Floral development and floral phyllotaxis in Anaxagorea (Annonaceae)

Background and Aims Anaxagorea is the phylogenetically basalmost genus in the large tropical Annonaceae (custard apple family) of Magnoliales, but its floral structure is unknown in many respects. The aim of this study is to analyse evolutionarily interesting floral features in comparison with other genera of the Annonaceae and the sister family Eupomatiaceae. Methods Live flowers of Anaxagorea crassipetala were examined in the field with vital staining, liquid-fixed material was studied with scanning electron microscopy, and microtome section series were studied with light microscopy. In addition, herbarium material of two other Anaxagorea species was cursorily studied with the dissecting microscope. Key Results Floral phyllotaxis in Anaxagorea is regularly whorled (with complex whorls) as in all other Annonaceae with a low or medium number of floral organs studied so far (in those with numerous stamens and carpels, phyllotaxis becoming irregular in the androecium and gynoecium). The carpels are completely plicate as in almost all other Annonaceae. In these features Anaxagorea differs sharply from the sister family Eupomatiaceae, which has spiral floral phyllotaxis and ascidiate carpels. Flat stamens and the presence of inner staminodes differ from most other Annonaceae and may be plesiomorphic in Anaxagorea. However, the inner staminodes appear to be non-secretory in most Anaxagorea species, which differs from inner staminodes in other families of Magnoliales (Eupomatiaceae, Degeneriacae, Himantandraceae), which are secretory. Conclusions Floral phyllotaxis in Anaxagorea shows that there is no signature of a basal spiral pattern in Annonaceae and that complex whorls are an apomorphy not just for a part of the family but for the family in its entirety, and irregular phyllotaxis is derived. This and the presence of completely plicate carpels in Anaxagorea makes the family homogeneous and distinguishes it from the closest relatives in Magnoliales.     

Thrips Cross-Pollination of Popowia pisocarpa (Annonaceae) in a Lowland Dipterocarp Forest in Sarawak1

This paper reports thrips (Thysanoptera) cross-pollination in the primitive angiosperm, Popowia pisocarpa (Annonaceae), in lowland rain forest of Sarawak, Malaysia. Flowers of P. pisocarpa have a tiny pollination chamber (3–4 mm in depth) with the entrance almost closed by the disk-shaped stigmatic heads, allowing only small insects to enter. Experiments showed that thrips were effective pollinators and flowers ofP. pisocarpa were self-incompatible. Seed set was limited by pollen. Clumped adult trees had higher seed-set than more distant individuals (>5 m from nearest flowering neighbor), indicating limited inter-tree movement by thrips.     

Seed development and function inArtabotrys hexapetalus (Annonaceae)

Until now seeds ofAnnonaceae were characterized as mesotestal only. The seed ofArtabotrys hexapetalus, however, is meso- and endotestal. An outer mechanical layer which surrounds the seed as a lignified fibrous tissue is derived from the mesotesta. A complex inner mechanical layer develops from a partially multi-layered endotesta built up by crystal-containing stone cells. The multi-layered endotesta forms a prominent seed plug in the micropylar region which is prolonged along both sides of the perichalaza as inner walls. The endotesta is one-layered on the sides of the seed and participates in rumination. In addition the endotesta may serve for deposition of end-products of metabolism. The complex growing process of the perichalaza and its surrounding tissues is described in detail. The perichalazal pad of tanniferous cells forms an U-shaped septum, in conjunction with the endotesta, dividing the seed into two chambers. During seed development it functions as transmitter of nutrients from the outer chamber filled with starch grains to the nucellus, endosperm and embryo contained in the inner one. During germination this pad probably serves for the uptake of water. — At the initial phases of germination the seed dehisces into two valves along the raphal and antiraphal side. Later on an additional parenchymatous operculum covering the seed apex disintegrates and the endotestal plug fixed by its two prolongations splits along a preformed fracture line into two parts to release the seedling. Rudiments of an aril are recognizable in young seeds only. — The data obtained fromArtabotrys hexapetalus are discussed and compared with published information on seeds in other annonaceous taxa. For systematic considerations the necessity to define the origin of the annonaceous seed plug from one or the other integument is emphasized as it may prove to be an important differential character withinAnnonaceae.     

Early floral development of Camellioideae (Theaceae)

The early floral development of Camellioideae was studied. Two major evolutionary lineages were recognized for this subfamily. The earlier evolved lineage (Camellia, Polyspora, and Pyrenaria) has normally 11-14 perianth members, which are initiated in a continuous spiral and are differentiated into sepals and petals at late floral development, and numerous stamens initiated individually and centrifugally on the whole androecial region. The later derived lineage (Franklinia, Hartia, Schima, and Stewartia) has five sepals and five petals arranged in two whorls, and numerous individual stamens originating centrifugally from the five petal-opposed zones. Hartia-Stewartia and Franklinia-Schima further diverged as two branches - the former is characterized by having androecial fascicles and axile-basal placentation. The androecial fascicle is considered to be derived within this subfamily. The latter exhibits a higher degree of carpellary congenital fusion and axile-central placentaion, and as a whole, is concluded to be the most advanced group in the Camellioideae. A taxonomic treatment of the Camellioideae at the tribal level is also proposed.     

Contrasting floral biology of Artabotrys species (Annonaceae): Implications for the evolution of pollinator trapping

Artabotrys comprises a species-poor early divergent grade (EDG) and a main species-rich clade (“main Artabotrys clade,” MAC). All members of the MAC exhibit a remarkably well-conserved floral Bauplan characterized by a tightly enclosed floral chamber with an elaborate rim between the inner petal blade and claw. Conversely, EDG resembles the sister genus Xylopia in lacking the inner petal rim, with one species (Artabotrys brachypetalus) bearing petals that lack the distinction between blade and claw altogether. The floral phenology and pollination ecology of two exemplar species—Artabotrys brachypetalus from the EDG and Artabotrys blumei from the MAC—are compared, including assessment of effective pollinators and their activity patterns, scent chemistry and thermogenesis. Our study revealed that Artabotrys blumei exhibits abbreviated anthesis (c. 27 hr), with a floral phenology and morphology that are clearly consistent with pollinator trapping, and may be pollinated by small beetles. Artabotrys brachypetalus has a typical anthetic duration (c. 45 hr), lacks a pollinator trapping mechanism, and is pollinated by honey bees and curculionid beetles. The “xylopioid” traits of the EDG are likely to be plesiomorphic, whereas the tightly enclosed floral chamber is likely to be apomorphic for the MAC and functionally significant in trapping pollinators.     

The genus Goniothalamus (Annonaceae) in Sumatra

A comprehensive taxonomic revision of the species of Goniothalamus (Blume) Hook. f. & Thomson (Annonaceae) occurring in Sumatra and adjacent islands is presented for the first time. Fourteen species are recognized, including six endemics that are described as new to science ( G. acehensis, G. alatus, G. dewildei, G. loerzingii, G. longistaminus and G. miquelianus ). In addition, two species are newly recorded from Sumatra, viz. G. parallelivenius Ridl. (previously reported from Borneo), and G. wrayi King (previously reported from Peninsular Malaysia). The extensive nomenclatural confusion regarding the application of the names G. costulatus Miq. and G. opacus Bakh. f. is clarified: the names are shown to be synonymous, with the former having nomenclatural priority. The utility of specific taxonomic characters are also discussed, with particular emphasis on petal indumentum, staminal connective shape, ovary indumentum, stigma shape, monocarp size and shape, and seed indumentum. Biogeographical relationships in the genus are discussed, and the significance of the Barisan mountain range and the Quaternary volcanic tuffs around Lake Toba are highlighted as potential ecological barriers limiting dispersal.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 225–254.     

Comparative floral development in Lardizabalaceae (Ranunculales)

Lardizabalaceae, one of seven families of Ranunculales, represent a monophyletic group. The family has functionally unisexual flowers with the organs in trimerous whorls, petaloid sepals and sometimes nectariferous petals. Among Ranunculales, Lardizabalaceae share several floral characters and climbing habit with Menispermaceae, but molecular analyses indicate that Circaeasteraceae and Lardizabalaceae form a strongly supported clade. Morphological and ontogenetic studies of flowers have proved to be a good complement to molecular data in clarifying relationships. Floral organogenesis has been studied in very few species of the family. This study investigates the comparative floral development of three species from three genera (Decaisnea, Akebia and Holboellia) of Lardizabalaceae using scanning electron microscopy. Flowers have a whorled phyllotaxis. Within each whorl, the organs are initiated either simultaneously or in a rapid spiral sequence. In Akebia, six sepals are initiated, but one to three sepals of the second whorl do not further develop. The presence of three sepals in Akebia is thus a developmentally secondary simplification. The petals (if present) are retarded in early developmental stages; stamens and petals are different in shape from the beginning of development. The retarded petals may not be derived from staminodes in Lardizabalaceae. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 171–184.     

The floral nectary of Hymenaea stigonocarpa (Fabaceae, Caesalpinioideae): structural aspects during floral development

BACKGROUND AND AIMS: Considering that few studies on nectary anatomy and ultrastructure are available for chiropterophilous flowers and the importance of Hymenaea stigonocarpa in natural 'cerrado' communities, the present study sought to analyse the structure and cellular modifications that take place within its nectaries during the different stages of floral development, with special emphasis on plastid dynamics. METHODS: For the structural and ultrastructural studies the nectary was processed as per usual techniques and studied under light, scanning and transmission electron microscopy. Histochemical tests were employed to identify the main metabolites on nectary tissue and secretion samples. KEY RESULTS: The floral nectary consists of the inner epidermis of the hypanthium and vascularized parenchyma. Some evidence indicates that the nectar release occurs via the stomata. The high populations of mitochondria, and their juxtaposition with amyloplasts, seem to be related to energy needs for starch hydrolysis. Among the alterations observed during the secretory phase, the reduction in the plastid stromatic density and starch grain size are highlighted. When the secretory stage begins, the plastid envelope disappears and a new membrane is formed, enclosing this region and giving rise to new vacuoles. After the secretory stage, cellular structures named 'extrastomatic bodies' were observed and seem to be related to the nectar resorption. CONCLUSIONS: Starch hydrolysis contributes to nectar formation, in addition to the photosynthates derived directly from the phloem. In these nectaries, the secretion is an energy-requiring process. During the secretion stage, some plastids show starch grain hydrolysis and membrane rupture, and it was observed that the region previously occupied by this organelle continued to be reasonably well defined, and gave rise to new vacuoles. The extrastomatic bodies appear to be related to the resorption of uncollected nectar.     

依兰(番荔枝科)雌配子体发育研究

荔枝科是被子植物的基部类群之一,依兰属是番荔枝科较为原始的类群,其有性生殖过程,特别是胚胎发生与发育的研究结果,可以补充被子植物胚胎学原始特征的相关基础资料。该研究利用常规石蜡切片技术,对依兰胚珠、大孢子和雌配子体的发生发育过程进行了观察。结果表明:依兰的胚珠为倒生胚珠、厚珠心、三层珠被,第三层珠被(中间珠被)发生在大孢子母细胞时期,于外珠被与内珠被之间、胚珠合点端两侧发生并隆起;雌配子体为蓼型。此外,依兰的个别胚珠中存在双雌配子体现象,且两个雌配子体均由大孢子母细胞发育而来,大小、形状相近,呈线形排列。该研究结果对于揭示原始被子植物胚胎发育特征具有重要意义。     

Revision of Disepalum (Annonaceae)

The relationship between the Asian generaDisepalum Hook. f. andEnicosanthellum Ban (Annonaceae) is examined in a revisionary study. Despite the disparate perianth morphologies of the two genera, other characters support inclusion of all species in a single genus with nine species. The monocarp stalks in all species are found to be derived from the receptacle rather than the ovary, and are thus not homologous with those found in most other Annonanceae genera. Cladistic analysis indicates that the species on the mainland of Asia and of montane habitats are more primitive than the species of the lowlands and of Sumatra and Borneo. Two new combinations,Disepalum petelotii andD. plagioneurum, are necessary as a result of merging the two genera, and one species,D. aciculare, is described as new.     

The evolution of key functional floral traits in the early divergent angiosperm family Annonaceae

Potential key functional floral traits are assessed in the species‐rich early divergent angiosperm family Annonaceae. Pollinators (generally beetles) are attracted by various cues (particularly visual, olfactory, and thermogenic), with pollinators rewarded by nectar (generally as stigmatic exudate), heat, and protection within the partially enclosed floral chamber. Petals sometimes function as pollinator brood sites, although this could be deceptive. Annonaceae species are self‐compatible, with outcrossing promoted by a combination of protogyny, herkogamy, floral synchrony, and dicliny. Pollination efficiency is enhanced by pollen aggregation, changes in anthesis duration, and pollinator trapping involving a close alignment between petal movements and the circadian rhythms of pollinators. Most Annonaceae flowers are apocarpous, with syncarpy restricted to very few lineages; fertilization is therefore optimized by intercarpellary growth of pollen tubes, either by stigmatic exudate (suprastylar extragynoecial compitum) or possibly the floral receptacle (infrastylar extragynoecial compitum). Although Annonaceae lack a distinct style, the stigmas in several lineages are elongated to form “pseudostyles” that are hypothesized to function as sites for pollen competition. Flowers can be regarded as immature fruits in which the ovules are yet to be fertilized, with floral traits that may have little selective advantage during anthesis theoretically promoting fruit and seed dispersal. The plesiomorphic apocarpous trait may have been perpetuated in Annonaceae flowers as it promotes the independent dispersal of fruit monocarps (derived from separate carpels), thereby maximizing the spatial/temporal distance between seedlings. This might compensate for the lack of genetic diversity among seeds within fruits arising from the limited diversity of pollen donors.     

REM-Untersuchungen anMilesia vogesiaca undMilesia whitei (Uredinales)

Central European specimens of twoMilesia species, both growing onPolystichum, were investigated by SEM. The uredospores ofM. vogesiaca are not smooth, as stated in literature, but finely verrucose; size and density of the verrucae are rather variable. In contrast, the uredospores ofM. whitei are finely echinulate.

     

Floral ontogeny of Annonaceae: evidence for high variability in floral form

Background and Aims

Annonaceae are one of the largest families of Magnoliales. This study investigates the comparative floral development of 15 species to understand the basis for evolutionary changes in the perianth, androecium and carpels and to provide additional characters for phylogenetic investigation.

Methods

Floral ontogeny of 15 species from 12 genera is examined and described using scanning electron microscopy.

Key Results

Initiation of the three perianth whorls is either helical or unidirectional. Merism is mostly trimerous, occasionally tetramerous and the members of the inner perianth whorl may be missing or are in double position. The androecium and the gynoecium were found to be variable in organ numbers (from highly polymerous to a fixed number, six in the androecium and one or two in the gynoecium). Initiation of the androecium starts invariably with three pairs of stamen primordia along the sides of the hexagonal floral apex. Although inner staminodes were not observed, they were reported in other genera and other families of Magnoliales, except Magnoliaceae and Myristicaceae. Initiation of further organs is centripetal. Androecia with relatively low stamen numbers have a whorled phyllotaxis throughout, while phyllotaxis becomes irregular with higher stamen numbers. The limits between stamens and carpels are unstable and carpels continue the sequence of stamens with a similar variability.

Conclusions

It was found that merism of flowers is often variable in some species with fluctuations between trimery and tetramery. Doubling of inner perianth parts is caused by (unequal) splitting of primordia, contrary to the androecium, and is independent of changes of merism. Derived features, such as a variable merism, absence of the inner perianth and inner staminodes, fixed numbers of stamen and carpels, and capitate or elongate styles are distributed in different clades and evolved independently. The evolution of the androecium is discussed in the context of basal angiosperms: paired outer stamens are the consequence of the transition between the larger perianth parts and much smaller stamens, and not the result of splitting. An increase in stamen number is correlated with their smaller size at initiation, while limits between stamens and carpels are unclear with easy transitions of one organ type into another in some genera, or the complete replacement of carpels by stamens in unisexual flowers.     

Constituents from Miliusa balansae (Annonaceae)

The styryl derivatives 3,4-dimethoxy-6-styryl-pyran-2-one and (2E,5E)-2-methoxy-4-oxo-6-phenyl-hexa-2,5-dienoic acid methyl ester were isolated from leaves and branches of Miliusa balansae (Annonaceae). In addition, the geranylated homogentisic acid derivative miliusate, four flavanones and two dihydrochalcones were identified. Their structures were elucidated by spectroscopic means.     

Reproductive biology ofPolyalthia littoralis (Annonaceae)

Flowering phenology of some annonaceous trees and reproductive biology ofPolyalthia littoralis (Annonaceae) were studied. The trees showed various types of flowering phenology within the family. Among them,P. littoralis had hermaphroditic and protogynous flowers, and exhibited continuous flowering throughout the year. Bagged flowers set fruits and seeds comparable to the control. The observations of meiotic stages and the results of castrated tests indicated no possibility of apomictic reproduction. The abscised anthers attached to torus by the extended spiral thickenings, and accomplished self-pollination. Outbreeding possibly occurs, but the following self-pollination guarantees seed set.     

Aperture types withinSapranthus andPolyalthia (Annonaceae)

Within the large palaeotropical genusPolyalthia so far five different pollen types are described (two monosulcate types, two disulcate types, and a single omniaperturate type). One of the disulcatePolyalthia types is similar to the disulcate neotropical genusSapranthus. All the newly described types differ predominantly not in exine but rather in intine characters. From this it can be concluded that seemingly inaperturate grains are disculcate in function, generally with two clearly recognizable germination zones, or omniaperturate, with the whole sporoderm capable of germination. The functions of the intine layers within the germination zones and within the nongerminating areas are very different and cooperate during the first germination steps in bursting the exine. It is difficult clearly to define the germination zones of pollen grains if the exine exhibits no modifications. Based on our and other results a more precise definition is suggested.     

Early floral development and androecium organization in Fouquieriaceae (Ericales)

Early floral development with focus on the androecium was studied with the help of scanning electron microscopy and serial microtome sectioning in Fouquieria columnaris and F. splendens. Perianth organs appear in a spiral pattern on the floral apex. The spiral may be a clockwise or anti-clockwise. The androecium is best interpreted as two-whorled with all the stamens arranged in a single series. In F. splendens, two or more of the five epipetalous stamen positions are doubled, i.e. they are occupied by stamen pairs. Unusual features in the floral development of Fouquieriaceae include (1) a strong spiral component even in whorled organ categories and (2) a pronouncedly asymmetric floral apex during an early phase of floral development. From a phylogenetic point of view, it seems plausible that the common ancestor of Fouquieriaceae and its sister family Polemoniaceae was characterized by two alternating, pentamerous stamen-whorls.     

阔叶杨桐的花器官发生(山茶科)

利用扫描电镜首次观察了山茶科厚皮香亚科植物阔叶杨桐的花器官发生过程。阔叶杨桐的花被片和五束雄蕊都是2/5螺旋向心发生,且有逆时针和顺时针两种螺旋方式;五束雄蕊在环形雄蕊原基上产生,且每一束都是由中间向两端发生;由五心皮形成的中轴胎座内出现一衍生的可育胎座。阔叶杨桐的花器官发生过程与本亚科的猪血木明显不同,该研究为厚皮香亚科乃至山茶科的系统发育与演化提供花器官方面的依据。     

A redescription of the trigonotarbid arachnidPocononia whitei (Ewing 1930)

The trigonotarbid arachnid,Pocononia whitei (Ewing 1930), is redescribed and referred to the family Eophrynidae as the oldest known eophrynid. It suggests that trigonotarbids had diversified into the recognised Upper Carboniferous families by the Lower Carboniferous.