Do leaves of plants on phosphorus-impoverished soils contain high concentrations of phenolic defence compounds?

Prominent theories of plant defence have predicted that plants growing on nutrient-poor soils produce more phenolic defence compounds than those on richer soils. Only recently has the Protein Competition Model (PCM) of phenolic allocation suggested that N and P limitation could have different effects because the nutrients are involved in different cellular metabolic processes. 2. We extend the prediction of the PCM and hypothesize that N will have a greater influence on the production of phenolic defensive compounds than P availability, because N limitation reduces protein production and thus competition for phenylalanine, a precursor of many phenolic compounds. In contrast, P acts as a recyclable cofactor in these reactions, allowing protein and hence phenolic production to continue under low P conditions. 3. We test this hypothesis by comparing the foliar concentrations of phenolic compounds in (i) phenotypes of 21 species growing on P-rich alluvial terraces and P-depleted marine terraces in southern New Zealand, and (ii) 87 species growing under similar climates on comparatively P-rich soils in New Zealand vs. P-depleted soils in Tasmania. 4. Foliar P concentrations of plants from the marine terraces were about half those of plants from alluvial soils, and much lower in Tasmania than in New Zealand. However, foliar concentrations of N and phenolic compounds were similar across sites in both comparisons, supporting the hypothesis that N availability is a more important determinant of plant investment in phenolic defensive compounds than P availability. We found no indication that reduced soil P levels influenced plant concentrations of phenolic compounds. There was wide variation in the foliar N and P concentrations among species, and those with low foliar nutrient concentrations produced more phenolics (including condensed tannins). 5. Our study is the first trait comparison extending beyond standard leaf economics to include secondary metabolites related to defence in forest plants, and emphasizes that N and P have different influences on the production of phenolic defence compounds. © 2009 British Ecological Society.

Towards a Normative Defence of Provocation in England and Ireland

This article compares, in the light of the House of Lords’ decision in R v Smith (Morgan James), the English and Irish approaches to the objective test in provocation. Though the law on this point has developed in radically different directions as between England and Ireland, both jurisdictions demonstrate a profound dissatisfaction with the objective test in its traditional formulation combined with a reluctance to dispense with it altogether. It is suggested that Lord Hoffmann’s approach in Morgan Smith, by drawing out the essentially normative function of the objective test, provides a useful way forward for the law on both sides of the Irish Sea.

Heterogeneously catalysed selective hydrogenation reactions in ionic liquids

The selective hydrogenation of , unsaturated aldehydes has been performed in a range of room temperature ionic liquids. The reaction data reported show that it is possible to enhance the selectivity of supported palladium catalysts for the reduction of the conjugated CC bond by using ionic liquids as solvents compared with conventional molecular organic solvents. The catalyst system is easily recycled without the need to isolate or filter the catalyst and may be used without further treatment.

Novel bradykinins and their precursor cDNAs from European yellow-bellied toad (Bombina variegata) skin

Two novel bradykinin-related peptides (Ala3,Thr6)-bradykinin and (Val1,Thr3,Thr6)-bradykinin, were identified by a systematic sequencing study of peptides in the defensive skin secretion of the yellow-bellied toad, Bombina variegata. These peptides are the first amphibian skin bradykinins to exhibit amino acid substitutions at the Pro3 position of the bradykinin nonapeptide. Previously reported bradykinins from other Bombina species were not detected. Respective precursor cDNAs, designated BVK-1 and BVK-2, respectively, were cloned from a skin library by 3'- and 5'-RACE reactions. BVK-1 contained an open-reading frame of 97 amino acids encoding a single copy of (Ala3,Thr6)-bradykinin and similarly, the open-reading frame of BVK-2 consisted of 96 amino acids encoding a single copy of (Val1,Thr3,Thr6)-bradykinin. Synthetic replicates of each novel bradykinin were found to be active on mammalian arterial and small intestinal smooth muscle preparations. The structural diversity of bradykinins in amphibian defensive skin secretions may be related to defence against specific predators.

Reactions of polycarbonate with cyclohexene oxide and phosphites: A density functional study

Epoxides and phosphites are often used as additives to stabilize the properties of polymers, including bisphenol A polycarbonate (BPA-PC). We describe density functional (DF) calculations of the reactions of cyclohexene oxide (CHO, cyclohexane epoxide) and phosphites with chain segments of BPA-PC, with the aim of identifying possible reaction paths and energy barriers. The reactions of CHO with the OH-terminated PC chains and with the carbonate group are exothermic, although there is an energy barrier in each case of more than 10 kcal/mol. A comparison of results for different CHO isomers demonstrates the importance of steric effects. The reactions between the same groups of the PC chain and the phosphites 2-[2,4-bis(tert-butyl)phenoxy]-5,5-dimethyl-1,3,2-dioxaphosphorinane] (BPDD) and trimethyl phosphite (TMP), and their phosphonate isomers are characterized by large energy barriers.

Density functional study of reactions of phenoxides with polycarbonate

Density functional calculations with simulated annealing have been used to study the reactions of chains of bisphenol A polycarbonate (BPA-PC) with sodium phenoxide (NaOPh), diphenyl carbonate (DPC), and tetraphenylphosphonium phenoxide (PPh4OPh). These calculations extend our work on the reactions of LiOPh, NaOPh, and phenol with the cyclic tetramer of BPA-PC. We study, in particular, chain growth catalyzed by NaOPh and PPh4OH. The energy barriers for reactions with PPh4OPh are somewhat larger than those involving LiOPh and NaOPh, but they are significantly lower than those involving phenol (HOPh), due in part to the collective rearrangement of phenyl groups in the reacting molecules. We discuss in the Appendix the bonds between alkali metal atoms (Na in the present calculations) and other atoms (here oxygen) that are analogous to the more familiar "hydrogen bonds".