黄河三角洲柽柳的开花特性及传粉生态学研究

野外定位观测了柽柳(TamarixchinensisLour.)的开花物侯、开花动态、访花者的种类、行为和访花频率,并对其繁育系统、花粉-胚珠比(P/O)、花粉活力进行了检测。结果表明,柽柳单朵花的花期仅1d,P/O为390.9±81.0,繁育系统属于自交亲和、需要传粉者的类型。花的结构和开花式样适合以食蚜蝇为主的多种昆虫传粉。自然条件下的结实率为95.23%。柽柳的果实成熟期较短(15d),整个居群有长达几个月的花期,开花数目众多,因此能产生大量的种子,在适宜条件下会形成大片的柽柳灌丛。     

侧柏和北美香柏(柏科)的传粉机制(英)

观察了侧柏（Phaycladusorientalis（L．）Franco）和北美香柏（ThujaoccidentalisL．）散粉后花粉进入珠孔的过程。在散粉期,这两种植物的胚珠均分泌出传粉滴。当花粉落到传粉滴上后,引起传粉滴表面的形状发生改变或减弱胚珠的继续分泌,使得该传粉滴蒸腾加快,导致其比未授粉的传粉滴明显收缩。观察结果表明：不同植物的花粉导致侧柏传粉滴的收缩速率不尽相同。其中,与侧柏亲缘关系较近的植物花粉引起传粉滴的收缩速率和侧柏自身花粉引起的传粉滴收缩速率相似;反之,收缩速率变慢。侧柏传粉滴的收缩可能主要是由于花粉减弱胚珠分泌的结果。     

华凤仙花部特征和传粉系统研究

研究了华凤仙（Impatiens chinensis L.）的花部特征和传粉系统,结果表明华凤仙单花期为2.3 d,雄性期是雌性期的6.8倍。花蜜量和花蜜可溶性糖含量分别为0.56 μL和28.2%。开花当天柱头即具有可授性,花粉活力在花朵刚开放时最高（95%）,至花朵凋谢之前仍保持较高的活力（55%）。花粉胚珠比（5 730.3±2 941.1）和套袋实验的结果表明华凤仙属于自交亲和但以异交为主的繁育系统,传粉过程需要传粉者。蜜蜂、熊蜂、蝶类和几种芦蜂是华凤仙的主要访花者,最有效的传粉者为三条熊蜂。考氏无垫蜂作为盗蜜者,可能是除正常访花者之外,对华凤仙的有性繁殖影响最大的生物因素。     

叶下珠科花粉组织化学、花粉数和胚珠数及其与传粉者关系的研究

植物花粉中营养物质的储存形式以及单花的花粉数与胚珠数被认为与其传粉系统有一定的联系。本文研究了叶下珠科部分种类的花粉组织化学、花粉数和胚珠数, 以及它们与传粉者之间的关系。结果显示: 在叶下珠科内, 植物花粉所含营养成分和传粉者之间存在相关性: 蛾类传粉的类群主要属“淀粉型”花粉, 蝇类和蜂类传粉的类群主要属“非淀粉型”花粉。蝇类传粉和蛾类传粉的植物花粉数没有一定规律。蝇类传粉的类群比蛾类传粉的类群胚珠数少, 这可能是由于蝇类携带花粉能力及传粉精确性均较小, 导致植物以减少胚珠数来适应的结果。对同一属内不同生活型植物的花粉数比较, 发现乔木的单花花粉数高于灌木, 灌木的单花花粉数明显高于草本。这可能是由于不同生活型的植株, 其花朵大小不同, 导致花粉数出现明显差别。另外, 通过扫描电子显微镜对花粉形态的观察, 发现蝇类传粉的类群和蛾类传粉的类群间的花粉表面纹饰存在显著差异。     

锦带花的花粉活力、柱头可授性及传粉者的观察

在野外实地观测锦带花(Weigela florida(Bunge)A．DC．)的开花动态和访花者,在显微镜下观测柱头和花粉的形态及花粉-胚珠比,用TTC法测定锦带花花粉的活力,用联苯胺-过氧化氢法测定柱头可授性。结果表明,锦带花的花粉活力在开花时达70％以上,且能维持3d,之后明显下降。锦带花的柱头在开花3h后多数呈白色、二裂、具可授性,柱头的可授期持续2～3d。柱头与花药之间有5．3士0．9mm的空间距离,自然条件下难于自花授粉．开花当天7．00～10．00之间访花者最丰富,开花第2天访花者减少,开花第3天时访花者更少。在锦带花上记录到的访花者隶属于膜翅目、鳞翅目和双翅目,其中,熊蜂和蜜蜂是主要传粉者。     

狭域物种广西秋海棠传粉生物学研究

为了检验广西秋海棠（Begonia guangxiensis）的交配系统和该物种是否依赖原生境的特殊传粉昆虫进行传粉及其能否在人工生境中实现有性繁殖,展开了广西秋海棠的单花花期观察、花部特征测定、授粉、访花者观察及种子萌发测定等试验。结果显示：广西秋海棠具有较长的单花花期,不同生境下的花冠大小表现出一定差异;自交和异交之间座果率及种子萌发率和两生境之间的自然对照座果均无显著差异;访花者包括蜂类（中华蜜蜂（Apis cerana）与萃熊蜂（Bombus eximius））和食蚜蝇（黑带食蚜蝇（Episyrphus balteatus）与刺腿食蚜蝇（Ischiodon scutellaris））,不同生境和不同年份访花者组成有差异。以上结果一致表明,自交亲和的广西秋海棠依赖传粉者进行有性繁殖,但并不依赖某种特殊类型传粉者,而是具有较泛化的传粉系统,因此在非自然生境中也能成功进行有性繁殖。     

侧穗凤仙花的传粉生态和繁育系统

通过对峨眉山特有种侧穗凤仙花的开花生物学特性、花器官结构、传粉者种类和访花行为、繁育系统、花粉胚珠比(P/O)及花粉活力的研究.发现居群之间花的寿命变化比较大,它们的雄蕊期长,雌/雄蕊期比为0.12～0.17;花粉胚珠比达到4.6万,花粉在开花第一天有很高的活力(＞90%);传粉者为熊蜂和天蛾,熊蜂包括贞洁熊蜂、白背熊...     

山地五月茶的蝇类传粉研究

观测了山地五月茶Antidesma montanum的开花物候、开花动态、访花者种类和访花行为,并对其繁育系统、花粉组织化学、花粉胚珠比（P／O）、花粉活力进行了检测。结果表明：山地五月茶是雌雄异株植物;其总状花序花期可长达7天;雄花／雌花花序数目为140．33±27．79／208．33±33．65（n=6）,雌雄花的颜色为很淡的黄绿色小型花;雄花单花花期为2天,花药开裂当天有活力,花粉为非淀粉型,花粉胚珠比为3333．33±607．18;单花花蜜量可达0．34±0．03μL,花蜜含糖量3．69％±0．30％。花的结构和开花式样适合蝇类传粉。芳香的气味是吸引蝇类的直接物质：花蜜是传粉者的报酬。主要的传粉昆虫为双翅目Diptera丽蝇科Calliphoridae的Chrysomya megacephala、Chrysomyasp．、寄蝇科Tachinidae的Drino sp．和蝇科Muscidae的Spilogona sp．、Mitroplatia sp．。套网不授粉的处理不结实,表明山地五月茶不存在无融合生殖,人工辅助授粉的坐果率（39．1％）略高于自然坐果率（36．7％）,二者无显著差异,表明其坐果率主要受自身资源分配限制。还讨论了蝇类传粉与雌雄异株性系统以及蝇类传粉与热带林中小型黄绿色花植物的相关性。     

侧柏和北美香柏（柏科）的传粉机制

观察了侧柏和北美香柏散粉后花粉进入珠孔的过程。在散粉期,这两种植物的胚珠均分泌出传粉滴。当花粉落于传粉滴上后,引起传粉滴表面的形状发生改变或减弱胚珠的继续分泌,使得该传粉滴药膳加快,导致其比未授粉的传粉滴明显收缩。观察结果表明;不同植物的花粉导致侧柏传粉滴的收缩速度不尽相同,其中,与侧柏亲缘关系较近的植物花粉引起传粉滴的收缩速率和侧柏自身花粉引起的传粉滴收空速率相似;反之,收缩速率变慢。侧柏传粉滴     

同域分布柽柳属两种植物的传粉生物学研究

以同域分布于新疆南部的早春开花植物短穗柽柳(Tamarix laxa Willd)和紫杆柽柳(T.androssowii Litw)为材料,对它们的开花式样、花部特征、花报酬特点、传粉特性及交配方式进行比较研究。结果表明,2种植物居群和个体水平的花期及单花寿命间存在显著差异;紫杆柽柳的居群花期比短穗柽柳短,而短穗柽柳个体花期和单花寿命比紫杆柽柳长。2种柽柳的花瓣、雌雄蕊长度、花粉胚珠数及花粉/胚珠比值(P/O)间也存在显著差异。二者的花瓣、雌雄蕊均能分泌香味,访花频率与花蜜量均存在正相关。主要传粉者在短穗柽柳上的访花频率和沉积花粉效率高于紫杆柽柳,且存在显著差异。2种植物通过自花和异花授粉均可结实,属于混合交配系统;二者的自交不亲和指数及花粉限制程度间存在显著差异;紫杆柽柳的自交亲和性高于短穗柽柳,而短穗柽柳的花粉限制指数高于紫杆柽柳。因此,2种柽柳的开花式样、花部特征及花报酬的差异,是它们在传粉者受限的早春环境中为吸引更多的访花昆虫、提高雌性繁殖率所形成的繁殖对策。     

Pollination effectiveness and pollen dispersal in a Rhododendron ferrugineum (Ericaceae) population

Many alpine plants are predominantly outcrossing, thus plant reproductive success is highly dependent on effectiveness of pollinators. How pollinators transfer pollen from one flower to another is of great interest in understanding the genetic structure in plant populations. We studied (1) the role and effectiveness of insect visitors for pollination, and (2) their contribution as pollen vectors for gene dispersal in a Rhododendron ferrugineum population. Various insect visitors were recorded, including Hymenoptera, Diptera, Coleoptera, and Lepidoptera. The most frequent and effective insects were honey bees and bumblebees. Muscid flies were considered as important pollinators, particularly due to their relatively high visitation rate. Syrphid flies, Formicidae, and Coleoptera were ineffective in transporting pollen, while the effectiveness of Lepidoptera and Empididae was negligible. A fluorescence labelling experiment revealed that pollen dispersal was restricted (0 - 2 m) in a dense R. ferrugineum stand and decreased in a leptokurtic fashion. This might lead to geitonogamous self-pollination that could explain the close relationship between individuals found in genetic studies of R. ferrugineum. However, some pollen grains may travel 40 - 45 m, which implies the occurrence of cross-pollination through the foraging activities of bumblebees and honey bees.     

Feeding friend and foe: ample pollen mitigates the effects of pollen theft for a gynodioecious plant,Polemonium foliosissimum (Polemoniaceae)

Background and AimsMost angiosperms rely on pollinators to transport pollen and effect fertilization. While some floral visitors are effective pollinators, others act as thieves, consuming pollen but effecting little pollination in return. The importance of pollen theft in male and female reproductive success has received little attention. Here, we examined if pollen consumption by flies altered pollen receipt and exacerbated pollen limitation for a bumblebee-pollinated plant, Polemonium foliosissimum (Polemoniaceae).MethodsTo examine the effect of pollen-thieving flies, we took a three-pronged approach. First, we used single-visit observations to quantify pollen removal and pollen deposition by flies and bumblebees. Second, we manipulated pollen in the neighbourhood around focal plants in two years to test whether pollen reduction reduced pollen receipt. Third, we combined pollen reduction with hand-pollination to test whether pollen thieving exacerbated pollen limitation. Polemonium foliosissimum is gynodioecious in most populations in the Elk Mountains of central Colorado, USA. Thus, we also tested whether pollen theft affected hermaphrodites and females differently.ResultsFlies removed significantly more pollen and deposited less pollen per visit than did bumblebees. Reduction of pollen in the neighbourhood around focal plants reduced pollen receipt in both years but only nearly significantly so in 2015. In 2016, plants were significantly pollen-limited; hand-pollination significantly increased seeds per fruit for both hermaphrodites and females. However, the reduction of pollen around focal plants did not exacerbate pollen limitation for either hermaphrodites or females.ConclusionsOur results suggest that plants tolerate significant consumption of pollen by thieves and pollinators by producing ample pollen to feed both and fertilize available ovules. Our results demonstrate that pollen limitation in P. foliosissimum is driven by lack of effective pollinators rather than lack of pollen. Teasing out these effects elucidates the relative importance of drivers of reproductive success and thus the expected response to selection by different floral visitors.     

Diurnal and nocturnal pollination of Silene alba (Caryophyllaceae)

Flowers that are open for >12 h may be visited by both diurnal and nocturnal pollinators. I compared the effectiveness (measured as seed production and pollen movement distance) of diurnal and nocturnal pollinators of Silene alba, a species whose flowers open in evening but close by midmorning the following day. By bagging flowers either during evening hours or during daylight hours or both day and night, I compared seed production caused by diurnal and nocturnal pollinators. Flowers exposed only to nocturnal visitors (mostly sphingid and noctuid moths) produced significantly more seeds than flowers exposed only to diurnal visitors (bees, flies, and wasps). Fluorescent dye applied to anthers moved significantly further and to more stigmas at night than during the day. In both measures of pollination effectiveness, nocturnal-visiting moths are better pollinators of S. alba than are the diurnal-visiting bees, flies, and wasps. These data support the hypothesis that floral phenology is an adaptation to expose flowers to the most effective pollinators.     

Are empidine dance flies major flower visitors in alpine environments? A case study in the Alps,France

Pollination is one of the most important ecosystem services and bees the most important pollinators. As a population decline of bees has been documented in numerous regions of the world, it is crucial to develop understanding on other possible pollinators. Here, we study the potential pollination impact of Diptera, and among them Empidinae, in an alpine environment, where the abundance of bees is naturally lower. Interactions between 19 entomophilous plants and their flower visitors were recorded in a subalpine meadow in the French Alps during six weeks. Visitation frequencies were used to build the flower–visitor network. Our results show that interactions between flies and plants are dominant; flies represent more than 60% of all visitors, with 54% of them being Empidinae. We especially found that flies, Empidinae and bees are the main visitors of 11, three and one plants, respectively. When considering both bees and Syrphidae together, six plants were more visited by Empidinae; when considering bees and Syrphidae separately, 10 plants were more visited by Empidinae than by bees or Syrphidae. The results support the idea that flies widely replace bees as main flower visitors at altitude, and among them the Empidinae might play a key role in pollination.     

The pollination of the gynomonoecious Bdallophytum oxylepis (Cytinaceae,Malvales)

Bdallophytum oxylepis is a rare and endemic species belonging to the Cytinaceae family, a root holoparasitic plant in which most resources are allocated to attracting pollinators. This species is gynomonoecious with intraindividual variation in flower size and sex. Moreover, the flowers exhibit sapromyophilous traits, as do other species of Bdallophytum. Firstly, this study aimed to determine whether all floral morphs can form seeds and be pollen donors (in the case of bisexual flowers). Secondly, as this species has floral traits hypothesized to adapt to particular types of pollen vectors (carrion flies), we also studied the pollination of B. oxylepis to confirm whether the syndromes correspond to what occurs in nature. Through pollination treatments, we determined that all floral morphs are functional. By monitoring the inflorescences, we found that pollination is specialized in the studied population. Stingless bees performed pollination, as they have a high visitation rate, frequency, and constancy, and they are unique visitors that deposit pollen on the stigmas. Thus, they appear to be effective pollinators rather than carrion flies, as predicted by the syndrome. As shown here, animal–plant interaction studies can help establish a basis for conserving rare species such as holoparasites. Moreover, knowledge about the reproductive aspects of B. oxylepis reveals essential clues about its life cycle and role in maintaining native pollinators with economic and cultural value, such as stingless bees.     

Foraging behavior affects pollen removal and deposition in Impatiens capensis (Balsaminaceae)

Flowers of most plant species are visited by a variety of animals. Some of these visitors are effective pollinators while others remove resources without transferring pollen. Studies comparing the effectiveness of different visitors as pollinators often compare taxa without considering variation in behavior within a taxon. Wilson and Thomson (Ecology 72: 1503-1507, 1991) documented the effects of honey bees and bumble bees on the pollination dynamics of Impatiens capensis. They found that pollen-collecting honey bees removed large numbers of pollen grains from anthers but deposited little of it on stigmas; bumble bees, which sought nectar, removed less pollen but deposited more of it on stigmas. It is unclear whether the low pollen transfer efficiencies of honey bees are explained by their morphology or by their pollen-collecting behavior. We repeated the work of Wilson and Thomson at a site where honey bees were foraging for nectar, not pollen. We measured the quantity of pollen remaining in anthers, the number of pollen grains deposited on stigmas, and seed production after single visits by honey bees and bumble bees. The differences between the taxa disappeared when they were foraging in a similar manner. Our results clearly demonstrate the importance of foraging behavior on the pollination effectiveness of floral visitors.     

Flower biology of the cactus Coryphantha elephantidens in the tropical dry forest of Central Mexico

Floral traits and sexual systems in angiosperms are strategies that enhance outcrossing within hermaphrodite flowers and among individuals in a population. Sexual systems with unisexual flowers have also evolved among angiosperms, resulting in sex specialization. Furthermore, the interaction of floral traits and floral visitors determines successful plant reproduction. Globose cacti are bee pollinated, and variation in the diversity of their pollinator assemblages is strongly associated with floral phenotype. Our objective was to describe the floral biology of the cactus Coryphantha elephantidens and to determine its relationship with pollinators. Floral traits were studied by direct observations in live and fixed flowers. The breeding system was determined using two estimators based on floral morphology: pollen grains to ovules per flower (P/O) ratio and outcrossing index. Pollination treatments were conducted to determine the mating system. Floral visitors were recorded using direct observation. Flowers of C. elephantidens are variable in color, protandric, herkogamous and nectarless. Estimators of the breeding system indicated xenogamy, which is consistent with the obligate outcrossing revealed by the pollination experiment. Thirty-seven percent of the plants have female flowers that do not produce pollen, making this population functionally gynodioecious. Both fruit and seed set were high compared to other globose cacti. Pollinators included eight species of native bees, a more diverse pollinator assemblage than other globose cacti. Given the high pressure on pollen due to functional gynodioecy, nectarless flowers, an outcrossing mating system, and the necessity of pollinators to set seeds, we concluded that native bees are highly efficient pollinators that play a crucial role in the sexual reproduction of C. elephantidens.     

Floral variation in the generalist perennial herb Paeonia broteroi (Paeoniaceae): differences between regions with different pollinators and herbivores

This paper investigates the differences in floral phenotype in Paeonia broteroi (Paeoniaceae) in four populations at two distant mountainous regions in southern Spain. Paeonia broteroi flowers exhibit traits of a highly generalized pollination system, but previous studies have revealed that not all flower visitors are effective at pollen delivery. Plants differed between regions in the number of flowers per plant, petal size, number of stamens per flower, and ovules per carpel. Differences between regions could not be attributable to differences in the size structure of the plants. Flower visitors in the two regions differed in assemblage and body size at all the spatiotemporal scales. Larger visitors were more effective as pollinators in the region with the largest and more rewarding (as measured by the number of stamens) flowers, suggesting that pollinators may create opportunities for selection of certain floral traits. In contrast, the two regions did not differ in the probability of damage by herbivores, which did not select flowers based on any of the measured traits, nor affected maternal fecundity. Despite the differences in flower phenotype, potential maternal fecundity, and pollinator effectiveness, plants did not differ between regions in seed production. The role of pollinators as determinants of the differences between regions in floral phenotype, through male and female reproductive success, is discussed. Also, alternative explanations to divergence are addressed, with special reference to the patterns of resource allocation between sexual functions and genetic drift.     

Secondary pollen presentation: More than to increase pollen transfer precision

Pollination precision and efficiency have been deemed to be important driving forces in floral evolution. Herkogamy reduction is a main mechanism to increase pollination precision. Secondary pollen presentation (SPP), by which pollen is presented on other floral organs especially pistils, has been widely accepted as a special mechanism to increase pollen transfer precision through spatial reduction of the anther–stigma distance, that is, minimized herkogamy. This overlooks a potential driving force, that is expanding the pollination niche through converting pollen thieves and nectar robbers into effective pollinators. We selected two species as study models with typical pistillate SPP, Pavetta hongkongensis Bremek. (Rubiaceae) and Scaevola taccada (Gaertn.) Roxb. (Goodeniaceae). In both species, two distinct pollinator functional groups were recognized. Short-tongued bees and flies fed on pollen on stigmas but also stole pollen from anthers and robbed nectar, whereas long-tongued hawkmoths and butterflies only collected nectar. Emasculation had no influence on long-tongued pollinators, but significantly decreased the visitation frequency of short-tongued visitors and fruit set, compared to intact flowers, demonstrating short-tongued visitors did not effectively pollinate and acted merely as pollen thieves or nectar robbers when SPP was absent. Data from the two plant species clearly indicated pistillate SPP has additional adaptive advantages of converting ineffective visitors into pollinators and consequently widening the pollination niche, which could help plants overcome environmental stochasticity. Our results suggest that multiple selective forces drive the evolution of SPP and the minimization of herkogamy.     

The Effects of Inflorescence Size and Flower Position on Biomass and Temporal Sex Allocation in <Emphasis Type="Italic">Lobelia sessiliflora</Emphasis>

To test the prediction of sex allocation theory that plants or flowers high in resource status emphasize the female function, we explored the variation in both biomass (the number of pollen grains and ovules) and temporal (male and female durations) sex allocation among and within plants of protandrous Lobelia sessilifolia in relation to plant size and flower position within plants. Among plants, the mean number of pollen grains and ovules per flower of a plant increased with plant size, whereas the mean P/O ratio (number of pollen grains/number of ovules ratio) decreased with plant size. The mean male duration, the mean female duration, and the mean ratio of male duration/flower longevity per flower of a plant were not correlated with plant size. Thus, large plants emphasized female function in terms of biomass sex allocation, which is consistent with the prediction of size-dependent sex allocation theory. The results for temporal sex allocation, however were inconsistent with the theory. Within plants, the mean number of pollen grains and ovules per flower at each position decreased from lower to upper flowers (early to late blooming flowers) and that of the P/O ratio increased from lower to upper flowers. The mean male duration and the mean female duration per flower decreased from lower to upper flowers, whereas the mean ratio of male duration/flower longevity increased from lower to upper flowers. The population sex ratio changed from male-biased to female-biased. Thus, later blooming flowers emphasized the male function in terms of both biomass and temporal sex allocation, consistent with the sex allocation theory, regarding the change in the population sex ratio.