A revision of ligule and labium in Isoëtes

Review of Palaeobotany and Palynology, 2003

The general morphology, organization, structure and ornamentation of the sporoderm of megaspores and microspores of Isoetes savatieri Franchet have been studied with a stereoscopic microscope, light microscopy, transmission and scanning electron microscopy. The megaspores are trilete, 420^580 Wm in equatorial diameter, subtriangular to globose in polar view with an evident equatorial flange (zone). The ornamentation is rugulate. A siliceous cover with a three-dimensional network overlies an exospore sporopolleninous apparently laminar with an equatorial^distal separation of laminae. Each exospore lamina is fused to those of other planes delimiting lacunae. The lacunae located in the outer part of the exospore are filled with silica. The endospore is thick, its structure is fibrillar. In section it is apparently composed of two zones. The microspores are monolete, 35^40 Wm long and 20^25 Wm wide and elliptic in polar view. A supra-laesural expansion is present. The sculpture is microechinate. A contrasted perispore composed of thin joined threads that form a lacunose structure can be distinguished in the microspore sporoderm. Two parts of the underlying exospore structurally different are evident: a laminar outer part and an inner part, mostly compact. An equatorial^distal separation between both parts of the exospore is evident. The endospore is fibrillar. The ultrastructural similarity of the spores of I. savatieri with those previously studied in Isoetes can be regarded as indicative of the homogeneity of this group of living lycopsids. ß

Botanical Journal of the Linnean Society, 2005

Isoetes anatolica sp. nov. is described from a population growing in seasonal ponds of a mountain near the southern coast of the Black Sea in Bolu, Turkey. It is a robust, amphibious quillwort, characterized by semiterete, carnose microphylls, semicircular foliar section, smooth cuticle, prominent cuticular pegs, stomata, several collenchymatous strands, abundant pectic filaments and connections in the cells of the translacunar diaphragms, incurved alae, well developed ligula, small carnose labium, no velum, well-formed bulliform megaspores and obscurely muriform microspores. Plants were investigated anatomically and a description with additional diagnostic characters is included. Morphological affinities with other species of the genus are discussed. Intercellular pectic protuberances (IPP) were studied in the cells of the translacunar diaphragms of the microphylls of several species of Isoetes including I. anatolica. The IPP were examined to determine if they could provide diagnostic characters. They were detected with TBO and analysed using light and scanning electron microscopy. Types of IPP and species bearing them were as follows: warts in I. adspersa, I. andina, I. boliviensis, I. duriei, I. engelmannii, I. lechleri, I. longissima, I. melanopoda, I. storkii, I. velata. ssp. velata, and I. velata ssp. asturicense; warts and filaments in I. brochonii, I. lacustris, and I. setacea, and connections in I. anatolica and I. malinverniana. IPP are lacking in I. boryana, I. echinospora, I. histrix and I. novogranadensis. Combination of type, density, and distribution of IPP promises to be a useful vegetative character in a genus in which diagnostic characters are scarce.

TURKISH JOURNAL OF BOTANY, 2015

Introduction Cephaloceraton gymnocarpum, described for Caprera Island (Sardinia, Italy), was established by Gennari (1862) on the basis of the following putative distinctive characters compared with C. histrix: a) the phyllopodia shape, described as astatine-rhombic and tricuspidate for C. gymnocarpum and showing 2 long corns in C. histrix; b) the putative absence of a velum covering the sporangia, occurring instead in C. histrix. Concerning var. subinerme, indeed described for the first time by Gennari himself (1862), this author studied some specimens collected in Tuscany, identified by G. Savi (1769-1844) and O. Beccari (1843-1920), and indicated as a distinctive character compared with C. histrix the putative presence of shorter teeth in phyllopodia. Just 2 years after the description of C. gymnocarpum, Braun (1864) validated the combination Isoetes gymnocarpa (Gennari) A.Braun, but considered it as falling within the variability of I. histrix. Nearly in the same period Todaro (1866) described Isoetes sicula, putatively differing from I. histrix var. subinermis mainly in the shape of the phyllopodia. Just 2 years later, Cesati et al. (1868) considered I. sicula as a synonym of I. histrix var. subinermis. Béguinot (1907) evidenced the polymorphic nature of Sardinian populations: of about 800 specimens collected in Caprera (locus classicus of C. gymnocarpum), he was able to recognize, according to the characters presented by Braun (1864), 2 main typologies attributable respectively to: a) a type described as var. subinermis, an epithet used also, in eventually different combinations, by Gennari (1862) and Braun (1864), and b) a type originally described as C. gymnocarpum (Gennari, 1862, 1865; Braun, 1864), but also intermediate forms. Possibly on this basis, Fiori (1923) recognized in the Italian flora 2 varietal taxa within I. histrix: "var. typica" (var. histrix, according to the current nomenclatural rules) and var. subinermis (= C. gymnocarpum and I. sicula Tod). Later, he reiterated the same interpretation (Fiori, 1943). Thereafter, all these names were neglected for a long time (e.g., Pignatti, 1982; Jermy and Akeroyd, 1993), while the name I. sicula only was reported as a synonym of I. histrix by Greuter et al. (1984) and by Ferrarini et al. (1986). Cesca and Peruzzi (2001) raised var. subinermis to species level. This choice was wrong on nomenclatural grounds, because a) the authors referred to an incorrect basionym (I. histrix f. subinermis Durieu nomen nudum), b) the authors listed among the synonyms other taxa originally described at species level (i.e. prioritary), such as, according to Fiori (1923, 1943), Cephaloceraton gymnocarpum. This error was "corrected" by Arrigoni (2005) by proposing for this systematic unit the name Isoetes gymnocarpa. However, although he claimed to follow the work of Braun (1864), the latter author, as Gennari (1862), actually considered var. subinermis as distinct from I. gymnocarpa. Furthermore, he indicated among the synonyms of I. gymnocarpa also I. sicula Tod.

Brittonia, 2005

Radish (Raphanus sativus) is an important crucifer vegetative crop in Japan. We studied the morphological and anatomical characteristics of radish roots over a 6-week period using three radish cultivars with three different root shapes: long-type (Lt), round-type (Rt), and thin-type (Tt). We found that significant differences in the thickness of the roots first appeared 4 weeks after sowing. In Lt and Rt plants, the roots thickened rapidly, especially in the middle section that is composed of the lower part of the hypocotyl and the upper part of the taproot. The taproot increased in length in Lt plants, but failed to elongate in Rt plants. In Tt plants, the roots showed much smaller increases in mean diameter and length. Transverse sections through the taproots showed significant differences, both in cell number and in cell size 4 weeks after sowing. Lt and Rt plants contained more cells in the secondary xylem and phloem than Tt plants, and cell expansion was also greater in the storage roots of the Lt and Rt cultivars. These results will contribute to a better understanding of the development of radish roots of different shape.

For the first time the morphology of fossil and recent macro-and microspores of Isoetes L. was subjected to SEM studies and it was established that the spores belong to one and the same species, Isoetes lacustris L. Data of spore-pollen and macrofossil analyses have shown that in Late Quaternary and Early Holocene (11800-7000 BP) Isoetes lacustris was widely spread in Bulgaria. The shrinking of its area during Holocene was related to gradual overgrowth and drying up of the water basins inhabited by it.

Grana, 2012

Megaspore ornamentation is one of the few morphological characters used in the taxonomy of the genus Isoëtes. In the present work, we test the application of this character for distinguishing some Isoëtes species occurring in the Mediterranean: Isoëtes sicula, which according to some authors should be included as a variety in I. histrix, and the recently described I. todaroana, whose affinity with other taxa is currently unknown. Two additional species (I. duriei, I. velata) were also included in the analysis. The megaspores were studied using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and chemical treatment. In all species, the megaspore surface is covered by a siliceous coating; removal of this coating reveals an underlying three-dimensional network of fused rodlets. A unique pattern of this network occurs in I. sicula, supporting its separation from I. histrix. Comparison between the patterns observed in the examined Mediterranean species shows that I. todaroana is most similar to I. histrix.

The Botanical Review, 2006

Microspores of the 24 species of Isoetes that grow in southem South América were analyzed under a light microscope and scanning electrón microscope. The microspores are monolete, elliptic in polar view, 30-40 ptrn long, and 20-25 j±m wide. A background with various characteristics is seen on each surface. A supra-laesural expansión is present. The perispore is omamented and has a perforated background. In section, it has a lacunose structure. The exospore is smooth, and it has a compact structure in section. The studied species could be divided into three groups by their perispore omamentation: equinate, rugulate, and tuberculate. Microspore size was positively correlated with increasing ploidy level, and larger microspores were associated with terrestrial habitats. A convergence in omamentation was found between spores produced by the studied species and those that grow in regions outside of the area under study.

Protoplasma, 1985

The development of the testa was studied in Erythrina lysistemon using both light and electron microscopy. Cells of the outer epidermis of the outer integument divide anticlinally and undergo radial elongation to form a palisade layer. The outer tangential walls are thickened at an early stage, and deposition of fluted thickenings on the radial walls occurs at maturity. Palisade cells in the hilar region differentiate from sub-funicular tissue, and at maturity the outer ends of the cells undergo extensive deposition of secondary walls and associated lignification. The light line occurs at the junction between the outer, thickened portions of the cells and the inner, iess thickened portions. An electron-translucent (suberised) cap develops in the outer tangential walls of the palisade cells at a late stage. Microtubules and dictyosomes are closely associated with the developing thickenings in palisade and tracheid bar, and the microtubules run parallel to the wall microfibrils. Differentiation of the tracheid bar coincides with final secondary wall deposition and lignification in the hilar palisade. The cells of the tracheid bar are dead at maturity, but are surrounded by sheaths of elongate parenchyma.

Many aspects of difficult interpretation exist in the phylogenetic history of land plants. Already on the origin of plant lineage, we still have no safe dating for the endosymbiotic event, i.e., the integration of a cyanobacterium to form the precursor of chloroplasts. Similarly, we have no knowledge of the kind of eukaryote cell partner that participated in this symbiosis (as well as for the ancestor cell of animal lineage). 1

Botanical Journal of the Linnean Society, 1994