Band structure of absorptive two-dimensional photonic crystals

The band structure for an absorptive two-dimensional photonic crystal made from cylinders consisting of a Drude material is calculated. Absorption causes the spectrum to become complex and form islands in the negative complex half-plane. The boundaries of these islands are not always formed by the eigenvalues calculated for Bloch vectors on the characteristic path, and we find a hole in the spectrum. For realistic parameter values, the real part of the spectrum is hardly influenced by absorption, typically less than 0.25%. The employed method uses a Korringa-Kohn-Rostoker procedure together with analytical continuation. This results in an efficient approach that allows these band-structure calculations to be done on a Pentium III personal computer

How plants might recognize rhizospheric bacterial volatiles

In contrast to animals, plants possess neither olfactory organs nor a central nervous system. However, they do perceive and systemically react to volatile stimuli. Such function serves in monitoring the immediate and remote environments and translates into optimized responses to biotic and abiotic stresses. While the ecological relevance of volatile-mediated plant–plant and plant–insect interactions is today unquestioned, both above- and below-ground plant–microbe communication through VOCs has only gained attention recently. The common metabolic origins that yield the vast chemical diversity of plant and microbes allow for a substantial overlap between plant and microbial volatile species. Hence, it remains unclear if plants recognize and/or distinguish plant-like from foreign cues. The identities of the cellular components ensuring such recognition are even more obscure. Easy-to-score plant outputs in response to microbial VOCs elicitation, like plant growth promotion and innate immunity stimulation, will be instrumental to pinpointing VOCs-sensing proteins. Several major phytohormones have a gaseous nature and dedicated perception machineries that could serve as a basis to envisage how volatile semiochemicals might be sensed by plants. If volatile-mediated communication represents an ancestral cellular feature, VOCs perception and signalling might rely on basal protein families and define a universal chemical language