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SUMMARYConditions favouring the infection of isolated tobacco mesophyll protoplasts by potato virus X (PVX) were studied in detail, and a procedure to effect infection in 7o ~ of protoplasts was developed. PVX required higher concentrations of both inoculum virus and poly-L-ornithine than tobacco mosaic virus (TMV) or cucumber mosaic virus (CMV). PVX infection showed a unique response to varying pH of the inoculation medium. The time course of PVX multiplication in protoplasts resembled that of TMV. Unlike the infection by TMV and CMV, PVX infection was partially inhibited by actinomycin D. Inclusion bodies characteristic for PVX infection were present in the infected protoplasts, but their involvement in virus production appeared to be unlikely.

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This paper proposes an efficient compensation method using a first-order approximation of time axis scaling for the variations of the room acoustic transfer function. The time axis scaling model is based on the fact that the change of the sound velocity due to the change of room temperature is a dominant factor for the variations of room impulse response affected by environmental conditions. In this paper, the effectiveness of the compensation method is evaluated using room impulse responses measured in the real environment. As the results, it is clarified that the variations of room impulse response can be modeled by the first-order approximated time axis scaling when the successive re-estimation is performed every small change of temperature. Furthermore, it is shown that the compensation method applied to an inverse filtering based dereverberation approach improves the intelligibility and speech recognition rates dramatically.