Breeding system and fruit set in African Marantaceae

Marantaceae are a pantropically distributed family of perennial herbs and lianas in the understory of tropical rainforests. They are characterized by a unique pollen transfer mechanism. To understand its functional significance and evolution, field investigations have been conducted in Gabon.Data from 28 (of 35) species from Central Africa are achieved. The pollen–ovule ratio (34–140:1; exception Sarcophrynium 2.5:1) falls into the range of facultative autogamous species. All investigated species were proven to be self-compatible; however, only two were autogamous. Natural fruit set was generally low (10.9 ± 10%). The highest natural fruit set was found in Marantochloa purpurea (29.7%), Ma. grandiflora (33.5%) and the two autogamous species Halopegia azurea (31%) and Marantochloa leucantha (35%). Considerable higher fruit set could be reached in all species by hand-self-pollination.We conclude that autogamy is generally avoided through herkogamy based on secondary pollen presentation on the back of the style head – a central component of the specific pollen transfer mechanism. However, with respect to the consecutive visit of pollinators to several flowers of the same individual geitonogamy cannot be excluded. The aggregated pollen transfer via the explosive pollination mechanism might be interpreted as an adaptation to low pollinator visitation rate, pollen limitation might explain the low fruit set.     

Pollination, breeding system and seed abortion in some African acacias

TYBIRK, K., 1993. Pollination, breeding system and seed abortion in some African acacias . Studies of the flower visitors and pollination ecology of Acacia albida Del., A. nilotica (L.) Willd. ex Del. A. tortilis (Forssk.) Hayne and A. Senegal (L.) Willd. in Senegal and Kenya showed a high diversity of floral foragers. One hundred and eighteen taxa of insects mainly from Hymenoptera, Lepidoptera, Coleoptera and Diptera were collected. The most important pollen vectors were bees from the families Megachilidae and Halictidae, and wasps from the families Scoliidae and Eumenidae. Beetles, flies and butterflies were secondary pollen vectors. Diversity and frequency of flower visitors of species with floral nectar ( A. Senegal and A. albida ) were not clearly different from species without floral nectar ( A. tortilis, A. nilotica ). Acacia tortilis was almost exclusively outcrossed (Index of Self Incompatibility = 0.2), with 5.5% of the inflorescences (0.13% of the flowers) developing fruits. The number of seeds per pod was positively correlated with dispersal type. Wind dispersed species had fewer seeds per pod than animal dispersed species. About 5% of the seeds were aborted in A. tortilis and A. nilotica , while 22–48% of the seeds were aborted in A. Senegal, A. ataxacantha DC. and A. polyacantha Willd. Most abortions in the latter three species occur in the proximal end of the pods, indicating selective seed abortion.     

Leaf movement in Calathea lutea (Marantaceae)

Summary Calathea lutea is a broad-leaved, secondary successional plant which shows complex leaf movements involving both elevation and folding of the leaf surface about the pulvinus. In the plants studied, mean leaf elevation increased from approximately 34 degrees in the early morning to 70 degrees at noon while the angle of leaf folding increased from 13 degrees to 50 degrees over the same time period. During the period from early morning to noon, these movements resulted in a significant decrease in the cosine of the angle of incidence, a measure of the direct solar radiation intercepted. The observed changes in elevational angle significantly reduce the cosine of angle of incidence while folding does not significantly reduce the fraction of direct solar radiation intercepted during the period of direct exposure of the leaf surface to the solar beam. Since elevational changes seem to account for the reduction in exposure to direct solar radiation, the role of folding remains unclear.     

Nomenclatural notes on neotropical Marantaceae

Two new combinations are made:Stromanthe macrochlamys (Woodson & Standley), transferred fromCalathea, andCtenanthe amabilis (Morren), transferred fromStromanthe. Calathea crotalifera S. Watson from Guatemala is an earlier name forC. insignis Petersen.     

利用传粉综合征预测:长瓣兜兰模拟繁殖地欺骗雌性食蚜蝇传粉

在花部进化受传粉者主导这一经典理论影响下,传粉综合征一直被认为是被子植物对应于某些特定传粉者的标志,因此,可以利用传粉综合征来预测传粉者。近年来,这种对应和预测受到多因素影响,以及花部进化理论和传粉者泛化理论的冲击。在本研究中,我们选择长瓣兜兰Paphiopedilum dianthum作为实验材料,来探讨传粉综合征与传粉者的关系以及利用前者预测后者的有效范围。长瓣兜兰具有的一系列特征,同其他依靠假繁殖地欺骗食蚜蝇传粉的兜兰种类相似,包括倒盔状唇瓣,较大的中萼片以及花瓣上的黑色突起和睫状毛,而且长瓣兜兰同这些种类有很近的亲缘关系和相似的生境。根据传粉综合征概念,长瓣兜兰应该是由食蚜蝇传粉,通过模拟繁殖地来欺骗传粉者。为了检验这些预测,我们对长瓣兜兰进行了传粉生物学研究。长瓣兜兰是自交可亲和的物种,不存在自动自交授粉现象,必须依靠昆虫传粉才能结实。结果表明,雌性黑带食蚜蝇Episyrphus balteatus是长瓣兜兰的主要传粉者,并且这种兜兰是通过模拟繁殖地来欺骗食蚜蝇传粉的。根据本实验结果,我们认为传粉综合征只是对应于不同的传粉选择压力而不是简单对应于传粉者种类,而使用传粉综合征预测时还需要考虑生境和演化历史等因素对花部形态的影响,这样才可能得到有效的结果。     

Setting-up tension in the style of Marantaceae

The Marantaceae stand out from other plant families through their unique style movement which is combined with a highly derived form of secondary pollen presentation. Although known for a long time, the mechanism underlying the movement is not yet understood. In this paper, we report an investigation into the biomechanical principles of this movement. For the first time we experimentally confirm that, in Maranta noctiflora, longitudinal growth of the maturing style within the 'straitjacket' of the hooded staminode involves both arresting of the style before tripping and building up of potential for the movement. The longer the style grows in relation to the enclosing hooded staminode, the more does its capacity for curling increase. We distinguish between the basic tension that a growing style builds up normally, even when the hooded staminode is removed beforehand, and the induced tension which comes about only under the pressure of a too short hooded staminode and which enables the movement. The results of our investigations are discussed in relation to previous interpretations, ranging from biomechanical to electrophysiological mechanisms.     

Notes on Ischnosiphon (Marantaceae)

Four new species are described, viz. Ischnosiphon bahiensis (Brazil), I. ursinus (French Guiana and Rio Negro Basin), I. crassispicus (vicinity of Manaus), and I. fusiformis (NE Peru). New data on ecology, morphology, or distribution are presented for I. inflatus Anderss., I. enigmaticus Anderss., I. centricifolius Anderss., I. gracilis (Rudge) Koern., I. helenae Anderss., I. macarenae Anderss., I. polyphyllus (P. & E.) Koern., and I. surumuensis Loes. The typification of I. arouma (Aubl.) Koern. is briefly discussed.     

Pollination in conifers

Our understanding of pollination in conifers has advanced rapidly in recent years, but it still lags behind our knowledge of this process in angiosperms. In part this is because conifers are not considered to be high priority crops and, unlike many cultivated flowers, conifer seed cones are generally neither large nor colorful. The use of genetics to improve tree growth has primarily been through selection and asexual propagation rather than breeding, and because incompatibility is not thought to occur in conifer pollination systems, concern about pollination has primarily been with regard to seed production. Here we examine the ancestral wind-pollination mechanism in conifers and discuss how the process may have evolved to improve pollination success.     

Anatomic insights into the thigmonastic style tissue in Marantaceae

The irreversible style movement in Marantaceae is one of the quickest plant movements ever recorded. It is largely based on a special tissue construction, which is analysed herein for the first time. Histological sections, fluorescence and different electron microscopic techniques are used to study the style tissue of eight species in six genera of the Marantaceae. Tissue sections prior to the thigmonastic movement are only obtained after ether or chloroform narcosis. The tissue in the bending zone of the style has the construction of a lamellar collenchyma with elongated cells and extended intercellular spaces. The thicker cell walls abut the intercellular spaces, while the thinner walls between adjacent cells are extraordinarily porous. The tissue is thus characterised by strongly perforated cell bundles which are able to slide alongside each other and the intercellular spaces. Cell-wall loosening starts about 24 h before flowering and is interpreted as a result of enzymatic ageing processes. It is also found in other members of the Zingiberales, but only the Marantaceae take advantage of the maceration process. We conclude that the specific tissue construction contributes to the rapid style movement. It combines qualities for stabilisation (collenchyma), pliability (intercellular spaces) and water transport (extremely porous tissue), thus supporting the irreversible style bending by a sudden and final shift of fluid.     

Sanblasia, a new genus of the Marantaceae

Sanblasia dressleri is described from material from the Serranía de San Blas, E Panamá. The inflorescence has the general appearance of an Ischnosiphon , but the ovary is 3–ovulate, as in Calathea , and the bracteole is channeled and keeled, as in many species of Calathea , and in Pleiostachya.     

Additional Ecuadorian species in Calathea series Comosae (Marantaceae)

Three new species in Calathea series Comosae (Petersen) Schumann are described from Ecuador: Calathea pallidicosta, C. attenuata and C. lagoagriana. Calathea pallidicosta is currently known only from Ecuador, C. lagoagriana occurs in both Colombia and Ecuador while C. attenuata is more widespread, occurring in Colombia, Ecuador, Perú and Brasil. Calathea attenuata and C. pallidicosta are in the monomorphic-bracted group of C. series Comosae while C. lagoagriana is in the dimorphic-bracted group. Calathea lagoagriana possibly hybridizes with C. loeseneri Macbride.     

Studies on Pollination in Musaceae

Observations and experiments on several species of Musaceaein West Java and Central Sumatra showed that the species withpendent inflorescences are pollinated by macroglossine bats,principally by the long-tongued fruit bats, Macroglossus minimusand Eonycteris spelaea. Among the species with an erect inflorescenceM. velutina proves to be self pollinating, while M. salaccensishas sunbirds (Nectariniidae) and tree shrews (Tupaia) as pollinators.A discussion on pollination in this family is presented in thispaper.     

Revision of the Thalia geniculata complex (Marantaceae)

Within the Thalia geniculata complex, which corresponds to subgen. Arthrothalia Schum., three species have been recognized in recent taxonomic literature, viz. T. geniculata L., T. trichocalyx Gagnepain, and T. welwitschii Ridley. The variation pattern within this complex has been analyzed with the aid of pictorialized scatter diagrams and it is concluded that the entire complex is made up of a single polymorphic species, of which no further subdivision is justified. T. geniculata is redescribed and full synonymy is given.     

少花柊叶传粉生物学的研究

竹芋科Marantaceae植物所具有的雄蕊先熟(protandry)、次级花粉展示(secondary pollen presentation)以及不可逆转的爆发性花柱运动(explosive style movement)等特点,造就了其独特的传粉机制.本文对竹芋科多年生草本植物少花格叶Phrynium oliganthum的花生物学特性、传粉操控实验和传粉者行为观察三个方面做了较为系统的研究,以掌握该植物基本的开花行为及繁殖特性.实验结果表明,少花格叶自交亲和,但不存在自动自交机制,其传粉过程依赖于传粉者.传粉者为每天沿固定路线访花、被称为有序觅食者(trapliner)的独居蜂类(无垫蜂Amegilla spp.).在传粉实验中,无论是人工授粉还是自然状态下坐果率都很低(<10%),这可能是由于资源限制以及严重的花序腐烂及虫食.少花柊叶每天开花数约11朵,但并不同步,而是在4h内逐次开放,这种开花格局连同传粉者在一天之内会重复同一线路的拜访特点,有利于少花格叶在一定程度上减少同株异花授粉的发生,增加异交的机会.     

Four new species of Calathea (Marantaceae) from French Guiana

Four new species are described: Calathea erecta, C. dilabens, C. granvillei , and C. squarrosa , based on material from French Guiana. Calathea erecta and C. granvillei are known also from the central Amazon Basin. Calathea squarrosa probably also occurs in Surinam. Calathea dilabens is presently known only from French Guiana, but probably occurs in adjacent Brazil and Surinam. A tentative key is provided to the species of Calathea known to occur in French Guiana.     

The neotropical genera of Marantaceae. Circumscription and relationships

The delimitation of the neotropical genera of the Marantaceae has been revised, using evidence mainly from the morphology of inflorescences and flowers. It is concluded that the generic concepts of Schumann in "Das Pflanzenreich", often questioned by 20th century American authors, are essentially sound, but that his grouping of the genera into two tribes is quite artificial. Main deviations from the treatment of Schumann are the rearrangement of the genera, somewhat different stress on diagnostic characters and a much narrower concept of the genus Myrosma. A new genus, Koernickanthe is proposed for the long known species Maranta orbiculata (Koern.) Schum. The genera are arranged into informal groups and the groups and genera recognized are: Maranta group (Maranta L., Monophyllanthe Schum.), Myrosma group (Myrosma L. f., Saranthe (Regel et Koern.) Eichl., Hylaeanthe Jonker et Jonker, Ctenanthe Eichl., Stromanthe Sond.), Calathea group (Calathea G. F. W. Meyer, lschnosiphon Koern., Pleiostachya Schum.), Monotagma group (Monotagma Schum., Koernickanthe gen. nov.) and Thalia "group" (Thalia L.). It is suggested, that each group has its closest affinities with Old World genera and that this indicates that the diversification of the marantaceous stock was far–reaching already before the Old and the New World became effectively isolated. It is further suggested that the early diversification of the family took place in Africa, the flora of which, although poor in species, is morphologically very diverse. Two new combinations are made, viz. Stromanthe stromanthoides (Macbr.) Anderss. and Koernickanthe orbiculata (Koern.) Anderss.     

Pollination by brood-site deception

Pollination is often regarded as a mutualistic relationship between flowering plants and insects. In such a relationship, both partners gain a fitness benefit as a result of their interaction. The flower gets pollinated and the insect typically gets a food-related reward. However, flower-insect communication is not always a mutualistic system, as some flowers emit deceitful signals. Insects are thus fooled by irresistible stimuli and pollination is accomplished. Such deception requires very fine tuning, as insects in their typically short life span, try to find mating/feeding breeding sites as efficiently as possible, and following deceitful signals thus is both costly and time-consuming. Deceptive flowers have thus evolved the ability to emit signals that trigger obligate innate or learned responses in the targeted insects. The behavior, and thus the signals, exploited are typically involved in reproduction, from attracting pheromones to brood/food-site cues. Chemical mimicry is one of the main modalities through which flowers trick their pollen vectors, as olfaction plays a pivotal role in insect-insect and insect-plant interactions. Here we focus on floral odors that specifically mimic an oviposition substrate, i.e., brood-site mimicry. The phenomenon is wide spread across unrelated plant lineages of Angiosperm, Splachnaceae and Phallaceae. Targeted insects are mainly beetles and flies, and flowers accordingly often emit, to the human nose, highly powerful and fetid smells that are conversely extremely attractive to the duped insects. Brood-site deceptive plants often display highly elaborate flowers and have evolved a trap-release mechanism. Chemical cues often act in unison with other sensory cues to refine the imitation.