Growth, Mg nutrition and photosynthetic activity in Pinus radiata: evidence that NaCl addition counteracts the impact of low Mg supply

We investigated effects of low Mg and moderately raised NaCl, as occurs in plantations irrigated with tertiary municipal effluent in New Zealand, on growth, Mg nutrition and photosynthetic activity of Pinus radiata D. Don seedlings grown in nutrient solutions with a Perlite medium. Seedlings were grown with either sufficient (0.35 mM; H[Mg]) or limited (0.033 mM; L[Mg]) Mg supply, without NaCl or with NaCl addition (8.7 mM; +[NaCl]). After 30 weeks, seedlings grown at L[Mg] displayed severe Mg deficiency symptoms, and had significantly less biomass than those at H[Mg]. While NaCl addition had an adverse effect on seedling growth at H[Mg], it increased growth at L[Mg]. The +[NaCl] treatment greatly increased the Mg uptake rates, which were associated with increased stomatal conductance and increased root to shoot ratio. Magnesium deficiency reduced the rates of light-saturated photosynthesis and stomatal conductance, but not the quantum efficiency of photosystem II, which was reduced mainly by the +[NaCl] treatment, especially at H[Mg]. Our study clearly indicated that NaCl addition could counteract the impact of low Mg supply by enhancing Mg uptake from the rooting medium.     

Optimization of isolation and cultivation of bacterial endophytes through addition of plant extract to nutrient media

Many endophytes have beneficial effects on plants and can be exploited in biotechnological applications. Studies hypothesize that only 0.001–1% of all plant‐associated bacteria are cultivable. Moreover, even after successful isolations, many endophytic bacteria often show reduced regrowth capacity. This research aimed to optimize isolation processes and culturing these bacteria afterwards. We compared several minimal and complex media in a screening. Beside the media themselves, two gelling agents and adding plant extract to media were investigated to enhance the number and diversity of endophytes as well as the growth capacity when regrown after isolation. In this work, 869 medium delivered the highest numbers of cultivable bacteria, as well as the highest diversity. When comparing gelling agents, no differences were observed in the numbers of bacteria. Adding plant extract to the media lead to a slight increase in diversity. However, when adding plant extract to improve the regrowth capacity, sharp increases of viable bacteria occurred in both rich and minimal media.     

Expression of type I interferon by splenic macrophages suppresses adaptive immunity during sepsis

Early during Gram-negative sepsis, excessive release of pro-inflammatory cytokines can cause septic shock that is often followed by a state of immune paralysis characterized by the failure to mount adaptive immunity towards secondary microbial infections. Especially, the early mechanisms responsible for such immune hypo-responsiveness are unclear. Here, we show that TLR4 is the key immune sensing receptor to initiate paralysis of T-cell immunity after bacterial sepsis. Downstream of TLR4, signalling through TRIF but not MyD88 impaired the development of specific T-cell immunity against secondary infections. We identified type I interferon (IFN) released from splenic macrophages as the critical factor causing T-cell immune paralysis. Early during sepsis, type I IFN acted selectively on dendritic cells (DCs) by impairing antigen presentation and secretion of pro-inflammatory cytokines. Our results reveal a novel immune regulatory role for type I IFN in the initiation of septic immune paralysis, which is distinct from its well-known immune stimulatory effects. Moreover, we identify potential molecular targets for therapeutic intervention to overcome impairment of T-cell immunity after sepsis.     

Coppicing shifts CO2 stimulation of poplar productivity to above-ground pools: a synthesis of leaf to stand level results from the POP/EUROFACE experiment

A poplar short rotation coppice (SRC) grown for the production of bioenergy can combine carbon (C) storage with fossil fuel substitution. Here, we summarize the responses of a poplar ( Populus ) plantation to 6 yr of free air CO₂ enrichment (POP/EUROFACE consisting of two rotation cycles). We show that a poplar plantation growing in nonlimiting light, nutrient and water conditions will significantly increase its productivity in elevated CO₂ concentrations ([CO₂]). Increased biomass yield resulted from an early growth enhancement and photosynthesis did not acclimate to elevated [CO₂]. Sufficient nutrient availability, increased nitrogen use efficiency (NUE) and the large sink capacity of poplars contributed to the sustained increase in C uptake over 6 yr. Additional C taken up in high [CO₂] was mainly invested into woody biomass pools. Coppicing increased yield by 66% and partly shifted the extra C uptake in elevated [CO₂] to above-ground pools, as fine root biomass declined and its [CO₂] stimulation disappeared. Mineral soil C increased equally in ambient and elevated [CO₂] during the 6 yr experiment. However, elevated [CO₂] increased the stabilization of C in the mineral soil. Increased productivity of a poplar SRC in elevated [CO₂] may allow shorter rotation cycles, enhancing the viability of SRC for biofuel production.     

Wind mediated dispersal of freshwater invertebrates in a rock pool metacommunity: differences in dispersal capacities and modes

Current evidence suggests regular overland transport of different freshwater invertebrates by wind, mainly over short distances. Yet, very little is known about the mechanism and scale of this process or about differences in wind dispersal dynamics and capacities among taxa and propagule types. We investigated wind dispersal of freshwater invertebrates in a cluster of temporary rock pools (spatial scale: 9,000 m²) in South Africa. Dispersing propagules and propagule bank fragments (i.e. aggregates of sediments and propagules) were intercepted during 1 month using a combination of windsocks (1.5 m above ground level) and sticky traps (ground level). The potential movement of propagule bank fragments (i.e. aggregates of propagules and sediments) was also simulated by tracking inter-pool movements of differently sized artificial substrate fragments similar to dry propagule bank fragments. We detected differences in the composition of dispersing communities intercepted at different altitudes (ground level and at 1.5 m). Comparison of dispersal distance distributions also revealed significant differences among taxa. Overall, larger propagule types (e.g. adult ostracods and oribatid mites) dominantly travelled near ground level while small resting eggs and cryptobiotic life stages of copepods were most frequently collected at higher altitudes (1.5 m) and dispersed over the longest distances. Finally, not only dispersal of single propagules but also ground level transport of propagule bank fragments was shown to contribute to local dispersal dynamics in temporary aquatic habitats.     

Growth-dependent modulation of capacitative calcium entry in normal rat kidney fibroblasts

Normal rat kidney (NRK) fibroblasts have electrophysiological properties and intracellular calcium dynamics that are dependent upon their growth stage. In the present study we show that this differential behavior coincides with a differential calcium entry that can be either capacitative or non-capacitative. Confluent cells made quiescent by serum deprivation, which have a stable membrane potential near ? 70 mV and do not show spontaneous intracellular calcium oscillations, primarily exhibit the capacitative mechanism for calcium entry, also called store-operated calcium entry (SOCE). When the quiescent cells are grown to density-arrest in the presence of EGF as the sole polypeptide growth factor, these cells characteristically fire spontaneously repetitive calcium action potentials, which propagate throughout the whole monolayer and are accompanied by intracellular calcium transients. These density-arrested cells appear to exhibit in addition to SOCE also receptor-operated calcium entry (ROCE) as a mechanism for calcium entry. Furthermore we show that, in contrast to earlier studies, the employed SOCs and ROCs are permeable for both calcium and strontium ions. We examined the expression of the canonical transient receptor potential channels (Trpcs) that may be involved in SOCE and ROCE. We show that NRK fibroblasts express the genes encoding Trpc1, Trpc5 and Trpc6, and that the levels of their expression are dependent upon the growth stage of the cells. In addition we examined the growth stage dependent expression of the genes encoding Orai1 and Stim1, two proteins that have recently been shown to be involved in SOCE. Our results suggest that the differential expression of Trpc5, Trpc6, Orai1 and Stim1 in quiescent and density-arrested NRK fibroblasts is responsible for the difference in regulation of calcium entry between these cells. Finally, we show that inhibition or potentiation of SOCE and ROCE by pharmacological agents has profound effects on calcium dynamics in NRK fibroblasts.