Colour saturation triggers innate reactions to flower signals: Flower dummy experiments with bumblebees

Summary Innate behavioural reactions, i.e. reactions of untrained, flower-naive bumblebees (Bombus terrestris L., B. lucorum L.; Apidae) were observed in flower dummy experiments. It was proven that an innate releasing mechanism responds to optical flower signals: the spectral purity of corolla colour was found to be crucial for far attraction toward flower dummies. During the subsequent near orientation, that is when a bumblebee finally reaches a flower dummy, the bumblebee's antennae contact the part of highest spectral purity while the bee is still in flight. Guides such as stamen patches present in the center of flower dummies are used only for near orientation. Flower dummies receiving the greatest number of antennae reactions at the guide were always those with low spectral purity in the surrounding background colour, high spectral purity at the corolla colour and highest spectral purity at the guide colour. In contrast, dominant wavelength and intensity of flower dummy colours had no detectable influence on innate behavioural reactions, while colour contrast had some. These results are interpreted as follows: orientation toward guides is based upon a gradient of centripetally increasing, bee-subjective colour saturation which directs the bumblebee's approach toward the center of the flower dummy where additional factors may contribute to stimulating the landing reaction.     

Visual detection of diminutive floral guides in the bumblebee <Emphasis Type="Italic">Bombus terrestris</Emphasis> and in the honeybee <Emphasis Type="Italic">Apis mellifera</Emphasis>

Many flowers display colour patterns comprising a large peripheral colour area that serves to attract flower visitors from some distance, and a small central, contrastingly coloured area made up by stamens or floral guides. In this study, we scaled down the size of floral guides to detect the minimal size bumblebees (Bombus terrestris) and honeybees (Apis mellifera) require for guidance. We analyzed the approach and the precise contact of the antennal tips with the floral guide of artificial flowers which precedes landing and inspection. Both bumblebees and honeybees were able to make antennal contact with circular floral guides which were 2 mm in diameter; bumblebees performed better than honeybees and antennated also at floral guides smaller than 2 mm. In discrimination experiments with bumblebees, a minimum floral guide size of 2 mm was required for discrimination between artificial flowers with and without floral guides. With increasing experience bumblebees targeted close to the site of reward instead of making antennal contact with the floral guide, whereas honeybees did not alter their initial behaviour with growing experience. Bumblebees and honeybees spontaneously target diminutive floral guides to achieve physical contact with flowers by means of their antennae which helps them to inspect flowers.     

A new interpretation of flower guide colouration: Absorption of ultraviolet light enhances colour saturation

In melittophilous plants the colour pattern of the flowers, as perceived by bumblebees, is a gradient of centripetally increasing spectral purity. This pattern serves as a signal for innate flower recognition in naive bumblebees permitting orientation to flowers and landing on flowers. Structures which make up the total signal pattern can include the background (e.g., green leaves), corollas, and stamens or floral guides. How various colour parameters, such as dominant wavelength, intensity, and spectral purity influence the colour signal pattern of flowers is analyzed. The process of strong absorption of ultraviolet light is shown to be a mechanism for the enhancement of spectral purity in flower guides. The importance of other mechanisms is also demonstrated. The presence of a gradient of centripetally increasing spectral purity in floral colour patterns as perceived by a bumblebee's eyes is demonstrated by a comparison of the spectral reflectance in different parts of the flower and a representation of colour loci in the colour triangle.     

Bumblebees require visual pollen stimuli to initiate and multimodal stimuli to complete a full behavioral sequence in close‐range flower orientation

Flower visits are complex encounters, in which animals are attracted by floral signals, guided toward the site of the first physical contact with a flower, land, and finally take up floral rewards. At close range, signals of stamens and pollen play an important role to facilitate flower handling in bees, yet the pollen stimuli eliciting behavioral responses are poorly known. In this study, we test the response of flower‐naive bumblebees (Bombus terrestris) toward single and multimodal pollen stimuli as compared to natural dandelion pollen. As artificial pollen stimuli, we used the yellow flavonoid pigment quercetin, the scent compound eugenol, the amino acid proline, the monosaccharide glucose, and the texture of pollen‐grain‐sized glass pellets as a tactile stimulus. Three test stimuli, dandelion pollen, one out of various uni‐ and multimodal stimulus combinations, and a solvent control were presented simultaneously to individual bumblebees, whose response was recorded. The results indicate that bumblebees respond in an irreversible sequence of behavioral reactions. Bumblebees approached the visual stimulus quercetin as often as natural dandelion pollen. An additional olfactory stimulus resulted in slightly more frequent landings. The multimodal stimulus combinations including visual, olfactory, gustatory, and tactile stimuli elicited approaches, antennal contacts, and landings as often as natural pollen. Subsequent reactions like proboscis extension, mandible biting, and buzzing were more often but not regularly observed at dandelion pollen. Our study shows that visual signals of pollen are sufficient to trigger initial responses of bumblebees, whereas multimodal pollen stimuli elicit full behavioral response as compared to natural pollen. Our results suggest a major role of pollen cues for the attraction of bees toward flowers and also explain, why many floral guides mimic the visual signals of pollen and anthers, that is, the yellow and UV‐absorbing color, to direct bumblebees toward the site where they access the floral rewards.     

月季花瓣数量遗传分析

以‘窄叶藤本月季花’( Rosa chinensis ‘Zhaiye Tengben Yuejihua’)ב月月粉’( R. chinensis ‘Old Blush’)杂交群体为材料, 分析其花瓣数量的分离特点, 对单瓣花与重瓣花的花芽分化过程进行观察, 并对花瓣、雄蕊及瓣化雄蕊进行表皮细胞超微结构的观察.结果显示...     

Consequences of floral complexity for bumblebee-mediated geitonogamous self-pollination in Salvia nipponica Miq. (Labiatae)

Abstract.— I address how floral complexity influences geitonogamous self-pollination through manipulation of pollinator behavior in Salvia nipponica . The pivoting stamens of S. nipponica hinder nectar-collecting bumblebees from crawling into flowers, increasing the probing time per flower. I predicted that longer probing times would reduce the relative cost of moving between plants, causing bees to leave plants earlier. To test this prediction, I simplified S. nipponica flowers by removing the stamens from all open flowers within a 75-m² quadrat. Bumblebees probed these flowers more quickly than intact flowers, but the stamen removal affected neither the frequency of flower revisitation nor the flight distance between plants. In response to the decrease in the probing time per flower, bees probed more flowers on these plants. Therefore, in S. nipponica , floral complexity reduces the opportunity for geitonogamous self-pollination. Stamen removal also increased bee visitation per flower, suggesting that this sort of complexity deters visitation. To keep complex flowers attractive, therefore, selection might increase floral rewards or longevity. Floral complexity might evolve in an integrative manner with the rest of the floral phenotype.     

Ingenious floral structure drives explosive pollination in Hydrilla verticillata (Hydrocharitaceae)

• In explosive pollination, many structures and mechanisms have evolved to achieve high‐speed stamen movement. The male flower of the submerged plant Hydrilla verticillata is reported to be able to release pollen explosively some time after leaving the mother plant time, but the mechanism of stamen movement and the related functional structure in this species are unclear.
• In this study, we observed the male flower structure and pollen dispersal process of H. verticillata. We analysed the stamen movements during the pollen dispersal process and conducted several controlled experiments to study the process of storage and release of elastic potential energy in explosive pollination.
• When the male flower of H. verticillata is bound to the united bracts, the sepals accumulate elastic potential energy through the expansion of basal extensor cells. After the male flower is liberated from the mother plant, the stamens unfold rapidly with the sepals under adhesion and transfer the elastic potential energy to the filament in seconds. Once stamens unfold to a critical angle, at which the elasticity of the filament just exceeds the adhesion between sepals and anthers, the stamens automatically rebound and release pollen in milliseconds.
• These results reveal that Catapult‐like stamens, spoon‐shaped sepals and enclosed united bracts in the spathe together constitute the functional structure in rapid stamen movement of H. verticillata. They ensure that the pollen can be released on the water surface, and thus adapt successfully to the pollen‐epihydrophilous pollination.

     

花内雄蕊分化及其适应意义

对花内雄蕊存在显著分化的现象进行了分析与归纳, 总结了花内雄蕊分化的各种主要形式及其繁殖适应意义。“花内雄蕊分化”是指花内雄蕊与雄蕊之间存在显著分化的现象, 这一概念可以把二强雄蕊、四强雄蕊和异型雄蕊等以往单独进行研究的相关性状结合起来, 并明确区分了几种新的花内雄蕊分化形式, 以期更准确全面地认识这些相关性状的适应意义与进化。该文将花内雄蕊分化区别为花丝的分化、花药的分化、雄蕊合生的分化、雄蕊运动的分化、退化雄蕊5大类。花丝的分化主要是花丝长度的分化, 如四强雄蕊、二强雄蕊和单强雄蕊; 花药分化主要指花药颜色、花药与花粉粒大小和花药开裂时间等的分化; 雄蕊合生的分化主要体现为花内部分雄蕊合生而部分雄蕊离生; 雄蕊运动的分化指的是花内雄蕊在运动时间或方式上存在差异, 造成雄蕊处于不同的成熟阶段和位于不同的空间位置; 退化雄蕊则是花内部分雄蕊失去了生产花粉的繁殖功能, 通常也发生了花药形态上的巨大改变。异型雄蕊不仅存在花丝和花药的形态分化, 还存在着明显的功能分化, 是分化程度很高的一类特殊的花内雄蕊分化形式。一些特殊的繁育系统, 如异长花柱和镜像花柱等在种内不同个体上存在着不同形式的花内雄蕊分化。花内雄蕊分化在花内造成了多个不同的花药位置, 在很大程度上影响了雌雄异位程度, 对植物自交与异交水平、花内雌雄功能干扰等有着潜在作用; 花内雄蕊分化形成的多个不同空间位置的雄蕊还增加了对多种访花者的吸引与适应潜力, 有可能影响到访花者的类型与访花行为, 得以适应多种传粉者。此外, 花内雄蕊分化可将花粉逐渐分批次分发给访花者, 提高花粉散布效率, 可看成是“花粉呈现理论”所指的花粉装配与分发机制之一。现有的实验研究发现, 花内雄蕊分化能够吸引传粉者、保护正常花药和花粉、促进花粉散发(降低花粉竞争)、实行延迟自交和降低花内雌雄功能干扰等。花内雄蕊分化还缺少系统研究, 有些雄蕊分化形式如单强雄蕊和雄蕊运动的分化还没有针对性的实验揭示其适应意义, 鸭跖草科和某些豆科植物的雄蕊三型分化等现象也缺少进化适应意义的研究。花内雄蕊分化对植物雌性和雄性适合度可能不同的影响、如何与访花者相互作用、如何与其它花部特征一起影响植物繁殖过程等, 可能是这一领域值得今后优先研究的课题。     

商陆属2种植物花器官发生过程观察

该研究采用扫描电镜观察红蕊商陆(Phytolacca esculenta)和浙江商陆(Phytolacca zhejiangensis)的花器官发生过程,以明确商陆属植物花的基数,以及雄蕊和雌蕊是否具有叶性器官发生的特点,阐明商陆属植物花发生的模式。观察结果显示:(1)红蕊商陆和浙江商陆在花原基发生后,小苞片以2/5圆周相继发生,花被片的发生紧接小苞片的发生进行,花被与小苞片的发生均有顺时针和逆时针方向,且二者的发生方向始终一致。(2)花被发生结束后,雄蕊在花顶端分生组织的环状分生组织上发生,没有明显的发生顺序,近似同时发生;2轮雄蕊时内轮雄蕊先发生;外轮雄蕊有少数有时偶然与花被互生,但因外轮雄蕊数多于花被数,雄蕊与花被常不互生,也没有规律性。(3)红蕊商陆和浙江商陆的心皮都在雄蕊发生后,紧接着开始发生,且雌蕊与雄蕊(或内轮雄蕊)互生发生;心皮没有发生的先后次序,且每个心皮在基部连成一个整体形成雌蕊基部并发育成为子房。(4)红蕊商陆和浙江商陆的花基数为5,雄蕊和雌蕊的发生及数目不符合5基数的特点。研究认为,红蕊商陆和浙江商陆为5基数花,该研究结果不支持商陆属植物为3基数花的发生模式。     

Quantitative genetics of stamen number in the selfing Scleranthus annuus (Caryophyllaceae)

Heritability of stamen fertility—different scores were given to sterile stamens developed to different degrees as well as to fertile stamens with one or two pollen sacs—was studied in Scleranthus annuus (Caryophyllaceae), a selling annual that shows extensive phenotypic variation in stamen fertility. Variation within and among 172 maternal families, derived from plants representing 20 natural populations from southern Sweden, was used to estimate heritabilities of stamen fertility for stamens/staminoids at each of the ten stamen positions in the flower. The hierarchical design of the study allowed partitioning of variation at four levels of organization using nested analysis of variance. Heritabilities ranged from 0.631 to 0.714 for stamen positions in the outer whorl of stamens and from 0.235 to 0.555 for positions in the inner whorl. When stamen fertility was pooled across all stamen positions of a flower, the heritability was 0.807. The nested ANOVA indicated that stamen positions in the outer whorl have comparatively higher proportions of among-family and among-population variation than those in the inner whorl. Furthermore, highly significant genetic correlations exist among stamen positions within the inner whorl and among positions within the outer whorl, but not so between positions from each of the two whorls.     

Temporal and spatial patterns in the production of pollen, ovules and seeds in pseudogamous blackberries (Rubus subgenus Rubus)

Significant variation in the number of stamens and ovules per flower, the stamen/ovule ratio, and the number of seeds per berry was found among seven blackberry species, each represented by one clone, and to a much lesser extent among inflorescences within species. Inflorescence size and architecture were found to have no major influence on these reproductive parameters.
The position of a flower within the inflorescence strongly influences its onset of anthesis, which in turn is closely correlated with these reproductive parameters. Ovule number decreases with time, although in some species it increases again at the end of the flowering season. Number of seeds decreases more or less linearly with time, although there is an unexpectedly high number of the earliest berries of the triploid species, which is probably the result of interspecific pollination. Pollen production estimated in one species decreases with time, per theca, per flower and per ovule, whereas the percentage of good pollen grains remains unaltered.     

掌叶木的花器官发生及其系统学意义

利用扫描电子显微镜和光学显微镜观察了掌叶木的花器官发生过程。观察结果表明: 花序原基最先发生, 然后形成两个大小不一的花原基; 萼片原基的发生不同步, 螺旋状向心发生; 4-5枚花瓣原基以接近轮状方式近同时发生; 不存在花瓣-雄蕊复合原基; 7-8枚雄蕊原基为近同时发生, 其生长较花瓣原基快; 心皮原基最后发生, 3枚心皮原基为同时发生。花为单性花。在雌花中, 子房膨大而雄蕊退化。在雄花中, 雄蕊正常发育, 子房退化。讨论了掌叶木花器官发生和发育的系统学意义。     

舌瓣鼠尾草退化杠杆雄蕊的相关花部特征及传粉机制

杠杆状雄蕊是鼠尾草属(Salvia)物种形成的关键性状, 背部杠杆传粉模式作为该属植物与传粉者精确互作的经典案例被广泛深入研究, 但是在该属物种中还存在许多非典型的杠杆结构和传粉模式。雄蕊结构及其与传粉者互作的多样性, 使得鼠尾草属成为研究植物传粉模式转变的模式材料, 舌瓣鼠尾草(S. liguliloba)即是一种具非典型的退化杠杆状雄蕊结构和传粉特征的代表性物种。该文着重对舌瓣鼠尾草的花器官结构和传粉特征进行研究, 并与具有短药隔杠杆的毛地黄鼠尾草 (S. digitaloides)做比较分析, 以期揭示退化杠杆可能的进化选择压力及其生态学意义。结果表明, 舌瓣鼠尾草具有较短的花冠、更窄的冠筒和较短的雄、雌蕊(p < 0.05)。退化萎缩的雄蕊下臂, 冠筒内的狭小空间限制了唯一的有效传粉昆虫——三条熊蜂(Bombus trifasciatus)推动雄蕊做杠杆状运动, 而是靠近花药直接利用头部完成授粉。相比经典的杠杆状雄蕊结构及其传粉过程, 小型花冠和退化杠杆雄蕊是对专一性和活跃度较高传粉昆虫的适应, 可能具有完全不同的进化途径和繁殖策略。     

Sex-allocation trade-offs in Nigella sativa (Ranunculaceae) examined with flower manipulation experiments

Sex-allocation trade-offs have long been invoked as a primary factor underlying the evolution of separate sexes and the reduction of pollen production accompanying the evolution of selfing. In the present study, I conducted stamen and style removal experiments to explore the existence of such trade-offs in Nigella sativa, a hermaphroditic plant species whose flower structure allows early manipulation of both male and female function. Plants on which all stamens were removed at the bud stage had a higher rate of flower initiation and produced significantly heavier seeds than did plants whose flowers remained intact, apparently by using resources that were released when the stamens were removed. However, there was no effect of stamen removal on the number of flowers that reached anthesis, the total biomass allocated to seed production, or the vigour of plants in the progeny generation. In contrast, prevention of fruit production (style removal) increased the amount of biomass invested in stamen by 57% relative to plants whose flowers were allowed to set fruit. These observations verify the existence of a sexual trade-off in N. sativa but also raise the possibility that stamen-suppressing mutations sometimes lack the pleiotropic consequences of increasing female function, at least in species with large, expensive fruits.     

How drone flies (Eristalis tenax L., Syrphidae,Diptera) use floral guides to locate food sources

In this study we show how inexperienced syrphid flies, Eristalis tenax, orient on artificial flowers by means of floral guides. To test the effect of floral guides such as line and ring markings on the probability and speed of the location of a potential food source, we exploited the spontaneous proboscis reaction triggered by yellow colour stimuli. We tested whether and how fast the flies, when placed on the edge of a circular dummy flower, found a small central yellow spot and touched it with the proboscis extended. The flies found the central yellow spot more often and faster if guide lines from the margin to the yellow spot were present. The effect of guide lines was dependent on the colour of the dummy flower, and independent of the colour of the guide lines, except for yellow guide lines releasing the proboscis reaction. The effect of guide lines was stronger if the yellow spot was hidden in a 2 mm deep depression and thus not as easily visible to the flies. Ring guides had a significant effect on performance only when the intensity of the central yellow spot was low.     

THE DEVELOPMENTAL BASIS OF TRISTYLY IN EICHHORNIA PANICULATA (PONTEDERIACEAE)

Eichhornia paniculata is a tristylous, self-compatible, emergent aquatic. A given plant produces flowers with either long, mid or short styles and two levels of stamens equal in length to the styles not found in that flower. Flowers of each morph have two whorls of three tepals, six stamens and three fused carpels. The six stamens differentiate into two sets of three stamens each. A relatively short set, having either short- or mid-level stamens, occurs on the upper side of the flower, while a relatively long set, having either mid- or long-level stamens, occurs on the lower side. Stamen level depends on differences among stamens in filament length and position of insertion on the floral tube. Floral parts arise in whorls of three, but the two stamen whorls do not form the two sets of stamens found in each mature flower. Instead, stamens from both whorls make up a given set. Floral differences among morphs are not present at flower origin or floral organ initiation. Morphological differences arise first among stamen sets. The two sets within a flower differ prior to meiosis in the size, number, and timing of comparable developmental events in the sporogenous cells. After these initial differences arise, anther size diverges. In later developmental stages differences in filament and floral tube length, cell size, and cell number, as well as differences in the length, cell size, and cell number of styles, develop among morphs. This sequence of developmental events suggests that the genes controlling development in different morphs do not control flower and floral organ initiation but are first morphologically visible in sporogenous cell differentiation.     

Flower development and anatomy of Clusia valerioi,a Central American species of Clusiaceae offering floral resin

The present paper is part of a study dealing with various aspects of reproduction of two Costa Rican Clusia species offering resin as a floral reward. It provides data on the floral development and flower (especially stamen and staminode) anatomy of one of the species, Clusia valerioi. In the early stages, both male and female flowers develop in the same manner. The bracts are distinguished by a decussate arrangement from the five sepals and five petals, which emerge in a spiral manner. In the male flowers the apical meristem forms five meristematic mounds (common stamen primordia) that are pentagonally arranged around the apical meristem in epipetalous position. From these mounds, the primordia of the proper stamina emerge in 3–5 whorls. Direction is centrifugal. In the centre, five hemispherical bulges arise which develop into carpel primordia. These, however, cease growth, stay rudimentary and are hidden by the stamens in the mature male flower. The adult stamens consist mainly of a thick angular filament column, while the two anthers situated at the flattened top are very small. One anther is annular and surrounds a second, hemispherical one right in the centre. At the periphery, these two pollen sacs (provided with a distinct wall of customary anatomy) are surrounded by a ring-like protuberance of the filament. The resin canals are situated at the periphery of the filament. Their schizogenous development is documented in cross sections. At anthesis, the resin is released from the ring-like filament protuberance by burst of the single-layered epidermis. In the female flower, the five meristematic mounds produce two whorls of staminode primordia. The development of the staminodes does not essentially differ from that of the fertile stamens, but some staminodes lack the central pollen sac and the other tissues do not develop into pollen grains. An attempt is made to derive the peculiar stamen morphology of Clusia valerioi and similar species from conventional stamens. Three hypotheses are proposed and discussed.     

Developmental evidence for stamen number reductionin populations of Hibbertia fasciculata (Dilleniaceae)

Discrete Australian populations of Hibbertia fasciculata R. Br. ex DC. differ in stamen number per flower: three to four in isolated, northeastern coastal populations in New South Wales vs. 10–12 in southeastern Australian populations. In all populations, the stamen bases are attached to three broad flat pedestals regardless of number of stamens present. In certain other Hibbertia species, each pedestal results from initiation via a common stamen primordium that usually produces at least 3–4 stamens per common primordium. In H. fasciculata, each of the three pedestals is associated with three to four stamens in flowers of southeastern populations, but with only one stamen per pedestal in the coastal populations of New South Wales. Because the pedestals (remnants of common primordia) have persisted, the evolutionary trend probably has been one of reduction in stamen number. General observations and comparative studies suggest that this population-based reduction series in stamen number (as well as reduced plant size and flower size) reflects a locally successful trend towards smaller organs throughout the plant body together with a shift in pollination ecology.     

OVERLAPPING ORGAN INITIATION AND COMMON PRIMORDIA IN FLOWERS OF PISUM SATIVUM (LEGUMINOSAE: PAPILIONOIDEAE)

The floral ontogeny of Pisum sativum shows a vertical order of succession of sepals, petals plus carpel, antesepalous stamens, and antepetalous stamens. Within each whorl, unidirectional order is followed among the organs, beginning on the abaxial side of the flower, as in most papilionoids. Unusual features include the four common primordia which precede initiation of discrete petal and antesepalous stamen primordia, and the marked overlap of organ initiations between whorls which are usually separately initiated. The stamens arise in free condition, then become diadelphous by intercalary growth at the base of nine stamens, and finally become pseudomonadelphous by surface fusion between the vexillary stamen filament and the adjacent edges of the filament tube. The early initiation of the carpel is not unique among papilionoids, but is somewhat unusual.     

两性花的雄蕊运动:多样性和适应意义

雄蕊运动指雄蕊在自身能量支持下发生的主动运动,不包括雄蕊在访花者触碰下造成的被动位移。该文总结了雄蕊的应激运动、快速猛烈弹射、缓慢运动以及级联运动等4种主要类型,分析了这些运动类型的系统分布及繁殖适应意义等方面的研究进展。雄蕊的应激运动由访花者或其他外力诱发,可能起到促进散粉和实现繁殖保障的作用;雄蕊快速猛烈的弹射运动可将花粉猛然撒向空中或访花者身上,促进了花粉的风媒或虫媒散布;缓慢运动的雄蕊可能通过在不同花期改变雄蕊的空间位置和雌雄异位程度来调节繁殖策略,或主动将雄蕊花药移至特定部位(如柱头表面)实现自交;雄蕊逐一、依次发生的级联运动较为复杂,主要分布在刺莲花科、梅花草科、旱金莲科和芸香科中,目前还缺乏实验研究;但根据"花粉呈现理论"以及其他类型的雄蕊运动研究结果,雄蕊的级联运动可以将花粉分批呈现给不同的传粉者,通过不同传粉者的分别传粉来提高花粉的输出;而且可避免已散粉雄蕊对即将散粉雄蕊的干扰,同时可能也降低了雌雄功能干扰和(或)花内自交。在芸香(Ruta graveolens)中,级联运动之后的雄蕊还会在花末期再同时向花中央运动;这种多向、多次运动方式是目前发现的最复杂的雄蕊运动类型。雄蕊运动领域值得今后开展进一步实验研究的方向主要有:1)雄蕊运动尤其是级联运动对雌雄功能干扰(性别间干扰)、雄蕊与雄蕊的"性别内干扰"等植物繁殖格局的影响;2)雄蕊运动与雌雄异熟、雌雄异位等花部特征的相互作用;3)雄蕊运动复杂类型的生理与发育机制。