After inoculation of pine-wood nematodes (Bursaphelenchus xylophilus (STEINER et BUHRER) NICKLE), two peaks in ethylene production were observed in susceptible pine trees such as Pinus thunbergii PARL. The first appeared before the cessation of oleoresin exudation, and the second one followed. However, resistant pine trees such as Pinus jeffreyi GREY. et BALF. and P. taeda L. had only the first peak. Even in the susceptible trees, the inoculated tree that recovered from the disease did not have the second peak. The first peak always appeared in all of the inoculated trees, although the extent of the stimulation of ethylene production differed with the physiological conditions of the host and the parasite. This stimulation probably was due to the migration of the nematodes. Commercial cellulases (Onozuka R 10 and Cellulysin) could induce ethylene production when they were applied to the cambial zones of isolated pine and poplar stems. Ethylene production also was induced by a frozen suspension of nematodes which contained dead nematodes and active cellulase. Consequently, a large part of the ethylene production in the inoculated trees was apparently caused by the nematodes themselves through the intermediation of cellulase, because this nematodes excrete a considerable amount of cellulase. The resistant and susceptible pine species showed no clear differences in the cellulase-induced ethylene production in the isolated stems.

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Total and reflected short-wave radiation and net radiation were measured to analyze the radiation balance over a hinoki (Chamaecyparis obtusa S. et Z.) stand. Reflected and absorbed short-wave radiation, net radiation, and net long-wave radiation expressed as percentages of total short-wave radiation were 10.7, 89.3, 58.4, and -30.9% on annual basis, respectively. The percentage of net radiation was larger than those of other plant communities because of the small albedo of the stand and showed seasonal variation, varying from 78.3% in July to 16.9% in December. On the other hand, net long-wave radiation also had a seasonal variation, falling within the range -9.8% in August to -73.4% in December. It had a significant influence on the radiation balance, particularly in winter. The linear regression equations between net radiation and total short-wave radiation were derived from different time periods of measurement, such as monthly totals, daily totals, and instantaneously. As a result, it has become known that the slopes and the intercepts of the equations were different from the time scale used in the analysis and had a close relationship to the albedo and net long-wave radiation of the stand. But the extent of the effects of the albedo and the net long-wave radiation on the constants of the equations varied largely depending on the time scale, season, and weather conditions.

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