Embryology of Zippelia begoniaefolia (Piperaceae) and its systematic relationships

Microsporogenesis and embryology of the monotypic Zippelia (Z. begoniaefolia) Blume (Piperaceae) is described for the first time to assess its systematic relationships. The formation of the anther wall is of Basic Type such that the anther wall, consisting of an endothecium with fibrous thickenings, two middle layers, and a glandular septum with 2‐nucleate cells, is derived from a primary parietal layer. Simultaneous cytokinesis follows meiosis of the microspore mother cell thence forming a tetrahedral tetrad of microspores. The single basal ovule is orthotropous, crassinucellate and bitegmic but only the inner integument forms the micropyle. The sporogenous cell of the nucellus functions directly as a megaspore mother cell. A coenocyte with four nuclei forms after meiosis of the megaspore mother cell. The formation of the embryo sac is tetrasporic ab initio and is of, or similar to, the Drusa Type of embryo sac in which the nuclei of the coenocyte undergo two successive mitoses and forms a 16‐celled or 16‐nucleate embryo sac that is ovoid in shape. The embryo sac has an egg apparatus consisting of an egg cell and two synergids (but one of the latter is less discernable). Two polar cells occur just beneath the egg apparatus and 11 antipodal cells or nuclei are arranged along the lower part of the inner wall of the embryo sac. They are linked by threads of cytoplasm. The two polar cells are separated or fused before fertilization. A large primary endosperm nucleus with many nucleoli, which resulted from the fertilized polar cells and with the participation of antipodal cells, divides into a free nuclei stage. The free nuclei are arranged along the lower part of the inner wall of the embryo sac or rarely assemble at the central part. The development of endosperm is thus of the Nuclear Type. The zygote remains undivided and fails to develop even when the seed is nearly mature. Frequently, the zygote and the endosperm abort later and leave an empty chamber in the top part of the seed. Most of the seed content is starchy perisperm. Only the inner integument forms the seed coat and the pericarp develops glochidiate hairs (anchor‐like hairs) when the endosperm begins to develop. By comparison with the other piperaceous taxa using embryological and botanical features, Zippelia is referred to as a basal taxon and a more isolated evolutionary line or a blind branch in the Piperaceae. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140 , 49–64.     

Embryology of Handeliodendron bodinieri (Sapindaceae) and its systematic value: development of male and female gametophytes

Embryological characters of Handeliodendron bodinieri (Sapindaceae) are reported for the first time. Anthers are tetrasporangiate. Cytokinesis in microsporocyte meiosis is of the simultaneous type and the microspore tetrads are tetrahedral. The tapetum is secretory and parietal. Mature pollen is bicellular. The ovary is trilocular. There are two ovules in each locule. The placenta is axile. The ovule is crassinucellate, bitegmic and hemitropous, without hypostase when mature. The development of the embryo sac is of the Polygonum type. The systematic significance of the embryological characters of Handeliodendron bodinieri is discussed.     

柽柳大、小孢子发生和雌、雄配子体发育的观察

利用常规石蜡制片技术,对柽柳(Tamarix chinensis Lour.)的大、小孢子发生及雌、雄配子体发育过程进行了观察。主要结果如下:(1)花药壁由五层细胞组成,从外向内分别为表皮、药室内壁,两层中层和绒毡层。药壁的发育属于基本型。绒毡层为分泌型。(2)孢原细胞为多孢原起源。小孢子母细胞减数分裂过程中的胞质分裂为连续型,形成的四分孢子为四面体型;同一药室的小孢子母细胞减数分裂几乎完全同步。(3)成熟花粉粒为2细胞型,具3个萌发孔。(4)柽柳为三心皮构成的单室复子房,每子房具有10~20个胚珠,基底胎座,胚珠为双珠被、厚珠心、倒生型。大孢子母细胞减数分裂形成1+3排列的4个大孢子, 4个大孢子全部参与胚囊的形成。(5)胚囊发育为贝母型,反足细胞在胚囊成熟时充分发育。(6)同一朵花中,前期雄蕊的发育早于雌蕊的发育,后期当花粉成熟时,雌配子体也达到成熟,雌雄蕊发育趋于同步。     

Evolution ofPeperomia (Piperaceae) in the Juan Fernandez Islands,Chile

Four species ofPeperomia (Piperaceae) occur in the Juan Fernandez Islands, Chile:P. berteroana, P. margaritifera, P. skottsbergii, andP. fernandeziana. The last species is found also in continental Chile, whereas the other three are endemic to the archipelago.Peperomia margaritifera is found only on the older island of Masatierra, whereasP. skottsbergii is confined to the younger island of Masafuera, andP. berteroana occurs on both islands. Phenetic analyses of mainland taxa suggest thatP. fernandeziana belongs to subg.Sphaerocarpidium whereas the endemic taxa form their own subg.Tildenidium connecting to subg.Tildenia. Cladistic analyses indicate thatP. margaritifera is the most primitive species in the archipelago and thatP. berteroana is the most derived, especially patristically. Chromosomally, the four species are all n = 22, which may be tetraploid on a base of x = 11. Sulfated flavones occur only inP. berteroana andP. skottsbergii, which are otherwise unknown for the family. Dispersal of propagules to the islands from the continent and between islands is believed to have been accomplished by birds.     

Sex‐linked microsatellite marker detected in the female gametophytes of Undaria pinnatifida (Phaeophyta)

In our microsatellite analysis of three male and three female gametophytes of Undaria pinnatifida (Harv.) Suringar, a microsatellite marker (part of the locus Up‐AC‐2A8, GenBank accession no. AY738602.1) was only polymerase chain reaction‐amplified in three female gametophytes. This putative female‐specific marker was further tested by the use of 32 male and 21 female gametophytes maintained in the Marine Biological Culture Collection Centre, China. In addition, three sporophytes were included for confirmation. Results showed that the marker was present in all of the female gametophytes and sporophyte cultures, but absent in all of the male gametophytes. To our knowledge, this is the first sex‐related marker ever reported in U. pinnatifida. The discovery of this marker will accelerate gender identification and shed light on our understanding of the mechanisms of sex determination at a molecular level in this commercially important seaweed.     

Development of the gametophytes, flower, and floral vasculature in Cochliostema odoratissimum (Commelinaceae)

Flowers of Cochliostema odoratissimum are trimerous with three fertile stamens, three unequal antherless staminodes. and three connate carpels. The fertile stamens are on one side of die flower and united by their filaments, forming a compound structure that curves to the flower's right as the flower opens. The thecae arc longitudinally dehiscent, spirally coiled, and enveloped by pctaloid extensions of the filaments of the two lateral stamens contributing to the three-staminate structure. Anther wall development is of the monocotyledonous type. Tapetal raphides are formed and appear to be widespread in CCommelinaceae. Also known from Philydraceae and. perhaps. Haemodoraccae, tapetal raphides and their taxonomic distribution may be of phylogenetic utilitv. Microsporogcnesis is successive, forming both isobilateral and decussate tetrads. Pollen is shed as single binucleatc grains. Each ovary locule contains ten to twelve hemianatropous, crassinucellar. bitegmic ovules on axile placentae. The micropyle is formed by both the inner integument and one side of the outer integument. Megagamctophyte development is of the Polygonum type. The mature megagamctophyte consists of an egg apparatus, fusion nucleus, and three antipodals. the latter showing signs of degeneration. The salient features of the floral vasculature are the same as in the few other commclinaceous species for winch complete data are available. Relative to the floral vasculature in the other species, differences in the vasculature lie primarily in the presence and origin of lateral carpel bundles and in the number of sepal and ovule traces.     

Development of the gametophytes, flower, and floral vasculature in Dichorisandra thyrsiflora (Commelinaceae)

The flowers of Dichorisandra thyrsiflora (Commelinaceae) are monosymmetric and composed of three sepals, three petals, six stamens, and three connate carpels. The anthers are poricidal and possess a wall of five cell layers (tapetum included). This type of anther wall, not previously observed in the Commelinaceae, is developmentally derived from the monocotyledonous type via an additional periclinal division and the persistence of the middle layers through anther dehiscence. Secondary endothecial thickenings develop in the cells of the two middle layers only. The tapetum is periplasmodial and contains raphides. Microsporogenesis is successive and yields both decussate and isobilateral tetrads. Pollen is shed as single binucleate grains. The gynoecium is differentiated into a globose ovary, hollow elongate style, and trilobed papillate stigma. Each locule contains six to eight hemianatropous to slightly campylotropous crassinucellar ovules with axile (submarginal) placentation. The ovules are bitegmic with a slightly zig-zag micropyle. Megagametophyte development is of the Polygonum type. The mature megagametophyte consists of an egg apparatus and fusion nucleus; the antipodals having degenerated. The floral vasculature is organized into an outer and inner system of bundles in the pedicel. The outer system becomes ventral carpellary bundles. All other floral vascular traces originate from the inner system.     

Floristic Geography of Piper (Piperaceae) in China

Piper is the largest genus and important Pantropical components of the Piperaceae family with approximately 1000-2000 species in the world. China is in the northern verge of its natural distribution. In this study, floristic geography of the Piper genus in China was analyzed to reveal its botanical characteristic, origins of speciation and its dispersal channels. The study results showed Yunnan province is one of the very important distribution regions for Piper species, served as the center of the Piper species dispersal toward to the eastern and northern regions of China with gradually reduced species numbers. The similarity level appeared to be low for its species among different provinces, and the Piper distribution regions could be approximately clustered into three clades: tropical clade, subtropical clade and Taiwan clade. Cladistically, Piper species found in China have the highest proportions which were endemic to China, and then followed by Piper species distributed in Tropical Asia, only few species belonged to Pantropical and East Asia areal types. The floristic geography of Piper genus in China is related to that of Indo Chinese Peninsula, Java Islands and Indian Peninsula in some degrees, but not closely related. This study revealed Yunnan province is one of the central of origins for the Piper species, and or one of the central of regions for its species diversification, and the Piper species of Taiwan mainly came from Philippine islands and further diversified into Taiwan clade. Our study results presented a useful method for the systematic studying of Piper genus taxonomy and the evolution of Piper speciation.     

In vitro fertilization from co-cultured pollen tubes and female gametophytes of Douglas fir (Pseudotsuga menziesii)

 Our previous attempt on in vitro fertilization (IVF) in conifers resulted in pollen tube penetration of female gametophytes, but because of the rapid decline in egg viability, no further interaction occurred. In this report, we describe for the first time that IVF has been achieved in conifers. Using Douglas fir (Pseudotsuga menziesii), we describe a two-step process which involved induction of pollen tubes in culture followed by introduction of isolated female gametophytes at the tips of growing pollen tubes. Pollen tubes penetrated the introduced isolated female gametophytes at various places, but a number of tubes entered the egg cell through the neck cells similar to the in vivo condition. Under our current culture conditions, longevity of pollen tubes and eggs has been improved resulting in the release of sperms, fusion of gametes, and initial formation of the proembryo. Continued plasmolysis of the egg limited the number of successful gametic interactions. IVF has been accomplished in flowering plants in several ways, but the gametophyte-gametophyte IVF system described in this paper is unique. IVF offers a novel breeding technology that takes advantage of the sexual reproductive route. When coupled with hybridization and genetic transformation, IVF could result in the development of stable novel genotypes of economically superior trees. Received: 28 October 1997 / Accepted: 9 December 1997     

Protoplast production in Chondrus crispus gametophytes (gigartinales,rhodophyta)

Protoplasts were isolated from female gametophytes of Chondrus crispus (Stackh.) using commercial cellulase and various carrageenases prepared from marine bacteria. Depending on the nature of the donor tissue (apices or whole thallus, wild or cultivated strains), yields ranged from 1.0–8.5×10⁸ protoplasts per gram of fresh tissue. Preincubating the tissue with a potassium chelator, Kryptofix 222, enhanced protoplast yields by 30–50 %. Based on staining with fluorescein diacetate most protoplasts were viable. A few protoplasts regenerated a cell wall and divided.     

Preliminary study on flg22-induced defense responses in female gametophytes of Saccharina japonica (Phaeophyta)

Flg22, which is the most conserved 22-amino acid peptide in the N-terminal part of flagellin, functions as an effective elicitor in higher plants. Marine algae and higher plants share some conserved characteristics on defense response pathways. Flg22-induced defense responses were investigated in female gametophytes of Saccharina japonica. Condensation of chloroplasts and thickened cell walls, as well as relatively stable structures of mitochondria and nucleus indicated that there were hypersensitive programmed cell death occurred after induction by flg22. By using luminol-dependent luminescence detection method, rapid release of H₂O₂ was detected in the induced female gametophytes and reached a peak concentration of about 46 μM at 2 h. Reactive oxygen species production was also observed histologically using the fluorescent dye 2′,7′-dichlorofluorescein diacetate, showing a consistent result with quantitative analysis of H₂O₂. Furthermore, results of antioxidant enzyme activities indicated that there was a trend in the order of catalase > superoxide dismutase > glutathione peroxidase. Finally, high level phenol content of cell-free extracts was found after flg22 induction. According to our results, flg22 could be an effective elicitor which could induce defense responses in female gametophytes of S. japonica.     

Taxonomic notes on the genus Piper (Piperaceae)

Sixteen lectotypifications of Asian Piper species are provided. Piper argyrites, P. baccatum, P. leptostachyum, P. majusculum, P. peepuloides, P. quinqueangulatum and P. sulcatum are accepted as species and many new synonyms are proposed. Useful diagnostic characters are described and geographical distribution data of each species are provided.     

Embryology of Eusideroxylon (Cryptocaryeae, Lauraceae) and character evolution in the family

Lauraceae are relatively well-known embryologically and embryological data are available for 23 of about 50 genera. In this paper we present the embryology of Eusideroxylon , an unstudied and key genus within Cryptocaryeae, which are positioned basally in the evolution of Lauraceae, and discuss the evolution of embryological characters in the family. Based on comparisons of over 50 characters, it was found that Eusideroxylon is consistent with Aspidostemon , the core Cryptocaryeae ( Beilschmiedia , Cryptocarya , Endiandra and Potameia ), Caryodaphnopsis and Cassytha in having a glandular anther tapetum. The core Cryptocaryeae further agrees with both Caryodaphnopsis and Cassytha in having an embryo sac protruding from the nucellus. In light of the phylogenetic trees available, both the glandular tapetum and the embryo sac protruding from the nucellus have evolved as homoplasies in Lauraceae, once each in a clade of Cryptocaryeae, and the Caryodaphnopsis and Cassytha clade, respectively. Such character-state distributions suggest that it is better to place both Caryodapnopsis and Cassytha in the same clade as the core Cryptocaryeae. Embryologically, Eusideroxylon appears to have an intermediate state between Hypodaphnis , a genus positioned basal-most in the family, and the core Cryptocaryeae. Supplementary data on the anther and seed of Hypodaphnis are also provided.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 187–201.     

Ultrastructure and cytochemistry of the pearl gland in Piper regnellii (Piperaceae)

Pearl glands are scattered throughout the lamina of developing leaves and rarely found on adult leaves of Piper regnellii (Piperaceae). The pearl gland is a bicellular secretory trichome composed of a short broad basal cell and a spatula-like, semiglobular apical cell. Four different stages of the pearl gland were determined during its ontogenesis: origin, pre-secretory, secretory and post-secretory. During the pre-secretory stage, mitochondria, ribosomes, dictyosomes, rough endoplasmic reticulum, and plastids with electron dense inclusions were present in the cytoplasm of the apical cell. During the secretory stage, the most remarkable characteristics of the apical cell are the proliferation of dictyosomes and their vesicles, rough endoplasmic reticulum, and modified plastids. At this stage, electron-dense oil drops occur in the plastids as well as scattered within the cytoplasm, proteins and polysaccharides are seen in the plastids, vesicles, and vacuoles. Only polysaccharides are present in the periplasmic space, wall cavities, and on the surface of the apical cell. The polysaccharides are one of the main components of the mucilagenous exudate that covers the developing leaf structures. The apical cell of the senescing trichomes undergoes a progressive degeneration of its cellular components, the plastids being the first organelles to undergo lysis.     

Phylogeny and patterns of floral diversity in the genus Piper (Piperaceae)

With ～1000 species distributed pantropically, the genus Piper is one of the most diverse lineages among basal angiosperms. To rigorously address the evolution of Piper we use a phylogenetic analysis of sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA based on a worldwide sample. Sequences from a total of 51 species of Piper were aligned to yield 257 phylogenetically informative sites. A single unrooted parsimony network suggested that taxa representing major geographic areas could potentially form three monophyletic groups: Asia, the South Pacific, and the Neotropics. The position of Pothomorphe was well supported among groups of New World taxa. Simultaneous phylogenetic analysis of an expanded alignment including outgroups suggested that taxa from the South Pacific and Asia formed a monophyletic group, provisionally supporting a single origin of dioecy. Within the Neotropical sister clade, resolution was high and strong bootstrap support confirmed the monophyly of several traditionally recognized infrageneric groups (e.g., Enckea [including Arctottonia], Ottonia, Radula, Macrostachys). In contrast, some of the species representing the highly polytypic subgroup Steffensia formed a clade corresponding to the previously recognized taxon Schilleria, while others were strongly associated with several of the more specialized groups of taxa. The distribution of putatively derived inflorescence and floral character states suggested that both umbellate and solitary axillary inflorescences have multiple origins. Reduction in anther number appears to be associated with highly packaged inflorescences or with larger anther primordia per flower, trends that are consistent with the suppression of later stages of androecial development.     

Embryology of Calenduleae (Compositae)

Microsporangial conditions, macrosporogenesis, embryo sac development and in some species endosperm formation have been studied in 5 species of Dimorphotheca Vaill. ex Mnch, 2 species of Castalis Cass., 16 species of Osteospermum L., 6 species of Calendula L., 1 species of Gibbaria Cass., and 1 species of Chrysanthemoides Tourn. ex Fabr.
The microsporangial wall consists of four different layers of cells. Miocrospore formation is simultaneous. The tetrads are mostly arranged in tetrahedrals. A tapetal periplasmodium develops.
The archespore of the macrosporangium is in most cases 1-celled, sometimes 2-or many-celled. The meiosis gives rise to a linear tetrad. Usually the chalazal macro-spore develops. The embryo sac development is monosporic of the Polygonum type. In a few cases in Dimorphotheca venusta T. Norl. a tetrasporic embryo sac development was observed besides the Polygonum type. Castalis tragus (Ait.) T. Norl. may have a bisporic embryo sac development in addition to the Polygonum type. All the Calendula species develop synergid haustoria. Antipode haustoria occur in Osteospermum sinuatum (DC.) T. Norl. and Chrysanthemoides monilifera (L.) T. Norl. Chalazally situated extra embryo sacs below the ordinary one in Dimorphotheca sinuata DC, D. venusta , and Castalis nudicaulis var. graminifolia (L.) T. Norl. are regarded to be aposporic. Six species have more than three antipodes per embryo sac. The antipodes occasionally become 2-or 4-nucleate.     

Female gametophyte and early seed development in Peperomia (Piperaceae)

The evolution of female gametophyte development provides an example of how minor ontogenetic modifications can impact the functional biology of seeds. Mature Peperomia-type female gametophytes are normally depicted as 16-nucleate, nine-celled structures. However, recent ultrastructural data have demonstrated that many previous reports were incorrect, suggesting that our understanding of the Peperomia-type ontogeny is incomplete. In this investigation, female gametophyte and early seed development is described in Peperomia dolabriformis, P. jamesoniana, and P. hispidula. Nuclear positioning, nuclear division, and vacuole morphology are documented during the syncytial stages of development, and two mature female gametophyte cellular configurations are described. Endosperm ploidy is measured in each species using microspectrofluorometry. We conclude that a 10-celled construction is likely the most common cellular configuration in Peperomia and that a three-celled female gametophyte exists in P. hispidula. We also describe how developmental modifications of wall formation could produce the diverse cellular configurations observed throughout Peperomia. Interestingly, the onset of female gametophyte diversification within Piperales correlates with the origin of the perisperm in the common ancestor of Piperaceae + Saururaceae. We posit that the origin of the perisperm may have relaxed selection on endosperm genetic constructs, thereby promoting diversification of female gametophyte ontogeny.     

狭叶柴胡大小孢子发生和雌雄配子体发育的研究

用石蜡切片法、半薄切片法对狭叶柴胡的大、小孢子发生和雌、雄配子体发育进行观察研究。结果显示:(1)狭叶柴胡花药壁的发育为双子叶型,腺质绒毡层;小孢子母细胞减数分裂过程中的胞质分裂为同时型,四分孢子为正四面体形;成熟的花粉粒为3-细胞型,具3个萌发孔。(2)倒生型胚珠,单珠被,薄珠心;大孢子母细胞常为一个雌性孢原直接发育而成,大孢子四分体呈线型,多数情况为合点端一个大孢子分化为功能大孢子;由功能大孢子发育为蓼型成熟胚囊。(3)八核胚囊时期,珠心基部和两侧的一些珠心细胞留存较久,成为珠心座细胞。此外,珠被内表皮细胞发育为珠被绒毡层。     

Evolutionary trends in the Central American species of Piper (Piperaceae)

The gross morphology of the Central American species ofPiper is surveyed in respect to habit and habitat, protection of the shoot-tip, form and condensation of the inflorescence and floral parts, and anther-dehiscence. The cap-like structure covering the shoot-tip in many species is interpreted as a modified prophyll. A ligulate development and the inclusion of the inflorescence within the sheathing leaf-base in a few species are discussed. Diminution and compaction of the floral parts are interpreted as an evolutionary response to the activities of small pollen-collecting bees. Compaction of the floral parts is correlated with a truncation of the pistil apex and, in a few species, with a change in the mode of anther dehiscence. Apical and upward dehiscence of the anthers are interpreted as similar adaptations caused by a restriction of the pollinator’s activity to the surface of the spike. A relationship between ants and certain hollow-stemmed species is mentioned. The multiple origins and independent lines of evolutionary development discussed here suggest a complex phyletic history of the genus.