Identification of the volatile component(s) causing the characteristic foxy odor in various cultivars of Fritillaria imperialis L. (Liliaceae)

To identify the component(s) causing the foxy odor, characteristic for some Fritillaria imperialis cultivars, the headspace of flower bulbs was analyzed using gas chromatography-olfactometry (GC-O) and GC-mass spectrometry (GC-MS). Six Fritillaria species and cultivars were selected as follows: F. imperialis cv. Premier (very strong foxy odor), F. imperialis cv. Lutea (strong foxy odor), F. imperialis ssp. Inodora (no odor), Fritillaria eduardii (weak mousy odor), Fritillaria raddeana (no odor), and an F1 of F. imperialis Lutea x Inodora (weak foxy odor). Volatiles from these flower bulbs were accumulated on Tenax and injected into the GC by thermodesorption. The majority of the volatiles consisted of low molecular weight aliphatic compounds. GC-O revealed that the foxy odor was caused by a single component, identified as 3-methyl-2-butene-1-thiol on the basis of smell in GC-O analyses (two GC columns), mass spectra, and retention times. Chemical identification was substantiated by GC-O and GC-MS of an authentic standard of 3-methyl-2-butene-1-thiol, prepared by organic synthesis.     

Phytophthora genome sequences uncover evolutionary origins and mechanisms of pathogenesis

Draft genome sequences have been determined for the soybean pathogen Phytophthora sojae and the sudden oak death pathogen Phytophthora ramorum. O?mycetes such as these Phytophthora species share the kingdom Stramenopila with photosynthetic algae such as diatoms, and the presence of many Phytophthora genes of probable phototroph origin supports a photosynthetic ancestry for the stramenopiles. Comparison of the two species' genomes reveals a rapid expansion and diversification of many protein families associated with plant infection such as hydrolases, ABC transporters, protein toxins, proteinase inhibitors, and, in particular, a superfamily of 700 proteins with similarity to known o?mycete avirulence genes.     

Probing the solvent-assisted nucleation pathway in chemical self-assembly

Hierarchical self-assembly offers a powerful strategy for producing molecular nanostructures. Although widely used, the mechanistic details of self-assembly processes are poorly understood. We spectroscopically monitored a nucleation process in the self-assembly of p-conjugated molecules into helical supramolecular fibrillar structures. The data support a nucleation-growth pathway that gives rise to a remarkably high degree of cooperativity. Furthermore, we characterize a helical transition in the nucleating species before growth. The self-assembly process depends strongly on solvent structure, suggesting that an organized shell of solvent molecules plays an explicit role in rigidifying the aggregates and guiding them toward further assembly into bundles and/or gels.     

A method for three-dimensional stem analysis and its application in a study on the occurrence of resin pockets in <Emphasis Type="Italic">Pinus patula</Emphasis>

Information on the external shape, internal properties and defects of a tree is important for the forest and wood-processing industries. Resin pockets are internal defects, associated with some softwood species, and are especially undesirable in furniture, joinery and veneer products. In this study, we propose a new lower-cost method for measuring tree shape and macroscopic internal characteristics. The objectives of this study were to: (1) design, construct and test a mobile system that can be used in field to obtain a three-dimensional model of a log or tree stem indicating selected macroscopic internal characteristics and (2) to use the system to investigate the occurrence and causes of resin pockets in Pinus patula from the Mpumalanga escarpment in South Africa. In order to establish the cause of resin pocket formation in Pinus patula, four 3-m logs from 24 trees from three compartments were dissected and digitally reconstructed into three-dimensional models. The results from the study suggest that the formation of Type 1 resin pockets in Pinus patula was due to bending stresses caused by wind sway. It was not possible to establish with certainty the cause of Type 2 resin pocket formation. However, there was evidence that damage events, and specifically thinning damage, have been the cause of some of the Type 2 resin pockets observed.