南天竹属的花部器官发生及其系统学意义

报道了南天竹（ＮａｎｄｉｎａｄｏｍｅｓｔｉｃａＴｈｕｎｂ．）（小檗科）的花部器官发生。发现该属植物萼片、花瓣和雄蕊的发生式样为三数轮生;雄蕊与花瓣是经它们所具有的共同原基进行侧向分裂而形成的;花瓣发育早期存在迟滞发育的阶段;心皮发生属于瓶状发生类型。讨论了花器官的三基数性质,小檗科花瓣的来源,雄蕊对瓣着生及单心皮雌蕊的形成等问题。对本属的花部个体发育性状同小檗科中已有报道的红毛七属（Ｃａｕｌｏｐｈｙｌｕｍ）、足叶草属（Ｐｏｄｏｐｈｙｌｕｍ）进行了比较,萼片多数轮列与心皮发生的多态现象是南天竹属的独特性状。     

吉祥草的花部器官发生及其系统学意义

利用扫描电镜（SEM）观察了吉祥草（Reineckia carnea）（铃兰科）的花部器官发生发育过程。吉祥草花被片、雄蕊的发生方式是由近轴端向远轴端发生的逆单向型（reversed unidirection）,花发育后期花被片合生形成花被筒,花丝与之贴生。伴随花被片、雄蕊发生,三枚心皮也由近轴向远轴方向相继发生,随后彼此合生发育。花序顶部的花易发生花器官数目变异。结合早期花原基形态以及花器官数目变异情况分析,吉祥草的花被片与雄蕊可能是由共同原基分化而成。从花部器官发生式样和花被筒形成时间两方面比较吉祥草属、白穗花属和铃兰属的特征发现,三属中,铃兰属处于相对进化的位置,而白穗花属比吉祥草属更为原始。     

蓝堇草属(毛茛科)花形态发生的扫描电子显微镜观察

花的发生和发育过程研究可以发现早期进化的轨迹,为系统发育的研究提供重要线索。蓝堇草属(Leptopyrum)为毛茛科唐松草亚科一单种属,仅包含蓝堇草一种,其花的发生和发育过程仍为空白。为了深入理解唐松草亚科乃至毛茛科花发育多样性和演化规律,该文运用扫描电子显微镜(SEM)观察了蓝堇草各轮花器官的形态发生和发育过程。结果表明:该属植物所有的萼片、花瓣、雄蕊和雌蕊均为螺旋状发生,花器官排列式样也为螺旋状; 5枚萼片原基宽阔,5枚花瓣原基圆球形、位于萼片原基的间隔,且在后期表现为延迟发育现象,雄蕊原基较小、为圆球形; 花瓣原基和雄蕊原基连续发生,无明显的时空间隔,但与萼片原基有时空间隔; 心皮原基为马蹄形对折,柱头组织由单细胞乳突组成; 胚珠倒生、具单珠被。该属花器官螺旋状排列、胚珠具单珠被在唐松草亚科中是独有的性状,花发育形态学证据支持了该属的特殊性。     

台闽苣苔（苦苣苔科）花部器官的形态发生

在扫描电镜下对台闽苣苔 (T .oldhamii (Hemsl.)Solereder)进行了花部器官形态发生的观察 ,为探索该类群的个体发育、类群间的系统发育关系和进化趋势提供依据。研究发现该属植物萼片、花冠和雄蕊发生式样均为五数花类型 ,它们各自来源于花原基上分化出来的萼片原基、花冠原基和雄蕊原基 ;花冠与雄蕊的两侧对称性与花冠上唇生长稍快和退化雄蕊原基发育迟滞相关 ;萼片原基的发生和发育的顺序是不一致的 :萼片原基发生的式样为近轴中原基—远轴 2原基— 2侧原基 ,发育式样则为近轴中萼片— 2侧萼片—远轴 2萼片 ,花蕾时为镊合状排列。花冠裂片原基的发生和发育式样是一致的 ,即远轴中裂原基 (下唇中裂片 )—远轴 2侧裂原基 (下唇 2侧裂片 )—近轴 2裂原基 (上唇 2裂片 )。花蕾期卷迭式为覆瓦状排列 ,从外向内 :下唇中裂片—下唇 2侧裂片—上唇 2裂片或下唇 2侧裂片—上唇 2裂片—下唇中裂片。雄蕊原基与花冠裂片原基互生 ,前方雄蕊原基在发生上稍迟于后方雄蕊原基 ,后者与退化雄蕊原基几乎同时发生 ,但较小 ,并与近轴心皮 (或柱头上唇 )对生。将该属与玄参科 (Scrophulari aceae)的地黄属 (Rehmannia)、苦苣苔科 (Gesneriaceae)的异叶苣苔属 (Whytockia)和尖舌苣苔属 (Rhynchoglossum)的花部器官比较发现     

台闽苣苔(苦苣苔科)花部器官的形态发生

在扫描电镜下对台闽苣苔 (T. oldhamii (Hemsl.) Solereder)进行了花部器官形态发生的观察,为探索该类群的个体发育、类群间的系统发育关系和进化趋势提供依据.研究发现该属植物萼片、花冠和雄蕊发生式样均为五数花类型,它们各自来源于花原基上分化出来的萼片原基、花冠原基和雄蕊原基;花冠与雄蕊的两侧对称性与花冠上唇生长稍快和退化雄蕊原基发育迟滞相关;萼片原基的发生和发育的顺序是不一致的:萼片原基发生的式样为近轴中原基-远轴2原基-2侧原基,发育式样则为近轴中萼片-2侧萼片-远轴2萼片,花蕾时为镊合状排列.花冠裂片原基的发生和发育式样是一致的,即远轴中裂原基(下唇中裂片)-远轴2侧裂原基(下唇2侧裂片)-近轴2裂原基(上唇2裂片).花蕾期卷迭式为覆瓦状排列,从外向内:下唇中裂片-下唇2侧裂片-上唇2裂片或下唇2侧裂片-上唇2裂片-下唇中裂片.雄蕊原基与花冠裂片原基互生,前方雄蕊原基在发生上稍迟于后方雄蕊原基,后者与退化雄蕊原基几乎同时发生,但较小,并与近轴心皮(或柱头上唇)对生.将该属与玄参科(Scrophulariaceae)的地黄属( Rehmannia )、苦苣苔科(Gesneriaceae)的异叶苣苔属( Whytockia)和尖舌苣苔属(Rhynchoglossum )的花部器官比较发现,这四个属在这方面呈现出多样性和交叉.过去一直按子房室数和胎座类型划分玄参科(子房2室、中轴胎座)和苦苣苔科(子房1室、侧膜胎座)这一做法受到了质疑.     

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。     

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。     

海韭菜的花器官发生

运用扫描电镜（SEM）观察了海韭菜（Triglochin maritimum）的花器官发生发育过程。结果表明：海韭菜花发育是典型的单子叶植物发生模式,即两轮花被片、两轮雄蕊和两轮心皮以三基数轮状交替发生,花器官是以向心向顶的方式发生的,未发现“花被片—雄蕊复合原基”。 发育后期雄蕊和与之对生的花被片之间的共同基部可能是相继向上居间生长的结果。花被片轮和雄蕊轮二者之间在发育位置、时间和速率上存在差异,内轮花被片原基和外轮雄蕊原基的不同发育时间和发育速度使得在成熟花中内轮花被片位于外轮雄蕊的内方。观察结果不支持水麦冬属植物的花是退化（或压缩）的花序侧分枝等假花的观点。     

黄连属(毛茛科)花的形态发生

本文运用扫锚电子显微镜(SEM)观察了黄连属(Coptis)植物花的形态发生和发育过程, 结果表明, 该属植物所有的花部器官均为螺旋状发生, 雄蕊为向心式发育, 花瓣原基有微弱的延迟发育, 心皮原基为对折型(即马蹄形), 子房为半封闭类型, 子房柄是在发育过程中形成的。通过与其它具T-型染色体类群在花形态发生上的比较, 认为黄连属表现出了某些原始的性状, 这一结果与分子系统学研究认为黄连属为毛茛科的基部类群的结论一致。     

驴蹄草属和金莲花属(毛茛科)花器官的形态发生及系统学意义

利用扫描电镜观察了驴蹄草Caltha palustris L.和川陕金莲花Trollius buddae Schipcz.花器官的发生和发育过程。结果显示:驴蹄草和川陕金莲花的所有花器官均螺旋状向心式发生、向心式发育,花器官的螺旋状发生方式在毛茛科Ranunculaceae可能是一种基本式样;苞片、萼片与其他花器官原基的形状明显不同,显示苞片、萼片与其他花器官在系统发生上有所不同;川陕金莲花的花瓣在早期延迟发育且基部具囊,花瓣的延迟发育在毛茛科具花瓣的属中非常普遍,而花瓣基部的囊类似于耧斗菜属Aquilegia一些植物;两个属雄蕊群一纵列雄蕊中的小孢子均向心式发育,这种发育方式在毛茛科可能为基本类型。两个属植物的心皮原基均为对折式,在发育过程中,驴蹄草心皮顶端沿腹缝线形成下延的柱头组织,川陕金莲花不形成明显的柱头组织。根据花形态发生和发育特点,并结合其他研究成果,认为这两个属不应当属于同一个族。     

The quantitative genetics of floral trait variation in Lobelia: potential constraints on adaptive evolution

Abstract Although pollinator-mediated natural selection has been measured on many floral traits and in many species, the extent to which selection is constrained from producing optimal floral phenotypes is less frequently studied. In particular, negative correlations between flower size and flower number are hypothesized to be a major constraint on the evolution of floral displays, yet few empirical studies have documented such a trade-off. To determine the potential for genetic constraints on the adaptive evolution of floral displays, I estimated the quantitative genetic basis of floral trait variation in two populations of Lobelia siphilitica . Restricted maximum likelihood (REML) analyses of greenhouse-grown half-sib families were used to estimate genetic variances and covariances for flower number and six measures of flower size. There was significant genetic variation for all seven floral traits in both populations. Flower number was negatively genetically correlated with four measures of flower size in one population and three measures in the other. When the genetic variance-covariance matrices were combined with field estimates of phenotypic selection gradients, the predicted multivariate evolutionary response was less than or opposite in sign to the selection gradient for flower number and five of six measures of flower size, suggesting genetic constraints on the evolution of these traits. More generally, my results indicate that the adaptive evolution of floral displays can be constrained by tradeoffs between flower size and number, as has been assumed by many theoretical models of floral evolution.     

Effects of pollination on floral attraction and longevity

The end of a flower's attraction to pollinators may be due toa range of visible cues such as permanent flower closure, acolour change, and withering or abscission of the petals. Floralattraction may be reduced by pollination. Pollination-inducedconclusion of floral attraction is often due to a colour changeor to flower closure. This may or may not be followed by a reductionin floral longevity, defined as the time to petal withering,wilting or shattering. In a few species floral longevity isincreased following pollination-induced flower closure or apollination-induced change in colour. Floral attraction, therefore,has to be disting uished from floral longevity. A literature survey shows that pollination rapidly reduces floralattraction in numerous orchids, but among other plant familiesonly about 60 genera have been found to show pollination-inducedshortening of floral attraction. Although only a few specieshave been investigated, it was invariably established that theeffect of pollination is blocked by inhibitors of ethylene synthesisor ethylene perception, hence is mediated by ethylene. The flowersthat cease to be attractive to pollinators, shortly followingpollination, tend to be from families that are known mainlyto comprise species in which flower longevity, petal colour,or flower closure, is sensitive to exogenous ethylene. Thisindicates that the effect of pollination on floral attractionis generally mediated by endogenous ethylene. Numerous species reportedly show a decrease in the period offloral attraction after exposure to ethylene, whereas only fora small number of species a decrease in the period of floralattraction induced by pollination has been observed. This discrepancymay be due to the greater attention that has been paid to theeffects of ethylene. Nonetheless, the possibility remains thatendogenous ethylene has a role in changing perianth form andcolour in addition to signalling the occurrence of pollination. Key words: Ethylene sensitivity, flower closure, flower longevity, pollination, petal colour, petal wilting, petal withering, petal abscission     

The search for Pleiades in trait constellations: functional integration and phenotypic selection in the complex flowers of Morrenia brachystephana (Apocynaceae)

Pollinator‐mediated natural selection on single traits, such as corolla tube or spur length, has been well documented. However, flower phenotypes are usually complex, and selection is expected to act on several traits that functionally interact rather than on a single isolated trait. Despite the fact that selection on complex phenotypes is expectedly widespread, multivariate selection modelling on such phenotypes still remains under‐explored in plants. Species of the subfamily Asclepiadoideae (Apocynaceae) provide an opportunity to study such complex flower contrivances integrated by fine‐scaled organs from disparate developmental origin. We studied the correlation structure among linear floral traits (i) by testing a priori morphological, functional or developmental hypotheses among traits and (ii) by exploring the organization of flower covariation, considering alternative expectations of modular organization or whole flower integration through conditional dependence analysis (CDA) and integration matrices. The phenotypic selection approach was applied to determine whether floral traits involved in the functioning of the pollination mechanism were affected by natural selection. Floral integration was low, suggesting that flowers are organized in more than just one correlation pleiad; our hypothetical functional correlation matrix was significantly correlated with the empirical matrix, and the CDA revealed three putative modules. Analyses of phenotypic selection showed significant linear and correlational gradients, lending support to expectations of functional interactions between floral traits. Significant correlational selection gradients found involved traits of different floral whorls, providing evidence for the existence of functional integration across developmental domains.     

Specific expression of the AGL1 MADS-box gene suggests regulatory functions in Arabidopsis gynoecium and ovule development

Several members of the MADS-box gene family have been shown to be important regulators of flower development, controlling such well-studied early events as the formation of the floral meristem and the specification of floral organ identity. Other floral-specific MADS-box genes, of as yet unknown function, have been isolated by homology and are proposed to be part of a regulatory hierarchy controlling flower development. Some of these genes might regulate later aspects of flower development, such as development of individual floral organs, which is less well studied at the molecular level. This paper presents a detailed analysis of the expression pattern of one such gene from Arabidopsis , AGL1 , using RNA in situ hybridization. It is found that AGL1 is specifically expressed in particular regions of the gynoecium and ovule, only during and after floral development stage 7. AGL1 expression at the tip of the growing carpel primordia, along the margins of the ovary valves in developing and mature gynoecia and in specific regions of developing and mature ovules provides important insights into the possible roles of AGL1 . It is proposed that AGL1 may have regulatory functions in the structural definition and/or function of the valve margins, in axis maintenance during ovule development, in nutritional supply to the growing ovule and embryo sac, and in pollen tube guidance. In the floral homeotic mutants ag-1 , ap3-3 and ap2-2 , AGL1 mRNA is expressed in an organ-dependent manner, suggesting that AGL1 is a carpel-specific gene and as such ultimately depends upon the carpel identity gene AG for proper gene expression.     

On ‘various contrivances’: pollination,phylogeny and flower form in the Solanaceae

Members of the euasterid angiosperm family Solanaceae have been characterized as remarkably diverse in terms of flower morphology and pollinator type. In order to test the relative contribution of phylogeny to the pattern of distribution of floral characters related to pollination, flower form and pollinators have been mapped onto a molecular phylogeny of the family. Bilateral flower symmetry (zygomorphy) is prevalent in the basal grades of the family, and more derived clades have flowers that are largely radially symmetric, with some parallel evolution of floral bilateralism. Pollinator types (‘syndromes’) are extremely homoplastic in the family, but members of subfamily Solanoideae are exceptional in being largely bee pollinated. Pollinator relationships in those genera where they have been investigated more fully are not as specific as flower morphology and the classical pollinator syndrome models might suggest, and more detailed studies in some particularly variable genera, such as Iochroma and Nicotiana, are key to understanding the role of pollinators in floral evolution and adaptive radiation in the family. More studies of pollinators in the field are a priority.     

Relationships between species’ floral traits and pollinator visitation in a temperate grassland

Knowledge about plant–plant interactions for pollinator service at the plant community level is still scarce, although such interactions may be important to seed production and hence the population dynamics of individual plant species and the species compositions of communities. An important step towards a better understanding of pollination interactions at the community level is to assess if the variation in floral traits among plant species explain the variation in flower visitation frequency among those species. We investigated the relative importance of various floral traits for the visitation frequency of all insects, and bumblebees and flies separately, to plant species by measuring the visitation frequency to all insect-pollinated species in a community during an entire flowering season. Visitation frequency was identified to be strongly positive related to the visual display area and the date of peak flowering of plant species. Categorical variables, such as flower form and symmetry, were important to the visitation frequency of flies only. We constructed floral similarity measures based on the species’ floral traits and found that the floral similarity for all species’ traits combined and the continuous traits separately were positively related to individual visitation frequency. On the other hand, plant species with similar categorical floral traits did not have similar visitation frequencies. In conclusion, our results show that continuous traits, such as flower size and/or density, are more important for the variation in visitation frequency among plant species than thought earlier. Furthermore, differences in visitation frequency among pollinator groups give a poor support to the expectations derived from the classical pollination syndromes.     

Pollinator parasites and the evolution of floral traits

The main selective force driving floral evolution and diversity is plant–pollinator interactions. Pollinators use floral signals and indirect cues to assess flower reward, and the ensuing flower choice has major implications for plant fitness. While many pollinator behaviors have been described, the impact of parasites on pollinator foraging decisions and plant–pollinator interactions have been largely overlooked. Growing evidence of the transmission of parasites through the shared‐use of flowers by pollinators demonstrate the importance of behavioral immunity (altered behaviors that enhance parasite resistance) to pollinator health. During foraging bouts, pollinators can protect themselves against parasites through self‐medication, disease avoidance, and grooming. Recent studies have documented immune behaviors in foraging pollinators, as well as the impacts of such behaviors on flower visitation. Because pollinator parasites can affect flower choice and pollen dispersal, they may ultimately impact flower fitness. Here, we discuss how pollinator immune behaviors and floral traits may affect the presence and transmission of pollinator parasites, as well as how pollinator parasites, through these immune behaviors, can impact plant–pollinator interactions. We further discuss how pollinator immune behaviors can impact plant fitness, and how floral traits may adapt to optimize plant fitness in response to pollinator parasites. We propose future research directions to assess the role of pollinator parasites in plant–pollinator interactions and evolution, and we propose better integration of the role of pollinator parasites into research related to pollinator optimal foraging theory, floral diversity and agricultural practices.     

Florivory indirectly decreases the plant reproductive output through changes in pollinator attraction

Species often interact indirectly with each other via their traits. There is increasing appreciation of trait‐mediated indirect effects linking multiple interactions. Flowers interact with both pollinators and floral herbivores, and the flower‐pollinator interaction may be modified by indirect effects of floral herbivores (i.e., florivores) on flower traits such as flower size attracting pollinators. To explore whether flower size affects the flower‐pollinator interaction, we used Eurya japonica flowers. We examined whether artificial florivory decreased fruit and seed production, and also whether flower size affected florivory and the number of floral visitors. The petal removal treatment (i.e., artificial florivory) showed approximately 50% reduction in both fruit and seed set in natural pollination but not in artificial pollination. Furthermore, flower size increased the number of floral visitors, although it did not affect the frequency of florivory. Our results demonstrate that petal removal indirectly decreased 75% of female reproductive output via decreased flower visits by pollinators and that flower size mediated indirect interactions between florivory and floral visitors.