Corolla tube formation in six species of apocynaceae

Corolla tube formation inTrachelospermum asiaticum, Nerium indicum var.leucanthum, Anodendrom affine, Vinca major, Catharanthus roseus andAmsonia elliptica was investigated anatomically. The corolla tube formation among these species is basically similar. The bases of petal primordia extend laterally to the interprimordial regions, the upward growth occurrig at those regions just beside the petal bases. The extending petal bases connect with each other at the bases of the abaxial side of stamen primordia in the early stage of the corolla development. The upward growth at the coonnected regions results in the formation of a short corolla tube but is weakened rapidly. At the stage of the mutual connection of petal bases, a common base of petal and stamen primordia is initiated. This common base develops into the lower portion of the corolla tube, i.e. the portion below the stamen insertion. In a relatively late stage, adjacent margins, of the corolla lobes fuse postgenitally at their lower portions, resulting in the formation of almost all of the upper portion of the corolla tube. The corona inNerium andVinca is initiated by the active adaxial growth of the upper portion of the corolla tube.     

Corolla tube formation in four species of solanaceae

Corolla tube formation inSolanum nigrum, Salpichroa rhomboidea, Datura stramonium var.chalybea andNicotiana tabacum cv. Xanthi nc was investigated anatomically. InSolanum, the formation of the lower portion of the corolla tube, including the portion below the stamen insertion and the inserted zones, begins with the extension of the bases of the petal primordia toward the interprimordial regions. The extension of the petal bases is caused by the successive incorporation of the interprimordial regions just beside the bases into the petal primordia by means of the upward growth at those regions. The extending petal bases reach the lower portions of stamen primordia and connect with them resulting in formation of a short tube, which later develops into the lower portion of a corolla tube accompanied by epipetalous stamens. The petal bases extend further, and connect with each other outside the stamen primordia. The upward growth occurs also at the connected regions resulting in formation of the upper portion of a corolla tube. Marginal meristems of the petal primordium differentiate not later than the connection of petal bases. After the connection, marginal meristems and meristems of connected regions become continuous with each other and develop in a similar pattern. In the other three species, the corolla tube is formed in a similar manner as in the species mentioned above. However, the connection of the petal primordia occurs much earlier than the differentiation of their marginal meristems. InSalpichroa andNicotiana, the developmental patterns of the connected region and the corolla lobe margin are different.     

Corolla tube formation in the Tubiflorae and Gentianales

Corolla tube formation was investigated anatomically for 22 species of the Polemoniaceae, Convolvulcaeae, Boraginaceae, Verbenaceae, Buddlejaceae. Scrophulariaceae, Gentianaceae, Menyanthaceae and Asclepiadaceae. The corolla tbe formation is basically similar among species, except for the cases ofNymphoides, Dichondra andCuscuta. The petal bases extend laterally to the interprimordial regions, the upward growth occurring at those regions just beside the petal bases, and connect mutually at the back of stamen primordia. The upward growth at the connected regions co-opeates with the growth of the expanding petal margins, resulting in the formation of the upper portion of the corolla tube. How-ever, developmental patterns are not always similar. InSwertia, Nymphoides andMenyanthes, the upward growth at the connected regions is meager. InDichondra andCuscuta, the mutual connection of petal bases is not seen. The lower portion of the corolla tube is formed by the elongation of the common base of petal and stamen primordia, resulting in the formation of the epipetalous condition of stamens, except for the case ofNymphoides. InNymphoides, the lower portion of the corolla tube results from the cup-like structure formed on the floral meristem before the initiation of petal primordia.     

Light and scanning electron microscopic studies of flower development inLindenbergia macrostachya Benth. (Scrophulariaceae)

All the floral primordia are homologous to leaves in their development inLindenbergia macrostachya. The sepals follow an anterior to posterior sequence of initiation. The petals and stamens are initiated almost simultaneously but sequentially in order of petals followed by stamens. There is no sign of development of fifth posterior stamen. p ]The calyx tube is formed by interprimordial growth followed by zonal growth. The combined interprimordial growth between the petal primordia and growth on the abaxial side of stamen primordia results in the formation of upper corolla tube whereas lower corolla tube is formed only by zonal growth. The zonal growth extends below the bases of stamen primordia also due to which they become epipetalous. The placentae arise from the carpellary margins, move inwards and get fused in the lower half and remain free in the upper part of the ovary. Thus the ovary appears biloeular with axile plaeentation in the lower haler and unilocular with parietal placentation in the upper half.     

Theligonum cynocrambe: Developmental morphology of a peculiar rubiaceous herb

The annual Mediterranean herbTheligonum cynocrambe shows a peculiar combination of morphological characters, e.g., switch from decussate to spiral phyllotaxis with 90–100° divergence, combined with a change from interpetiolar to lateral stipules, anemophily, lack of calyx, flowers often dimerous to trimerous, corolla fused in both male and female flowers, male flowers extra-axillary, with 2–19 stamens per flower, female flowers axillary, with inferior uniovulate ovary, basilateral style and perianth, nut-like fruits with elaiosome. In male flowers the androecium emerges as an (uneven) elliptical rim with a central depression. This common girdling primordium is divided up into several stamen primordia. In male flowers with low stamen number the stamen primordia may occupy the corners alternating with the corolla lobes. There are no epipetalous androecial primordia that secondarily divide into stamens. Male flowers occasionally show a hemispherical base that may be interpreted as remnant of the inferior ovary. In female flowers a ring primordium grows into a tube on which the petal lobes arise. The perianth and style become displaced adaxially by uneven growth of the inferior ovary. The ovary is basically bilocular. The lower region of the ovary is provided with a septum that is overtopped and hidden by the single curved ovule.Theligonum is referred to theRubiaceae-Rubioideae, with theAnthospermeae andPaederieae as most closely related tribes.     

Floral ontogeny inMazus pumilus (Scrophulariaceae)

InMazus pumilus, all the floral appendages are initiated in acropetal sequence in the second cell layer (except stamens) of the floral primordium by periclinal divisions. The actinomorphic calyx tube is formed due to zonal growth. The zygomorphy in corolla is evident from the inception of petal primordia which arise sequentially as independent units in order of one anterior, a pair of anterio-lateral followed by a pair of posterio-lateral. Later these primordia exhibit differential growth because of which zygomorphy becomes more pronounced. The upper corolla tube is formed by interprimordial growth and lower corolla tube by zonal growth. Stamens are initiated in the third layer of the floral apex. Unlike sepals and petals, in the development of stamens (4) underlying cells of corpus also contribute. Posterior stamen is absent. The stamens become epipetalous because of interprimordial and zonal growth in the common region below the bases of petals as well as stamens. The two carpel primordia arise as crescent shaped structures which become continuous due to interprimordial growth. The ovary is formed by a ring of zonal meristem. The style develops later between stigma and ovary because of intercalary growth. The residual apex grows vertically along with the ovary and forms the septum of the ovary. All the floral appendages exhibit similar pattern of histogenesis and early growth suggesting thereby the appendicular nature of these appendages.     

Floral development and systematics ofCistaceae

The floral development of representatives of six genera ofCistaceae has been studied. Calyx development involves the formation of a ring primordium in several taxa. Androecium development in species with intermediate or higher stamen numbers starts with the formation of a ring meristem on which the stamens are initiated in a centrifugal direction. In many taxa five alternipetalous leading stamen primordia can be observed. In the apetalous (cleistogamous) flowers ofTuberaria inconspicua androecium development appears to be unordered; this is probably due to the lack of petals. InLechea intermedia (also cleistogamous) the corolla is trimerous and three complex stamen primordia are produced, which give rise either to one or three stamens. Relationships withinCistaceae are discussed. Floral development inCistaceae is compared with that in otherMalvanae. Among the eight families ofMalvanae from which information on floral development is availableCochlospermaceae andBixaceae exhibit the greatest similarities toCistaceae. InCistaceae the leading stamen primordia are alternipetalous. InBixa the same condition seems to be present. InMalvales s. str. mostTiliaceae also show earliest stamen initiation in alternipetalous sectors, whereas the stamens of the innermost alternipetalous position are retarded early or even suppressed inSterculiaceae, Bombacaceae, andMalvaceae. WithinMalvales s. str. the diversity of androecial developmental patterns seems to decrease inBombacaceae andMalvaceae due to increasing synorganization in the mature androecium. The derivation of polyandry inMalvanae from diplo- or obdiplostemony is discussed by comparison with the sister clades ofMalvanae as shown in recentrbcL studies (i.e.Sapindales, Rutales, the glucosinolate producing clade, andMyrtales).     

宽叶泽苔草的花器官发生

通过扫描电镜观察了宽叶泽苔草Caldesia grandisSamuel.的花器官发生。宽叶泽苔草 的萼片3枚,逆时针螺旋向心发生 ;花瓣3枚,呈一轮近同时发生,未观察到花瓣_雄蕊复合原基;雄蕊、心皮原基皆轮状向心 发生,最先近同时发生的6枚原基全部发育成雄蕊,随后发生的6枚原基早期并无差别,在发 育过程中逐渐出现形态差异,直至其中1－4枚发育成心皮,其余的发育成雄蕊;而后的几轮 心皮原基,6枚一轮,陆续向心相间发生。本文揭示了3枚萼片螺旋状的发生方式,并推测这种螺旋方式是泽泻科植物进化过程中保留下来     

Comparative androecium morphogenesis ofSicyos angulatus andSechium edule (Cucurbitaceae)

“Androecium” ofSicyos angulatus andSechium edule is unique in having a solid central column below a head portion with thecae. Its morphogenesis was examined for the two species. The developmental course is composed of two distinct successive phases; (1) establishment of stamen primordia and (2) uplift of the stamen primordia caused by development of a central column below them. In the first phase, there is a difference between the two species; inSicyos angulatus, two bithecal and one monothecal stamen primordia are formed by congenital fusion among preformed five protrsions, whilst inSechium edule, three or four monothecal stamen primordia are formed without fusion. The central column is later produced by intercalary growth in a region below the stamen primordia in both species. Concomitant with central column development, the center of the floral primordium, which was surrounded by the early formed stamen primordia, is raised up to the top of the central column. The central column could be interpreted as a receptacular column, and not as congenitally fused stamen filaments, as currently believed. The “androecium” of the both species is considered an androecium complex, which consists of the stamens and a receptacular column.     

A comparative study of floral development inTrillium apetalon andT. kamtschaticum (Liliaceae)

Trillium apetalon Makino is unique amongTrillium in having apetalous flowers. Using scanning electron microscope, the early floral development was observed in comparison with that ofT. kamtschaticum Pallas ex Pursh having petalous flowers. Morphologically petal primordia closely resemble stamen primordia in their more or less narrow and radially symmetric shape and are clearly distinct from sepal primordia with broad bases. Early in floral development sepal primordia are first initiated and subsequently two whorls of three primordia each are formed in rapid sequence, the first three at the corners and the second three at the sides of the triangular floral apex. Based on comparison in position and early developmental processes of their primordia, petals and outer stamens ofTrillium kamtschaticum are equivalent to outer stamens and inner stamens ofT. apetalon. The replacement of petals by outer stamens apparently leads to the loss of petals inTrillium apetalon flowers. Such a replacement can be interpreted in terms of homeosis. The replacement of the petal whorl leads to the serial replacement of the subsequent whorls: outer stamens by inner stamens, and inner stamens by gynoecium inTrillium apetalon. The term ‘serial homeosis’ is introduced for this serial replacement.     

Comparative study of floral development in Onobrychis melanotricha, Hedysarum varium and Alhagi persarum (Leguminosae: Papilionoideae: Hedysareae)

Floral initiation and development of Hedysarum varium, Onobrychis melanotricha and Alhagi persarum was studied using epi-illumination light-microscopy techniques. The studied species belong to the tribe Hedysareae of the inverted repeat loss clade (IRLC clade), which is characterized by missing the large inverted repeat in the chloroplast genome. The main aim of our study was to determine developmental bases for similarities and differences among the three taxa and to verify the position of Alhagi relative to other genera of the IRLC clade. According to our observations, bracteoles are missing in Onobrychis melanotricha, but are present in the other two species. All three species share unidirectional sepal initiation starting with a median abaxial sepal and bidirectional petal initiation. Stamen initiation is unidirectional in all except in the outer stamen whorl of Hedysarum varium, where it is bidirectional. An important ontogenetic feature in O. melanotricha is the existence of five common primordia, which give rise to petal and stamen primordia. Although in H. varium and O. melanotricha common primordia are observed at some stages in floral organ initiations, in Alhagi all organs are initiated separately. Moreover, overlap in time of floral organs initiation occurs in H. varium and O. melanotricha, but not in A. persarum. The carpel initiates concurrently with the petal primordia in all. It might be presumed that Alhagi is primitive in relation to the other studied Hedysareae taxa, due to the presence of bracteoles, the absence of common primordia, and the lack of overlap in time of different organ initiations.     

Floral trait variation in fourCyclamen (Primulaceae) species

The purpose of this study is to examine floral trait variation between fourCyclamen species that show variation in their ability to reproduce in the absence of pollinators and in levels of inbreeding. Pollen and ovule production, pollen/ovule ratio, pollen volume, petal length and width, diameter of the corolla mouth, pistil and stamen length, and stigma-anther separation varied significantly between the four study species. Flower, pollen and ovule production, pollen volume and corolla size were generally highest inC. hederifolium, the species with the lowest level of inbreeding (mean F_is = 0.329), intermediate in both species with relatively high levels of pollinator-mediated inbreeding,C. repandum (mean F_is = 0.658) andC. creticum (mean F_is = 0.748), and lowest in the highly inbredC. balearicum (mean F_is = 0.930). The two species with the most different inbreeding coefficients,C. hederifolium andC. balearicum, had lower pollen-ovule ratios and shorter longevities of stigma receptivity and pollen viability thanC. creticum andC. repandum. These patterns of variation in floral traits are discussed in relation to the relatedness, pollination ecology and levels of inbreeding of the four species.     

臭椿花器官分化的初步研究

利用扫描电镜(SEM)和光镜(LM)对臭椿花序及花器官的分化和发育进行了初步研究,表明:1)臭椿花器官分化于当年的4月初,为圆锥花序;2)分化顺序为花萼原基、花冠原基、雄蕊原基和雌蕊原基。5个萼片原基的发生不同步,并且呈螺旋状发生;5个花瓣原基几乎同步发生且其生长要比雄蕊原基缓慢;雄蕊10枚,两轮排列,每轮5个原基的分化基本是同步的;雌蕊5,其分化速度较快;3)在两性花植株中,5个心皮顶端粘合形成柱头和花柱,而在雄株中,5个心皮退化,只有雄蕊原基分化出花药和花丝。本研究着重观察了臭椿中雄花及两性花发育的过程中两性花向单性花的转变。结果表明,臭椿两性花及单性花的形成在花器官的各原基上是一致的(尽管时间上有差异),雌雄蕊原基同时出现在每一个花器官分化过程中,但是,可育性结构部分的形成取决于其原基是否分化成所应有的结构:雄蕊原基分化形成花药与花丝,雌蕊原基分化形成花柱、柱头和子房。臭椿单性花的形成是由于两性花中雌蕊原基的退化所造成,其机理有待于进一步研究。     

Morphological differentiation of flower buds in Apple-Trees

The paper deals with the study of morphological differentiation of flower buds in 10 varieties of apple-trees in relation to the growth of summer shoots and the earliness of varieties. The data obtained indicate that in the warmer regions of Slovakia the critical season of transformation of flower buds from vegetative to generative forms takes place, on the average, between July 20 and 29, and, at the same time, the variety Yellow Transparent deviates from the average four week-earlier. According to the author we can speak neither of a positive relation between the onset of morphological differentiation and the active growth of summer shoots nor of the relation between the earliness of the variety in maturing and the onset of differentiation. The morphological differentiation may be classified into five phases: 1^st phase — the formation of the growing point primordium, 2^nd phase — the formation of the cup on sepal primordia, 3^rd phase — the formation of petal primordium, 4^th phase — the formation of carpel and stamen primordia, 6^th phase — completion of the differentiation through substantial enlargement of flower organs before the onset of winter.     

泽苔草的花器官发生

本文用扫描电镜观察了泽苔草的花器官发生过程,观察结果表明：花萼以螺旋状方式向心发生,花瓣以接近轮状方式近同时发生,不存在花瓣雄蕊复合原基。雄蕊和心皮均以轮状向心方式发生,6枚雄蕊分两轮分别在对萼和对瓣的位置先后发生,至发育的后期排成一轮,但仍分别处于对萼和对瓣的位置;随后发生的第一轮3个心皮原基与3枚萼片相对,第二、三轮心皮原基分别为1~3个,与前一轮心皮相间排列向心发生。本文首次揭示了泽苔草花被的外轮3个萼片螺旋状发生方式,这种螺旋状方式很可能是泽泻科植物的花部结构在进化过程中适应环境而保留下来的一种较原始的叶性特征。     

FLORAL ORGANOGENESIS IN FIVE GENERA OF THE MARANTACEAE AND IN CANNA (CANNACEAE)

The paired flowers of all species of the Marantaceae studied, except Monotagma plurispicatum, are produced through the division of an apical meristem with a tunica-corpus structure. The solitary flowers of M. plurispicatum develop from a similar meristem which does not bifurcate. The paired flowers of Canna indica are produced in the axil of a florescence bract through the formation of a bract and an axillary flower on the side of the primordium which gives rise to the largest flower of the pair. The sequence of organ initiation for both families is: calyx, corolla and inner androecial whorl, outer androecial whorl, gynoecium. The sequence of sepal formation is opposite in the two families. In the Cannaceae it leads directly into the spiral created by the formation of the other organs, while in the Marantaceae the sequence of sepal formation follows a spiral opposite to that of the other floral organs. The members of the corolla and inner androecial whorl separate from common primordia. In general these common primordia separate into a petal and an inner androecial member through the initiation of two growth centers, at the same level, in the dorsal and ventral flanks of the primordium. In Ischnosiphon elegans and Pleiostachya pruinosa the stamen is initiated at a lower position than the petal in the ventral flank of the common primordium. A similar pattern of initiation is described for the callose staminode in Marantochloa purpurea and Canna indica. This pattern is interpreted as a variation on the more generalized pattern of inner androecial formation found in the other genera.     

Analysis of theilv-linked genes that determine the morphology ofEscherichia coli Cells

The genetic location ofwee relative tocya was measured by cotransduction with a Tn5 insertion inilv. These experiments locatedwee at 84.8 min in the standardEscherichia coli map. Mutations incya andwee give rise to morphological changes, coccal morphology incya and short rods inwee, suggesting that both may be involved in the pathways of cell elongation. Addition of cAMP to the cultures reverted thecya but not thewee phenotype. Cells ofE. coli in the absence of thewee gene product were, contrary to what has been described forcya cells, as sensitive to mecillinam as in its presence. These results suggested that the action of Wee on elongation is exerted at a level different from that of adenyl cyclase.     

Homeosis in floral development of Sanguinaria canadensis and S. canadensis ‘Multiplex’ (Papaveraceae)

Sanguinaria canadensis is a member of the Papaveraceae that normally has eight petals rather than four as is usual in the family. Using epi-illumination microscopy to study floral development, we show that the four additional petal primordia are initiated in positions that correspond to the first four stamen positions in species of the Papaveraceae with four petals. Also, these additional petal primordia share early developmental features with stamen primordia: at inception they are circular in outline, and the relationship between organ length and width while very young is similar. The developmental pathway of the additional petals combines both stamen and petal features: initially stamenlike in appearance, they develop into typical petals. The additional petals of S. canadensis can therefore be interpreted as homeotic because petal features are expressed in stamen positions. Organogenesis in the ‘Multiplex’ cultivar is similar to that of its wild progenitor, but during development all primordia in the androecial region become petals. This cultivar, as well as variants within natural populations, show that replacement of stamens with petals occurs within the species.     

Flower development in Abrus precatorius (Leguminosae: Papilionoideae: Abreae) and a review of androecial characters in Papilionoideae

The jequirity bean (Abrus precatorius) is well known because of its shiny black and red coloured seeds and because of the poison (abrin) it contains. The genus Abrus is placed in a monogeneric tribe Abreae which is placed in a relatively isolated systematic position at the base of Millettieae. To contribute to a better understanding of this taxon, a detailed ontogenetic and morphologic analysis of its flowers is presented. Floral primordia are subtended by an abaxial bract and preceded by two lateral bracteoles which are formed in short succession. Sepal formation is unidirectional starting abaxially. All petals are formed simultaneously. The carpel is formed concomitantly with the outer (antesepalous) stamen whorl, which arises unidirectionally, starting in an abaxial position. In the inner, antepetalous stamen whorl two abaxial stamens are formed first, followed by two lateral stamen primordia. The adaxial, antepetalous position remains organ free (i.e. this stamen is lost). Later in development the nine stamen filaments fuse to form an adaxially open sheath. The filament bases of the two adaxial outer-whorl stamens grow inwards, possibly to provide stability and to compensate for the lost stamen. In the mature flower a basal outgrowth can be found in the position of the lost stamen. However this is more likely to be an outgrowth of the filament sheath rather than a remnant of the lost stamen. These ontogenetic patterns match in parts those found in other Millettieae (unidirectional formation of sepals and stamens, simultaneous petal formation). In contrast, the complete loss of a stamen is rather unusual and supports the isolated position of Abreae and probably justifies (among other characters) its tribal status. A review of androecial characters shows that androecial merosity is on the one hand extremely variable among Leguminosae, varying from a single stamen per flower to more than 500. On the other hand it is noteworthy that the number of stamens becomes stabilised in more derived Papilionoideae such as the large non-protein-amino-acid-accumulating clade (NPAAA clade). This indicates that the androecium has played an important role in the success of a major part of Leguminosae.     

Comparative inflorescence and floral ontogeny in the genus Mentha (Mentheae: Nepetoideae: Lamiaceae): variable sequences of organ appearance and random petal aestivation

The genus Mentha is a taxonomically complex genus, characterized by large morphological variations. Only a few, frequently overlapping, characters are of value in taxonomy. Comparative floral developmental studies provide an opportunity for better understanding the systematic relationships among different species. The inflorescence and floral ontogeny of three Mentha L. species (M. piperita L., M. pulegium L. and M. suaveolens Ehrh.) were investigated using epi-illumination light microscopy. All three species studied have thyrses with the same developmental pathway. The lack of higher order bracts and the monochasial branching of the higher order inflorescence apices were found as special features of inflorescence ontogeny. Sepals appear unidirectionally from the adaxial side in all except for M. pulegium which shows a modified unidirectional sequence. Variable sequences of petal and stamen appearance from unidirectional to reversed unidirectional sequence are present in all. Significant ontogenetic features include (1) appearance of the corolla as a rim before petal lobes become visible and (2) instability in petal aestivation. Morphological features including densely hairy calyx, five-lobed corolla tube, smaller adaxial stamens and hairy ovary with included style distinguish M. pulegium from the other species. On the basis of our results floral ontogenetic features could be considered important characters for delimiting or diagnosing different sections in the genus Mentha. Variable sequences of petal lobe appearance and instability in petal aestivation were found as unusual developmental characters.