中国桂樱属植物的分类研究

桂樱属(Laurocerasus Tourn.ex Duh.)是蔷薇科李亚科的一个属。它是De Tournefort(Institutiones rei Herbariae 627.t.403.1700)以Prunus laurocerasus L.和P.lusitanica L.两种奠定基础,而至1755年由Duhmal代为正式发表而建立。自该属建立以后的二百多年来,各国植物学家对其分类位置各持不同观点。     

大戟科麻疯树属三种植物花器官发生

利用扫描电子显微镜观察了大戟科Euphorbiaceae麻疯树属Jatropha麻疯树J. curcas L.、佛肚树J. podagrica Hook.和棉叶麻疯树J. gossypifolia L.花器官发生。结果表明: 麻疯树、佛肚树和棉叶麻疯树花萼原基均为2/5型螺旋发生。在同一个种不同的花蕾中, 花萼的发生有两种顺序: 逆时针方向和顺时针方向。远轴面非正中位的1枚先发生。5枚花瓣原基几乎同时发生。雄花中雄蕊两轮, 外轮对瓣, 内轮对萼。研究的3种麻疯树属植物雄蕊发生方式有两种类型: 麻疯树亚属麻疯树的5枚外轮雄蕊先同时发生, 5枚内轮雄蕊后同时发生, 佛肚树亚属佛肚树和棉叶麻疯树雄蕊8-9枚, 排成两轮, 内外轮雄蕊同时发生。雌花的3枚心皮原基为同时发生。麻疯树属单性花, 雌花的子房膨大而雄蕊退化, 雄花的雄蕊正常发育, 子房缺失。根据雄蕊发生方式, 支持将麻疯树属分为麻疯树亚属subgen. Jatropha和佛肚树亚属subgen. Curcas。     

长角凤仙花（凤仙花科）的花器官发生和发育

以不同发育时期的长角凤仙花Impatiens longicornuta Y.L.Chen（凤仙花科Balsaminaceae）为材料,利用扫描电镜技术观察了其花器官的分化及其发育过程。长角凤仙花为两侧对称花,具2枚侧生萼片,唇瓣囊状,旗瓣具鸡冠状突起,雄蕊5枚,子房上位,5心皮5室。其花器官分化顺序为向心式,萼片—花瓣—雄蕊—雌蕊原基。2枚侧生萼片先发生,然后近轴萼片（即唇瓣）原基和2枚前外侧萼片原基近同时发生;但是这3枚萼片原基的发育不同步,远轴的2枚前外侧萼片原基的发育渐渐滞后,然后停止发育,最后渐渐为周围组织所吸收,直至消失不见。花瓣原基中,旗瓣原基最先发生,4个侧生花瓣原基相继成对发生,且之后在基部成对愈合形成翼瓣;5枚雄蕊原基几乎同时发生,5个心皮原基轮状同时发生。本文结果支持凤仙花属植物为5基数的花,并进一步证实了唇瓣的萼片来源;此外,研究结果表明花器官早期发育资料对植物系统与进化研究具有重要参考价值。     

Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.

We characterized the distribution of AGAMOUS (AG) RNA during early flower development in Arabidopsis. Mutations in this homeotic gene cause the transformation of stamens to petals in floral whorl 3 and of carpels to another ag flower in floral whorl 4. We found that AG RNA is present in the stamen and carpel primordia but is undetectable in sepal and petal primordia throughout early wild-type flower development, consistent with the mutant phenotype. We also analyzed the distribution of AG RNA in apetela2 (ap2) mutant flowers. AP2 is a floral homeotic gene that is necessary for the normal development of sepals and petals in floral whorls 1 and 2. In ap2 mutant flowers, AG RNA is present in the organ primordia of all floral whorls. These observations show that the expression patterns of the Arabidopsis floral homeotic genes are in part established by regulatory interactions between these genes.     

Floral ontogeny in Scirpus, Eriophorum and Dulichium (Cyperaceae), with special reference to the perianth

BACKGROUND AND AIMS: Based on molecular phylogenetic analysis, it has been suggested recently that the Cyperaceae comprises only two subfamilies: the Mapanioideae and the Cyperoideae. In most flowers of the Cyperoideae, the whorl of inner stamens is reduced, resulting in tetracyclic flowers. In the more primitive (scirpoid) genera within the Cyperoideae, the perianth consists of two polysymmetric whorls, whereas the perianth parts in the more derived genera have been subject to modifications and/or reduction. Comparative studies of the many silky hairs of Eriophorum and of the eight bristles of Dulichium have given rise to much discussion about their homology. METHODS: The spikelet and floral ontogeny in freshly collected inflorescences was investigated using scanning electron microscopy. KEY RESULTS: Complete floral ontogenies are presented for Scirpus sylvaticus L., Eriophorum latifolium Hoppe and Dulichium arundinaceum (L.) Britton, with special reference to the perianth. The results in S. sylvaticus confirm the trimerous monocot-like organization of the flower. It is used as a model for floral development in Cyperoideae. In the early developmental stages, the androecium of E. latifolium is surrounded by a massive perigonial primordium, from which the many hair-like bristles originate. Consequently, the stamens develop among the hair primordia, more or less simultaneously. The hairs are arranged in whorls, which develop centripetally. The development of the perianth in D. arundinaceum starts with the formation of three initial perianth primordia opposite the stamens. Subsequently, two more abaxial bristle primordia, alternating with the stamens, originate simultaneously with the appearance of three adaxial bristle primordia in the zone where an adaxial inner perianth primordium is expected. CONCLUSIONS: The floral development in E. latifolium and D. arundinaceum can be considered as variations upon the scirpoid floral ontogenetic theme.     

'Living stones' reveal alternative petal identity programs within the core eudicots

Petals, defined as the showy laminar floral organs in the second floral whorl, have been shown to be under similar genetic control in distantly related core eudicot model organisms. On the basis of these findings, it is commonly assumed that the petal identity program regulated by B-class MADS-box gene homologs is invariant across the core eudicot clade. However, the core eudicots, which comprise >70% of angiosperm species, exhibit numerous instances of petal and sepal loss, transference of petal function between floral whorls, and recurrent petal evolution. In the face of these complex patterns of perianth evolution, the concept of a core eudicot petal identity program has not been tested. We therefore examined the petal identity program in the Caryophyllales, a core eudicot clade in which perianth differentiation into sepals and petals has evolved multiple times. Specifically, we analyzed the expression patterns of B- and C-class MADS-box homologs for evidence of a conserved petal identity program between sepal-derived and stamen-derived petaloid organs in the 'living stone' family Aizoaceae. We found that neither sepal-derived nor stamen-derived petaloid organs exhibit gene expression patterns consistent with the core eudicot petal identity program. B-class gene homologs are not expressed during the development of sepal-derived petals and are not implicated in petal identity in stamen-derived petals, as their transient expression coincides with early expression of the C-class homolog. We therefore provide evidence for petal development that is independent of B-class genes and suggest that different genetic control of petal identity has evolved within this lineage of core eudicots. These findings call for a more comprehensive understanding of perianth variation and its genetic causes within the core eudicots--an endeavor that will have broader implications for the interpretation of perianth evolution across angiosperms.     

The development of pistillate and perfect florets in Xeranthemum squarrosum (Asteraceae)

The formation of capitulum inflorescence with two different types of floret is an interesting issue in floral biology and evolution. Here we studied the inflorescence, floral ontogeny and development of the everlasting herb, Xeranthemum squarrosum, using epi‐illumination microscopy. The small vegetative apex enlarged and produced involucral bracts with helical phyllotaxy, which subtended floret primordia in the innermost whorl. Initiation of floret primordia was followed by an acropetal sequence, except for pistillate peripheral florets. The origin of receptacular bracts was unusual, as they derived from the floral primordia rather than the receptacular surface. The order of whorl initiation in both disc and pistillate flowers included corolla, androecium and finally calyx, together with the gynoecium. The inception of sepals and stamens occurred in unidirectional order starting from the abaxial side, whereas petals incepted unidirectionally from the adaxial or abaxial side. Substantial differences were observed in flower structure and the development between pistillate and perfect florets. Pistillate florets presented a zygomorphic floral primordium, tetramerous corolla and androecium and two sepal lobes. In these florets, two sepal lobes and four stamen primordia stopped growing, and the ovary developed neither an ovule nor a typical stigma. The results suggest that peripheral pistillate florets in X. squarrosum, which has a bilabiate corolla, could be considered as an intermediate state between ancestral bilabiate florets and the derived ray florets.     

AP2 Gene Determines the Identity of Perianth Organs in Flowers of Arabidopsis thaliana

We have examined the floral morphology and ontogeny of three mutants of Arabidopsis thaliana, Ap2-5, Ap2-6, and Ap2-7, that exhibit homeotic changes of the perianth organs because of single recessive mutations in the AP2 gene. Homeotic conversions observed are: sepals to carpels in all three mutants, petals to stamens in Ap2-5, and petals to carpels in Ap2-6. Our analysis of these mutants suggests that the AP2 gene is required early in floral development to direct primordia of the first and second whorls to develop as perianth rather than as reproductive organs. In addition, our results support one of the two conflicting hypotheses concerning the structures of the calyx and the gynoecium in the Brassicaceae.     

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。     

APETALA3 and PISTILLATA homologs exhibit novel expression patterns in the unique perianth of Aristolochia (Aristolochiaceae)

Several lines of evidence suggest that sterile floral organs, collectively known as the perianth, have evolved multiple times during the evolution of the angiosperms. In the family Aristolochiaceae, the perianth is formed by two whorls of organs in the genus Saruma but by only one whorl in the remaining genera, including Aristolochia. Although the morphology of Saruma is similar in appearance to the core eudicot perianth, with leaf-like sepals and showy colored petals, the unipartite perianth of Aristolochia combines morphological aspects of both calyx and corolla. To investigate the organ identity program functioning in the novel perianth of Aristolochia, we identified homologs of the B-class genes APETALA3 (AP3) and PISTILLATA (PI) in both Saruma and Aristolochia. The expression patterns of these genes in Saruma indicate they are functioning in the development of the second whorl petaloid organs and third whorl stamens. In Aristolochia, however, the expression of AP3 and PI homologs in the perianth does not suggest a role in organ identity but, rather, in promoting late aspects of cell differentiation. The implications of these findings for the evolution of both petaloidy and B gene function are discussed.     

Isolation of the tomato AGAMOUS gene TAG1 and analysis of its homeotic role in transgenic plants.

To understand the details of the homeotic systems that govern flower development in tomato and to establish the ground rules for the judicious manipulation of this floral system, we have isolated the tomato AGAMOUS gene, designated TAG1, and examined its developmental role in antisense and sense transgenic plants. The AGAMOUS gene of Arabidopsis is necessary for the proper development of stamens and carpels and the prevention of indeterminate growth of the floral meristem. Early in flower development, TAG1 RNA accumulates uniformly in the cells fated to differentiate into stamens and carpels and later becomes restricted to specific cell types within these organs. Transgenic plants that express TAG1 antisense RNA display homeotic conversion of third whorl stamens into petaloid organs and the replacement of fourth whorl carpels with pseudocarpels bearing indeterminate floral meristems with nested perianth flowers. A complementary phenotype was observed in transgenic plants expressing the TAG1 sense RNA in that first whorl sepals were converted into mature pericarpic leaves and sterile stamens replaced the second whorl petals.     

Evolution of petaloid sepals independent of shifts in B-class MADS box gene expression

Attractive petals are an integral component of animal-pollinated flowers and in many flowering plant species are restricted to the second floral whorl. Interestingly, multiple times during angiosperm evolution, petaloid characteristics have expanded to adjacent floral whorls or to extra-floral organs. Here, we investigate developmental characteristics of petaloid sepals in Rhodochiton atrosanguineum, a close relative of the model species Antirrhinum majus (snapdragon). We undertook this in two ways, first using scanning electron microscopy we investigate the micromorphology of petals and sepals, followed by expression studies of genes usually responsible for the formation of petaloid structures. From our data, we conclude that R. atrosanguineum petaloid sepals lack micromorphological characteristics of petals and that petaloid sepals did not evolve through regulatory evolution of B-class MADS box genes, which have been shown to specify second whorl petal identity in a number of model flowering plant species including snapdragon. These data, in conjunction with other studies, suggests multiple convergent pathways for the evolution of showy sepals.     

Developmental study on the inflorescence and flower of Caldesia grandis Samuel (Alismataceae)

The inflorescence and floral development of Caldesia grandis Samuel is reported for the first time in this paper. The basic units of the large cymo‐thyrsus inflorescence are short panicles that are arranged in a pseudowhorl. Each panicle gives rise spirally to three bract primordia also arranged in a pseudowhorl. The branch primordia arise at the axils of the bracts. Each panicle produces spirally three bract primordia with triradiate symmetry (or in a pseudowhorl) and three floral primordia in the axils of the bract primordia. The apex of the panicle becomes a terminal floral primordium after the initiations of lateral bract primordia and floral primordia. Three sepal primordia are initiated approximately in a single whorl from the floral primordium. Three petal primordia are initiated alternate to the sepal primordia, but their subsequent development is much delayed. The first six stamen primordia are initiated as three pairs in a single whorl and each pair appears to be antipetalous as in other genera of the Alismataceae. The stamen primordia of the second whorl are initiated trimerously and opposite to the petals. Usually, 9–12 stamens are initiated in a flower. There is successive transition between the initiation of stamen and carpel primordia. The six first‐initiated carpel primordia rise simultaneously in a whorl and alternate with the trimerous stamens, but the succeeding ones are initiated in irregular spirals, and there are 15–21 carpels developed in a flower. Petals begin to enlarge and expand when anthers of stamens have differentiated microsporangia. Such features do not occur in C. parnassifolia. In the latter, six stamen primordia are initiated in two whorls of three, carpel primordia are initiated in 1–3 whorls, and there is no delay in the development of petals. C. grandis is thus considered more primitive and C. parnassifolia more derived. C. grandis shares more similarities in features of floral development with Alsma, Echinodorus, Luronium and Sagittaria. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140 , 39–47.     

青城细辛的花器官发生

利用扫描电镜观察了青城细辛(Asarum splendens)的花器官发生过程。青城细辛的花器官为轮状结构,向心发生,依次为两轮3基数的花被原基,两轮6基数的雄蕊原基和一轮6基数的心皮原基。两轮花被原基互生,只有外轮(先发生的一轮)花被原基完全发育,而内轮(后发生的一轮)花被原基在发育过程中逐渐退化。两轮雄蕊原基为离心发生:位于内侧的一轮雄蕊原基先发生,每两个原基正对第一轮发生的花被原基,外侧的一轮雄蕊原基后发生,与内轮雄蕊原基互生。心皮与内侧的一轮雄蕊互生。     

Are Petals Sterile Stamens or Bracts? The Origin and Evolution of Petals in the Core Eudicots

BACKGROUND: The aim of this paper is to discuss the controversial origins of petals from tepals or stamens and the links between the morphological expression of petals and floral organ identity genes in the core eudicots. SCOPE: I challenge the widely held classical view that petals are morphologically derived from stamens in the core eudicots, and sepals from tepals or bracts. Morphological data suggest that tepal-derived petals have evolved independently in the major lineages of the core eudicots (i.e. asterids, Santalales and rosids) from Berberidopsis-like prototypes, and that staminodial petals have arisen only in few isolated cases where petals had been previously lost (Caryophyllales, Rosales). The clear correlation between continuous changes in petal morphology, and a scenario that indicates numerous duplications to have taken place in genes controlling floral organ development, can only be fully understood within a phylogenetic context. B-gene expression plays a fundamental role in the evolution of the petals by controlling petaloidy, but it does not clarify petal homology. CONCLUSIONS: An increased synorganization of the flower in the core eudicots linked with the establishment of floral whorls restricts the petaloid gene expression to the second whorl, reducing the similarities of petals with tepals from which they were originally derived. An increased flower size linked with secondary polyandry or polycarpelly may lead to a breakdown of the restricted gene expression and a reversal to ancestral characteristics of perianth development. An altered 'sliding boundary' hypothesis is proposed for the core eudicots to explain shifts in petaloidy of the perianth and the event of staminodial petals. The repetitive changes of function in the perianth of the core eudicots are linked with shifts in petaloidy to the outer perianth whorl, or losses of petal or sepal whorls that can be secondarily compensated for by the inclusion of bracts in the flower. The origin and evolution of petals appears to be as complex on a molecular basis as it is from a morphological point of view.     

商陆属植物的花器官发生

为进一步研究商陆科的系统位置提供花器官发生和发育的证据,在扫描电子显微镜下观察了商陆Phytolacca acinosa、多雄蕊商陆P. polyandra和垂序商陆P. americana的花器官发生.结果表明: 商陆属植物花被的发生均为2/5型螺旋发生.在同一个种不同的花蕾中,花被的发生有两种顺序:逆时针方向和顺时针方向.远轴侧非正中位的1枚先发生.雄蕊发生于环状分生组织.在单轮雄蕊的种中8-10枚雄蕊为近同时发生;两轮雄蕊的种8枚内轮雄蕊先发生,6-8枚外轮雄蕊随后发生,内轮雄蕊为同时发生,外轮雄蕊发生次序不规则.心皮原基也发生于环状分生组织,8-10枚心皮原基为同时发生.在后来的发育过程中,商陆的心皮发育成近离生心皮雌蕊;其他2种心皮侧壁联合发育成合生心皮雌蕊.对商陆属植物花器官发生的类型及发育形态学做了分析,结果支持商陆科在石竹目系统发育中处于原始地位的观点.     

Pseudodiplostemony, and its implications for the evolution of the androecium in the Caryophyllaceae

The androecium of the Caryophyllaceae is varied, ranging from a two-whorled condition to a single stamen. A number of species belonging to the three subfamilies, Caryophyl-loideae, Alsinoideae and Paronychioideae have been studied ontogenetically with the SEM to understand their peculiar androecial development in the broader context of the Caryophyllales alliance. Although patterns of initiation are highly variable among species, there are three ontogenetic modes of stamen initiation: all stamens simultaneous within a whorl, the antepetalous stamens simultaneous and the antesepalous sequentially with a reversed direction, or both whorls sequentially with or without a reversed direction. The most common floral (ontogenetic) sequence of the Caryophyllaceae runs as follows: five sepals (in a 2/5 sequence), the stamens in front of the three inner sepals successively, stamens opposite the two outermost sepals, five antepetalous stamens (simultaneously or in a reversed spiral superimposed on the spiral of the antesepalous stamens), five outer sterile (petaloid) organs arising before, simultaneously or after the antesepalous stamens, often by the division of common primordia. A comparison with the floral configurations of the Phytolaccaceae and Molluginaceae indicates that the outer petaline whorl of the Caryophyllaceae corresponds positionally to the alternisepalous stamens of somePhytolacca, such asP. dodecandra. The difference withP. dodecandra lies in the fact that an extra inner or outer whorl is formed in the Caryophyl-laceae, in alternation with the sepals. A comparable arrangement exists in the Molluginaceae, though the initiation of stamens is centrifugal. A comparison of floral ontogenies and the presence of reduction series in the Caryophyllaceae support the idea that the pentamerous arrangement is derived from a trimerous prototype. Petals correspond to sterillized stamens and are comparable to two stamen pairs opposite the outer sepals and a single stamen alternating with the third and fifth sepals. Petals are often in a state of reduction; they may be confused with staminodes and they often arise from common stamenpetal primordia. The antesepalous stamen whorl represents an amalgamation of two whorls: initiation is reversed with the stamens opposite the fourth and fifth formed sepals arising before the other, while the stamens opposite the first and second formed sepals are frequently reduced or lost. Reductive trends are correlated with the mode of initiation of the androecium, as well as changes in the number of carpels, and affect the antesepalous and antepetalous whorls in different proportions. It is concluded that the androecium of the Caryophyllaceae is pseudodiplos-temonous and is not comparable to diplostemonous forms in the Dilleniidae and Rosidae. The basic floral formula of Caryophyllaceae is as follows: sepals 5—petals 5 (sterile stamens)—antesepalous stamens 3+2—antepetalous stamens 5 gynoecium 5.     

青城细辛的花器官发生

利用扫描电镜观察了青城细辛（Asarum splendens）的花器官发生过程。青城细辛的花器官为轮状结构,向心发生,依次为两轮3基数的花被原基,两轮6基数的雄蕊原基和一轮6基数的心皮原基。两轮花被原基互生,只有外轮（先发生的一轮）花被原基完全发育,而内轮（后发生的一轮）花被原基在发育过程中逐渐退化。两轮雄蕊原基为离心发生：位于内侧的一轮雄蕊原基先发生,每两个原基正对第一轮发生的花被原基,外侧的一轮雄蕊原基后发生,与内轮雄蕊原基互生。心皮与内侧的一轮雄蕊互生。     

Mutants involved in floral and plant development in Petunia

The Petunia system is described together with its possible use for molecular research on floral development. Developmental mutants are described in some detail. The most interesting mutants are Blind and Green petals. In both the appearance of only the petals has changed, in Blind towards antheroid tissue, in Green petals towards sepals. Transposon tagging as an approach to isolate developmental genes in Petunia is also discussed.