Gating of aquaporins by heavy metals in Allium cepa L. epidermal cells

Changes in the water permeability, aquaporin (AQP) activity, of leaf cells were investigated in response to different heavy metals (Zn2+, Pb2+, Cd2+, Hg2+). The cell pressure probe experiments were performed on onion epidermal cells as a model system. Heavy metal solutions at different concentrations (0.05 μM–2 mM) were used in our experiments. We showed that the investigated metal ions can be arranged in order of decreasing toxicity (expressed as a decrease in water permeability) as follows: Hg>Cd>Pb>Zn. Our results showed that β-mercaptoethanol treatment (10 mM solution) partially reverses the effect of AQP gating. The magnitude of this reverse differed depending on the metal and its concentration. The time course studies of the process showed that the gating of AQPs occurred within the first 10 min after the application of a metal. We also showed that after 20–40 min from the onset of metal treatment, the water flow through AQPs stabilized and remained constant. We observed that irrespective of the metal applied, the effect of AQP gating can be recorded within the first 10 min after the administration of metal ions. More generally, our results indicate that the toxic effects of investigated metal ions on the cellular level may involve AQP gating

Variation in categorical variables describing the bedrock type, its pH and age for each species cluster.

<p>Values in bold are significantly different from those for the pooled data (p<0.05, χ² test). Abbreviations for age classes: <b>HoloSedi</b>-holocene sediments; <b>PostHist</b>-postglacial, historic, younger than AD 871; <b>PostPreHist</b>-postglacial, prehistoric, older than AD 871; <b>TertPleist</b>-Tertiary and Pleistocene, older 11000 years; <b>UppPleist</b>-Upper Pleistocene, younger than 0.8 m.y.; <b>UppLowPleist</b>-Upper Pliocene and Lower Pleistocene, 0.8–3.3 m.y.; <b>UppTerti</b>-Upper Tertiary, older than 3.3 m.y.; <b>Ind</b>–Indefinite.</p

Distribution and biogeographical affinities of species clusters.

<p>Maps of species distribution in the clusters: <i>Luzula arcuata</i> (A), <i>Carex rupestris</i> (B), <i>Nardus stricta</i> (C), <i>Saxifraga aizoides</i> (D) (maps) and their biogeographical affinities (diagrams A’, B’, C’, D’). For explanations see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102916#pone-0102916-g001" target="_blank">Figure 1</a>.</p

Results of principal component analysis, correlations of variables and principal components.

<p>Correlations >0.8 are marked in bold face.</p

Distribution patterns in the native vascular flora of Iceland.

The aim of our study was to reveal biogeographical patterns in the native vascular flora of Iceland and to define ecological factors responsible for these patterns. We analysed dataset of more than 500,000 records containing information on the occurrence of vascular plants. Analysis of ecological factors included climatic (derived from WORLDCLIM data), topographic (calculated from digital elevation model) and geological (bedrock characteristics) variables. Spherical k-means clustering and principal component analysis were used to detect biogeographical patterns and to study the factors responsible for them. We defined 10 biotic elements exhibiting different biogeographical patterns. We showed that climatic (temperature-related) and topographic variables were the most important factors contributing to the spatial patterns within the Icelandic vascular flora and that these patterns are almost completely independent of edaphic factors (bedrock type). Our study is the first one to analyse the biogeographical differentiation of the native vascular flora of Iceland