George P. Slater

Identification of olfactory cues used in host-plant finding by diamondback moth,Plutella xylostella (Lepidoptera: Plutellidae).

Olfactory attraction of female diamondback moths (Plutella xylostella) to odors of intact and homogenized host plants, as well as individual compounds characteristic of host plants, were investigated by behavioral and electrophysiological methods. Moths were attracted to odors ofBrassica juncea andB. napus seedlings in a Y-tube bioassay. Solvent fractions of homogenizedB. juncea leaves were attractive to moths whether or not isothiocyanates (IC) were present. Moths were attracted in Y-tube bioassays and to field traps baited with individual ICs. Volatiles fromB. juncea andB. napus elicited an electroantennogram (EAG) response and were attractive in the Y-tube bioassay. Allyl IC was shown to be the attractive component in homogenized plant volatiles but was found to be virtually absent from intact plant volatiles. Gas chromatographic fractionation of intact plant volatiles revealed a terpene-containing fraction to be most attractive to the moths. We were unable to isolate individual attractive compounds from this fraction. Our results suggest that certain elements of this fraction, possibly in combination, are important olfactory cues for host-plant finding by the diamondback moth with mustard oils playing an important and possibly synergistic role, particularly when plants are damaged.

Analysis of thiocyanates and isothiocyanates by ammonia chemical ionization gas chromatography-mass spectrometry and gas chromatography-Fourier transfo☆

Under NH3-chemical ionization (CI) conditions alkyl thiocyanates give mass spectra which show only the adduct ions (M + NH4) + (base peak) and Thiocyanates and isothiocyanates can also be differentiated on the basis of their gas-phase Fourier transform (FT) IR spectra. The spectra of isothiocy

Analysis of legume oligosaccharides by high-resolution gas chromatography

The suitability of high-resolution gas chromatography (HGRC) for the analysis of the raffinose family oligosaccharides (raffinose, stachyose, verbascose) was investigated. Aqueous methanol (80%) extracts of pea flour were dried and derivatized with either trimethylimidazole or N-methyl-bis(trifluoroacetamide). Separation of the sugar derivatives was achieved utilizing a 10-m DB5-60W capillary column. The effects of carrier gas (He) flow-rate and split ratio on resolution and reproducibility were studied. HRGC analysis was characterized by excellent resolution and satisfactory reproducibility, and proved to be a rapid, sensitive method for quantitation of oligosaccharides in pea flours.

Comparison of cell wall regeneration on maize protoplasts isolated from leaf tissue and suspension cultured cells

SummaryThe cell wall regeneration on protoplasts derived from maize mesophyll cells was compared with wall regeneration on protoplasts derived from suspension cultured cells using light microscopy, transmission electron microscopy, and mass spectrometry. The time course of cell wall regeneration has shown that the mesophyll protoplasts regenerated walls much slower than the protoplasts derived from cultured cells. Moreover, cell wall materials on the mesophyll protoplasts were often unevenly distributed. Electron microscopy has further demonstrated that the mesophyll protoplasts have less organized and compact walls than the protoplasts from cultured cells. Chemical analysis revealed that the mesophyll protoplasts had a lower ratio ofβ-(1–3)-glucan toβ-(1–4)-glucan than protoplasts from cultured cells. The significance of these results for the viability and development of protoplasts in culture is discussed.

Evaluation of Bacillus as a practical means for degradation of geosmin

SummaryA specific method for analysis of geosmin in bacterial cultures was developed which used a minimum of manipulation. Strains of Bacillus cereus, previously reported to degrade geosmin, were tested for their ability to degrade synthetic geosmin. The initial concentration of geosmin in media was not appreciably changed by the growth of the Bacillus strains. The natural isomer of geosmin was also tested with one of these strains and was not degraded. Previous evidence for the degradation of geosmin by Bacillus is discussed critically.