Acta Botanica Gallica, 2013, 160 (2)

Sommaire
:: E. DODINET, E. LAMBERT & M.A. SELOSSE
Editorial
Editorial
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 103-105. Anglais
 
:: E. LAMBERT , D. DESMOTS , J. LE BAIL , J.-B. MOURONVAL & J.-Cl. FELZINES
Tolypella salina R. Cor. on the French Atlantic coast: biology and ecology
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 107-119. Anglais
Abstract

Tolypella salina R. Cor. is a Charophyte only known from some French and Iberian stations. Its rarity and the specific richness of the salt marshes where it grows, on the Atlantic and Mediterranean coasts, have led to the proposal to add this species to the French list of protected plants. A survey of stations was realized on the Atlantic coast (Noirmoutier, Guérande) between 2010 and 2013 to complete the distribution map of this taxon. The aim of this work is to improve the knowledge of this plant’s biology and its ecological environment. It appears that the development of this species differs between stations, and also from one year to the next, a phenomenon due to the instability of its living environment (hydrological and salinity conditions, etc.). Phytosociological considerations related to the subassociation tolypelletosum salinae are added. Some recommendations are proposed for the management of these sites, taking into account the human activities there, in order to maintain the salt marsh mosaic that is necessary for the conservation of
Tolypella salina.

 
:: S. C. BRACAMONTE , N. G. MALDONADO & P. G. MURILLO
The genus Tolypella (A. Braun) A. Braun in the Iberian Peninsula
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 121-129. Anglais
Abstract

This study focuses on the presence and distribution of the species of Tolypella genus in the Iberian Peninsula
through a literature review and the examination of environmental, botanical and physicochemical data of the locations where T. salina, T. prolifera, T. intricata, T. hispanica and T. glomerata are settled. The shortage of herbarium material means that new collections are required to be able to conduct more detailed studies in the future, particularly on T. prolifera and T. intricata, of which the biological traits, ecology and distribution are poorly known in the Iberian Peninsula.

 
:: V. BERTRIN , S. BOUTRY , A. DUTARTRE & E. LAMBERT
Communautés de Characées des lacs médocains (Sud-Ouest de la France). Eléments d’écologie et de distribution.
Characeae communities in the Medoc area lakes (South-West France). Elements of ecology and distribution
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 131-140. Français
Résumé

Les communautés de macrophytes des lacs médocains (lac de Carcans-Hourtin et lac de Lacanau) ont fait l’objet en 2011 d’observations et de prélèvements sur la totalité de la périphérie des rives, ainsi que sur des profils perpendiculaires vers le large de ces plans d’eau. Les communautés végétales aquatiques comportent diverses espèces communes aux milieux lacustres, ainsi que des espèces patrimoniales, telles que les espèces des pelouses à littorelles, mais également des espèces exotiques à caractère envahissant. Les Characées sont bien représentées sur les lacs médocains. Chara fragifera colonise les deux tiers du linéaire des rives sur les deux lacs, jusqu’à une profondeur de 4,5 m sur le lac de Carcans-Hourtin. Nitella confervacea est moins abondante et moins fréquente, elle semble cependant coloniser les secteurs plus profonds des lacs. La répartition de ces deux espèces sur les rives des lacs est relativement homogène, les espèces n’ont pas été observées dans les secteurs d’anses protégées de vents et aux sédiments organiques fluides. Deux autres espèces de Characées, Chara globularis et Nitella translucens, sont également présentes dans ces lacs, mais d’une manière plus localisée. Le résultat de cet examen complet des rives et des prospections vers le large des lacs est cohérent avec les données disponibles dans la littérature. La présence de Chara fragifera et de Nitella confervacea dans les associations des Littorelletalia avec des Phanérogames telles que Lobelia dortmanna et Littorella uniflora, est relativement bien décrite dans ces lacs, mais aucun positionnement géographique des différentes populations de macrophytes n’avait à ce jour été effectué. De nombreuses questions liées à la gestion du niveau des eaux des lacs et à celle des espèces exotiques envahissantes (Lagarosiphon major et Egeria densa principalement) se posent pour la préservation des habitats aquatiques d’intérêt communautaire présents sur ces lacs, mais également pour ceux situés au sud du bassin d’Arcachon le long du littoral aquitain.

Abstract

The lakes from Medoc (Carcans-Hourtin and Lacanau lakes) are located in the Aquitaine region, France, close to the Atlantic coast of the Bay of Biscay. These shallow lakes are characterized by a sandy substratum and a non-symmetrical slope of the bottom from the west side to the east side of the lakes. They are exposed to the prevailing westerly winds and they are mesotrophic. In 2011, the macrophyte communities of the perimeters of these two lakes were inventoried throughout the littoral zones. The aquatic vegetation in the deepest parts of the lakes was detected with the aid of an echosounder along several profiles perpendicular to the shore line. Samples were taken with a rake or a grapnel at regular points along the profiles for the identification of taxa detected by the echosounding. These communities include species common to lake ecosystems: some are protected species, such as the species of Littorella lawns (Lobelia dortmanna, Littorella uniflora, Isoetes boryana, Caropsis verticillatinundata), and some are exotic invasive species (Lagarosiphon major, Egeria densa, Ludwigia peploides). Moreover, some species of Charophytes are abundant and frequent in these lakes. Chara fragifera colonizes two-thirds of the littoral zone from the shore line to a depth of 4.5 m in Carcans-Hourtin. Nitella confervacea is less abundant and frequent, but it appears to colonize the somewhat deeper parts of the lakes. The distribution of these two species is relatively homogeneous from west to east; they seem to colonize in a similar way both the shores exposed to the prevailing winds and those protected from them. Chara fragifera and Nitella confervacea were not found in the wind-protected fluid organic substrate coves on the west sides of the lakes. The distribution maps of these two species on each lake are presented in this paper. Two other species of Charophytes, Chara globularis and Nitella translucens, are also present in these lakes, but with a more localized distribution. The results of this thorough investigation of the shores and the deepest parts of the lakes correspond with the data available in the literature. The presence of Chara fragifera and Nitella confervacea in the associations of the Littorelletalia with phanerogams such as Lobelia dortmanna and Littorella uniflora, are relatively well described for these lakes, but so far, no geographical localization of the macrophyte populations had been performed. The survey raises many questions related to the management of the water level of the lakes and management of the invasive alien species for the protection of the native aquatic habitats of these lakes, as well as for the other lakes situated along the Atlantic coast, from the south of the Bay of Arcachon to the Adour estuary.

 
:: J. DELAY & D. PETIT
Contribution à la connaissance de quelques Characées du Nord de la France
Contribution to the knowledge of several Characeae of Northern France
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 141-148. Français
Résumé

L’étude de la flore hydrophytique de petits plans d’eau du nord de la France nous a permis d’observer quelques représentants de la famille des Characées. Dans un but pédagogique mais aussi pour inciter les botanistes de terrain à persévérer dans la détermination de ces organismes, la description illustrée de quelques représentants de cette famille a été réalisée.

Abstract

Survey of the hydrophytic flora of small stretches of water in northern France has allowed the observation of several taxa of the Characeae family here reported, namely Chara vulgaris, Chara vulgaris f. longibracteata, Chara globularis, Chara curta, Nitella gracilis and Tolypella glomerata. According to current literature, 25 taxa within Characeae are present in northern France, at species, variety or form level. Chara vulgaris, as a complex, is very frequently found in northern France in newly created stretches of water. It colonizes meso-eutrophic waters and shows a cosmopolitan distribution. The type species seems to be rarer locally than the longibracteata form, but more investigations are needed to confirm this observation. Chara globularis has been recorded on the coastline of northern France, in the peat bogs at the back of the coastline, in the humid dune slacks and further inland where the plant can survive winter, in some mining slag ponds in the area of Valenciennes, the water of which has been qualified as sub-briny. Nitella gracilis in the area is perceived as a meso-eutrophic to oligo-mesotrophic water species, although in Brittany and Germany its presence has been noted in acidophilous communities together with Potamogeton polygonifolius, Littorella uniflora or Sphagnum spp. The species is mostly present in western France, and is very rare in eastern France. Tolypella glomerata has been very rarely observed in northern France. The observation here reported in a small pond on the hill of Marchenelles is only the third report in the area. The species is not expressed there as a monospecific community (as usually reported) and must be searched for within a very dense Chara vulgaris var. longibreactata cover that develops in early spring. To facilitate the identification of these plants in the field, an
illustrated description of each taxa identified has been provided.

 
:: K. BOCIĄG , A. ROBIONEK , E. REKOWSKA & K. BANAŚ
Effect of hydrodynamic disturbances on the biomass and architecture of the freshwater macroalga Chara globularis Thuill.
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 149-156. Anglais
Abstract

The effect of wave-induced disturbances in the shallow littoral zone on Chara globularis individuals was studied in three populations located in three different lakes in Poland. In addition, an experiment was performed to check if the observed responses were confirmed in vegetative offspring grown ex situ. Individuals from wave-exposed sites were lighter than those from sheltered ones; they had more ramets and lateral branches. The main axes, branches, internodes and branchlets were shorter. The shortening of the main axis was a statistically significant response in each population. The reduction of biomass of thalli and shortening of branchlets under wave-exposed conditions was statistically significant only in part of the populations. The differences in underground biomass, number of branches, length of internodes and presence of holdfasts among individuals from wave-exposed and sheltered sites in the populations showed inconsistent trends between populations. This suggests a location-specific nature of some of the morphological variations. The vegetative offspring (new ramets obtained ex situ) from the fragments of individuals growing at wave-exposed sites were lighter, smaller, had shorter axes in a statistically significant way in comparison with the offspring from sheltered sites. The observed growth trend was the same as in the case of parent individuals. Hence the response noted in the parent population was confirmed in vegetative offspring. For all the remaining features, differences were more pronounced between new ramets than between parent individuals. Hence, in situ, the phenotypic responses to other environmental factors overlapped with the disturbance-related responses.

 
:: I. SOULIÉ-MÄRSCHE , F. TRIBOIT , M. DESPRÉAUX , A. REY-BOISSEZON , I. LAFFONT-SCHWOB & A. THIÉRY
Evidence of Chara fibrosa Agardh ex Bruzelius, an alien species in South France
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 157-163. Anglais
Abstract

The paper describes the discovery of a species of genus Chara, hitherto unknown in France. The morphological features of the plants and oospores are shown and identify the plant as Chara fibrosa ssp. benthamii, a tropical taxon, non-native to the European Charophyte flora. The ecological conditions of this particular find correspond to an artificial temporary pond located in the Crau plain, north of the Camargue. In contrast to the normal hydrological cycle ruled by local precipitation during winter, the studied pond is flooded from irrigation water in late spring and during summer. This context allowed C. fibrosa to out-compete the indigenous Chara species, Chara vulgaris and Chara globularis. The accidental introduction of C. fibrosa is attributed to original contamination from rice seed material imported to the nearby Camargue, rather than to dispersal by migratory water birds. Although the species has formed a very large population in that pond within a few years, it might not be classified as “invasive” because this occurrence is linked to a particular man-made habitat. However, spread of the species in the future, as a function of global warming related to climate change, cannot be excluded.

 
:: D. DELMAIL , M.-L. ABASQ , P. COURTEL , I. ROUAUD & P. LABROUSSE
DNA damage protection, antioxidant and free-radical scavenging activities of Myriophyllum alterniflorum DC (Haloragaceae) vegetative parts
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 165-172. Anglais
Abstract

DNA damage induced by free radicals is associated with mutation-based health impairment and cancers. The protective effect of five different extracts from an aquatic macrophyte, the alternate water-milfoil Myriophyllum alterniflorum DC (Haloragaceae), is investigated on the DNA disruption mediated by hydroxyl (HO•) and hydroperoxyl (HOO•) radicals, and their antioxidant activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and O2 • . Indeed, M. alterniflorum is supposed to be a good candidate for DNA protection as this species was recently used in ecological surveys as a bioindicator of water quality because of its ability to cope with and to reflect the heavy-metal pollution through variations of antioxidant contents. Moreover, preliminary results indicated higher levels of scavengers specialized in reactive oxygen species reduction, than common medicinal plants. Acetone and ethanol extracts from vegetative parts limit significantly the oxidative damage of plasmid DNA induced by Fenton-reaction reactive oxygen species. The radical antioxidant activities of acetone and aqueous extracts are higher than those of other solvents: [DPPH] IC50 = 2.4 ± 0.2 mg.ml–1 and [O2 • ] AI50 = 220.0 ± 14.1 μg.ml–1, respectively. Protection towards free radicals is correlated with high contents of antioxidant compounds in acetone extracts [phenol compounds: 21.00 ± 0.69 mg gallic acid.g–1 DW (dry weight)] and aqueous extracts (flavonoids: 125.48 ± 1.26 mg rutin.g–1 DW). Myriophyllum alterniflorum can be regarded as a promising natural-product source of antigenotoxics and antioxidants and could be envisaged for therapeutic purposes.

 
:: J.-Y. DUBUISSON , G. ROUHAN , A. GRALL , S. HENNEQUIN , B. SENTERRE , K. PYNEE & A. EBIHARA
New insights into the systematics and evolution of the filmy fern genus Crepidomanes (Hymenophyllaceae) in the Mascarene Archipelago with a focus on dwarf species
Paru dans Acta Botanica Gallica, 2013, 160 (2), pp. 173-194. Anglais
Abstract

The diversity of species belonging to the filmy fern genus Crepidomanes (Hymenophyllaceae) in the Mascarene archipelago was studied, based on morphological investigations and focusing especially on the most dwarf species that are easily confused in the field and in herbarium collections. Morphological potential clusters and discriminations were then compared with an rbcL phylogeny. As a result, we recognized at least eight morpho-species for the archipelago and defined characters for distinguishing the three smallest ones, Crepidomanes bonapartei, Crepidomanes minutum and Crepidomanes (Trichomanes) trinerve. Morphological evidence and molecules confirm the specific status for T. trinerve (newly combined in Crepidomanes), the inclusion of Crepidomanes mannii into a C. minutum complex, and new records of C. bonapartei for Mauritius. The neotropical Polyphlebium pyxidiferum is found to be closely related to Afro-Madagascan Crepidomanes inopinatum and Crepidomanes melanotrichum species and so is newly combined in Crepidomanes. A key for the eight species of the genus in the archipelago, description of a new section clustering Crepidomanes frappieri and Crepidomanes longilabiatum, and new enhanced descriptions for two dwarf taxa (C. bonapartei and C. trinerve) are provided, and biogeographical origins of the genus in the Western Indian Ocean area are discussed.