绣球茜的二型花柱及其传粉生物学初步研究

首次对绣球茜(Dunnia sinensis Tutch)的花药和柱头高度、花粉和柱头形态,以及人工辅助授粉的结实情况等进行了研究.结果表明:绣球茜在同一居群中同时具有长花柱(Pin 型)和短花柱(Thrum)两种花型,长花柱植株的柱头和雄蕊高分别为9.61±0.36 mm和6.79±0.38 mm,短花柱则为6.11±0.56 mm和8.96±0.59 mm,表现出互补式雌雄异位的花部特征.通过人工辅助授粉,两种花型植株的自交和同型植株间异交都不结实,仅在型间异交方能正常结实,说明绣球茜中存在极强的自交不亲和和型内不亲和现象.在花粉与柱头形态方面:长柱型花的单花花粉量(38555.6±6258.4)显著地小于短柱型花(52145.45±8924.5)(t=4.009,P＜0.01),长柱花和短柱型花的胚珠数分别为38.73±1.85和39.1±2.25(t=-4.13,P＞0.01);长柱型花花粉粒的大小(极径21.27±0.70 μm)显著地小于短柱花(21.92±0.79μm)类型(t=3.890,P＜0.01),而柱头乳突大小长柱类型要大于短柱类型,表现出明显的二型性.研究结果表明绣球茜是一种典型的二型花柱植物.此外,对其传粉昆虫及昆虫访花行为的观察表明,蝶类(青风蝶属Graphium)和蜂类(熊蜂Bombus sp.和木蜂Xylocopa magnifica Smith)为绣球茜的主要访花昆虫和传粉昆虫,它们能够在两种不同花型植株之间有效地传粉.     

Floral biology,reciprocal herkogamy and breeding system in four Psychotria species (Rubiaceae) in Brazil

Distylous species have two floral morphs with reciprocal positions of sexual whorls, functioning to promote cross‐pollination. Additionally, most distylous species have an incompatibility system linked to the discrete variation of anthers and stigmas. Here we provide new data on heterostyly, reproductive biology and pollination in four Psychotria spp. from the Cerrado Region (Brazil). Psychotria deflexa, P. nitidula and P. trichophoroides fitted the distylous morphological syndrome, whereas P. prunifolia was monomorphic and self‐compatible. Reciprocity varied across species, with the upper whorl of anthers and stigmas being more reciprocal than the lower whorl. Psychotria nitidula has a heteromorphic incompatibility system, whereas P. deflexa and P. trichophoroides showed partial self‐compatibility. Psychotria prunifolia and P. trichophoroides were visited by large bees and exhibited lower reproductive efficacy than P. nitidula and P. deflexa, which are visited by wasps and small bees. Our results provide new evidence that the morphological distylous syndrome does not always co‐occur with heteromorphic incompatibility and additional mechanisms (e.g. disassortative pollen transfer) may operate to maintain the polymorphism and isoplethy of species with different incompatibility system.     

Floral morphology and reproductive biology of Dendrobium jiajiangense (Orchidaceae) in Mt. Fotang,southwestern China

The relationships between floral morphology and the particular pollinator, flower shelter function and reproductive success as well as details of the breeding system of Dendrobium jiajiangense were investigated at Fotang Mountains in Jiajiang County, Sichuan Province, China. D. jiajiangense is pollinator-specific, being pollinated by Andrena parvula. There exists considerable mechanical fit between the floral morphology of D. jiajiangense and A. parvula. Importantly, A. parvula uses D. jiajiangense flowers as shelter both during rainy weather and at night during sunny weather. This significantly increase the pollination success of D. jiajiangens. D. jiajiangense is self-compatible but pollinator-dependent for fruit set. Fruit set of D. jiajiangens was 100% after hand-self-pollination, but seed viability was normally greatly reduced.     

关苍术花部综合特征与繁育系统的研究

采用定点观察,运用杂交指数估算、花粉/胚珠比(P/O)测定、套袋授粉等方法,对关苍术的花部综合特征及繁育系统进行研究。结果表明:种群花期为7月下旬至9月初,单花序花期为12~17 d,小花日开放高峰期为早上7:00~8:00;花粉活力最高(90%以上)在开花后2 h以内,而此时其柱头尚无可授性,柱头在花开48~72 h以内具有较强可授性;花粉/胚珠比为6 690,杂交指数为5,繁育系统为专性异交,优势访花者为蜂类和蝇类;套袋和授粉实验结果表明关苍术不存在无融合生殖现象,自交和同株异花结实率很低,其繁育系统以异交为主。通过关苍术花部综合特征和繁育系统的研究,进一步了解其生物学特性,为关苍术资源保护和人工培育提供了理论基础。     

Cryptic self‐incompatibility and distyly in Hedyotis acutangula Champ. (Rubiaceae)

Distyly, floral polymorphism frequently associated with reciprocal herkogamy, self‐ and intramorph incompatibility and secondary dimorphism, constitutes an important sexual system in the Rubiaceae. Here we report an unusual kind of distyly associated with self‐ and/or intramorph compatibility in a perennial herb, Hedyotis acutangula. Floral morphology, ancillary dimorphisms and compatibility of the two morphs were studied. H. acutangula did not exhibit precise reciprocal herkogamy, but this did not affect the equality of floral morphs in the population, as usually found in distylous plants. Both pin and thrum pollen retained relatively high viability for 8 h. The pollen to ovule ratio was 72.5 in pin flowers and 54.4 in thrum flowers. Pistils of pin flowers remained receptive for longer than those of thrum flowers. No apparent difference in the germination rate of pin and thrum pollen grains was observed when cultured in vitro, although growth of thrum pollen tubes was much faster than that of pin pollen tubes. Artificial pollination revealed that pollen tube growth in legitimate intermorph crosses was faster than in either intramorph crosses or self‐pollination, suggesting the occurrence of cryptic self‐incompatibility in this species. Cryptic self‐incompatibility functioned differently in the two morphs, with pollen tube growth rates after legitimate and illegitimate pollination much more highly differentiated in pin flowers than in thrum flowers. No fruit was produced in emasculated netted flowers, suggesting the absence of apomixis. Our results indicate that H. acutangula is distylous, with a cryptic self‐incompatibility breeding system.     

短葶飞蓬（Erigeron breviscapus）的花部综合特征与繁育系统

通过野外观察,运用杂交指数、花粉-胚珠比、套袋实验等方法,对短葶飞蓬自然种群的开花状态及繁育系统进行研究。结果如下：短葶飞蓬具头状花序,由外围舌状花及中央的管状花构成。种群花期一般为4~7月份,一个花序的花期约为19~25d。管状花单花花期一般为7~10d,聚药雄蕊,先熟,药室内向开裂,成熟的花粉散于花药筒中。花开后花柱快速伸长,导致雄蕊伸出花冠,同时将药筒中的花粉粒“推”出药筒,形成花冠、药筒、柱头三者在空间上的分离。花序中不断有小花开放,同一花序内的小花间具相互传粉的机会。杂交指数≥4,判断繁育类型属于异交,部分自亲和,需要传粉者。P/O值约为1373,判断繁育类型属于兼性异交。套袋实验证明短葶飞蓬异花授粉,虫媒,蜂、蝶为主要传粉者。在自然状况下,短葶飞蓬结实率较低的原因可能是花粉竞争。此外,短葶飞蓬存在天然雄性不育植株,为遗传育种提供了材料。     

Night and day service: Distyly and mixed pollination system in Faramea cyanea (Rubiaceae)

Currently, pollination is seen as involving more generalist interactions than specialized ones. Supporting this trend, some nocturnal distylous flowers may also receive floral visitors during the day, and since the latter contribute to fruit set, the pollination system is mixed and less specialized. Common among the Rubiaceae, distyly has been regarded as a reproductive strategy which requires a precise and specialized pollination system, and in this important tropical family, environmental disturbance and pollination failure have been used to explain anomalies in distylous features. Faramea cyanea Müll. Arg. is a common tree species in forest formations in the increasingly threatened Cerrado biome, the Neotropical savannas in Central Brazil. We evaluated the floral morphology, pollination biology and breeding system of a population of F. cyanea. Despite their moth pollination features, flowers were visited by diurnal (bees) as well as nocturnal (moths) pollinators. Experimental results showed that both pollinator groups contributed equally to pollen flow and legitimate pollination. The population presented distyly, isoplethy and heteromorphic self-incompatibility. Although F. cyanea did not present exact reciprocal herkogamy between floral morphs, pollination and reproductive success were not impaired. Floral features, which allowed pollination by complementary groups of pollinators, may explain the absence of anomalies in the isoplethy and distylous features in the studied population, anomalies which have been observed in other sympatric distylous Rubiaceae.     

Flower-visiting bees and the breakdown of the tristylous breeding system of Eichhornia azurea (Swartz) Kunth (Pontederiaceae)

Populations of Eichhornia azurea (Swartz) Kunth (Pontederiaceae) are often composed of three floral morphs that differ in style length and anther position. Hence, E. azurea is described as tristylous. For sexual reproduction the plant requires specialized pollinators able to transfer pollen from flowers with long-, mid-, or short-level anthers to flowers with long-, mid-, or short-styles, respectively. This is because within a floral morph, self-incompatibility is the rule. Populations of E. azurea were studied from six localities in south-eastern Brazil (São Paulo and Minas Gerais). The frequencies of floral morphs, floral morphology and flower-visiting bees were recorded in each population. Ten different bee species were observed visiting plants. Four of them were considered generalist bees and not appropriate for legitimate pollination of the three floral morphs. Another three species were considered opportunists and only three species were considered to be potential pollinators. At the coastal region (Juréia), the plant population lacked the short-styled morph and the mid-styled morph and exhibited a semi-homostylous condition, in which the low-level anthers were adjacent to the stigma. This morph showed high level of self-compatibility. The disappearance of the short-styled morph from this region is likely correlated with the absence of Ancyloscelis gigas Friese, a specialized long-tongued bee that is oligolectic on this plant in other localities.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 77 , 499–507.     

Patterns of Floral Variation between Dimorphic and Monomorphic Populations in Distylous Luculia pinceana (Rubiaceae)

Flower morphology plays an important role in the evolution and maintenance of plant mating systems, including disassortative mating of heterostylous species. The transition of mating patterns may be associated with the remodification of intraspecific flower morphology. To determine the functional relationship between floral variation and transition of mating patterns, we conducted a series of morphometric analyses in a distylous species Luculia pinceana, which possesses dimorphic and monomorphic populations. Our results indicate that floral variation was higher between different types of populations than between populations of the same type. Compared to dimorphic populations, some floral characters, reduced stigma anther separation within flowers and increased overlap of stigmas and anthers (illegitimate spatial matching of sexual organs) among individuals in populations containing only the long styled morph may have been modified to increase both selfing and intra morph crossing. The observed patterns of floral variation between dimorphic and monomorphic populations coincide with the transition of mating patterns from disassortative mating to selfing and/or intra morph crossing.     

短葶飞蓬(Erigeron breviscapus)的花部综合特征与繁育系统

通过野外观察,运用杂交指数、花粉．胚珠比、套袋实验等方法,对短葶飞蓬自然种群的开花状态及繁育系统进行研究。结果如下：短葶飞蓬具头状花序,由外围舌状花及中央的管状花构成。种群花期一般为4～7月份,一个花序的花期约为19～25d。管状花单花花期一般为7～10d,聚药雄蕊,先熟,药室内向开裂,成熟的花粉散于花药筒中。花开后花柱快速伸长,导致雄蕊伸出花冠,同时将药筒中的花粉粒“推”出药筒,形成花冠、药筒、柱头三者在空间上的分离。花序中不断有小花开放,同一花序内的小花间具相互传粉的机会。杂交指数≥4,判断繁育类型属于异交,部分自亲和,需要传粉者。P／O值约为1373,判断繁育类型属于兼性异交。套袋实验证明短葶飞蓬异花授粉,虫媒,蜂、蝶为主要传粉者。在自然状况下,短葶飞蓬结实率较低的原因可能是花粉竞争。此外,短葶飞蓬存在天然雄性不育植株,为遗传育种提供了材料。     

Floral features,pollination biology and breeding system of Chloraea membranacea Lindl. (Orchidaceae: Chloraeinae)

Background and Aims

The pollination biology of very few Chloraeinae orchids has been studied to date, and most of these studies have focused on breeding systems and fruiting success. Chloraea membranacea Lindl. is one of the few non-Andean species in this group, and the aim of the present contribution is to elucidate the pollination biology, functional floral morphology and breeding system in native populations of this species from Argentina (Buenos Aires) and Brazil (Rio Grande do Sul State).

Methods

Floral features were examined using light microscopy, and scanning and transmission electron microscopy. The breeding system was studied by means of controlled pollinations applied to plants, either bagged in the field or cultivated in a glasshouse. Pollination observations were made on natural populations, and pollinator behaviour was recorded by means of photography and video.

Key Results

Both Argentinean and Brazilian plants were very consistent regarding all studied features. Flowers are nectarless but scented and anatomical analysis indicates that the dark, clavate projections on the adaxial labellar surface are osmophores (scent-producing glands). The plants are self-compatible but pollinator-dependent. The fruit-set obtained through cross-pollination and manual self-pollination was almost identical. The main pollinators are male and female Halictidae bees that withdraw the pollinarium when leaving the flower. Remarkably, the bees tend to visit more than one flower per inflorescence, thus promoting self-pollination (geitonogamy). Fruiting success in Brazilian plants reached 60·78 % in 2010 and 46 % in 2011. Some pollinarium-laden female bees were observed transferring pollen from the carried pollinarium to their hind legs. The use of pollen by pollinators is a rare record for Orchidaceae in general.

Conclusions

Chloraea membrancea is pollinated by deceit. Together, self-compatibility, pollinarium texture, pollinator abundance and behaviour may account for the observed high fruiting success. It is suggested that a reappraisal and re-analysis of important flower features in Chloraeinae orchids is necessary.     

Chemical variability of the invasive neophytes Polygonum cuspidatum Sieb. and Zucc. and Polygonum sachalinensis F. Schmidt ex Maxim

Crude extracts of roots and stems of Polygonum cuspidatum Sieb. and Zucc. and Polygonum sachalinensis F. Schmidt ex Maxim from China and Switzerland were analyzed by online HPLC/UV/ESI-MS to ascertain the phytochemical differences between the original and invasive exotic varieties. A total of 36 constituents were identified by comparing their retention times, UV data, mass spectra with those of standards or with literature data. Certain constituents, such as flavanol gallate dimers, were reported for the first time from these species.     

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。     

Distyly and incompatibility in Psychotria homalosperma (Rubiaceae), an endemic plant of the oceanic Bonin (Ogasawara) Islands

Distyly rarely occurs on oceanic islands. Indeed, this form of polymorphism is absent on the Hawaiian Islands and in New Zealand. However, Psychotria homalosperma (Rubiaceae), which is endemic to the oceanic Bonin Islands of Japan, was presumed to maintain a distylous breeding system and floral morphology. We investigated the floral and reproductive characteristics of this species and examined incompatibility in self- and intramorph pollination. Psychotria homalosperma is morphologically and functionally distylous, based on findings with the examined populations, but its stigma and anther heights are not exactly reciprocal between the two morphs. This is the second example of distyly among the flora from the Bonin Islands, the other being the endemic P. boninensis. Both of these distylous species contrast with the Hawaiian Psychotria species, which have already become dioecious. The flowers of the long (L)-styled (pin) morph of the Bonin Islands plants are completely self- and intramorph incompatible, while the flowers of the short (S)-styled (thrum) morphs are partially intramorph compatible. The S-styled morph was more abundant in the examined populations from three islands of the archipelago, probably due to the existence of partial S–S intramorph compatibility.     

Pollination and breeding system of Melochia tomentosa L. (Malvaceae), a keystone floral resource in the Brazilian Caatinga

The main goals of the present paper were to investigate the floral biology and the breeding system of Melochia tomentosa in a semi-arid region in Brazil, comparing the role of Apis mellifera with other native pollinators, and to discuss the importance of this plant species as a floral resource for the local fauna in maintaining different guilds of specialized pollinators in the Caatinga. M. tomentosa is very common in Caatinga areas and blooms year-round with two flowering peaks, one in the wet and another in the dry period. The pink, bright-colored flowers are distylous and both morphs are homogamous. The trichomatic nectary is located on the inner surface of the connate sepals, and the nectar (ca. 7 μl) is accumulated in the space between the corolla and the calyx. Nectar sugar concentration reaches an average of 28%. The results of controlled pollination experiments show that M. tomentosa is self-incompatible. Pollen viability varies from 94% to 98%. In spite of being visited by several pollen vectors, flower attributes of M. tomentosa point to melittophily, and A. mellifera was the most frequent visitor and the principal pollinator. Although honeybees are exotic, severely competing with native pollinators, they are important together with other native bees, like Centris and Xylocopa species, for the fruit set of M. tomentosa. This species represents a keystone floral resource favoring the maintenance of many species of bees, butterflies and hummingbirds through the year in this deciduous tropical dry forest.     

Floral nectary morphology and evolution in Pedicularis (Orobanchaceae)

Intricate associations between floral morphology and pollinator foraging behaviour are common. In this context, the presence and form of floral nectaries can play a crucial role in driving floral evolution and diversity in flowering plants. However, the reconstruction of the ancestral state of nectary form is often hampered by a lack of anatomical studies and well‐resolved phylogenetic trees. Here, we studied 39 differentially pollinated Pedicularis spp., a genus with pronounced interspecific variation in colour, shape and size of the corolla. Anatomical and scanning electron microscopy observations revealed two nectary forms [bulged (N = 27) or elongated (N = 5)] or the absence of nectaries (N = 7). In a phylogenetic context, our data suggest that: (1) the bulged nectary should be the ancestral state; (2) nectaries were independently lost in some beaked species; and (3) elongated nectaries evolved independently in some clades of beakless species. Phylogenetic path analysis showed that nectary presence is indirectly correlated with beak length/pollinator behaviour through an intermediate factor, nectar production. No significant correlation was found between nectary type and nectar production, beak length or pollinator behaviour. Some beaked species had nectary structures, although they did not produce nectar. The nectary in beaked species may be a vestigial structure retained during a recent rapid radiation of Pedicularis, especially in the Himalaya–Hengduan Mountains of south‐western China. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 592–607.     

Chromosomal translocations in the evolution of Amorphophallus bonaccordensis from A. hohenackeri

In present study we have made an attempt to trace possible lines in the evolution of A. bonaccordensis separating from A. hohenackeri, where translocations at the chromosomal level could have resulted in a shift of the habitat during evolution of A. bonaccordensis. This species is occurring as an endemic taxon at a higher altitude than it may have been the case with its ancestor that occupied lower altitudes and possibly a broader ecological niche. Morphological and physiological differences between the recent two closely related taxa, in spadix and appendix characters, corm flesh colour, pollen morphology and oxalate content, may be attributed also to the translocation at the cytological level. Detailed karyotype studies have been done in these Amorphophallus species from Southern Western Ghats, where they are critically endangered in their habitats, indicating that the chromosome number in both species is 2n = 26. In both of them there is a considerable variation in the karyotype symmetry. Accordingly, A. hohenackeri is placed under 2B whereas A. bonaccordensis fits well to 3B category of Stebbins’ classification. The highly endemic species Amorphophallus bonaccordensis, known only from the type locality, is supposed to have originated from A. hohenackeri via many cycles of translocations resulting in heteromorphic, nearly telocentric chromosomes, peculiar satellites, and many mitotic abnormalities like bridges, laggards, micronuclei and heteromorpic bivalents, terminalised chiasmata, supernumerary chromosomes and multinucleate cells at meiosis. ISSR analysis with 17 ISSR primers revealed a higher number of unique bands in A. bonaccordensis. Also the ISSR data, when correlated with the karyotype data, indicate that A. bonaccordensis has probably originated from A. hohenackeri due to chromosomal rearrangements and high mutation of the SSR loci.