RESUMEN
UNLABELLED: ⢠PREMISE OF THE STUDY: Pollen dispersal is affected by the terminal settling velocity (Ut) of the grains, which is determined by their size, bulk density, and by atmospheric conditions. The likelihood that wind-dispersed pollen is captured by ovulate organs is influenced by the aerodynamic environment created around and by ovulate organs. We investigated pollen ultrastructure and Ut of Ephedra foeminea (purported to be entomophilous), and simulated the capture efficiency of its ovules. Results were compared with those from previously studied anemophilous Ephedra species.⢠METHODS: Ut was determined using stroboscopic photography of pollen in free fall. The acceleration field around an "average" ovule was calculated, and inflight behavior of pollen grains was predicted using computer simulations. Pollen morphology and ultrastructure were investigated using SEM and STEM.⢠KEY RESULTS: Pollen wall ultrastructure was correlated with Ut in Ephedra. The relative proportion and amount of granules in the infratectum determine pollen bulk densities, and (together with overall size) determine Ut and thus dispersal capability. Computer simulations failed to reveal any functional traits favoring anemophilous pollen capture in E. foeminea.⢠CONCLUSION: The fast Ut and dense ultrastructure of E. foeminea pollen are consistent with functional traits that distinguish entomophilous species from anemophilous species. In anemophilous Ephedra species, ovulate organs create an aerodynamic microenvironment that directs airborne pollen to the pollination drops. In E. foeminea, no such microenvironment is created. Ephedroid palynomorphs from the Cretaceous share the ultrastructural characteristics of E. foeminea, and at least some may, therefore, have been produced by insect-pollinated plants.
Asunto(s)
Ephedra/fisiología , Polen/fisiología , Polinización , Pared Celular/ultraestructura , Ephedra/ultraestructura , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión de Rastreo , Polen/ultraestructura , VientoRESUMEN
In the dry northern temperate regions of the northern hemisphere, the genus Ephedra comprises a series of native shrub species with a cumulative application history reaching back well over 2,000 years for the treatment of asthma, cold, fever, as well as many respiratory system diseases, especially in China. There are ethnological and philological evidences of Ephedra worship and utilization in many Eurasia Steppe cultures. However, no scientifically verifiable, ancient physical proof has yet been provided for any species in this genus. This study reports the palaeobotanical finding of Ephedra twigs discovered from burials of the Gumugou archaeological site, and ancient community graveyard, dated around 3800 BP, in Lop Nor region of northwestern China. The macro-remains were first examined by scanning electron microscope (SEM) and then by gas chromatography-mass spectrometry (GC-MS) for traits of residual biomarkers under the reference of modern Ephedra samples. The GC-MS result of chemical analysis presents the existence of Ephedra-featured compounds, several of which, including benzaldehyde, tetramethyl-pyrazine, and phenmetrazine, are found in the chromatograph of both the ancient and modern sample. These results confirm that the discovered plant remains are Ephedra twigs. Although there is no direct archaeological evidence for the indication of medicinal use of this Ephedra, the unified burial deposit in which the Ephedra was discovered is a strong indication of the religious and medicinal awareness of the human inhabitants of Gumugou towards this plant.
Asunto(s)
Ephedra/química , Ephedra/ultraestructura , Fósiles , Biomarcadores/análisis , Botánica/métodos , Cementerios , China , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Microscopía Electrónica de Rastreo/métodosRESUMEN
OBJECTIVE: Characters of stem epidermis, leaf epidermis and stoma could be used as important microcosmic morphological characteristic when inheritance trend is studied in Ephedra breeding and identification. METHOD: The stomatic density, stoma major axis and mimor axis, stomatic morphylogy, characters of leaf and stem epidermis of 6 Ephedra plants' stems were examined by SEM. RESULT: The stomatic density and characteristic of leaf epidermis and stem epidermis in six Ephedra species was differenc, there were no obvious morphological differences in stoma shape and size. The guard cells were covered with heavy cuticle and sunken stomata, which were the typical characteristics of xerophytes. The stomas of leaf lower epidermis were oblong or hexagon, but the stomas of steam epidermis were narrowed-oblong or dumbbell-shape, they all belonged to anomalous type. CONCLUSION: The stoma type and characters of Ephedra plants is stable and conservative, there was no obvious morphological differences in stoma shape and size between species, so it is difficult to distinguish different species by the variance of stomas, but that can be applyed to distinguish Ephedra from others at plant taxonomy.
Asunto(s)
Ephedra/ultraestructura , Epidermis de la Planta/ultraestructura , Hojas de la Planta/ultraestructura , Plantas Medicinales/ultraestructura , Ephedra/clasificación , Microscopía Electrónica de Rastreo , Tallos de la Planta/ultraestructura , Estomas de Plantas/ultraestructura , Especificidad de la EspecieRESUMEN
BACKGROUND AND AIMS: The extant species of the seed plant group Gnetales (Ephedra, Gnetum and Welwitschia) have been considered a remnant of a much greater, now extinct, diversity due to the pronounced differences in form and ecology among the genera. Until recently, this hypothesis has not been supported by evidence from the fossil record. This paper adds to the expanding information on Gnetales from the Early Cretaceous and describes coalified seeds from Barremian-Albian localities in Portugal and USA. METHODS: The fossils were extracted from sediment samples by sieving in water. Adhering mineral matrix was removed by chemical treatment. Seeds were investigated using light and scanning electron microscopy. Morphology and anatomy of the seeds were documented and compared with those of extant species. KEY RESULTS: The fossils share characters with extant Ephedra, for example papillae on the inner surface of the seed envelope and in situ polyplicate pollen grains that shed the exine during germination. They differ from extant Ephedra seeds in morphological and anatomical details as well as in their smaller size. Two new species of Ephedra are described together with one species assigned to a new genus of Gnetales. Other Ephedra-like seeds, for which pollen and critical morphological details are currently unknown, are also present in the samples. CONCLUSIONS: These Cretaceous seeds document that key reproductive characters and pollen germination processes have remained unchanged within Ephedra for about 120 million years or more. There is sufficient variety in details of morphology to suggest that a diversity of Ephedra and Ephedra-like species were present in the Early Cretaceous flora. Their presence in Portugal and eastern North America indicates that they were widespread on the Laurasian continent. The fossil seeds are similar to seeds of Erdtmanithecales and this supports the previously suggested relationship between Erdtmanithecales and Gnetales.
Asunto(s)
Ephedra/ultraestructura , Fósiles , Semillas/ultraestructura , Evolución Biológica , Ephedra/clasificación , Ephedra/embriología , Gnetophyta/clasificación , Gnetophyta/embriología , Gnetophyta/ultraestructura , Microscopía Electrónica de Rastreo , Filogenia , Polen/anatomía & histología , Portugal , Semillas/anatomía & histología , Semillas/citología , VirginiaRESUMEN
Ephedra sinica Stapf or Ma Huang has been used in traditional Chinese medicine for over 5000 years as a bronchodilating and stimulatory agent. In the West, it is popularly used in dietary supplements for weight loss and to enhance athletic performance. Adverse events have been reported following consumption of dietary supplements containing ephedrine alkaloids. There are about 50 known species of Ephedra. The ratio of ephedrine to other alkaloids varies from species to species; all North American species lack alkaloids. The method commonly used in the dietary supplement industry for botanical authentication is to analyze the product for the presence of chemical markers known to be present in the specific herb. However, this method does not ensure that the product contains authentic herb, especially if it has been spiked with chemical marker compounds. In the trade and raw drug market, Ephedra is available in the form of stem cuttings or powders, without any vouchers, thus making identification of the species difficult. Using light microscopy, we can detect the presence of Ephedra herb, even in powder form, and identify within certain limits its geographical origin. Identification of Chinese and North American species of Ephedra has been made easier by developing a key using leaf and internode length as key identification characters.
Asunto(s)
Ephedra/fisiología , Ephedra/ultraestructura , Alcaloides/análisis , China , Efedrina/análisis , Microscopía Electrónica de Rastreo/métodos , Microscopía Fluorescente/métodos , América del Norte , Hojas de la Planta , Especificidad de la Especie , Detección de Abuso de SustanciasRESUMEN
Gnetales comprise three unusual genera of seed plants, Ephedra, Gnetum, and Welwitschia. Their extraordinary morphological diversity suggests that they are survivors of an ancient, more diverse group. Gnetalean antiquity is also supported by fossil data. Dispersed "ephedroid" (polyplicate) pollen first appeared in the Permian >250 million years ago (Myr), and a few megafossils document the presence of gnetalean features in the early Cretaceous. The Cretaceous welwitschioid seedling Cratonia cotyledon dates the split between Gnetum and Welwitschia to before 110 Myr. Ages and character evolution of modern diversity are, however, controversial, and, based on molecular data, it has recently been suggested that Ephedra is very young, only 8-32 Myr. Here, we present data on the evolutionary history of Ephedra. Fossil seeds from Buarcos, Portugal, unequivocally link one type of Cretaceous polyplicate pollen to Ephedra and document that plants with unique characters, including the peculiar naked male gametophyte, were established already in the Early Cretaceous. Clades in our molecular phylogeny of extant species correspond to geographical regions, with African species in a basal grade/clade. The study demonstrates extremely low divergence in both molecular and morphological characters in Ephedra. Features observed in the fossils are present in all major extant clades, showing that modern species have retained unique reproductive characters for >110 million years. A recent origin of modern species of Ephedra would imply that the Cretaceous Ephedra fossils discussed here were members of widespread, now extinct sister lineage(s), and that no morphological innovations characterized the second diversification.