Fachgruppe Biologie

The purity of sacred lotus

2026-03-25T10:30:37Z

The purity of sacred lotus Barthlott, Wilhelm Main conclusion Superhydrophobicity and self-cleaning (Lotus Effect) came only in focus of research after 1997. Botanic systematic studies led to a paradigm shift in materials science and numerous technical applications. However, physics behind it is still not fully understood. Details on the discovery, consequences, and open questions are presented.

Extreme water repellency (superhydrophobicity) is a feature of many biological surfaces from terrestrial cyanobacteria to green plants and animals. The initially controversially discussed publication "Purity of sacred Lotus or escape from contamination on biological surfaces" (Planta 1997) showed that defined hierarchically structured superhydrophobic surfaces reduce the adhesion of pathogens and particles as defense mechanism. The technical applicability was indicated, and the publication initiated about 2000 publications annually and numerous applications in our daily life. Although cuticular plant surfaces are probably the largest homogenous interfaces on our planet, they came very late in the focus of research. Functional principles, occurrence of self-cleaning biological surfaces, the physical background, patenting consequences, and open questions are discussed.

Die Selbstreinigungsfähigkeit pflanzlicher Oberflächen durch Epicuticularwachse

2026-04-01T07:56:22Z

Die Selbstreinigungsfähigkeit pflanzlicher Oberflächen durch Epicuticularwachse Barthlott, Wilhelm Pflanzliche Oberflächen (z.B. Blätter) sind häufig durch mikroskopische epicuticulare Wachsausscheidungen für Wasser unbenetzbar. Es wurde nachgewiesen, daß abperlende Regentropfen partikuläre Depositionen, deren Adhaesion an die Oberfläche ebenfalls verringert ist, quantitativ entfernen. Dieser bislang übersehene Selbstreinigungsmechanismus ("Lotos-Effekt") kann durch Umwelteinflüsse wie "Sauren Regen" oder Tenside nachhaltig gestört werden. Eine Übertragung dieser Eigenschaften auf künstliche Oberflächen könnte für die Produktion von Lacken oder Folien von großer Bedeutung sein. Die Arbeiten werden vom Bundesminister für Forschung und Technologie gefördert und z.T. in Zusammenarbeit mit dem Institut für Obstbau durchgeführt.

Cooperative coding of continuous variables in networks with sparsity constraint

2025-12-29T12:30:29Z

Cooperative coding of continuous variables in networks with sparsity constraint Züge, Paul; Schieferstein, Natalie; Memmesheimer, Raoul-Martin A hallmark of biological and artificial neural networks is that neurons tile the range of continuous sensory inputs and intrinsic variables with overlapping responses. It is characteristic for the underlying recurrent connectivity in the cortex that neurons with similar tuning predominantly excite each other. The reason for such an architecture is not clear. Using an analytically tractable model as well as spiking neural networks, we show that it can naturally arise from a cooperative coding scheme. In this scheme neurons with similar responses specifically support each other by sharing their computations to obtain the desired population code. This sharing allows each neuron to effectively respond to a broad variety of inputs, while only receiving few feedforward and recurrent connections. Few strong, specific recurrent connections then replace many feedforward and less specific recurrent connections, such that the resulting connectivity optimizes the number of required synapses. This suggests that the number of required synapses may be a crucial constraining factor in biological neural networks. Synaptic savings increase with the dimensionality of the encoded variables. We find a trade-off between saving synapses and response speed. The response speed improves by orders of magnitude when utilizing the window of opportunity between excitatory and delayed inhibitory currents that arises if, as found in experiments, spike frequency adaptation is present or strong recurrent excitation is balanced by strong, shortly-lagged inhibition.

Low and facultative mycorrhization of ferns in a low-montane tropical rainforest in Ecuador

2025-12-29T11:00:26Z

Low and facultative mycorrhization of ferns in a low-montane tropical rainforest in Ecuador Michel, Jennifer; Lehnert, Marcus; Nebel, Martin; Quandt, Dietmar Kothe, Erika Arbuscular mycorrhizal fungi (AMF) are amongst the most studied obligate plant symbionts and regularly found in terrestrial plants. However, global estimates of AMF abundance amongst all land plants are difficult because i) the mycorrhizal status of many non-commercial, wild plant species is still unknown, ii) numerous plant species engage in facultative symbiosis, meaning that they can, but do not always do, associate with mycorrhiza, and iii) mycorrhizal status can vary within families, genera, and species. To gain deeper insights to the distribution of the plant-AMF symbiosis we investigated the mycorrhizal status in some of the oldest lineages of extant vascular plants, Polypodiophytina (ferns) and lycophytes, in one of the hotspots of natural plant diversification, the tropical rainforest. Providing a new data set of AMF abundance for 82 fern species representing 19 families, we hypothesized that (1) AMF would be found in 60–80% of the studied plants and (2) plant species with AMF symbionts would be more abundant than non-mycorrhizal species. Both hypotheses were rejected while the following observations were made: (1) AMF occurred in 30.5% of studied species, representing 63% of the studied fern families, (2) AMF colonisation was not correlated with species abundance, (3) a small proportion of AMF-hosting ferns was epiphytic (6%) and (4) mycorrhization was inconsistent among different populations of the same species (facultative mycorrhization). While these observations align with previous studies on ferns, they emphasise that mycorrhization is not a taxonomic trait and underscore the challenges in estimating the global abundance of AMF. In addition, the occurrence of AMF in epiphytic plants and no net benefits of AMF for plant abundance indicate that the mycorrhization observed in this study likely comprises the commensalism to parasitism range of the symbiosis spectrum.