Hamburg, Germany
Hamburg, Germany

Time filter

Source Type

Stamenkovic M.,Biozentrum Klein Flottbek | Stamenkovic M.,Sinisa Stankovic Institute for Biological Research | Hanelt D.,Biozentrum Klein Flottbek
Hydrobiologia | Year: 2016

Although conjugating algae are considered to have a cosmopolitan freshwater distribution, numerous ecological and taxonomic investigations revealed that many desmid taxa (at the level of genus, species and variety) are capable of occupying specific geographic zones, characterized by particular climatic attributes. Earlier studies have dealt with influences of temperature and irradiation (photosynthetically active radiation and ultraviolet radiation) on the physiology and ultrastructure of desmids. Yet, recent investigations demonstrated a clear relationship between these climatic factors and the distributional potential of conjugating algae, taking into account their photosynthetic, physiological and ultrastructural adaptations which had been revealed during and after certain temperature and irradiation treatments. Despite the fact that desmids can be considered as high-light-adapted algae, various species- and strain-specific characteristics and adaptations appeared in accordance with the light intensities predominating at their source localities, as estimated by their photosynthetic performance (obtained from PAM fluorometry and oxygen evolution measurements), pigment composition and morpho-anatomical characteristics. Interestingly, the high-light adaptation of photosynthesis as well as the relatively high growth temperature optima for majority of the desmid species investigated may provide some support for Coesel’s hypothesis on the origin of desmids in the tropical zone. © 2016 Springer International Publishing Switzerland

Stamenkovic M.,Biozentrum Klein Flottbek | Hanelt D.,Biozentrum Klein Flottbek
Photochemistry and Photobiology | Year: 2013

Numerous in vitro investigations have suggested that macroalgae exhibit regular geographic and depth distribution patterns in accordance with the light and temperature predominance at their habitats; however, there have been only a few similar studies concerning microalgae. We examined the potential influence of irradiance on patterns of distribution of four Cosmarium strains isolated from various climatic zones and cultured long term (>15 years) under a constant temperature-light regime. All the Cosmarium strains demonstrated physiological responses that were consistent with the light intensity prevailing at their source location, confirming that these responses are genetically preserved, as concluded from chlorophyll fluorescence and oxygen evolution rates measurements. Addition of inhibitors of chloroplast-encoded protein synthesis (chloramphenicol and streptomycin) and violaxanthin de-epoxidase (dithiothreitol) indicated that the Cosmarium strains developed "sun- or shade-plant" protection strategies, in accordance with the climate at their sampling sites. The polar Cosmarium strains exhibited a "shade-plant strategy" - to suffer some photoinhibition, but acquire increasing protection from photoinhibited PSII centers, whereas the tropical strains displayed a "sun-plant strategy" - to counteract photoinhibition of PSII by a high rate of repair of photoinhibited PSII reaction centers and a high xanthophyll cycle turnover. © 2013 The American Society of Photobiology.

Numerous detailed studies have been made of climatically and environmentally influenced macroalgal geographic distribution patterns. However, so far, there have been only a few intrinsic investigations of the geographic distributions of microalgae. In order to investigate the physiological differences among geographically different microalgal strains, six Cosmarium strains were collected from various climate areas and studied. They were grown under a constant light-temperature regime (16°C and 30 μmol photons m-2 s-1) and nutrient supply. The arctic representative, C. crenatum var. boldtianum, and the typical tropical desmid, C. beatum, behaved like algae adapted to high light intensities, as judged from the distinctly high values of photosynthetic capacity and saturating irradiance measured, in accordance with the high solar radiation prevailing in their sampling areas. The arctic taxon appeared more optimally suited to the low cultivation temperature, as evidenced by the relatively high values of growth rates, maximum quantum yield and photosynthetic efficiency measured. The cosmopolitan taxa, C. meneghinii and C. punctulatum var. subpunctulatum, exhibited a high maximum quantum yield and photosynthetic efficiency concomitantly during growth, which explained their ubiquitous distribution. Nevertheless, two clones belonging to C. punctulatum var. subpunctulatum, collected from polar and mountainous tropical regions, differed significantly with regard to cell volume, growth rates, surface area to volume ratio and photosynthetic parameters. The physiological differences between the Cosmarium strains were in accordance with their geographic origin; they are discussed in detail in this study. Moreover, these differences were maintained despite the long-term cultivation under identical and constant laboratory conditions. © 2011 Springer Science+Business Media B.V.

Hartmann H.E.K.,Biozentrum Klein Flottbek | Liede-Schumann S.,University of Bayreuth
Bradleya | Year: 2014

Based on extensive morphological studies in more than 1,000 populations, two new subgenera are established in the genus Drosanthemum: D. subg. Decidua H.E.K.Hartmann and subg. Quadrata H.E.K.Hartmann; in the latter, a new species is described: D. tetramerum H.E.K. Hartmann. A key and descriptions of the included species are provided. © 2014 BCSS.

Hartmann H.E.K.,Biozentrum Klein Flottbek | Meve U.,University of Bayreuth | Liede-Schumann S.,University of Bayreuth
Plant Ecology and Evolution | Year: 2011

Background and aims - The genus Trianthema (Aizoaceae - Sesuvioideae) is poorly known. Identification of two well circumscribed subgenera is followed by a revision of T. subg. Papularia, presenting for the first time a list of all species identified as members of the subgenus. Methods - Normal practices of herbarium taxonomy have been applied to study all herbarium material available, mainly from AD, B, BRI, C, DNA, E, HBG, K, L, MO, UTB, WAG, and Z. Key results - Based on an extensive investigation into as many characters as possible, results permitted the identification of new character states, supporting the division of the genus Trianthema into the two subgenera, Trianthema and Papularia. In consequence, species limits can be reliably re-circumscribed, resulting in the recognition of 17 species in the latter subgenus, of which five are described as new here: T. corallicola, T. mozambiquensis, T. pakistanensis, T. ufoensis, and T. vleiensis. Raised to species rank are T. clavata and T. corymbosa, and emended and re-circumscribed are T. crystallina, T. hereroensis, T. parvifolia, T. salsoloides, T. sanguinea, T. sedifolia, T. sheilae, T. transvaalensis, and T. triquetra. Unaltered is the description of T. argentina, for which, however, the critical features are also described and figured in order to permit a sound identification of each species in T. subg. Papularia. Distribution patterns are discussed and possible evolutionary pathways are suggested on a morphological base. © 2011 National Botanic Garden of Belgium and Royal Botanical Society of Belgium-ISSN 2032-3921.

Stamenkovic M.,Biozentrum Klein Flottbek | Hanelt D.,Biozentrum Klein Flottbek
European Journal of Phycology | Year: 2013

In contrast to the many investigations on possible relationships between climate and geographical distributions in macroalgae, there are almost no similar studies regarding microalgae. In this study we consider the potential influence of temperature on patterns of distribution of six Cosmarium strains isolated from various climate zones that have been cultured long-term (> 15 years) in a relatively low temperature-low light regime. Growth and photosynthetic parameters, obtained from PAM fluorometry, were used to estimate the physiological characteristics of the strains during and after various temperature treatments. Acclimation to constant temperature and light conditions tended to affect photosynthetic parameters more than algal growth characteristics. However, all of the Cosmarium strains demonstrated physiological responses that were consistent with their source location under both low and high temperature conditions, confirming that such responses are genetically preserved. The Cosmarium strains displayed photosynthetic capacities and levels of the onset of saturation that repeatedly exceeded values recorded for other microalgae and seaweeds, indicating that these desmid strains are adapted to high light. This observation, as well as the relatively high growth temperature optima for all of the Cosmarium strains, provides some support for Coesel's hypothesis on the origin of desmids in the tropical zone. Interestingly, the Cosmarium strains used in this study demonstrated not only adaptive characteristics in accordance with the temperature prevailing at their sampling sites, but also with regard to their evolutionary origin. © 2013 Copyright 2013 British Phycological Society.

Hartmann H.E.K.,Biozentrum Klein Flottbek
Bradleya | Year: 2013

Initiated by the description of a new species in Delosperma closely resembling members of the genus Ectotropis, an investigation was begun again to determine the circumscription of Ectotropis. As a result, Ectotropis as a genus can be confirmed, based mainly on flower and fruit morphology, and two species are recognized: E. alpina N.E. Br, and E. seanii-hoganii (Niederle) H.K. Hartmann & C. Schroder, comb. nov.

Hartmann H.E.K.,Biozentrum Klein Flottbek | Liede-Schumann S.,University of Bayreuth
Bradleya | Year: 2013

In a comprehensive study of the genus Drosanthemum, material was detected that differs fundamentally in molecular and morphological character states from the genus proper. Since it can neither be placed in any of the existing genera of the tribe Ruschieae, a new genus is described here, Knersia H.E.K. Hartmann & Liede gen nov., with K. diversifolia (L. Bolus) H.E.K. Hartmann & Liede comb. nov. as the single species.

Stamenkovic M.,Biozentrum Klein Flottbek | Woelken E.,Biozentrum Klein Flottbek | Hanelt D.,Biozentrum Klein Flottbek
Protoplasma | Year: 2014

Plant species collected from various climatic zones and stressed in vitro at various temperatures reveal changes in cellular ultrastructure which are in accordance with the climate at their sampling sites. This observation initiated the investigation to establish if stress at different temperatures may cause diverse extents of changes in the ultrastructure of microalgal strains originating from different geographic zones. The study revealed that the six Cosmarium strains demonstrated ultrastructural characteristics that were consistent with their source location under optimal, low and high temperature conditions, pointing to their preference to specific climatic niches. Interestingly, chloroplasts of all of the Cosmarium strains correspond to a sun-adapted type, which is concomitant with earlier statements that these strains are rendered as high-light adapted algae. The Cosmarium strains developed multiple ultrastructural responses which enabled them to cope with excessive temperatures, occasionally occurring in desmid natural habitats. The appearance of cubic membranes and increased number of plastoglobules may represent the first line in protection against high-temperature stress, which is accompanied by the alteration of protein synthesis and the appearance of stress granules in order to preserve cell homeostasis. However, the prolonged warm- or cold-temperature stress obviously initiated the programmed cell death, as concluded from the appearance of several ultrastructural features observed in all of the Cosmarium strains. The fair acclimation possibilities and the ability to undergo programmed cell death in order to save the population, certainly favor the cosmopolitan distribution of the genus Cosmarium. © 2014, Springer-Verlag Wien.

Hartmann H.E.K.,Biozentrum Klein Flottbek | Niesler I.M.,Biozentrum Klein Flottbek
Bradleya | Year: 2012

The confusion of names and species boundaries in and between the genera Acrodon and Brianhuntleya, resembling a Gordion knot, is analysed on the base of new collections, images from habitat and cultivation, and many new investigations into the character sets of most features. The genera are newly delimited against each other mainly based on characters of fruit morphology and features of the leaves. The species are attributed accordingly and differences between them have been found in flowers and growth forms.

Loading Biozentrum Klein Flottbek collaborators
Loading Biozentrum Klein Flottbek collaborators