Comparison of floral scent between and within Buddleja fallowiana and Buddleja officinalis (Scrophulariaceae)

Floral scents are important olfactory signals for communication between plants and pollinators. Several studies have focused on inter-specific variation of floral scents, but little is known about the intra-specific variation, especially in some polychromic species. In this study, we investigated the floral scent compositions of Buddleja fallowiana and Buddleja officinalis in situ by dynamic headspace collection and coupled GC–MS. Variations of scent compositions within and between populations as well as among species were compared. In spite of substantial intra- and inter-population variability, B. fallowiana and B. officinalis were clearly differentiated in their scent profiles. In B. fallowiana, obvious differentiation was found between studied populations, while all investigated populations in B. officinalis are part of a metapopulation. These high intra-specific variations are discussed in relation to the introgression through hybridization and founder effects from different populations.     

Ploidy differentiation and floral scent divergence in Buddleja macrostachya (Scrophulariaceae) complex

Floral scent has been suggested to be a key factor both in the diversification of the angiosperms, and the evolution and intra-specific differentiation of plants. In this study, we determined the ploidy and nuclear DNA content of B. macrostachya plants from 14 different populations across Yunnan using flow cytometry. The components of the floral scent were also identified using gas chromatography and mass spectrometry (GC-MS). Within these 14 populations, two new ploidy levels, tetraploid (2n = 4x) and octaploid (2n = 8x) were detected and identified for the first time here. The mean 2C DNA content of the tetraploids ranged from 1.81 ± 0.01 to 1.92 ± 0.02 G, but was 3.52 ± 0.15 to 3.73 ± 0.04 G in the octaploids. In addition, thirty-two scent compounds were identified, most of which could be categorized into four major classes: fatty acid derivatives (49.60 ± 7.45%); benzenoids (21.24 ± 3.96%); monoterpenes (25.28 ± 3.70%) and sesquiterpenes (3.88 ± 1.05%). Both tetraploids and octaploids emitted large relative amounts of 4-hydroxy-4-methyl-2-pentanone (42.21 ± 3.52% and 21.57 ± 3.10%, respectively) and benzadehyde (20.42 ± 2.35% and 28.45 ± 2.37%, respectively). Multivariate analysis of floral scent chemistry revealed marked dissimilarity (49.49%) between tetraploids and octaploids, and 4-hydroxy-4-methyl-2-pentanone and benzadehyde contributed greatly to this divergence in chemical scent profile. Our results suggest that B. macrostachya is a species complex with four different ploidy levels (2n = 4x, 6x, 8x, 12x). We believe the complex is in a process of pollinator-mediated rapid divergence.     

Floral scent composition predicts bee pollination system in five butterfly bush (Buddleja,Scrophulariaceae) species

Traditionally, plant–pollinator interactions have been interpreted as pollination syndrome. However, the validity of pollination syndrome has been widely doubted in modern studies of pollination ecology. The pollination ecology of five Asian Buddleja species, B. asiatica, B. crispa, B. forrestii, B. macrostachya and B. myriantha, in the Sino‐Himalayan region in Asia, flowering in different local seasons, with scented inflorescences were investigated during 2011 and 2012. These five species exhibited diverse floral traits, with narrow and long corolla tubes and concealed nectar. According to their floral morphology, larger bees and Lepidoptera were expected to be the major pollinators. However, field observations showed that only larger bees (honeybee/bumblebee) were the primary pollinators, ranging from 77.95% to 97.90% of total visits. In this study, floral scents of each species were also analysed using coupled gas chromatography and mass spectrometry (GC‐MS). Although the five Buddleja species emitted differentiated floral scent compositions, our results showed that floral scents of the five species are dominated by substances that can serve as attractive signals to bees, including species‐specific scent compounds and principal compounds with larger relative amounts. This suggests that floral scent compositions are closely associated with the principal pollinator assemblages in these five species. Therefore, we conclude that floral scent compositions rather than floral morphology traits should be used to interpret plant–pollinator interactions in these Asian Buddleja species.     

异果芥的花部综合征及其繁育系统

异果芥Diptychocarpus strictus是十字花科中为数不多的在同一花序上具有两种不同形态果实的短命植物。对其花部综合征及繁育系统的研究结果表明：（1）具有白色花与紫红色花两种不同花色的植株,且其花色是稳定遗传的。两种植株的比例基本上接近1：1。（2）两种植株花序上、下部发育成不同形态果实的花在形态特征上存在差异,同时不同花色植株的花在形态特征上也存在差异。（3）紫红色和白色花植株花序上、下部花的单花花粉量分别为7589.07±976.64、5428.93±900.45、7044.73±557.37和5138.60±813.48;胚珠数分别为31.83±3.36、25.03±3.72、32.03±3.43和25.70±2.61;P/O值分别为241.31±41.85、222.33±52.51、222.19±27.80和201.84±37.52。花粉败育率很低且两种花色植株花序上、下部花的长、短雄蕊之间的花粉败育率均差异显著（P〈0.05）。同一花中短雄蕊花粉量比长雄蕊的多。（4）两种花色植株花序上、下部花之间的长、短雄蕊每花药花粉数、单花花粉数、胚珠数均存在极显著差异（P〈0.01）,均是上部花比下部花的大。（5）两种植株花中长、短雄蕊花粉活力动态变化曲线相似,花粉寿命与柱头可授期具高度的同步性,其花粉活力最高的时期正是柱头的最佳可授期。（6）P/O值、套袋试验、传粉媒介观察和花粉萌发的荧光显微观察结果表明,该物种是以自交为主、异交为辅,具有兼性自交的繁育系统。     

Comparison of floral traits and pollinator assemblages of insular and mainland varieties of Lilium auratum

Lilium auratum var. platyphyllum, which is endemic to the Izu Islands, has white petals and emits a strong floral scent, typical of moth‐pollinated plants. Moths might be important pollinators within the Izu Islands because swallowtail butterflies are absent or rare there. Therefore, we investigated insular var. platyphyllum and widespread L. auratum var. auratum on the mainland of Japan to clarify the relationship between floral characteristics and pollinators. Measurement of floral scent intensity using an odor sensor indicated that the intensity increased in the evening and at night in var. platyphyllum, whereas intensity increased at night in var. auratum. Total sugar weight in nectar, which was calculated by nectar volume and sugar concentration, showed that the flowers of var. platyphyllum secreted nectar abundantly both in the evening and at night, whereas those of var. auratum secreted an almost constant amount of nectar throughout the day. Flower visitor assemblages and their frequencies studied using digital cameras suggested that crepuscular and nocturnal hawkmoths are important pollinators for var. platyphyllum. In contrast, both diurnal swallowtail butterflies and nocturnal large hawkmoths are important and effective pollinators for var. auratum. These conclusions were also supported by the exclusion experiments of either diurnal or nocturnal flower visitors using mesh bags. The rates of seed sets of var. platyphyllum were significantly higher from nocturnal pollination than from diurnal pollination. Thus, this study revealed that floral traits of var. platyphyllum show more adaptation for crepuscular and nocturnal hawkmoths, which are relatively abundant in the Izu Islands, than those of var. auratum.     

Variation in floral morphology and plant reproductive success in four Ipomoea species (Convolvulaceae) with contrasting breeding systems

• This study tested the hypothesis that self‐compatibility would be associated with floral traits that facilitate autonomous self‐pollination to ensure reproduction under low pollinator visitation. In a comparison of two pairs of Ipomoea species with contrasting breeding systems, we predicted that self‐compatible (SC) species would have smaller, less variable flowers, reduced herkogamy, lower pollinator visitation and higher reproductive success than their self‐incompatible (SI) congeners.
• We studied sympatric species pairs, I. hederacea (SC)– I. mitchellae (SI) and I. purpurea (SC)–I. indica (SI), in Mexico, over two years. We quantified variation in floral traits and nectar production, documented pollinator visitation, and determined natural fruit and seed set. Hand‐pollination and bagging experiments were conducted to determine potential for autonomous self‐pollination and apomixis.
• Self‐compatible Ipomoea species had smaller flowers and lower nectar production than SI species; however, floral variation and integration did not vary according to breeding system. Bees were primary pollinators of all species, but visitation rates were seven times lower in SC than SI species. SC species had a high capacity for autonomous self‐pollination due to reduced herkogamy at the highest anther levels. Self‐compatible species had two to six times higher fruit set than SI species.
• Results generally support the hypothesis that self‐compatibility and autonomous self‐pollination ensure reproduction under low pollinator visitation. However, high variation in morphological traits of SC Ipomoea species suggests they maintain variation through outcrossing. Furthermore, reduced herkogamy was associated with high potential for autonomous self‐pollination, providing a reproductive advantage that possibly underlies transitions to self‐compatibility in Ipomoea.

     

Floral scent emission is the highest at the second night of anthesis in Lonicera japonica (Caprifoliaceae)

Floral color change in diverse plants has been thought to be a visual signal reflecting changes in floral rewards, promoting pollinator foraging efficiency as well as plant reproductive success. It remains unclear whether olfactory signals co-vary with floral color change. We investigated the production rhythms of floral scent and nectar associated with floral color change in Lonicera japonica. The flowers generally last 2–3 days. They are white on opening at night (N1) and become light yellow the following day (D1), yellow on the second night (N2), and golden on the second day of flowering (D2). Our measurements in the four stages indicated that nectar production decreased significantly from N1 and D1 to N2 and D2, tracking the floral color change. A total of 34 compounds were detected in floral scent and total scent emission was significantly higher in N2 than in the other three stages. The scent emission of three major compounds, Linalool, cis-3-Hexenyl tiglate, and Germacrene D was also significantly higher in N2, but the relative content of Linalool decreased gradually, cis-3-Hexenyl tiglate increased gradually, and the relative content of Germacrene D did not differ among the four measured stages. Greater scent emission by night than by day suggested a strong olfactory signal to attract nocturnal hawkmoths, the effective pollinators. However, floral scent rhythms in the four stages did not match the color change and nectar secretion, suggesting that floral color (visual) and scent (olfactory) in this species may play different roles in attracting or filtering various visitors.     

木槿与野西瓜苗花特征和繁育系统的比较研究

为比较分析柱头裂片运动的野西瓜苗和不运动的木槿在花特征和繁育系统上的差异,对其花性状、花粉/胚珠比和不同授粉处理的座果率进行了测定。结果表明:(1)木槿与野西瓜苗在花冠大小、花瓣长及底宽、花萼长与宽、雄蕊长、最上轮雄蕊高度、雄蕊柱长及其底径、花柱长度和雌雄异位间均存在十分显著的差异(P<0.01),但二者的最下轮雄蕊高度间无显著性差异(P>0.05)。(2)木槿的花粉/胚珠比为874.90±20.79,繁育系统属兼性异交类型;野西瓜苗的花粉/胚珠比为24.72±0.68,繁育系统属专性自交类型。(3)木槿自然套袋的座果率为0%,人工自交为2.04%,人工杂交为35.85%;野西瓜苗自动自交和人工自交的座果率均为100%,人工杂交为95.30%。木槿与野西瓜苗在花性状、花粉/胚珠比及花部行为等方面形成了与其繁育系统(兼性异交vs.专性自交)相适应的花特征。     

醉鱼草属四个种的核型分析

报道了醉鱼草属（Btuldleja）4个种的染色体核型。云南醉鱼草（B.yunnanensis）的核型公式为2n=2x=38=22m＋16sm,皱叶醉鱼草（B．crispa）为2n=2x=38=26m＋10sm＋2st,密蒙花（B．officinalis）为2n=2x=38=20m＋16sm＋2st,口本醉鱼草（B．japonica）为2n=2x=38=20m＋16sm＋2st。日本醉鱼草的核型为2B型,其它3个种的核型为2A型。根据核型分析结果,结合形态学特征和已有的细胞学资料,初步讨论了醉鱼草组（Sect．Neemda）两个系（Series）可能的演化关系。     

云锦杜鹃的开花动态与繁育系统研究

对3个云锦杜鹃种群的开花动态和传粉方式等野外定位观测结果显示:花芽在花朵开放后形成雏 形,经过8～9月的生长后成形,次年4月复苏,形成含6～12朵花的总状伞形花序,5月初开花,花期接近25 d。花生命周期为5～8d,其中种群G的周期最短,平均为5.8d,主要原因是光照时间长,湿度相对较低,花形 态较小。开花后第二天到第三天,花药开裂,散出粘连成串的花粉,悬挂在花柱的中上部,同时柱头进入可授 期;第五天到第六天,花瓣与花托分开并前移到花柱,使花柱倒垂,花粉串能粘附到柱头上。根据人工授粉试 验和花粉落置观察的结果,云锦杜鹃的繁育系统为混合交配型,自然条件下为花后自花授粉,主要借助花瓣脱 落来传播花粉;但根据杂交指数估算和花粉-胚珠比测定,云锦杜鹃的繁育系统为异交,自交亲和,需要传粉 者,说明云锦杜鹃可能是由虫媒传粉向自花传粉演化。     

Breeding system features and a novel method for locating floral nectar secretion in a South American nightshade (Jaltomata quipuscoae)

Abstract

The location of nectar secretion in flowers of Jaltomata has not been identified with certainty until now: removal of the corolla and androecium from one side of living flowers allowed us to see, in progress, nectar secretion by the ovarian nectary. We studied Jaltomata quipuscoae, a wild plant that grows in southern Peru and produces copious, red floral nectar. Unmanipulated flowers do not set fruit in a pollinator-free greenhouse, demonstrating lack of autogamy, but self-compatibility was demonstrated by manual self-pollinations leading to fruit-set. Anther dehiscence is staggered with the anthers of a flower dehiscing over hours on the same day. The corolla and nectar are UV-absorptive. Flowers last 4–10 days, are usually protogynous during the first day the corolla is open, and do not close for the night.     

Bumblebee Pollination of Melampyrum ciliare (Scrophulariaceae)

Abstract Melampyrum ciliare has tubular flowers predominantly visited by Bombus diversus. Floral structure (including the positions of anthers and stigma) and structure of the distal part of the corolla indicate cross-pollination by bumblebees. In M. ciliare, young flowers with white spots on the labium, which disappeared with flower aging, produced larger amounts of nectar than older ones without spots. Bumblebees visited flowers with white spots significantly more frequently than would be expected if they chose flowers randomly. These findings and the high seed production of open-pollinated flowers suggest effective pollination of M. ciliare by bumblebees.     

Taxonomy and breeding system in a new species of Scrophularia L. (Scrophulariaceae) from Morocco

A new species of the genus Scrophularia, S. fontqueri Ortega-Olivencia & Devesa, is described for the Western Rif mountains in Morocco. Similarities and differences with the most closely related species (S. auriculata Loefl. ex L. and S. viciosoi Ortega-Olivencia & Devesa) are indicated, and ecological and distribution data are provided. The new species displays a high degree of polyploidy (2n = 56), and has palynological characteristics similar to those of other species in this genus. The new species shows protogynous dichogamy and produces considerable amounts of nectar in both sexual phases. Nectar secretion was maximum during the early hours of the morning. Mean longevity of the flowers was 2.66 days. Both nectar secretion and floral longevity correlated strongly with mean daytime air temperature. Pollination experiments showed that interaction with pollinators is necessary for reproduction, and gametophytic homomorphic self-incompatibility was documented. This feature was confirmed by observation of pollen tubes after hand self-pollination. The seed/ovule ratio was very low.     

Anatomy and ultrastructure of the floral nectary in Peganum harmala L. (Nitrariaceae)

Anatomy and ultrastructure of the floral nectary of Peganum harmala L. were studied using light and transmission electron microscopy. The floral nectary was visible as a glabrous, regularly five‐lobed circular disc encircling the base of the ovary. Anatomically, it comprised a single layered epidermis and 15–20 layers of small, subepidermal secretory cells overlying several layers of large, ground parenchyma cells. The floral nectary was supplied by phloem and both sieve tubes and companion cells were found adjacent to the ground parenchyma. Based on our ultrastructural observations, plastids of secretory cells during the early stages of development were rich in starch grains and/or osmiophilic plastoglobuli, but these disappeared as nectar secretion progressed. The nectar appeared to exude through the modified stomata along symplastic and apoplastic routes. The abundant plastids and mitochondria suggest an eccrine mechanism of nectar secretion in P. harmala.     

Anatomy and ultrastructure of the floral nectary of Tontelea micrantha (Celastraceae: Salacioideae)

Among several native species of the Brazilian cerrado, a shrub, Tontelea micrantha, is exploited by traditional communities for the valuable oil extracted from its seeds, which has anti‐inflammatory properties. There have been no studies on the anatomy of its flower, and so the aim of this study is to describe the anatomy and ultrastructure of its floral nectary. Flower buds and flowers in anthesis were collected, fixed and processed for light and electron microscopy. The discoid floral nectary is composed of epidermis and a secretory parenchyma. Secretory cells are rich in plastids with starch grains and mitochondria. The nectar, sucrose dominant, is just sufficient to form a thin film on the nectary. The secretory cells show starch and oil droplets; however, during nectar production there is no evidence of hydrolysis of starch and some lipid reserves remain unchanged. Our results suggest a reduction in the amount of oil in the secretory cells during the secretory phase but this does not appear to imply a release of oil as a nectar component. In addition to maintaining part of the reserves, the lower frequency of organelles involved in nectar synthesis reinforces the hypothesis that phloem sap is the origin of nectar sugars. The tiny nectar film, released through modified stomata, is attractive to small insects such as flies. Considering the importance and intensity of use of T. micrantha in the Brazilian cerrado, we think that these data about its floral nectary can help to better explain its reproductive biology with positive impacts on its management and conservation.