Three scales of wound-induced chemical responses in plants are identified: (1) highly localised chemical changes associated with disruption of cell compartmentation; (2) changes induced in cells surrounding the damaged area, forming a kind of halo around the damage, and (3) more widely-dispersed changes which may affect an entire organ, branch or plant. A brief review of the literature reveals that such chemical responses are very widespread in plants, and many of the substances formed are known to affect adversely the growth, development, or reproduction of insects. It is argued that wound-induced changes in plant chemistry represent for insects a powerful selective pressure for the dispersal of grazing. Levels and patterns of invertebrate grazing in a range of herbaceous and deciduous woody plants sampled at the end of the growing seasons were examined. Leaves of many species exhibited a strikingly evident over-dispersion of grazing initiations, and in some cases the arrangement of holes appeared close to regularity. The pattern of damage between leaves was, in most cases, heavily biased towards a large proportion of leaves receiving a low level of grazing. These highly dispersed patterns of grazing damage are consistent with the hypothesis that wound-induced responses play an important role in determining patterns of insect feeding. They have important implications for the expected levels of insect exploitation of host plants and for the advantages to the plant of distributing grazing damage evenly through the canopy.

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-The extracellular calcium-sensing receptor CaSR is expressed in blood vessels where its role is not completely understood. In this study, we tested the hypothesis that the CaSR expressed in vascular smooth muscle cells (VSMC) is directly involved in regulation of blood pressure and blood vessel tone. Mice with targeted CaSR gene ablation from vascular smooth muscle cells (VSMC) were generated by breeding exon 7 LoxP-CaSR mice with animals in which Cre recombinase is driven by a SM22␣ promoter (SM22␣-Cre). Wire myography performed on Cre-negative [wild-type (WT)] and Crepositive SM22␣ CaSR ⌬flox/⌬flox [knockout (KO)] mice showed an endothelium-independent reduction in aorta and mesenteric artery contractility of KO compared with WT mice in response to KCl and to phenylephrine. Increasing extracellular calcium ion (Ca 2ϩ ) concentrations (1-5 mM) evoked contraction in WT but only relaxation in KO aortas. Accordingly, diastolic and mean arterial blood pressures of KO animals were significantly reduced compared with WT, as measured by both tail cuff and radiotelemetry. This hypotension was mostly pronounced during the animals' active phase and was not rescued by either nitric oxide-synthase inhibition with nitro-L-arginine methyl ester or by a high-salt-supplemented diet. KO animals also exhibited cardiac remodeling, bradycardia, and reduced spontaneous activity in isolated hearts and cardiomyocyte-like cells. Our findings demonstrate a role for CaSR in the cardiovascular system and suggest that physiologically relevant changes in extracellular Ca 2ϩ concentrations could contribute to setting blood vessel tone levels and heart rate by directly acting on the cardiovascular CaSR. calcium-sensing receptor; CaSR; vascular smooth muscle cells; blood pressure regulation; G protein-coupled receptor; blood vessel tone regulation THE EXTRACELLULAR CALCIUM -sensing receptor CaSR was the first G protein-coupled receptor identified that has an ion, Ca 2ϩ

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