© 2007 Heron Publishing—Victoria, Canada
Correlation between acoustic emission, water status and xylem embolism in pine wilt disease
Kenji Fukuda (1, 2), Shin Utsuzawa (3–5) and Daisuke Sakaue (6)
1. Laboratory of Evaluation of Natural Environment, Institute of Environmental Studies, Graduate School of Frontier Sciences,
University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8563, Japan / 2. Corresponding author (fukuda@k.u-tokyo.ac.jp) / 3. MRTechnology, Inc., 169-1 Kouya Tsukuba-city Ibaraki, 300-2642, Japan / 4. Institute of Applied Physics, University of Tsukuba, Ibaraki, Japan / 5. Present address: New Mexico Resonance, 2301 Yale Blvd. SE, Suite C-1, Albuquerque, NM 87106, USA / 6. University Forest at Tanashi, University of Tokyo, Tokyo, Japan / Received January 6, 2006; accepted November 9, 2006; published online April 2, 2007
Summary
The occurrence of cavitation events and embolism during the latent, early stage and the late developmental stages of pine
wilt disease was monitored nondestructively by acoustic emission (AE) and high-resolution magnetic resonance microscopy, respectively,
and the results were compared with changes in leaf water potential and stem thickness. In the latent stage of the disease,
when no embolisms were observed, cavitation events were detected by AE during the daytime in water-stressed Japanese black
pine (Pinus thunbergii Parl.) seedlings, indicating that cavitation occurred at the individual tracheid level. In the early stage of the disease,
an increase in the frequency of AE events occurred coincidentally with the occurrence of patchy embolisms at the mass tracheid
level. The threshold water potential for such mass cavitation was higher than that causing cavitation of individual tracheids
during the latent stage of the disease. In the advanced stage of the disease, explosive AE events were observed coincidentally
with drastic enlargement of embolized areas and decreases in water potential. The AE events in the latent stage occurred only
during the daytime, whereas, in the early and advanced stages of the disease, they also occurred at night. The explosive occurrence
of cavitation in the advanced stage was thought to be a case of “runaway embolism.”
Keywords:
Bursaphelenchus xylophilus, cavitation, MRI, nondestructive observation, pinewood nematode, Pinus thunbergii, ultrasonic acoustic emission.
