New aspects in floral development of Papilionoideae: initiated but suppressed bracteoles and variable initiation of sepals

BACKGROUND AND AIMS: The increase of molecular data and the resulting insights into legume systematics make the search for new morphological characters and a careful re-investigation of already stated characters necessary. Bracteoles are small, reduced leaves borne close to the base of lateral branches. Although they seem unimportant in older buds, they have an ecological function in protecting the sepal primordia. Furthermore, a morphogenetic function in mediating the onset of sepal initiation is suspected in the literature. The occurrence of bracteoles varies within Papilionoideae, and their distribution is used in legume systematics. But this is open to criticism, because there is a tendency to use 'absent' for 'caducous'. Thus attention here was paid to the initiation of bracteoles as well as to the sequence of sepal initiation. METHODS: The floral development of 30 taxa out of 15 tribes of Papilionoideae was investigated using scanning electron microscopy (SEM). KEY RESULTS: In five taxa the bracteoles initiated, but suppressed early. Furthermore, a broad variability of sepal initiation was found. Besides the widely stated unidirectional pattern, modified unidirectionality, tendencies towards whorled, fully whorled, bidirectional and successive initiation of sepals were all found. CONCLUSION: Initiated but suppressed bracteoles are presented as a 'new' character in Papilionoideae. Considering the presence of bracteoles as a plesiomorphy, their suppression can be seen as a step towards completely reduced bracteoles. The remarkable variability of the sequence of sepal initiation questions the widely stated unidirectionality of organ initiation in Papilionoideae. The different modes of sepal initiation are deducible from the helical pattern of some caesalpinioids, which is seen as a developmental link of the flowers of Papilionoideae and Caesalpinioideae. The bidirectional sepal initiation is possibly a consequence of the morphogenetic function of bracteoles, although bidirectionality is not found in all taxa with reduced bracteoles.     

Bracteoles affect germination and seedling establishment in a Mediterranean population of Atriplex portulacoides

The germination and subsequent seedling establishment of Atriplex portulacoides from a population in SW Spain were investigated in response to the presence or absence of attached bracteoles, at a range of NaCl concentrations (0–6%). Increasing salinity reduced both the final germination percentage and the speed of germination. The presence of bracteoles greatly inhibited germination and this effect was more marked with increasing salinity; bracteoles completely inhibited germination at salinities higher than 2%. The effects of salinity were substantially reversible, as cumulative germination after transfer of ungerminated seeds to distilled water was similar in all salinity treatments. This enforced dormancy could serve to prevent germination of floating fruits during dispersal in seawater. However, after transfer to distilled water the germination of seeds with bracteoles was still significantly lower than those without them, as a result of both higher dormancy and lower viability (as revealed by tetrazolium testing). Bracteoles thus also appear to enforce some physical dormancy. Seedlings derived from seeds with bracteoles demonstrated higher survival rates in fresh water than those derived from seeds without bracteoles but at 2% salinity there was no difference, and at higher salinities no seedlings of either type survived.     

中国昆仑山地区棱子芹属植物苞片形态及其分类学意义

利用体视显微镜对中国昆仑山地区分布的棱子芹属10种植物的总苞片、伞辐、小总苞片、果棱等微形态特征进行了观察,并编排分种检索表。结果表明：该地区植物的苞片特征可分为三大类：（1）总苞、小总苞均为长披针形;（2）总苞、小总苞均为叶状分裂;（3）总苞、小总苞异形。因此,这些总苞、小总苞的形态和数量有显著差别,在一定程度上能反映出类群间的关系,可为探讨该地区棱子芹属植物种间分类学问题提供了新的证据。     

Diversity and evolution of pollinator rewards and protection by <Emphasis Type="Italic">Macaranga</Emphasis> (Euphorbiaceae) bracteoles

Flowering plants have modified their floral organs in remarkably diverse ways to optimize their interaction with pollinators. Although floral organs represent a major source of floral diversity, many plants also use extrafloral organs, such as bracts and bracteoles, in interacting with pollinators; however, the evolutionary dynamics of non-floral organs involved in pollination are poorly studied. The genus Macaranga is characterized by protective mutualisms with ants that potentially interfere with pollinators on flowers. Macaranga flowers lack perianths and, notably, bracteoles serve the dual function of rewarding pollinators and protecting them from guarding ants; in one group of species, bracteoles provide a nectar reward to generalist pollinators, while in another group, bracteole “chambers” protect thrips or hemipteran pollinators that use these structures as feeding and breeding sites. We examined the diversity and evolutionary dynamics of inflorescence morphology in Macaranga, focusing on bracteoles. We recognized three inflorescence types based on examination of herbarium materials: Discoid-gland, which possess disc-shaped glands on the bracteole surfaces (including all the generalist-pollinated species); Enclosing, in which bracteoles cover flowers (including all the thrips- and hemipteran-pollinated species); and Inconspicuous, in which bracteoles are small, narrow or absent. Ancestral state reconstruction indicated that inflorescence morphologies have changed multiple times in the genus. These findings suggest that morphological changes in non-floral characters (bracteoles) of Macaranga species have occurred as frequently as in the floral structures of many flowering plants. The multiple evolutions of the Enclosing bracteoles, which protect pollinators, might have been facilitated by pollination interference from mutualistic ants.     

杏属和樱属植物新组合

报道了蔷薇科李亚科两个种的改隶新组合,将广义李属中的背毛樱Prunus hypotrichodes改隶为杏属中的背毛杏Armeniaca hypotrichides;疏花稠李Prunus laxiflora改隶为疏花樱Cerasus laxifiora。进一步研究的结果,同意前苏联学者G．V．Eremin et V．S．Simagin的意见,将稠李属中的种斑叶稠李Padus maackii改隶为樱属中的斑叶樱Cerasus maackii。     

Effect of Bracteoles on Seed Germination and Dispersal of Two Species of Atriplex

The influence of bracteoles on the germination response of asalt marsh annual, Atriplex prostrata, and a salt desert perennial,A. griffithii, was determined. Attached bracteoles did not inhibitgermination of A. prostrata but completely inhibited germinationof A. griffithii seeds. Germination of seeds ofA. griffithiiwas also somewhat inhibited in the presence of detached bracteoles.The osmotic potential of dissolved substances in water-saturatedbracteoles was -4.8 ± 0.05 MPa for A. griffithii and-2.4 ± 0.15 MPa for A. prostrata. Ash content of bracteoleson a dry weight basis was 28.7 ± 0.37% for A. prostrataand 30.0 ± 0.29% for A. griffithii. The presence of relativelyhigh concentrations of dissolved salts in bracteoles may explainthe reduced germination of A. griffithii. Germination of seedsof the perennial A. griffithii may also be inhibited mechanicallyby the presence of persistent bracteoles, whereas the annualA. prostrata has ephemeral bracteoles that may serve to limitgermination in the autumn but are not present during the normalspring germination period. Bracteoles could affect the dispersalof seeds by water since some fruiting structures of A. griffithiiand A. prostrata are able to float in 1.0% NaCl solutions for5 and >30 d, respectively, compared with a maximum of 4 and3 d for seeds without bracteoles. Fruiting structures of A.prostrata floated for longer over a range of salinities thandid those ofA. griffithii ; this may play a significant rolein the dispersal of this salt marsh species. Copyright 2001Annals of Botany Company Atriplex, bracteoles, dispersal, flotation, germination, salinity, temperature     

Floral ontogeny in <Emphasis Type="Italic">Astragalus compactus</Emphasis> (Leguminosae: Papilionoideae: Galegeae): variable occurrence of bracteoles and variable patterns of sepal initiation

Comparative studies of floral ontogeny represent a growing field that promise to provide new insights on floral evolution. Floral ontogenetic information has been used successfully in Leguminosae for re-examining phylogenetic relationships at different levels. Using epi-illumination light microscopy, we present original ontogenetic data in Astragalus compactus, which was chosen because of its unusual arrangement of inflorescence and variable occurrence of bracteoles on flowers. Based on our results, uncommon ontogeny of the inflorescence led to the arrangement of flowers in four different positions. Variation was observed not only in the presence of bracteoles, but also in the order of sepal initiation in flowers of the same inflorescence. Surprisingly, besides the widely stated unidirectional pattern, bidirectional, sequential and an atypical unreported order were observed. High degree of overlapping between whorls and formation of two types of common primordia also were found. The variable occurrence of bracteoles suggests that the species is in an intermediate state towards fully lacking of bracteoles. We propose that the variability of the sequence of sepal initiation is possibly a consequence of the function of mechanical forces generated by surrounding leaves. Relationships between mechanical force and auxin signalling are discussed.     

Phylogeny and evolution of bracts and bracteoles in Tacca (Dioscoreaceae)

Most species in the genus Tacca (Dioscoreaceae) feature green to black purple, conspicuous inflorescence involucral bracts with variable shapes, motile filiform appendages (bracteoles), and diverse types of inflorescence morphology. To infer the evolution of these inflorescence traits, we reconstructed the molecular phylogeny of the genus, using DNA sequences from one nuclear, one mitochondrial, and three plastid loci (Internal Transcribed Spacer (ITS), atpA, rbcL, trnL-F, and trnH-psbA). Involucres and bracteoles characters were mapped onto the phylogeny to analyze the sequence of inflorescence trait evolution. In all analyses, species with showy involucres and bracteoles formed the most derived clade, while ancestral Tacca had small and plain involucres and short bracteoles, namely less conspicuous inflorescence structures. Two of the species with the most elaborate inflorescence morphologies (T. chantrieri in southeast China and T. integrifolia in Tibet), are predominantly self-pollinated, indicating that these conspicuous floral displays have other functions rather than pollinator attraction. We hypothesize that the motile bracteoles and involucres may facilitate selfing; display photosynthesis in the dim understory, and protect flowers from herbivory.     

Intra-individual heterostyly in Atriplex halimus L. (Amaranthaceae)

Classically, the Atriplex halimus L. female flower is perianthless, has two bracteoles, one ovary and one style. Considering bracteoles, one can distinguish, among the representatives of two Tunisian populations, three phenotypes of female flowers, each of them being distributed in three types according to the style length. Male flowers produce three types of pollen. This is the only known example of intra-individual heterostyly in unisexual flowers. These results question the classical concept of individual. The authors discuss a possible process implying indirectly hybridisation and introgression between A. halimus and A. nummularia.     

Correlations between chromosomal and morphological characters in subspecies of Ulex europaeus L. (Genisteae, Leguminosae) from the north-west of the Iberian Peninsula

The two subspecies of Ulex europaeus L. (subsp. europaeus and subsp. latebracteatus) are easily differentiated by the shape and size of their bracteoles, and by their chromosome number. However, in the north-west of the Iberian Peninsula, the areas of both subspecies are not clearly delimited, the shape of the bracteoles is intermediate and the width is close to the diagnostic limit. Thus, allocation of some specimens to either subspecies is diffcult. Recendy, a controversy has arisen concerning the intrapopulational uniformity of the chromosome number in U. europaeus from west France and north Spain, and the usefulness of ploidy level and chromosome number as clear-cut indicators of the two subspecies. Thus, the merits of recognizing the subspecies as independent are re-analysed here. Our results for north-west Spain show that the chromosome number is uniform and stable within populations and is clearly related to the morphological characters. Correlation and discriminant analyses show that bracteoles and stomata sizes are highly correlated and are good predictors of ploidy level. Furthermore, the results support the maintenance of two subspecies in U. europaeus , which can be delimited by a combination of morphological characters, chromosome number and geographical distribution.     

Taxonomic notes on Mexican Ruellia (Acanthaceae)

The new nameRuellia comonduensis is provided for the species previously known asR. cordata Brandegee.Ruellia chilpancingana, a new species known only from Guerrero in southwestern Mexico, is described and compared to morphologically similar species. It is unique among Mexican species ofRuellia based on the following combination of characters: caducous bracteoles and secondary bracteoles, multiflowered dichasia from leaf axils, yellowish and cylindric-funnelform corollas, exserted stamens, and few (four or fewer) seeds per capsule. Macromorphological features and pollen ofR. chilpancingana are illustrated.     

Floral development in the legume tree Colophospermum mopane, Caesalpinioideae: Detarieae

Floral ontogeny of Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Leonard, an apetalous member of the Crudia group with four sepals and a large number (20–25) of stamens, was studied as part of a larger project on reproductive biology of this much-utilized tree. The flowers have been described as being inserted in the axil of a bract, but lacking lateral bracteoles. Four outer, light cream or white 'sepals' are present. The first two sepals are initiated in a lateral position, where the bracteoles, if present, develop in other members of the Caesalpinioideae. The inner sepals arise simultaneously adaxially and abaxially. These four structures, conventionally regarded as sepals, enclose the bud. The outer two 'sepals' should be regarded as lateral bracteoles inserted at the apex of the pedicel. The inner structures represent the only two sepals. The large number of stamens arise on a large meristematic surface and different whorls were not observed. The filaments elongate within the bud and after anthesis become exposed outside the flowers. The filaments are of equal length and the large anthers form a suspended cluster. One carpel develops terminally and gives rise to an indehiscent one-seeded fruit.     

THE ANATOMY OF THE PISTILLATE INFLORESCENCE AND FLOWER OF CASUARINA VERTICILLATA LAMARCK (CASUARINACEAE)

The pistillate inflorescence of Casuarina verticillata is described as consisting of a primary axis bearing whorls of bracts with a cymule in the axil of each bract of the more central whorls. Each cymule consists of an atepallate, two-carpellate, syncarpous floret and two, lateral, once-lobed bracteoles. A “peripheral intercalary” meristem, in which divisions are primarily periclinal, forms a meshwork beneath the bracts from early development and moves the connate bracts centrifugally around the cymules and extends and binds the bracts, and to some extent the bracteoles, of the fertile part of the inflorescence together. Each bract receives a single trace; each cymule receives two traces. Each bundle extension of a cymule trace supplies: 1) a branch which joins its counterpart to become the anterior common carpellary bundle; 2) a second branch which joins its counterpart to become the posterior common carpellary bundle; and 3) a central branch which supplies a lateral bracteole. Within each floret, each common carpellary bundle provides a dorsal carpellary bundle, two ventral carpellary bundles (fertile anterior carpel) or one common ventral bundle (sterile posterior carpel). The ventral bundle-supplies join and form a single placental bundle which lies in the gynoecial septum, and which, in turn, supplies the two ovules in the anterior carpel. Whether the inflorescence is a simple racemose or a condensed cymose type cannot be determined from this species alone. The function of the sclerenchymatous, enclosing bracteoles and connate bracts is discussed.     

Aspalathus abbottii (Fabaceae: Crotalarieae), a new species from KwaZulu-Natal, South Africa

A new species Aspalathus abbottii C.H. Stirt. & Muasya, is described. The species is known only from Oribi Flats, KwaZulu-Natal, where it grows in grassland vegetation. The new species is characterised by its rigid spreading habit, densely and shortly villous branches, glabrous bracts and bracteoles, and 1(2) bright yellow flowers borne on short lateral shoots. It is most similar to other grassland species, A. frankenioides DC. and A. gerrardii H. Bol., all from the summer rainfall area of South Africa but differs in its rigid spreading habit, few bright yellow flowers per flowering branchlet, glabrous bracts and bracteoles, villous yellowish-green seasonal shoots, and its pale brown to tan over-seasonal branches with a blackish lattice of peeled bark.     

Taxonomic position and distribution of Atriplex lapponica (Chenopodiaceae)

The arctic, halophytic species Atriplex lapponica Pojark has flowers of two kinds: perfect ones surrounded by a pentamerous perianth and pistillate flowers enclosed in bracteoles. Thus, A. lapponica is closely related to the species of sect. Dichospermum Dumort, not to species of sect. Teutliopsis Dumort. as generally believed.     

Inflorescence structure and generic delimitation of Triplaris and Ruprechtia (Polygonaceae)

A revision of the generic limits between Triplaris and Ruprechtia (Polygonaceae), which were confused in earlier literature, led to the conclusion that the two genera should be maintained. Triplaris is characterized by 1–flowered pistillate partial inflorescences, absence of a basal pedicel–like extension of the fruiting perianth–tube, which is always as long as or longer than the achene, bracteoles completely fissured on the abaxial side, and sessile or subsessile male flowers with perianth segments always connate for more than half of their length.
Ruprechtia has 2–3–flowered monochasial pistillate part–inflorescences (except the 1–flowered R. triflora) , a basal pedicel–like extension of the fruiting perianth–tube, which is at most 3/4 as long as the achene, more or less tubular bracteoles only exceptionally fissured down on the abaxial side, and pedicellate male flowers with perianth segments never connate for more than one third of their lenght. Preliminary paly–nological studies have shown that the pollen of Triplaris are microreticulate or punc–tate–microreticulate while Ruprechtia pollen have perforate–rugulose surfaces.     

Floral development in Aphandra (Arecaceae)

The organogenesis of staminate flower clusters and flowers and some observations on the corresponding pistillate structures of Aphandra natalia are described and compared with those of the other two genera in the Phytelephantoideae (Arecaceae). In Aphandra, staminate flowers are borne in monopodial clusters of mostly four (1-6) flowers. Each flower is surrounded by two pairs of subopposite bracteoles and has two rather indistinctly four-parted whorls of perianth parts. Stamen primordia arise on a shallow apical dome and then centrifugally down the sides of a long, angled, and laterally flattened receptacle. Immediately before the staminate bud opens, the floral receptacle below the androecium rapidly elongates, becoming funnel-shaped, with the bracteoles and a perianth sheath adnate to it forming a pseudopedicel. Epidermal and subepidermal layers of these pseudopedicels split at anthesis and release a great number of raphide idioblasts that resemble the pollen grains in shape and size. It is hypothesized that the idioblasts deter pollen feeding or ovidepositing insects. The phylogenetic implications of these findings are important within the Phytelephantoideae and among palms in general.     

Persicaria changhuaensis sp. nov. (Polygonaceae) from northwestern Zhejiang,China

Persicaria changhuaensis sp. nov., belonging to P. sect. Echinocaulon (Polygonaceae), from Zhejiang, eastern China, is described and illustrated. The new species is morphologically similar to P. senticosa (Meisn.) H. Gross ex Nakai and P. sagittata (L.) H. Gross ex Nakai var. sieboldii (Meisn.) Nakai, but differs from the former in having an ocrea without a reniform‐orbicular wing at apex, pubescent peduncle, triangular bracteoles, white perianth, and stamens exserted from the perianth. Compared to P. sagittata var. sieboldii, it differs in having the leaf blade triangular‐hastate, sparsely retrorsely‐prickled on abaxial veins, sparsely ciliate at the margin, pubescent peduncle, triangular bracteoles, and stamens exserted from the perianth.     

Phacelophrynium sapiense (Marantaceae) a new species from Sabah, Malaysia

Phacelophrynium sapiense , a new species from Sabah, Malaysia, is described and illustrated. It differs from other known Phacelophrynium species in its light green to yellow leaf variegation, purple leaf underside, creamy white inflorescence and cream white flowers. The species is furthermore unusual in having a pair of membranaceous bracteoles associated with each flower, a feature otherwise known only in species of the New World genus Calathea.     

Developmental Morphology of Hop Stunt Viroid-infected Hop Plants and Analysis of Their Cone Yield1)

Infection of hop plants with hop stunt viroid (HSV) results in the retardation of the growth rate except for the rate of leaf emergence and the disappearance of the fold-like structure over the epidermal cell. Mature cones from HSV-infected hop plants remained small-sized and the content of α-acid was half to one third of that of HSV–free hop cones. In HSV-infected hop cones, the lupulin glands are distributed most abundantly on the bracteoles and the perianths and their numbers are reduced by at least 60% of that in the HSV-free control. Scanning electron micrographs confirm that most of the lupulin glands on bracteoles from HSV-infected hop cones shrivel severely, but not those from HSV-free hop cones. They also reveal that the lupulin glands on the perianths from both, HSV-free and HSV–infected hop cones become withered. Moreover, spherical granules (1.2 to 1.9μm in diameter) were not observed on the surface of the lupulin glands from HSV-infected hop cones.