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Premise of research. In advanced ferns that possess an egg envelope and a fertilization pore, a sac that persistently blocks the fertilization pore is considered a barrier for preventing polyspermy. However, for those ferns with no egg envelope and fertilization pore, the cytological mechanism for preventing polyspermy is still unclear. In this investigation, the main cytological processes during fertilization and zygote formation of the primitive fern Osmunda japonica are observed, and a novel cytological mechanism for preventing polyspermy is described.Methodology. The fertilization process was observed under stereomicroscope, and the fertilization time was recorded. The selected plants were fixed with glutaraldehyde and osmic acid and embedded in pure Spurr’s resin. Specimens were first thick-sectioned and then thin-sectioned for LM and TEM observations.Pivotal results. The observations showed that only one spermatozoid penetrates into the egg at the center in the upper surface of the mature egg. The e...

Control of seed germination and dormancy is important in seed plant adaptation and evolution. When studying seed dormancy of Quercus species, we observed a substantially delayed shoot emergence following a fast root emergence in Quercus chungii F.P.Metcalf. Since epicotyl physiological dormancy (PD) has not been reported in Quercus section Cyclobalanopsis, we examined seed morphology and germination in Q. chungii and aimed to document epicotyl PD in the seeds. The embryo was fully developed in fresh ripe seeds. The elongating cotyledonary petiole pushed the embryo axis out of the seed during germination, which differed from observations in other Quercus species. Shoots emerged from seeds with developing roots after 3 months of warm stratification (35/25 °C), reaching the highest percentage of shoot emergence in seeds after 5 months. Seeds were recalcitrant and displayed a yet unreported epicotyl PD type, for which we propose the formula Cnd(root) ‒ Cp’’ 2b(shoot). Early emergence and development of the root system in Q. chungii seeds with epicotyl PD appears to be a mechanism to maintain a constant water supply to the shoot during plumule development and emergence. Our documentation of seed germination will provide guidance for the conservation and restoration of this species from seeds.

The seasonal dynamics of the total flavonoid contents in various parts of Dryopteris erythrosora, a traditional Chinese medicinal fern, and their antioxidant activity were investigated. The total flavonoids content in various parts of D. erythrosora showed an obvious seasonal dynamic change. The total flavonoid contents in stems (from 4.3% to 12.5%) were much higher than that in leaves with an average content of 2.01%. In spring, the total flavonoid contents in stems were relatively low, but increased rapidly from summer to winter. However, the seasonal dynamics of total flavonoid contents in leaves showed different model. The total flavonoid contents in the stems showed a negative correlation with that in the leaves from January to July. The correlation coefficient of about -0.7 was obtained. The antioxidant activity of the extracts also altered in proportion to the change of total flavonoid contents. In general, the extracts from stems always showed highest antioxidant potentials and it was suggested that the stems can be used as crude medicine.

Natural hybridization has been commonly found in ferns and is generally believed to happen independently at different locations if the range of the parent species overlaps. In 2013, we collected seven species of Adiantum from Yuanjiang, Yunnan, China. The identity of one of these collections remained in doubt; the plant is very similar to A. meishanianum ( A. malesianum × A. philippense ), a natural hybrid from Taiwan, China. Morphological comparison showed that this unidentified collection was different from other related taxa. Sequencing of a single copy of an exon ( CRY2 exon 3) of the nuclear genome suggested this plant contained haplotype sequences of both A. sinicum and A. menglianense. Therefore, it should be treated as a new hybrid. Phylogenic analysis based on five chloroplast DNA sequences ( rbc L, atp B, atp A, trn L-F and rps 4- trn S) indicated that the plant was clustered in A. sinicum, which could be considered to be the female parent of the hybrid. This new hybrid is not only similar to A. meishanianum in morphology, but also its parental taxa are in sister groups in the phylogeny. Hence, the new hybrid was considered to be a cryptic hybrid species. Our methods could be extended to identify other potential natural fern hybrids in China. The habit of clonal propagation potentially occurs in nature, so this natural hybrid could easily survive in the field because clonal growth can offset the lack of fitness caused by sexual reproductive isolation, which may be an important reason why so many hybrid ferns exist in nature.

The flavonoids in bryophytes may have great significance in phylogeny and metabolism research. However, to date there has been little research on bryophyte metabolites, especially flavonoids. To redress this somewhat, we determined flavonoid concentrations of bryophytes from Tianmu Mountain through a colorimetric assay and considered the factors influencing the results. This is the first time that the flavonoid contents of bryophytes have been examined in detail. The results revealed a range of total flavonoid concentrations in 90 samples collected from Tianmu Mountain from 1.8 to 22.3 mg/g (w/w). The total flavonoid contents of liverworts were generally higher than those of mosses; acrocarpous mosses had generally higher values than that of pleurocarpous mosses. The total flavonoid contents of bryophytes growing at lower light levels were general higher than those growing in full-sun. The total flavonoid contents of epiphytic bryophytes were highest, while those of aquatic bryophytes were the lowest. Total flavonoid contents of species growing at low-latitudes were much higher than those at high-latitude individuals. In conclusion, total flavonoid contents of bryophytes have some connection with plant phylogeny; more flavonoids might be contained in relatively primitive bryophytes. Meanwhile, the effects of ecological factors on total flavonoid contents of bryophytes exist; light and habitat (especially tree habitat and river habitat) might be representative factor.

This paper mainly studies the formation and development of the rhizoids of Marchantia polymorpha L. using light and electron microscopy, and cytochemical methods. Marchantia polymorpha has highly specialized rhizoids that can be divided into two types, namely, tuberculate rhizoids and smooth-walled rhizoids. Tuberculate rhizoids individually originate from the lower superficial cells of the apical meristem. Obvious tubercles exist in the lumen of rhizoids, which always lie parallel to the thallus surface and converge toward the midrib. Smooth-walled rhizoids always exist in clusters in free portions near the midrib in the posterior of the thallus. These smooth rhizoids always grow toward moist soil and lie perpendicular to the thallus surface. Developmental observations show that the initial cell of a tuberculate rhizoid that arises from the lower epidermis possesses a dense cytoplasm. The rapid polar growth of a rhizoid produces a non-pigmented tubular cell. A growing rhizoid possesses an apical...

The flavonoids profiles and bioactivities of flavonoids-rich extract from Davallia cylindrica Ching were investigated. The total flavonoids content in D. cylindrica was determined as about 164.41 mg/g. The main flavonoids in D. cylindrica were tentatively identified as quercetin-3-O-rutinoside, quercetin 7-O-glucoside, quercetin 7-O-glucoside, kaempferol 3-O-rutinoside, and quercitrin by UV and ESI-MS spectra. Flavonoids-rich extract (0.258 mg/ml) from D. cylindrica showed similar or higher free radical (O 2 − , DPPH and ABTS ) scavenging potential with that of rutin (0.25 mg/ml). The reducing power of flavonoids-rich extract (0.258 mg/ml) was slightly stronger than that of 0.25 mg/ml rutin. The flavonoids extract from D. cylindrica exhibited cytotoxic effects on A549 cells. It exhibited a dose-dependent inhibition against acetylcholinesterase.

The present investigation examines the oogenesis of the gleichenioid fern, Diplopterygium glaucum (Thunb. ex Houtt.) Nakai using transmission electron microscopy. The results demonstrate that the oogenesis of D. glaucum is similar to the core leptosporangiate ferns. The egg cell of D. glaucum was progressively isolated from the adjacent cells by forming a separation cavity and an egg envelope during maturation. However, during this process, a pore region consistently connected the egg and the ventral canal cell. Ultimately, a fertilization pore formed at the pore region when the egg matured. The nucleus produced conspicuous evaginations during later stages of egg development. The cytological features during oogenesis in D. glaucum more closely resembled the core leptosporangiate ferns rather than the basal leptosporangiate ferns (Lygodium and Osmunda), which possess no egg envelope or fertilization pore. The results provide new characteristics for interpreting the evolutionary history of the gleichenioid ferns.

Egg development in Pteridium aquilinum var. latiusculum was studied using ultrastructural and cytochemical methods to examine structural features influencing fertilization in leptosporangiate ferns. Ultrastructural observations indicate a separation cavity is first formed above the egg during oogenesis with a pore region persistently connecting the egg and the ventral canal cell. The egg envelope is formed by deposition of amorphous materials in the separation cavity on the outer surface of plasmalemma. The egg envelope was not formed across the pore region; instead, a fertilization pore was formed. During oogenesis, the egg nucleus produced extensive evaginations containing osmiophilic bodies. Cytochemical experiments revealed that the egg envelope displays strong periodic acid-Schiff reaction indicative of polysaccharides, with negligible Sudan black B staining for lipids, suggesting that the egg envelope is composed principally of polysaccharides, and not lipids. The present manuscript provides new insights into egg structure and development of Pteridium, including discovery and characterization of the fertilization pore and observations on the chemical nature of the egg envelope, thus contributing to the understanding of the cytological mechanism of the sexual reproduction of ferns.

The cytological features of the cells taking part in archegonial development and oogenesis in the fern Plagiogyria euphlebia (Kunze) Mett. were described in detail by means of light and electronic microscopy. The archegonium develops from an initial cell, which contains dense cytoplasm in contrast to the somatic cells. Two divisions of the initial cell result in a tier of three cells. The middle of which finally develops into a neck canal cell, a ventral canal cell and an egg by two unequal divisions. During maturation, the egg cell becomes progressively isolated from the adjacent cells by forming a separation cavity, a casual wall and an egg envelope. Series sections show that a fertilization pore forms in the upper egg envelope. During maturation of the egg, the nucleus produces conspicuous evaginations. The phylogenetic relationship of the fern P. euphlebia is discussed according to the cytological features in oogenesis. The cytological features observed during oogenesis support the inclusion ...

The northwest region of Yunnan province (southwest China), belonging to the Pan-Himalaya, is a hotspot of biodiversity. We report Stegnogramma leptogrammoides from Yunnan as a new discovery for China. This species was identified based on morphological comparison with the type specimens of all similar species, and DNA barcoding was performed to obtain additional evidence. As it was previously recorded to be endemic to Sikkim, the new record provides a case for confirming floristic affinities between Sikkim and Yunnan within the Pan-Himalaya at the species level.

Oogenesis in the fern Adiantum flabellulatum was studied using transmission electron microscopy. The newly formed egg is closely appressed to the archegonial jacket cells. Plasmodesmata connect the egg and the ventral canal cell, but are absent between the egg and the jacket cells. During maturation, a separation cavity forms around the egg. However, a pore region, persistently connecting the egg and the ventral canal cell, is reported for the first time. Subsequently, an osmiophilic egg envelope is formed, from a combination of the products of sheets of endoplamic reticulum and osmiophilic bodies in the egg cytoplasm. The absence of this envelope from the region where the egg and ventral canal cell were formerly interconnected produces a fertilization pore, which is believed to be an entrance for the sperm penetrating the egg. In the mid stages of egg maturation, the nucleus envelope produces extensive evaginations which then appear to be sequestered into the egg cytoplasm recalling a similar ph...

The profiles and bioactivities of flavonoids extracted from Dryoathyrium boryanum (Willd.) Ching were investigated. The total flavonoids content in extract from D. boryanum is about 145.8mg/g. By means of HPLC-DAD-ESI-MS, the main flavonoids in D. boryanum were tentatively identified as 3-hydroxyphloretin 6'-O-hexoside, quercetin-7-hexoside, apigenin7-O-glucoside, luteolin 7-O-glucoside, apigenin 7-O-galactoside, acacetin 7-O-(α-D-apio-furanosyl) (1→6)-β-d-glucoside, 3-hydroxy phloretin 6-O-hexoside, luteolin-6-C-glucoside. 0.21mg/ml flavonoids extract from D. boryanum showed very strong superoxide anion radical scavenging potential, which is higher than that of rutin (0.25mg/ml). The extract (0.21mg/ml of flavonoids) from D. boryanum exhibited similar DPPH scavenging potential with that of rutin (0.25mg/ml). However, rutin (0.25mg/ml) showed a significantly higher reducing power and ABTS scavenging potential than that of 0.21mg/ml flavonoids extract from D. boryanum. It had no effect on acetylcholinesterase. D. boryanum can be considered as a medicinal plant and the flavonoids from D. boryanum are excellent antioxidants.

Adiantum × ailaoshanense Y.H.Yan & Y.Wang, a new natural hybrid that belongs to Pteridaceae, is described and illustrated. Molecular studies show that A. × ailaoshanense arose from a hybridization between the maternal A. sinicum and the paternal A. menglianense. In this report, the morphology, palynology, and geographic distribution of A. × ailaoshanense are documented.