Time resolved sulphur and nutrient distribution in Norway spruce drill cores using ICP-OES

Methods were developed for detailed dendrochemical studies of low sulphur contents in Norway spruce (Picea abies L. Karst.). This tree species is the dominant conifer species in Northern and Central Europe and therefore predestined for a possible use as an environmental archive. Two independent digestion procedures were investigated with respect to their suitability for element determination and optimised for analysis of the low sulphur content in wood. A modified oxygen bomb combustion procedure and a microwave acid digestion procedure were evaluated with the goal to obtain sufficient detection limits in order to access low concentrated non-metals with an appropriate time resolution. Method development included evaluation of strategies preventing losses of volatile sulphur species. Digestion efficiency was demonstrated by recovery rates for various certified plant standard reference materials (NIST 1572, NIST 1547, RM 8436, BCR 101, NIST 1515, RM 8436, NIST 1573, NIST 1575) as well as self prepared standards with defined low sulphur content of 20 to 200mg kg−1, which are typical for Norway spruce wood samples. Ultra sonic nebulisation (USN) was evaluated with respect to signal enhancement for sample introduction to inductively coupled plasma optical emission spectrometry (ICP-OES). The optimised procedure was applied to Norway spruce drill cores from locations with different environmental conditions in Switzerland, in order to investigate the anthropogenic impact of sulphur and the suitability of Norway spruce as an environmental archive for sulphu

Effect of glucose on assimilatory sulphate reduction in Arabidopsis thaliana roots

With the aim of analysing the relative importance of sugar supply and nitrogen nutrition for the regulation of sulphate assimilation, the regulation of adenosine 5′‐phosphosulphate reductase (APR), a key enzyme of sulphate reduction in plants, was studied. Glucose feeding experiments with Arabidopsis thaliana cultivated with and without a nitrogen source were performed. After a 38 h dark period, APR mRNA, protein, and enzymatic activity levels decreased dramatically in roots. The addition of 0.5% (w/v) glucose to the culture medium resulted in an increase of APR levels in roots (mRNA, protein and activity), comparable to those of plants kept under normal light conditions. Treatment of roots with d‐sorbitol or d‐mannitol did not increase APR activity, indicating that osmotic stress was not involved in APR regulation. The addition of O‐acetyl‐l‐serine (OAS) also quickly and transiently increased APR levels (mRNA, protein, and activity). Feeding plants with a combination of glucose and OAS resulted in a more than additive induction of APR activity. Contrary to nitrate reductase, APR was also increased by glucose in N‐deficient plants, indicating that this effect was independent of nitrate assimilation. [35S]‐sulphate feeding experiments showed that the addition of glucose to dark‐treated roots resulted in an increased incorporation of [35S] into thiols and proteins, which corresponded to the increased levels of APR activity. Under N‐deficient conditions, glucose also increased thiol labelling, but did not increase the incorporation of label into proteins. These results demonstrate that (i) exogenously supplied glucose can replace the function of photoassimilates in roots; (ii) APR is subject to co‐ordinated metabolic control by carbon metabolism; (iii) positive sugar signalling overrides negative signalling from nitrate assimilation in APR regulation. Furthermore, signals originating from nitrogen and carbon metabolism regulate APR synergisticall

Impact of European Beech Forest Diversification on Soil Organic Carbon and Total Nitrogen Stocks–A Meta-Analysis

Drought-sensitive European beech forests are increasingly challenged by climate change. Admixing other, preferably more deep-rooting, tree species has been proposed to increase the resilience of beech forests to drought. This diversification of beech forests might also affect soil organic carbon (SOC) and total nitrogen (TN) stocks that are relevant for a wide range of soil functions and ecosystem services, such as water and nutrient retention, filter functions and erosion control. Since information of these effects is scattered, our aim was to synthesize results from studies that compared SOC/TN stocks of beech monocultures with those of beech stands mixed with other tree species as well as monocultures of other tree species. We conducted a meta-analysis including 38 studies with 203, 220, and 160 observations for forest floor (i.e., the organic surface layer), mineral soil (0.5 m depth) and the total soil profile, respectively. Monoculture conifer stands had higher SOC stocks compared to monoculture beech in general, especially in the forest floor (up to 200% in larch forests). In contrast, other broadleaved tree species (oak, ash, lime, maple, hornbeam) showed lower SOC stocks in the forest floor compared to beech, with little impact on total SOC stocks. Comparing mixed beech-conifer stands (average mixing ratio with regard to number of trees 50:50) with beech monocultures revealed significantly higher total SOC stocks of around 9% and a smaller increase in TN stocks of around 4%. This equaled a SOC accrual of 0.1 Mg ha$^{-1}$ yr$^{-1}$. In contrast, mixed beech-broadleaved stands did not show significant differences in total SOC stocks. Conifer admixture effects on beech forest SOC were of additive nature. Admixing other tree species to beech monoculture stands was most effective to increase SOC stocks on low carbon soils with a sandy texture and nitrogen limitation (i.e., a high C/N ratio and low nitrogen deposition). We conclude that, with targeted admixture measures of coniferous species, an increase in SOC stocks in beech forests can be achieved as part of the necessary adaptation of beech forests to climate change

Insect haptoelectrical stimulation of Venus flytrap triggers exocytosis in gland cells

The Venus flytrap Dionaea muscipula captures insects and consumes their flesh. Prey contacting touch-sensitive hairs trigger traveling electrical waves. These action potentials (APs) cause rapid closure of the trap and activate secretory functions of glands, which cover its inner surface. Such prey-induced haptoelectric stimulation activates the touch hormone jasmonate (JA) signaling pathway, which initiates secretion of an acidic hydrolase mixture to decompose the victim and acquire the animal nutrients. Although postulated since Darwin’s pioneering studies, these secretory events have not been recorded so far. Using advanced analytical and imaging techniques, such as vibrating ion-selective electrodes, carbon fiber amperometry, and magnetic resonance imaging, we monitored stimulus-coupled glandular secretion into the flytrap. Trigger-hair bending or direct application of JA caused a quantal release of oxidizable material from gland cells monitored as distinct amperometric spikes. Spikes reminiscent of exocytotic events in secretory animal cells progressively increased in frequency, reaching steady state 1 d after stimulation. Our data indicate that trigger-hair mechanical stimulation evokes APs. Gland cells translate APs into touch-inducible JA signaling that promotes the formation of secretory vesicles. Early vesicles loaded with H⁺ and Cl⁻ fuse with the plasma membrane, hyperacidifying the “green stomach”-like digestive organ, whereas subsequent ones carry hydrolases and nutrient transporters, together with a glutathione redox moiety, which is likely to act as the major detected compound in amperometry. Hence, when glands perceive the haptoelectrical stimulation, secretory vesicles are tailored to be released in a sequence that optimizes digestion of the captured animal

Significance of current weather conditions for foliar traits of old-growth sessile oak (Quercus petraea Liebl) trees

The aim of the present study was to elucidate the significance of current weather conditions for foliar traits of adult sessile oak (Quercus petraea), one of the most valuable forest tree species in Central Europe. For this purpose, structural and functional traits were analysed in fully expanded, sun exposed leaves collected in south-west Germany from five old-growth forest stands, representing the meteorological and pedospheric conditions in the growing region, but differing in aridity during the 12 days before harvest in two consecutive years. Across the forest stands, most foliar traits differed significantly between wet and dry weather conditions before harvest as indicated by partial least square discriminant analysis (PLS-DA). These traits included fresh weight/dry weight ratio, leaf hydration, leaf-C content, leaf-C/N ratio, structural N, soluble protein-N, total amino acid-N, cell wall composition, numerous specific amino acids as well as soluble sugar content. Structural biomass, δ13C signature, total N and total C as well as H2O2 contents were not affected by the weather before harvest. These results indicate a high plasticity of the foliar metabolism of drought-tolerant sessile oak to current weather conditions. They also suggest that sessile oak is characterized by a high potential to cope with the growth conditions expected as a consequence of future climate change

Surviving Volcanic Environments — Interaction of Soil Mineral Content and Plant Element Composition

Different plant species were investigated fromtwo Aeolian Islands located in close vicinity, one with fumarolic activity (Vulcano) and one without (Lipari). On Vulcano, elevated concentrations of SO2/H2S determined in ambient air indicated the need of plants to adapt to harmful sulphur concentrations by detoxification strategies. The current study was focused on evaluating the element composition of plant leaves in relation to soil mineral contents. The soil of Volcano was characterised by a significantly lower pH on all three sampling sites as well as very high amounts of sulphur and plant available sulphate due to volcanic activities, compared to Lipari. By contrast, a general difference in the composition of trace elements in the soil was not observed between the islands, apart from arsenic, which was increased at all three sampling sites on Vulcano. Element accumulation in the leaves differed between the two islands. The tested species showed a significant higher accumulation of numerous elements (Al, B, Fe, K, Mg, Mn, Ni, and Zn) on Vulcano compared to Lipari, while excluding Ca and Mo. These differences in element accumulation in the leaves between the islands may be caused by the lower soil pH on Vulcano. Extreme sulphur accumulation was found for all tested species on Vulcano, but was lower in woody species with higher dry matter content compared to herbaceous species with lower dry matter content. This caused a significantly negative correlation between plant sulphur and dry matter content. From these results, it is concluded that species with higher dry matter contents possess a more effective protection against extreme sulphur accumulation. Strategies to cope with other potentially toxic elements in the soil ranged from exclusion to hyper-accumulation. Hierarchical cluster analyses of the leaf element content revealed a clear separation between two groups: First, herbaceous perennial plants as strong accumulators; and second, woody perennial plants such as shrubs or trees as less strong accumulators, with the primordial species Fumaria capreolata representing an outside group