;Tucker et al., 1993;Wu and Kubitzki, 1993;Liang and Tucker, 1995;Tucker and Douglas, 1996;Buddell and Thieret, 1997;Bernardello et al., 1999;Lei and Lang, 1999;Tseng et al., 1999;Xia and Brach, 1999;Sampson, 2000;Gonzalez and Rudall, 2001;Jaramillo and Manos, 2001;Kelly, 2001;Mulder, 2003;Jaramillo et al., 2004. Type locality-Princeton Chert, east bank of the Similkameen River, ca. ...
Investigations of small permineralized flowers from the Middle Eocene Princeton Chert, British Columbia, Canada have revealed that they represent an extinct species of Saururus. Over 100 flowers and one partial inflorescence were studied, and numerous minute perianthless flowers are borne in an indeterminate raceme. Each flower is subtended by a bract, and flowers and bracts are borne at the end of a common stalk. Five stamens are basally adnate to the carpels. Pollen is frequently found in situ in the anthers. Examined under SEM and TEM, pollen grains are minute (6-11 μm), monosulcate, boat-shaped-elliptic, with punctate sculpturing and a granulate aperture membrane. The gynoecium is composed of four basally connate, lobed carpels with recurved styles and a single ovule per carpel. Flower structure and pollen are indicative of Saururaceae (Piperales), and in phylogenetic analyses using morphological characters, the fossils are sister to extant Saururus. The fossil flowers are described here as Saururus tuckerae sp. nov. These fossil specimens add to the otherwise sparse fossil record of Piperales, represent the oldest fossils of Saururaceae as well as the first North American fossil specimens of this family, and provide the first evidence of saururaceous pollen in the fossil record.
... On the other hand, in some of the self-compatible species it is suggested that agamospermy might occur ( Sasikumar et al., 1992;Figueiredo and Sazima, 2000). Cytogenetic studies reveal two groups in the Piperaceae: one represented by Peperomia (x = 11) and the other by Piper, Ottonia, and Pothomorphe (x = 13) ( Bai and Subramanian, 1985;Okada, 1986;Samuel, 1987), suggesting that Peperomia is the most specialised and derived genus of the family ( Tucker, 1980;1982;Tucker et al., 1993;Judd et al., 1999). Most Piper, Ottonia, and Potomorphe species rely on wind and insects as pollen vectors ( Semple, 1974;Fleming, 1985; Figueiredo and Sazima, 2000), and Brazilian Piper species are regularly visited by dozens of insect species ( Figueiredo, 2003). ...
Data on flowering phenology and pollination of Peperomia species are virtually non-existent. This study presents data on the pollination biology of eight Peperomia species from south-eastern Brazil, including the flowering phenology, pollination system, and reproductive success. Data on flowering phenology were recorded weekly and exclusion experiments on inflorescences provided data on autonomous self- and wind pollination. Direct visual observations were made and insect visits were recorded. Four Peperomia species showed continuous flowering, while the others were seasonal and flowered in the wet season. Pollination by wind and Syrphidae was confirmed for two self-incompatible Peperomia species. The remaining species are self-compatible and their high fruit set may be accounted for by autonomous self-pollination and perhaps agamospermy. Although the floral morphology of Peperomia species suggests wind- and/or insect pollination, most of the species studied exhibit autogamy and perhaps agamospermy as the main method of reproduction.
Floral symmetry plays an important role in plant-pollinator interactions and may have remarkable impacts on angiosperm diversification. However, spatiotemporal patterns in floral symmetry and drivers of these patterns remain unknown. Here, using newly compiled floral symmetry (actinomorphy versus zygomorphy) data of 279,877 angiosperm species and their distributions and phylogenies, we estimated global geographic patterns and macroevolutionary dynamics of floral symmetry. We found that frequency of actinomorphic species increased with latitude, while that of zygomorphic species decreased. Solar radiation, present-day temperature, and Quaternary temperature change correlated with geographic variation in floral symmetry frequency. Evolutionary transitions from actinomorphy to zygomorphy dominated floral symmetry evolution, although the transition rate decreased with decreasing paleotemperature throughout the Cenozoic. Notably, we found that zygomorphy may not favor diversification of angiosperms as previously observed in some clades. Our study demonstrates the influence of (paleo)climate on spatiotemporal patterns in floral symmetry and challenges previous views about role of flower symmetry in angiosperm diversification.
Floral symmetry plays an important role in plant-pollinator interactions and may have remarkable impacts on angiosperm diversification. However, spatiotemporal patterns in floral symmetry and drivers of these patterns remain unknown. Here, using newly compiled floral symmetry (actinomorphy versus zygomorphy) data of 279,877 angiosperm species and their distributions and phylogenies, we estimated global geographic patterns and macroevolutionary dynamics of floral symmetry. We found that frequency of actinomorphic species increased with latitude, while that of zygomorphic species decreased. Solar radiation, present-day temperature, and Quaternary temperature change correlated with geographic variation in floral symmetry frequency. Evolutionary transitions from actinomorphy to zygomorphy dominated floral symmetry evolution, although the transition rate decreased with decreasing paleotemperature throughout the Cenozoic. Notably, we found that zygomorphy may not favor diversification of angiosperms as previously observed in some clades. Our study demonstrates the influence of (paleo)climate on spatiotemporal patterns in floral symmetry and challenges previous views about role of flower symmetry in angiosperm diversification.
In Angiosperms placentae or ovules are formed on carpels or the floral apex. Hence, in a developmental sense, there are carpellate and acarpellate gynoecia. The latter occur in about 11% of all Angiosperm families. Basella rubra is an example of the noncarpellate condition. Its single basal ovule is formed directly from the floral apex. In young developmental stages it even retains the tunica-corpus organization of the floral apex. In later developmental stages, three septa arise only at the base of the ovule. The single vascular strand of the ovule is symmetrically derived from the bases of all six strands that supply the ovary wall, i.e., it is not associated with the vascular strand of only one of the three gynoecial appendages. Hence, neither development nor vascularization support a carpellate interpretation of the Basella gynoecium. With regard to the evolution of basal placentation in Basella and other taxa of Angiosperms three possibilities exist: 1) It is derived from the carpellate condition, 2) It is primitive and the carpellate condition is derived, 3) Both carpellate and noncarpellate organizations have coexisted during the evolution of Angiosperms which may have been monophyletic or polyphyletic.
About two-thirds of the more than 100 genera in the Araceae lack tepals and their absence is considered derived. Unlike most of these atepalate genera, Calla palustris has about twice as many stamens per flower. Using epi-illumination microscopy, we studied floral development in Calla to see if the supernumerary stamens form in positions corresponding to tepal positions in perigonate Araceae. If so, this would be an example of homeosis—in this case, the replacement of tepals with stamens—in the evolution of this genus. We found the positions of stamen primordia in many floral buds too irregular to conclude that they replace tepals positionally. However, in more regular floral buds the first formed stamens do form in what correspond to tepal sites in related genera. If the immediate ancestor to Calla had tepals, as is generally assumed, stamen positions in the more regular flowers, at least, support a homeotic interpretation. There is no evidence that the supernumerary stamens arise by dédoublement, but since morphogenesis in Calla is only partly comparable to other aroids, and the phylogeny in the family is not well understood, further studies are needed to resolve the interpretation of the flower in Calla. With regard to systematics and evolution, the absence of tepals in Calla may not be homologous with atepaly in other members of the family, as has been assumed for the past century.
Mature wood of Lactoris, not previously available for study, reveals ten distinctive characters: vessels with simple perforation plates; vessels in pore multiples; vessel-to-axial parenchyma pits scalariform or transitional, vessel-to-vessel pits alternate; fiber-tracheids with vestigial pits; fiber-tracheids, vessels, and axial parenchyma storied; axial parenchyma vasicentric scanty; axial parenchyma either not subdivided or, if subdivided, with thin nonlignified walls between the cells (like the septa in septate fibers); rays wide and tall, little altered during ontogeny; ray cells upright; and ray cells taller adjacent to fascicular areas. All of these features occur in woods of Piper and other Piperaceae. The systematic position of Lactoris is therefore reassessed. Evidence available to date is consonant with placement of Lactoridaceae in Piperales, in which it would be more primitive than Piperaceae or Saururaceae. Features cited as evidence for alternative placements of Lactoridaceae are reviewed.
The inflorescence development of three species of Piper (P. aduncum, P. amalago, and P. marginatum), representing Sections Artanthe and Ottonia, was studied. The spicate inflorescences contain hundreds or even thousands of flowers, depending on the species. Each flower has a tricarpellate syncarpous gynoecium and 4 to 6 free stamens, in the species studied. No sepals or petals are present. In P. marginatum the apical meristem of the inflorescence is zonate in configuration and is unusually elongate: up to 1,170 μm high and up to 480 μm wide during the most active period of organogenesis. Toward the time of apical cessation both height and diameter gradually diminish, leaving an apical residuum which may become an attenuate spine or may be cut off by an abscission zone just below the meristem. The active apex produces bract primordia; when each is 40–55 μm high, a floral apex is initiated in its axil. Both bract and floral apex are initiated by periclinal divisions in cells of the subsurface layer. The bracts undergo differentiation rather early, while the floral apices are still developing. The last-produced bracts near the tip of the inflorescence tend to be sterile.
The development of the inflorescence and flowers are described for Gymnotheca chinensis Decaisne (Saururaceae), which is native only to southeast China. The inflorescence is a short terminal spike of about 50–70 flowers, each subtended by a small bract. There are no showy involucral bracts. The bracts are initiated before the flowers, in acropetal order. Flowers tend to be initiated in whorls of three which alternate with the previous whorl members. No perianth is present. The flower contains six stamens, and four carpels fused in an inferior ovary containing 40–60 ovules on four parietal placentae. Floral symmetry is dorsiventral from inception and throughout organ initiation. Floral organs are initiated in the following order: 1) median adaxial stamen, 2) a pair of lateral common primordia which bifurcate radially to produce two stamen primordia each, 3) median abaxial stamen, 4) a pair of lateral carpel primordia, 5) median adaxial carpel, 6) median abaxial carpel. This order of initiation differs from that of any other Saururaceae previously investigated. The inferior ovary results from intercalary growth below the level of stamen attachment; the style elongates by intercalary growth, and the four stigmas remain free. The floral structure of Gymnotheca is relatively advanced compared to Saururus, but its assemblage of specializations differs from that of either Anemopsis or Houttuynia, the other derived genera in the Saururaceae.
Floral development in Piper was compared between four-staminate species (P. aduncum and P. marginatum) and six-staminate species (P. amalago). All Piper species have a syncarpous gynoecium composed of three or four carpels. The floral apex is initiated by a periclinal division in the subsurface layer in the axil of a bract 40-55 μm high; initiation of the bracts occurs separately and considerably earlier. The floral primordium widens and the first pair of stamens are initiated at either side. The median anterior stamen forms next, and the median posterior later. This sequence is common to all species studied. In the six-staminate P. amalago, the last two stamens form simultaneously in lateral-anterior positions. The stamens hence arise as pairs, and symmetry is bilateral or dorsiventral. The three or four carpels arise simultaneously; they are soon elevated on a gynoecial ring by growth of the receptacle below the level of attachment of the carpels to produce a syncarpous gynoecium. The floral apex lastly produces the solitary basal ovule and is used up in its formation.
Foliar ontogeny of Magnolia grandiflora was studied to elucidate possible unique features of evergreen leaves and their development. The apex of Magnolia grandiflora is composed of a biseriate or triseriate tunica overlying a central initial zone, a peripheral zone and a pith rib meristem. Leaf primordia are initiated by periclinal divisions on the apical flank of the tunica in its second layer. This initiation and expansion is seasonal just as in related deciduous magnolias. Following leaf initiation, a foliar buttress is formed and the leaf base gradually extends around the apex. As growth continues, separation of the leaf blade primordium from the stipule proceeds by intensified anticlinal divisions in the surface and subsurface layers near the base. Marginal growth begins in the blade primordium when it reaches approximately 200 μm in height and results in the formation of two wing-like extensions, the lamina. This young blade remains in a conduplicately folded position next to the stipule until bud break.
Zippelia begoniaefolia Bl., a monotypic species having characteristics of both Piperaceae and Saururaceae, has racemes of about 20 small flowers lacking a perianth, each with six free stamens and a four-carpellate syncarpous gynoecium. The inflorescence apical meristem initiates bracts acropetally and helically, each of which subtends a later initiated single floral apex; there are no “common” primordia. The six stamens are initiated as two lateral pairs and two solitary successive primordia, the latter two opposite in median sagittal positions. Four carpel primordia are initiated as a lateral pair and two successively initiated in the median sagittal plane. This order of organ inception is unique among Piperaceae and Saururaceae. Intercalary growth below carpellary attachment raises them up on a common cylindrical base that becomes the syncarpous ovary, covered with unique glochidiate hairs and containing a single basal ovule. The free portions of the carpels become the reflexed papillate stigmas. The floral vascular system has a single bundle at base that branches to supply the bract and flower traces. The floral vasculature is similar but not identical to that of Saururus (Saururaceae) and some Piper species (Piperaceae). Plesiomorphic character states of Zippelia that are shared with Saururus include hypogyny, free stamens, cleft stigma, and a similar floral groundplan. Synapomorphies, derived shared character states that unite Zippelia with Piperaceae, include syncarpy, solitary ovule, basal placentation, fused ventral carpellary bundles, and a double vascular cylinder in the stem. Cladistic analysis aligns Zippelia with Piperaceae because they share apomorphies, and because Zippelia shares only plesiomorphies with Saururus.
All flowers of Anemopsis californica, the most specialized taxon of the family Saururaceae, are initiated as individual primordia subtended by previously initiated bracts, in contrast to the common-primordium initiation of all flowers of Saururus cernuus and of most flowers of Houttuynia cordata. Floral symmetry is bilateral and zygomorphic, and the sequence of initiation among floral parts is paired or whorled. In A. californica, the six stamens arise as three common primordia, each of which later bifurcates to form a pair. The three common primordia occupy sites corresponding to the positions of the three stamens in H. cordata flowers. In Anemopsis, the filaments of each pair are connate. Each stamen pair is vascularized by a single bifurcating vascular bundle. The three carpels per flower are usually initiated simultaneously although there may be some variation. Adnation between stamens and carpels results from zonal growth. Downward extension of the locule, and proliferation and expansion of receptacular tissue and inflorescence cortical tissue around the locule below the bases of the carpels produce the inferior ovary. The inflorescence terminates its activity as a flattened apical residuum, surrounded by bracts subtending reduced flowers most of which have stamens only.
The inflorescence of Houttuynia cordata produces 45–70 sessile bracteate flowers in acropetal succession. The inflorescence apical meristem has a mantle-core configuration and produces “common” or uncommitted primordia, each of which bifurcates to form a floral apex above, a bract primordium below. This pattern of organogenesis is similar to that in another saururaceous plant, Saururus cernuus. Exceptions to this unusual development, however, occur in H. cordata at the beginning of inflorescence activity when four to eight petaloid bract primordia are initiated before the initiation of floral apices in their axils. “Common” primordia also are lacking toward the cessation of inflorescence apical activity in H. cordata when primordia become bracts which may precede the initiation of an axillary floral apex. Many of these last-formed bracts are sterile. The inflorescence terminates with maturation of the meristem as an apical residuum. No terminal flowers or terminal gynoecia were found, although subterminal gynoecia or flowers in subterminal position may overtop the actual apex and obscure it. Individual flowers have a tricarpellate syncarpous gynoecium and three stamens adnate to the carpels; petals and sepals are lacking. The order of succession of organs is: two lateral stamens, median stamen, two lateral carpels, median carpel. The three carpel primordia almost immediately are elevated as part of a gynoecial ring by zonal growth of the receptacle below the attachment of the carpels. The same growth elevates the stamen bases so that they appear adnate to the carpels. The trimerous condition in Houttuynia is the result of paired or solitary initiations rather than trimerous whorls. Symmetry is bilateral and zygomorphic rather than radial. No evidence of spiral arrangement in the flower was found.
The development of plant population biology (SOLBRIG et al., 1979) as a discipline which connects plant systematics with ecology has been one of the most important trends within recent years, though at present more questions have been asked than answered. Likewise, the study of reproductive biology, notably of tropical plants, has turned into a field of tremendous activity; most of it will be reviewed in this volume under pollination ecology, but the results are of course of great interest for the evolution and systematics of seed plants. Methodological progress has been made in the interpretation of phytochemical data. Apart from that, the trends mentioned in the last review (Progr. Bot. 41, 239) are still of interest. As to the problems of classification in general, the number of cladistic studies has increased, but it is still doubtful if they will have a major impact. Comprehensive, integrated approaches to the systematics and biology of major groups include the Solanaceae symposium (HAWKES et al., 1979), and the resumption of the Natürliche Pflanzenfamilien series with a multi-authored treatment of the Loganiaceae (LEEUWENBERG, 1980).
The perianthless members of the Piperales are unique among the basal lineages of angiosperms because they are mainly herbaceous plants with over 2000 species possessing highly reduced flowers. There have been several attempts to address the evolution of the flower morphology in the group, but no previous study has included a DNA-based estimate of phylogeny. Here we present a robust reconstruction of the phylogenetic relationships of the genera in the perianthless Piperales using DNA sequence data from three genes (rbcL, atpB, and 18S) and two genomes (nuclear and chloroplast). We estimated the likelihood values of ancestral character states of mature floral structures. Developmental sequences also were analyzed using step matrices under specific models of character state change to examine the origin of meristic differences of the androecium and gynoecium. Developmental lability is the general theme in the evolution of floral merosity in the perianthless Piperales, with different developmental processes giving rise to morphologically identical mature stages. Our findings confirm this notion based on several distinct patterns: (1) nonidentical ontogenies give rise to homoplasious, six-staminate androecia of Saururaceae and some Piperaceae most likely through terminal addition; (2) identical ontogenies produce the homoplasious two-staminate flowers in Peperomia and Piper umbellatum through deletion; and (3) nearly identical ontogenies produce homplasious tricarpellate gynoecia of Piper and Anemopsis + Houttuynia clade, and the apocarpous gynoecium of Saururus may be secondarily derived, both end products occurring through deletion. We note that changes in organ number and the degree of carpel fusion have been important during the evolutionary history of the perianthless Piperales as well as the basal angiosperms in general and should be studied more extensively. Overall we emphasize the lability of developmental pathways, especially in the flower, and endorse the methodological utility of developmental sequences for directing future investigations of floral evolution.
Peperomia is with approximately 1,600 species one of the species rich angiosperm genera. Several characters on which current infrageneric
classifications are based are influenced by parallel evolution. A well-resolved molecular backbone phylogeny of the genus
is needed to address evolutionary questions about morphological traits. Based on separate and combined analyses of a morphological
data set and three molecular data sets, phylogenetic relationships within Peperomia are investigated with respect to character evolution. The resulting trees from different datasets are highly congruent. Morphological
characters are mapped on a combined molecular tree, visualizing the contrast between previously used homoplastic characters
and some newly observed characters, that can be used to delimit monophyletic groups. Length mutational events of the chloroplast
dataset are coded and plotted on the respective tree, to test if indels support alternative hypothesis of relationships found
in the nuclear datasets as well as the overall performance of indels compared with substitutional mutations. Our findings
indicate that length distribution of indels is highest among five and six bp events. Autapomorphic and synapomorphic length
mutations are most frequent in both insertions and deletions and are also more frequent independent of the length of the mutation.
Concluding, independent of the length, mutations are of phylogenetic importance and should not be disregarded. None of the
homoplastic indels turn into synapomorphic indels, supporting the different topology of the nrDNA tree but indicate areas
of molecular evolution in favour of length mutations resulting in independent events.
Peperomia Ruiz et Pavón comprises an indetermined number of species distributed in tropical and subtropical regions of both hemispheres. One reason for interest in this genus is the difficulty of determining its species. Microscopic features were studied for fruit and seed of 17 Mexican Peperomia species representing six subgenera (Acrocarpidium, Micropiper, Ogmocarpidium, Rhyncophorum, Sphaerocarpidium, and Tildenia). Results show that all 17 materials can be distinguished by fruit characters. The differences among fruits are: (a) location and insertion of fruit on rachis, (b) ovary form, (c) curvature, (d) celular composition in exocarp and endocarp, (e) style form, (f) stigma position, (g) presence of crystals in the pericarp, and (h) dermal cuticle ornamentation. New taxonomic characters are reported, and common terms concerning the insertion and appearance of the fruit are clarified. The seeds of all these species have voluminous perisperm, scarce endosperm, and an undeveloped embryo. Fruit characters in Peperomia can be useful for identifying the species of this genus. However, a thorough search in more species is suggested for additional characters or character states.
The inflorescence of Saururus cernuus L. produces lateral “common” primordia in acropetal succession on the flanks of the inflorescence meristem; curiously, the “subtending” bract is initiated upon the lateral primordium rather than subtending it. On the basis of mature floral structure, flowers of S. cernuus have previously been described as having spiral initiation of parts. The current ontogenetic investigation contradicts this interpretation. Stamens arise in three successive pairs; the carpels also are initiated in pairs. Floral symmetry is shown to be bilateral from the onset of organ initiation, a rare feature among primitive angiosperms. On the basis of symmetry and paired initiation of organs, the possibility of close relationships between Saururaceae and Magnolialian or Ranalian lines appears remote.
Paired initiation of stamens and carpels on the apical meristem and bilateral symmetry of the flower are shown to prevail in Saururus cernuus. The carpels are initiated in two successive pairs of two members each, in a decussate arrangement. The floral apex shows plastochronic expansion in area between initiation of the last stamens and the first carpels, and also a less marked expansion between the two pairs of carpels. Vascularization appears to be whorled, with all carpels being supplied at once and at the same level. The vasculature of the flower is basically four-stranded, such that each strand supplies a carpel and one, two, or three stamens. Carpels of a flower become unequal in size and level of attachment through post-initiatory changes; these changes obscure the paired, decussate sequence of initiation. Phylogenetic conclusions about Saururus based on its supposedly spiral initiation of parts are in need of reexamination; Saururus exhibits a highly specialized pattern of paired organ initiation which is bilaterally organized, rather than radial and helical as in most primitive angiosperms. Vasculature of the flower involves divergence of appendage traces at approximately the same time for all stamens, and simultaneously for all carpels, contrary to previous reports that divergence is helical or spiral in succession. All carpel bundles diverge from sympodia which supply at least one stamen, also contrary to previous descriptions.
The spicate inflorescence of Saururus cernuus L. (Saururaceae) results from the activity of an inflorescence apical meristem which produces 200–300 primordia in acropetal succession. The inflorescence apex arises by conversion of the terminal vegetative apex. During transition the apical meristem increases greatly in height and width and changes its cellular configuration from one of tunica-corpus to one of mantle (with two tunica layers) and core. Primordia are initiated by periclinal divisions in the subsurface layer. These are “common” primordia, each of which subsequently divides to produce a floral apex above and a bract primordium below. The bract later elongates so that the flower appears borne on the bract. All common primordia are formed by the time the inflorescence is about 4.4 mm long; the apical meristem ceases activity at this stage. As cessation approaches, cell divisions become rare in the apical meristem, and height and width of the meristem above the primordia diminish, as primordia continue to be initiated on the flanks. Cell differentiation proceeds acropetally into the apical meristem and reaches the summital tunica layers last of all. Solitary bracts are initiated just before apical cessation, but no imperfect or ebracteate flowers are produced in Saururus. The final event of meristem activity is hair formation by individual cells of the tunica at the summit, a feature not previously reported for apical meristems.
The inception of the inflorescence in Arum maculatum L. takes place in July or early August, flowering occurring in the following spring. Inflorescence inception always occurs in a specifically positioned bud in the axil of the second foliage leaf below the current year’s spathe, after the bud has first formed a minimum of 6-10 foliar primordia and the stem tuber has reached a minimum weight of 7.4 g in July. A study of the potential inflorescence showed that the initial vegetative shoot is formed as a result of the activity of an apical meristem consisting of a 2-layered tunica and a corpus. This apex, in transition from the vegetative to the inflorescence stage, elongates, widens, and becomes asymmetrical at the base, and some slight asymmetry persists in the axis hereafter. A parenchymatous core is formed within the tunica and corpus layers. Throughout all phases of development, except during the final phase of spadix formation, the inception of primordia occurs at various levels on the apical meristem. All nascent primordia so formed originate from the same histogenic layers and are generally comparable histologically. However, the foliar primordia originate more superficially within these layers than those of flower or vegetative buds. At an early stage in their subsequent development the several categories of primordia can readily be distinguished from one another. Attempts to carry out surgical experiments on the apex failed and indicated the unsuitability of this plant for experiments of this type.
The presence of oil cells has been used as a unifying characteristic for the woody ranalian complex. Very little information is available concerning the development of the oil cell and, thus, the validity of this characteristic is questioned. Shoot tips of representatives of 27 genera from nine woody ranalian families were studied. The early stages of oil cell ontogeny are similar in all species studied. The oil cell initial is larger and contains a higher RNA and protein content than the surrounding parenchyma cells. The oil sac is attached to the cell wall by a peg-like structure, which is composed, at least partially, of insoluble carbohydrates. As the oil sac enlarges the protoplast decreases in volume until the entire lumen of the cell is occupied by the sac. In some species not all young oil cells develop into mature oil cells but, instead, give rise to mucilage cells and cavities, lysigenous cavities, and acidic cells which contain tannin-like substances. The secondary structures formed by oil cells appear to be, in some cases, significant generic and familial characteristics, but not significant at the ordinal level. The uniformity of at least the early stages in the ontogeny of oil cells does appear to be significant as an ordinal characteristic.
THE PHYLOGENETIC TAXONOMY OF FLOWERING PLANTS CHARLES E. BESSEY University of Nebraska I. Geisteeal Discussion Seventeen years ago in presenting a somewhat similar paper1 to a smaller body of botanists, I began by saying that "it is as yet impossible to present a ...
A B S T R A C T Paired initiation of stamens and carpels on the apical meristem and bilateral symmetry of the flower are shown to prevail in Saururus cernuus. The carpels are initiated in two successive pairs of two members each, in a decussate arrangement. The floral apex shows plastochronic expansion in area between initiation of the last stamens and the first carpels, and also a less marked expansion between the two pairs of carpels. Vascularization appears to be whorled, with all carpels being supplied at once and at the same level. The vasculature of the flower is basically four-stranded, such that each strand supplies a carpel and one, two, or three stamens. Carpels of a flower become unequal in size and level of attachment through post-initiatory changes; these changes obscure the paired, decussate sequence of initiation. Phylogenetic conclusions about Saururus based on its supposedly spiral initiation of parts are in need of reexamination; Saururus exhibits a highly specialized pattem of paired organ initiation which is bilaterally organized, rather than radial and helical as in most primitive angiosperms. Vasculature of the flower involves divergence of appendage traces at approximately the same time for all stamens, and simultaneously for all carpels, contrary to previous reports that divergence is helical or spiral in succession. All carpel bundles diverge from sympodia which supply at least one stamen, also contrary to previous descriptions. FLORAL ONTOGENY of a member of the Saurura
An account is presented of floral histogenesis in Luzula campestris (L.) DC., Juncus articulatus L., and Juncus vaginatus R. Br. The pattern of floral histogenesis in these species is similar to that in species of the Gramineae and Cyperaceae. Bracts, bracteoles, perianth members, and carpellary tissue arise by divisions of cells of the tunica. Periclinal divisions in the outer tunica layer (dermatogen) always occur in the initiation of these "foliar" type organs. The primordia of inflorescence branches, flower primordia, and stamens, on the other hand, arise as a result of cell division in the outer layers of the corpus and
the inner layer of the tunica. Periclinal divisions in the dermatogen are not involved in the differentiation of these "cauline" type structures. The morphological nature of the placentas in Juncus is discussed; they appear to arise independently of the carpellary tissue and after the manner of "cauline" structures. The ovules in both Luzula and Juncus arise in similar fashion.
Es wurden postgenitale Verwachsungen an oberständigen, apokarpen, latent peltaten und epeltaten Karpellen aus den Familien der Magnoliaceae, Calycanthaceae, Ranunculaceae, Crassulaceae, Rosaceae, Leguminosae, Asclepiadaceae und Alismataceae an 140 Arten untersucht. Es handelt sich in allen Fällen um Verwachsung, im Unterschied zu bloßer Kutikularverzahnung. Verwachsung entsteht durch Wachstum, oft unter periklinalen Teilungen, der Epidermiszellen, bevor sie eine mit den gewöhnlichen Methoden nachweisbare Kutikula gebildet haben. Die Verwachsungslinie bleibt entweder bis zur Ausbildung der Trennungsgewebe der Frucht deutlich sichtbar (Magnoliaceae, Calycanthaceae, Ranunculaceae, Alismataceae) oder sie ist schon lange vor der Blütezeit völlig unkenntlich (Papilionatae, Asclepiadaceae) oder sie verhält sich intermediär (Crassulaceae, Rosaceae, Mimosoideae, Caesalpinioideae, Sophoreae, schließfrüchtige Ranunculaceae-Karpelle). Das verschiedene endgültige Aussehen kommt dadurch zustande, daß verschieden alte Stadien des Verwachsungsvorganges als Endzustände erhalten bleiben. Früher Verwachsungsbeginn macht ein Durchlaufen des gesamten Vorganges möglich, bei spätem Beginn werden nur die ersten Stadien, die sonst Durchgangsstadien sind, erreicht und als endgültige Zustände festgehalten.
Der Grad der Verwachsung ist — abgesehen von den schließfrüchtigen Ranunculaceae — unabhängig von der Öffnungsweise der Frucht, steht aber anscheinend in Beziehung zur phylogenetischen Höhe.
Die Ontogenese der schildfrmigen Brakteen vonPeperomia zeigt eindeutig, da der Aufbau der Schildflche durch das Wachstum normaler Blattrnder allein durchgefhrt wird, also in der gleichen Weise wie bei den epipeltaten Schildblttern. Nur besteht gegenber diesen der Unterschied, da der Zusammenschlu der Spreitenrnder dorsal ber der Ansatzstelle des Blattstieles vorsichgeht. Der Blattstiel zeigt sich von Anfang an als unifazial, und zwar ist an ihm die Oberseite allein entwickelt, er ist superunifazial gebaut. Durch weiteres Wachstum der Blattrnder und der dorsalen Querzone entwickelt sich die Lamina schildfrmig ber die Ansatzstelle des Stieles hinaus. Es liegen hier also tatschlich hypopeltate Schildbltter im SinneDe Candolles vor, die im wesentlichen die gleichen, aber entgegengesetzt angewendeten Bauprinzipien wie die epipeltaten Schildbltter verwirklichen.
Acidified 2,2-dimethoxypropane was used to chemically dehydrate biologic tissues for examination in the electron microscope. The ultrastructural integrities of single-celled algae, plant tissues (cotyledon, root, leaf) and animal tissues (liver, pancreas, muscle, cartilage) were maintained. Our technique was simpler and quicker than physically exchanging water for organic solvents (e.g., acetone, ethanol) as generally performed in microscopy.
Entwicklungsgeschichtliche Untersuchungen über die Piperaceen—Peperomia verschaffeltii und P. metallica
- Abele K.
Memoire sur la familie des Piperacées
- Candolle C.
Placentation in Peperomia
- Murty Y. S.
Studies in the order Piperales. II. A contribution to the study of vascular anatomy of the flower of Peperomia
- Murty Y. S.
On the morphology of the flower in Peperomia (Piperaceae) species
- Sastrapradja S.
On relative position, including a new arrangement of phanerogamous plants
- Clarke B.
Studien über Süd‐ und Central‐Amerikansche Peperomien
- Dahlstedt H.
The Piperaceae of Costa Rica
- Trelease W.
Organogenesis of flowers
- R. Sattler
Histoire des Plantes
- H Baillon
Elements de Botanique Paris
- P Tieghem
Elements de Botanique
- P Tieghem
- Van