Broadleaf seedling responses to warmer temperatures “chilled” by late frost that favors conifers

Climate change includes not only shifts in mean conditions but also changes in the frequency and timing of extreme weather events. Tree seedlings, as the potential future overstory, are responding to the selective pressures of both mean and extreme conditions. We investigated how increases in mean temperature and the occurrence of late spring frosts affect emergence, development, growth, and survival of 13 native and non-native broadleaf and conifer tree species common in central Europe. Three temperature levels (ambient, +3, and +6 °C) and three spring frost treatments (control, late, and very late) were applied. Development responses of first-year seedlings to warmer temperatures were similar in direction and magnitude for broadleaf and conifer species. Stem size also increased with rising mean temperature for most species, though broadleaf species had maximal height advantage over conifer species in the warmest treatment. Sensitivity to frost differed sharply between the broadleaf and conifer groups. Broadleaf survival and stem length exhibited strong reductions due to frost events while conifer species only showed minor decreases in survival. Importantly, more rapid development and earlier leaf-out in response to warmer temperatures were associated with increased mortality from frost for broadleaf species but decreased mortality for conifer species. This research suggests that compositional shifts in the direction of species favored by increasing mean temperatures may be slowed by extreme events, and thus, the occurrence and impacts of such weather events must be acknowledged and incorporated into research and forest planning.     

Organic fertilizers derived from plant materials Part I: Turnover in soil at low and moderate temperatures

The aim was to investigate different organic fertilizers derived from plant materials with respect to their nitrogen and carbon turnover in soil in comparison with organic fertilizers derived from animal‐waste products. In a 64‐day incubation study at 5°C and 15°C, the following fertilizers were used: coarse faba bean–seed meal (Vicia faba L.), coarse meals of yellow and white lupin seeds (Lupinus albus L. and Lupinus luteus L.), Phytoperls^® (waste products of maize [Zea mays L.] processing), coarse meal of castor cake (Ricinus communis L.) as a widely used organic fertilizer, and horn meal as a reference fertilizer‐derived from animal waste products. At 15°C, horn meal showed the highest apparent net N mineralization of fertilizer‐derived N, followed by castor cake and the two lupin meals. At 5°C, apparent net N mineralization of fertilizer‐derived N from horn meal and coarse meal of yellow lupin seeds was nearly identical, followed by castor‐cake meal. Net N mineralization from legume‐seed meals showed no or even a negative temperature response, at least temporarily. In contrast, the other fertilizers showed a positive temperature response of net N mineralization. The content in recalcitrant structural components and the decoupling of decomposition of N‐rich and C‐rich tissue components in time are discussed as controlling factors of fertilizer‐N turnover at low temperature. Microbial residues seem to be an important temporary sink of fertilizer‐derived C and N. Legume‐seed meals induced considerable N‐priming effects. Temperature induced differences in the decomposition of total fertilizer C, indicated by changes in the sum of cumulative CO₂‐C evolution, total K₂SO₄‐soluble organic C and microbial‐biomass C were much smaller than indicated by cumulative CO₂‐C evolution alone. Our results indicate that legume‐seed meals have the potential to replace horn meal and castor‐cake meal in organic vegetable production, especially when soil temperatures in early spring are still low.     

Organic fertilizers derived from plant materials Part II: Turnover in field trials

Our aim was to investigate two different organic fertilizers derived from plant materials (OFDP) with respect to their nitrogen (N) and carbon (C) turnover in field trials planted with small radish (Raphanus sativus L. var. sativus) and white cabbage (Brassica oleracea L. convar. capitata var. alba) or fallow. The two fertilizers investigated were coarse seed meal of yellow lupin (Lupinus luteus L.) and coarse meal of castor cake (Ricinus communis L.). Under cool spring conditions, the soil turnover of yellow lupin–seed meal was slightly enhanced compared to castor‐cake meal. During the vegetation period of the vegetables, N added with both fertilizers was metabolized more or less completely by soil microorganisms. Due to similar efficiencies of the fertilizers tested, no significant difference could be found in the N uptake of plants. From this point of view, yellow lupin–seed meal, which can be produced by farmers themselves, has the potential to replace the widely used castor‐cake meal. Considerable amounts of N may remain in the field after fertilization with OFDPs either as mineral N or as easily mineralizable organic N. This N should be utilized immediately by a succeeding crop to avoid leaching losses.     

Use of microcalorimetry to study microbial activity during the transition from oxic to anoxic conditions

Microbial heat production is a nonspecific measure for microbial activity irrespective of O₂ availability in soils. In a series of long-term batch microcalorimeter experiments with closed ampoules, we examined the microbial activity in glucose-amended soil aggregates from different soil depths of a clay forest soil during the transition from aerobic to anaerobic conditions. Furthermore, the influence of the soil aggregate size on the long-term metabolic heat production was examined. Heat output curves showed a distinct pattern for soil samples from different soil depths and aggregate sizes and led to the following conclusions: 1. Microbial biomass and microbial activity strongly decreased with increasing soil depth as well as increasing soil aggregate size despite relatively constant organic C concentrations. 2. The transition from aerobic to anaerobic conditions led to a considerable drop in microbial activity. However, based on the energy balance, 10-26% of the heat production during the aerobic phase is attributable to anoxic or partly anoxic metabolism. 3. After O₂ exhaustion, a lag phase of low but constant heat output was observed, followed by a peak of anaerobic metabolic activity. Heat production during the lag phase was hypothesised to be an indicator for the biomass of facultatively anaerobic microorganisms in the soil.     

Beryllium effects on potatoes and oats in acid soil

The most likely means of Be entry into the food chain would appear to be via root, tuber, and forage crops grown on acid soils. Potatoes (Solanum tuberosum) and oats (Avena sativa) were grown in greenhouse pots of a strongly acid soil treated with 0 to 300 ppm Be and 0 to 1000 ppm CaC0₃. Germination and yield decreased, and plant Be content increased, with increasing soil Be content. The Be content of the potato tubers appeared to be low and unaffected by the soil Be content. Liming the soil and increasing the time between Be contamination and crop planting lessened the effect of Be.     

Compost and P amendments for stimulating microorganisms and maize growth in a saline soil from Pakistan in comparison with a nonsaline soil from Germany

A 92 d greenhouse pot experiment with maize (Zea mays L.) was carried out with a strongly saline soil from Pakistan (P‐s) in comparison with a nonsaline soil from Germany (G‐s) similar in pH and texture. The aim was to evaluate salinity effects on the decomposition of compost and effects of compost and P amendments on (1) plant growth and (2) microbial‐biomass formation. The yield of maize shoot‐C and root‐C increased in both soils in the order nonamended control < +triple superphosphate (TSP) (A1) < +compost (A2) < +(compost + TSP) (A3) < +TSP‐enriched compost (A4). In comparison with the control, the highest yield in treatment A4 was nearly doubled on the G‐s, but was increased more than 8‐fold on the saline P‐s. Averaging the three compost treatments, 32% of the compost added was decomposed in the German soil and 36% in the Pakistani soil on the basis of the compost recovered as particulate organic matter. These data were roughly in agreement with the CO₂‐evolution data. This indicates that the decomposition of compost was not affected by salinity. Compost‐derived CO₂ was mainly evolved until day 32, the root‐derived CO₂ from day 74 until the end of the experiment. The addition of compost resulted in higher contents of microbial biomass C and biomass P, but also in that of NaHCO₃‐extractable P. These three properties were significantly interrelated (r = 0.64–0.85), but on a lower level of significance than the relationships between shoot‐C, root‐C, and NaHCO₃‐extractable P (r = 0.90–0.93). Applying compost enriched with TSP (incubation of compost and TSP for 24 h) provided considerably more P to plants and microorganisms than the separate addition of these two components. The results suggest that the role of the microbial biomass as a sink and source for available P deserves further attention.     

Adrenal medulla grafts enhance recovery of striatal dopaminergic fibers

The drug, 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP), depletes striatal dopamine levels in primates and certain rodents, including mice, and produces parkinsonian-like symptoms in humans and nonhuman primates. To investigate the consequences of grafting adrenal medullary tissue into the brain of a rodent model of Parkinson's disease, a piece of adult mouse adrenal medulla was grafted unilaterally into mouse striatum 1 week after MPTP treatment. This MPTP treatment resulted in the virtual disappearance of tyrosine hydroxylase-immunoreactive fibers and severely depleted striatal dopamine levels. At 2, 4, and 6 weeks after grafting, dense tyrosine hydroxylase-immunoreactive fibers were observed in the grafted striatum, while only sparse fibers were seen in the contralateral striatum. In all cases, tyrosine hydroxylase-immunoreactive fibers appeared to be from the host rather than from the grafts, which survived poorly. These observations suggest that, in mice, adrenal medullary grafts exert a neurotrophic action in the host brain to enhance recovery of dopaminergic neurons. This effect may be relevant to the symptomatic recovery in Parkinson's disease patients who have received adrenal medullary grafts.     

A stable aminyl radical metal complex

Metal-stabilized phenoxyl radicals appear to be important intermediates in a variety of enzymatic oxidations. We report that transition metal coordination also supports an aminyl radical, resulting in a stable crystalline complex: [Rh(I)(trop2N.)(bipy)]+OTf- (where trop is 5-H-dibenzo[a,d]cycloheptene-5-yl, bipy is 2,2'-bipyridyl, OTf- is trifluorosulfonate). It is accessible under mild conditions by one-electron oxidation of the amide complex [Rh(I)(trop2N)(bipy)], at a potential of -0.55 volt versus ferrocene/ferrocenium. Both electron paramagnetic resonance spectroscopy and density functional theory support 57% localization of the unpaired spin at N. In reactions with H-atom donors, the Rh-coordinated aminyl behaves as a nucleophilic radical.     

Enhanced morphine analgesia in mice lacking beta-arrestin 2

The ability of morphine to alleviate pain is mediated through a heterotrimeric guanine nucleotide binding protein (G protein)-coupled heptahelical receptor (GPCR), the mu opioid receptor (muOR). The efficiency of GPCR signaling is tightly regulated and ultimately limited by the coordinated phosphorylation of the receptors by specific GPCR kinases and the subsequent interaction of the phosphorylated receptors with beta-arrestin 1 and beta-arrestin 2. Functional deletion of the beta-arrestin 2 gene in mice resulted in remarkable potentiation and prolongation of the analgesic effect of morphine, suggesting that muOR desensitization was impaired. These results provide evidence in vivo for the physiological importance of beta-arrestin 2 in regulating the function of a specific GPCR, the muOR. Moreover, they suggest that inhibition of beta-arrestin 2 function might lead to enhanced analgesic effectiveness of morphine and provide potential new avenues for the study and treatment of pain, narcotic tolerance, and dependence.     

Identification of the antibacterial compound produced by the marine epiphytic bacterium Pseudovibrio sp. D323 and related sponge-associated bacteria

Surface-associated marine bacteria often produce secondary metabolites with antagonistic activities. In this study, tropodithietic acid (TDA) was identified to be responsible for the antibacterial activity of the marine epiphytic bacterium Pseudovibrio sp. D323 and related strains. Phenol was also produced by these bacteria but was not directly related to the antibacterial activity. TDA was shown to effectively inhibit a range of marine bacteria from various phylogenetic groups. However TDA-producers themselves were resistant and are likely to possess resistance mechanism preventing autoinhibition. We propose that TDA in isolate D323 and related eukaryote-associated bacteria plays a role in defending the host organism against unwanted microbial colonisation and, possibly, bacterial pathogens.