Structure and Development of Stomata in Some Leptosporangiate Ferns

The structure and development of stomata are described for 17species of leptosporangiate ferns. In these species the maturestomata are anomocytic, diacytic, Pyrrosia(applied), tetracytic,suspended, or floating type. Stomata are present on both surfacesof floating as well as sub merged leaves of Azolla and Marsilea.In a few species twin stomata, arrested development, and persistentstomatal initials are present Floating stomata result from disintegrationof the anticlinal suspending wall in Pleopeltis, and by detachmentand displacement in Azolla pinnata. The development of stomatais haplocheilic, syndetocheilic, or syndetohaplocheilic. InCyathea spinulosa the guard cell nuclei divide amitoticallyand the resulting two daughter nuclei occupy the opposite polesof the guard cells     

New insights into seminal and stomatal morphology and their contribution to the taxonomy of the Old World succulent perennial Salicornioideae

Seminal and stomatal morphology of three succulent halophyte genera (Sarcocornia, Halocnemum and Arthrocnemum) around the Mediterranean basin and surroundings areas were investigated. Scanning electron microscopy (SEM) investigations showed well-different seminal coat ornamentations among the studied taxa. Both Arthrocnemum macrostachyum and Halocnemum strobilaceum do not show trichomes. Conversely, the species Sarcocornia perennis and S. fruticosa can be easily identified by the presence of long curved hairs against papillae or short conic hairs, respectively. Because most of the herbarium vouchers of Sarcocornia lack seeds, and thus the permanency of seeds on plants is quite short, an alternative vegetative character as stomata was also studied using SEM and light microscope. The detailed stomatal morphological features were analysed for the first time to infer taxonomic relationships among these perennial halophytes. Stomata are constantly paracytic for the four studied species, but two morphotypes were identified related to the level arrangement of guard cells, named as sunken and prominent stomata, respectively. Sunken stomata are found in A. macrostachyum, H. strobilaceum and S. fruticosa, whereas prominent stomata are only characteristic for S. perennis. Besides, we have found somehow relationships among the ecology of these plants based on the frequency of floodings and the observed morphology and density of stomata. Nonetheless, each observed morphotype is a stable character, without any influence of climate or environmental conditions. As a result, seminal coat ornamentation and stomata morphology are the two most reliable characteristics for discriminating Mediterranean halophytes taxa, especially related to Sarcocornia taxa.     

华北地区繁缕属（Stellaria L.）植物叶表皮微形态特征研究

采用光学显微镜,对华北地区分布的繁缕属植物16种2变种,其它4属4种植物的叶表皮微形态进行了观察。结果表明：繁缕属植物叶片的下表皮均存在气孔器,而上表皮仅少数种类缺乏气孔器。气孔器类型比较多样,有不等细胞型、无规则型、无规则四细胞型;表皮细胞主要为不规则型,垂周壁从平直、弓形、浅波状、波状、到深波状;上表皮气孔指数在5.23~31.65之间;下表皮气孔指数在10.02~29.44。叶表皮被毛或无,毛被分为星状毛、腺柔毛、柔毛、绢毛。该研究说明叶表皮的微形态特征在种间差异明显,可以为分种及属间亲缘关系的探讨提供依据,但是对组的划分存在一定的局限性。     

Structure,ontogeny and taxonomic significance of trichomes and stomata in some Capparidaceae

The present work embodies epidermal structure, structure and ontogeny of stomata in five genera embracing sixteen species of the Capparidaceae namely Cleome (8 species) Capparis (5 species), Cadaba (1 species), Crataeva (1 species) and Maerua (1 species). The epidermal cells are polygonal, isodiametric or elongated arranged irregularly, with evenly or unevenly thickened, sinuous, straight or arched anticlinal walls. Two main types of trichomes: glandular (four types) and eglandular (five types) are noticed. The stomatal types include cyclocytic, triacytic, staurocytic, tetracytic, anomocytic, anisocytic, paracytic and with a single subsidiary cell. The ontogeny of stomata with a single subsidiary cell is perigenous or mesoperigenous, of paracytic mesoperigenous or mesogenous, of anisocytic is mesoperigenous or mesogenous, while that of the other types is perigenous. Abnormalities observed are: single guard cell; aborted guard cells; complete or incomplete division of guard cells; contiguous stomata; giant stomata and cytoplasmic connections. The present observations do not support the separation of Cleomaceae from the Capparidaceae.     

Comparative morphology of the leaf epidermis in Fritillaria (Liliaceae) from China

The leaf epidermis of 16 species and one putative species of Fritillaria was examined using light microscopy (LM) and scanning electron microscopy (SEM). The results showed that the stomatal and other epidermal features were constant within species. Epidermal cells of Fritillaria under LM were usually polygonal and anticlinal cell walls were straight or curved. In a few species they were irregular, with sinuous anticlinal cell walls. The cuticular membrane of Fritillaria was usually striated, and the wax ornamentations were flaked, granular or concomitant. Based on leaf epidermal characteristics, the subdivision of Fritillaria is discussed, and the statistical t‐test method was used to ascertain the significance level of the differences in the stomata of each species. All orientations of the stomatal poles in Fritillaria were the same, and this phenomenon was named ‘stomatal orientation’. The stomatal characteristics support the origin of section Fritillaria in China from two floristic elements. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 93–109.     

TheAzolla-Anabaena association: Historical perspective,symbiosis and energy metabolism

The heterosporous water-fern genusAzolla is one of the few symbioses with a cyanobacterium in the genusAnabaena. TheAzolla-Anabaena association includes six extant speciesof Azolla, which are widely distributed in relatively placid tropical and/or temperate freshwater environments. The earliest mention of the plant seems to be in an ancient Chinese dictionary that appeared about 2000 years ago.Azolla was used in about the 11th century in Vietnam. By 1980 renewed interest in this symbiotic association was shown by the demand for a less fossil energy-dependent agricultural technology. The importation of a variety ofA. filiculoides may have been a most significant breakthrough for the improvementof Azolla cultivation in China. The history of research may be divided into three periods and a new biotechnological stageof Azolla research has recently begun. Each mature dorsal leaf lobe has an ellipsoid cavity which containsAnabaena azollae throughout its development. HeterocystousA. azollae from sixAzolla species share identical and highly specific antigens.Azolla and its endophyte exhibit a coordinated pattern of differentiation and development. Epidermal hair cells of the host are probably interactive with the symbiont. The interior surface of a mature leaf cavity is lined with an envelope and covered by a mucilaginous layer.A. azollae shares the cavity with small populations of the bacteriaPseudomonas andAzotobacter. Endophyte-freeAzolla may rarely occur in nature and can be generated by aseptic techniques.Anabaena azollae can be isolated fromAzolla fronds by gentle pressure and by enzymatic digestion. The free living cultures derived from theAnabaena so obtained differ in some respects, however, from the freshly extracted symbiont, and might better be called the presumptive isolate. BothAzolla andAnabaena contain specific photosynthetic pigments. The optimum conditions for photosynthesis have been measured.Azolla is a C₃ plant and has high net photosynthesis. PSII activity in the symbiont is low. Nitrogenase is localized in the heterocysts of the symbiont and has some advantages compared with free-living cyanobacteria. SymbioticA. azollae has a high frequency of heterocysts. Unidirectional hydrogenase occurs in the symbiont and recycles electrons and ATP. Simultaneous measurements of N₂ fixation and photosynthesis show the dependence of nitrogenase on photosynthetically captured radiation for energy by an indirect dependence on CO₂ fixation. The host contains most of the total GS and GDH activities, and the symbiont excretes a substantial portion of its newly fixed nitrogen as ammonium. The two partners in the association exhibit a comparable developmental gradient and a mechanism of cooperative integration for their energy metabolism, thus improving the efficiency of solar energy conversion and presenting a unique model for biotechnology.     

蚕豆气孔运动中脱落酸对周质微管排列的影响

气孔由一对保卫细胞组成,且其壁具有不均一加厚的特性(图1),并能敏感地感受内、外环境信号而调节K~ 等渗透调节物质进出保卫细胞引起膨压变化,从而控制气孔的大小、调节植物体与外界环境所进行的水分和气体交换。进一步研究发现,以K~ 为主的渗透调节物质引起的膨压变化受到许多因子的调控,如ABA可以中介Ca~(2 )作用抑制K~ 内向通道或直接作用于K~ 外向通道使K~ 外流,但ABA影响K~ 通道的信号转导途径仍是一个有待进一步探索的课题。大量研究表明,细胞运动与细胞骨架有关。如丝瓜卷须的卷曲运动、胞质环流、花粉管萌发与伸长、含羞草的感震性运动,以及细胞器的运动等都与细胞骨架有关。我们用植物微管特异性解聚剂——甲基胺草磷(APM)以及微丝专一性抑制剂——细胞松驰素B(CB)预处理蚕豆开放或关闭气孔后可明显地抑制Ca~(2 )、ABA、光、K~ 等引起的气孔运动,表明微管、微丝可能参与调节气孔的运动过程。Couot-Gastelier和Louguet经电镜观察证     

Stem and wood allometric relationships in Cacteae (Cactaceae)

Allometric relationships in organisms are considered a universal phenomenon. A positive scaling has been reported between stem size and cellular size of tracheary elements in wood of different vascular plants, but few studies have been carried out in slow-growing succulent plants. The aim of this study was to evaluate if a relationship exists between size, growth form and wood cell size among individual species of Cacteae. Forty-four species belonging to 16 genera of the tribe Cacteae with differing growth forms and sizes were studied. When analyzing plant size, we found a positive allometric scaling and the larger-sized species showing a higher percentage of succulent tissue and less accumulation of wood tissue. The positive scaling found between plant size (height and diameter) and vessel elements and fiber length support the universality of the allometric relationship proposed for other vascular plants with non-succulent stems. Notably, wide-band tracheids do not scale with plant size or growth form. Succulence associated with narrow vessel elements with distinctive helical secondary walls and wide-band tracheids suggest they are the key adaptations to tolerate drought and provide support to the stems of most taxa in Cacteae. Fibers do not have the primary role of giving mechanical support; therefore, we assume the scarce fibers in clusters represent reaction wood that, along with the fundamental tissue, maintains the vertical position and shape of those species growing in rocky cracks. Our results with species having short succulent stems support the universal theory of positive allometric scaling of vascular plants.     

Morphological and genetic diversity of the family Azollaceae inferred from vegetative characters and RAPD markers

Family Azollaceae has seven species with a controversial taxonomy. The identification of species without reproductive structures relies on vegetative characters but some are variable, leading to misinterpretations. The molecular methods may be helpful, but until now, they did not provide a conclusive Azolla taxonomy. Therefore, we studied the family Azollaceae at vegetative and molecular levels. Analysis of vegetative, random amplified polymorphic DNA (RAPD) and combined data showed a comparable grouping of the Azolla species in two main clusters: cluster I, referred to as section Rhizosperma (A. pinnata and A. nilotica) and cluster II, referred to as section Azolla (A. filiculoides, A. microphylla, A. caroliniana and A. mexicana), with the exception of A. rubra, which clustered differently depending on the method. All the Azolla species were distinguished by the 13 polymorphic vegetative characters, the 211 RAPD markers or the combined data, with the latest showing the highest discrimination. The Shannon Index diversity was greater with RAPD (2.276) than with vegetative characters (0.054), highlighting the higher discriminating power of the molecular data. The partitioning of diversity was, as expected, high among species for all the types of data and low within species, with the lowest diversity obtained for morphological data. Both data sets (vegetative and RAPD) allowed the distinction of all the species and their clustering into sections Rhizosperma and Azolla, suggesting this as the most correct for this family. The dendrogram from the combined data was the most accurate, highlighting the benefit of integrating different types of data to study the family Azollaceae.     

Taxonomic, evolutionary and ecological implications of the leaf anatomy of rhizomatous Iris species

The leaf anatomy of the rhizomatous Iris species with ensiform leaves and the related genera Pardanthopsis and Belamcanda is described. Their isobilateral leaves may or may not have a pseudo-dorsiventral structure. Variable characters of their leaf blades include: outline in transverse section, height and shape of papillae, form and structure of stomata, transverse section outline of marginal fibre strands and sclerenchy matous inner bundle sheath at phloem and xylem poles, forms of mesophyll arrangement, mesophyll structure and air canals, vascular bundle arrangement and the detailed structure of the larger vascular bundles, distribution of tannin, size and distribution of crystals. The taxonomic and ecological significance of these characters has been evaluated.
The anatomical characteristics of 25 supraspecific taxa in three genera are presented and compared in tables. The relationships and evolutionary position of these taxa are discussed. Each of the three subgroups within Iris appears to be correlated with a syndrome of anatomical characters. Some species currently of uncertain taxonomic position are discussed, and their classification based on anatomical data is suggested.
Some characters related to xeromorphy or helomorphy are mentioned.     

Comparative anatomy and morphology of nectar-producing Melastomataceae

Background and Aims

Most neotropical Melastomataceae have bee-pollinated flowers with poricidal anthers. However, nectar rewards are known to be produced in about 80 species in eight genera from four different tribes. These nectar-producing species are pollinated by both vertebrates and invertebrates.

Methods

The floral morphology and anatomy of 14 species was studied in six genera of nectar-producing Melastomataceae (Blakea, Brachyotum, Charianthus, Huilaea, Meriania and Miconia). Anatomical methods included scanning electron microscopy, and serial sections of paraffin-embedded flowers.

Key Results

All vertebrate-pollinated melastome flowers have petals that do not open completely at anthesis, thus forming a pseudo-tubular corolla, while closely related species that are bee pollinated have rotate or reflexed corollas. In most species, nectar secretion is related to stomatal or epidermal nectaries and not filament slits as previously reported. Moreover, the nectar is probably supplied by large vascular bundles near the release area. Blakea and Huilaea have nectary stomata located upon the dorsal anther connective appendages. Brachyotum also has nectary stomata on the anther connectives, but these are distributed lengthwise along most of the connective. Meriania may release nectar through the anther connective, but has additional nectary stomata on the inner walls of the hypanthium. Miconia has nectary stomata on the ovary apex. Charianthus nectaries were not found, but there is circumstantial evidence that nectar release occurs through the epidermis at the apex of the ovary and the lower portions of the inner wall of the hypanthium.

Conclusions

Nectar release in Melastomataceae is apparently related to nectary stomata and not filament slits. The presence of nectary stomata on stamens and on ovary apices in different lineages suggests that the acquisition of nectaries is a derived condition. Nectary location also supports a derived condition, because location is strongly consistent within each genus, but differs between genera.Key words: Blakea, Brachyotum, Charianthus, Huilaea, Meriania, Melastomataceae, Miconia, nectaries, nectary stomata, pollination     

Observations on developmental and structural aspects of stomata in six succulent species ofSenecio (Compositae)

The development and structure of stomata on the succulent leaves of six species ofSenecio are reported. It was found that in all the species investigated the development of stomata was of the mesogenous type and the structure of the stomata was anisocytic. The constancy in the development and structure of stomata in all the species of the genus investigated agrees with the view that a stomatal type and its developmental modes are constant at the genus level. Abnormalities such as contiguous stomata, degenerated guard cells, abortive and single guard cells are also recorded as natural phenomena.     

骆驼蓬营养器官的旱生结构

 骆驼蓬是生长在荒漠或盐碱地区的旱生植物,具有显著的旱生结构特征。主根粗壮,其中柱周围产生2或3轮呈同心环状排列的异常维管束。这种异常结构对旱生植物具有重要的生态学意义。茎肉质,其皮层、韧皮部,尤其是髓内具有发达的贮水薄壁组织细胞。叶片肉质,光滑无毛。其表皮细胞的外切向壁有较厚的角质层,表面具皱纹状突起。气孔器与表皮细胞平齐,面积较大,而密度较小。栅栏组织发达,为环栅型,包围着发达的贮水组织。叶脉维管束不发达。其叶表面积与体积之比远比中生植物小。根据以上营养器官形态结构特征,可以认为骆驼蓬是典型的多浆汁旱生植物。     

Stomata on the pericarp of species of the genus Rosa L. (Rosaceae)

Achenes of 36 species representing all subgenera and sections of the genus Rosa were studied. All have stomata on the pericarp that seem to be normal in appearance. They are usually few, scattered, mostly on the upper part of fruit, and open or closed. This is the first report of stomata on fruits of Rosa.     

Contributions to the anatomy of Freycinetia species from the Solomon Islands

A preliminary investigation of six species of Freycinetia from the Solomon Islands indicates that the anatomy of this genus is relatively uniform, and differs only in degree rather than fundamental distinction from that of Pandanus. The complex elaboration of stomata found in some species of Pandanus is not seen in Freycinetia ; in the latter genus the elaboration, if any, involves only a few simple outgrowths from cells bordering the stomata, or extensions of the cuticle, whereas in some species of Pandanus well-developed branched papillae occur. The vascular bundles of both leaves and stems are strongly sheathed by thickened cells and the phloem is in two distinctive strands. The ovules of species of Freycinetia may provide characters useful taxonomically; the presence or absence, and orientation, of raphide bundles in the long funicles and the presence or absence and character of the strophiole appear to vary from species to species. Current work involving more species of Freycinetia from a wider area, together with Sararanga , may throw further light on the possible use of anatomical features as diagnostic aids.     

DNA Probes Show Genetic Variation in Cyanobacterial Symbionts of the Azolla Fern and a Closer Relationship to Free-Living Nostoc Strains than to Free-Living Anabaena Strains

Twenty-two isolates of Anabaena azollae derived from seven Azolla species from various geographic and ecological sources were characterized by DNA-DNA hybridization. Cloned DNA fragments derived from the genomic sequences of three different A. azollae isolates were used to detect restriction fragment length polymorphism among all symbiotic anabaenas. DNA clones were radiolabeled and hybridized against southern blot transfers of genomic DNAs of different isolates of A. azollae digested with restriction endonucleases. Eight DNA probes were selected to identify the Anabaena strains tested. Two were strain specific and hybridized only to A. azollae strains isolated from Azolla microphylla or Azolla caroliniana. One DNA probe was section specific (hybridized only to anabaenas isolated from Azolla ferns representing the section Euazolla), and five other probes gave finer discrimination among anabaenas representing various ecotypes of Azolla species. These cloned genomic DNA probes identified 11 different genotypes of A. azollae isolates. These included three endosymbiotic genotypes within Azolla filiculoides species and two genotypes within both A. caroliniana and Azolla pinnata endosymbionts. Although we were not able to discriminate among anabaenas extracted from different ecotypes of Azolla nilotica, Azolla mexicina, Azolla rubra and Azolla microphylla species, each of the endosymbionts was easily identified as a unique genotype. When total DNA isolated from free-living Anabaena sp. strain PCC7120 was screened, none of the genomic DNA probes gave detectable positive hybridization. Total DNA of Nostoc cycas PCC7422 hybridized with six of eight genomic DNA fragments. These data imply that the dominant symbiotic organism in association with Azolla spp. is more closely related to Nostoc spp. than to free-living Anabaena spp.     

Potential of Plants from the Genus Agave as Bioenergy Crops

Agave is a succulent genus within the monocot family Agavaceae. The plants have a large rosette of thick fleshy leaves, each ending generally in a sharp point, and are native to arid and semi-arid regions from the southern USA to northern South America. The most important commercial species is Agave tequilana grown for production of tequila. Several cultivated species of Agave such as Agave sislana and Agave salmiana can perform well in areas where rainfall is insufficient for the cultivation of many C₃ and C₄ crops. The key feature of the crassulacean acid metabolism photosynthetic pathway used by agaves is the stomata opening and CO₂ uptake during the night, thus allowing less water to be lost by transpiration. Alcoholic beverages, sweeteners, fibers, and some specialty chemicals are currently the main products coming from agave plants. The recovered information related to productivity, biofuel processability, by-products, etc. suggests that some Agave species have a real potential to compete economically with other bioenergy crops. But more than compete, it could complement the list of bioenergy crops due to its capacity to grow with very little rainfall and/or inputs and still reach good amount of biomass, so unused semi-arid land could be productive. Although Agave has great potential to be developed as a bioenergy crop, more laboratory and field research are needed.     

EM-studies on Salviniaceae Megaspores from the Middle Miocene Fasterholt Flora,Denmark

Reproductive organs of Salvinia and Azolla were found together with other small plant remains in the Middle Miocene Fasterholt flora, Denmark. They were examined by the use of SEM and TEM; this was done with the three species of Azolla for the first time. Salvinia is represented by one, or possibly two, species. The megaspore of S. cerebrata has a characteristic surface sculpture of irregular, rounded ridges. Some specimens differ from the typical S. cerebrata by having strongly developed verrucae or clavae. They are described as Salvinia sp., but it is possible that they represent a variety of S. cerebrata. Azolla is represented by three species. A. nikitinii and A. ventricosa have nine floats in two tiers; massulae have not been found. A. tuganensis has three floats in one tier, massulae have anchor-shaped glochidia.     

Fingerprinting of freshly separated and cultured cyanobionts from different Azolla species using morphological and molecular markers

Differentiation of freshly separated (uncultured) and cultured cyanobionts of Azolla species was carried out employing morphological markers and profiles generated using SDS-PAGE and PCR–RFLP of 16S rRNA. The cell dimensions of vegetative cells, heterocysts and heterocyst frequency (25–28%) of the freshly separated cyanobionts were distinctly higher than that those recorded for the cultured cyanobionts (7–10%). The SDS-PAGE profiles of whole cell proteins of cultured cyanobionts (comprising 28–30 bands) and those of freshly separated cyanobionts (consisting of 6–10 bands) exhibited distinct differences and unique bands. AluI was able to discriminate freshly separated cyanobionts from cultured cyanobionts of same species of Azolla. The profiles of cyanobionts (freshly separated and cultured) of A. rubra (RU6503) generated using the restriction enzyme AluI were distinctly different from other cyanobionts and unique bands were observed in both cyanobionts. The cultured cyanobionts from A. microphylla (MI4018), A. filiculoides (FI1001) and A. pinnata (PP7001) showed the presence of a distinct band of 450, 622 and 307 bp, respectively. Three common bands of 500, 400 and 275 bp were recorded in the AluI restriction profiles of all the freshly separated cyanobionts. 16S rRNA PCR–RFLP analyses confirmed the existence of primary and secondary cyanobionts in the leaf cavities of different Azolla species. These techniques can be utilized for discriminating between freshly separated and cultured cyanobionts of Azolla and provide reliable fingerprints for these strains.     

湖南安息香属植物的叶片比较解剖学研究

利用光学显微镜和扫描电镜对湖南产安息香属10种植物叶表皮微形态和解剖结构进行了观察和测量。结果表明:(1)表皮均由单层细胞构成,细胞形状为多边形和无规则形,垂周壁式样为平直、弓形、波状;(2)气孔器大小及密度在种间的差异明显;(3)气孔外拱盖内缘主要为波状和浅波状,气孔器外围角质纹饰以越南安息香的鸟巢状和栓叶安息香的碗状为显著区别特征;(4)老鸹铃、垂珠花和白花龙的气孔器保卫细胞两极有"T"形加厚;(5)栓叶安息香和大果安息香叶上表皮由大型细胞组成;(6)叶肉分化为栅栏组织和海绵组织,二者的厚度及比值在种间有明显的差异,其中越南安息香栅栏组织分化为2层;(7)大果安息香和芬芳安息香的主脉维管组织构成一圈封闭的环状结构,而其他种则为开放的半圆形结构;(8)叶片及主脉的厚度在种间差异明显。安息香属植物的表皮微形态及解剖结构特征比较稳定,可作为种间鉴定和分类的重要依据。