The circadian rhythms of the swelling and shrinkage behaviors for the stems of Cryptomeria japonica cloned saplings grown in a phytotron were investigated in this study. The results obtained were summarized as follows.
1) The diurnal fluctuations of tangential stain on the surface of the inner bark were remained in constant permanent light and darkness.
2) The irrigation preceded further than physical stimulus and circadian rhythm.
3) The circadian rhythm of tangential strain on the inner bark in constant permanent light was 22 hours 58 minutes 20 seconds. In this case, the lighting and dark considerable period were 11 hours 33 minutes 20 seconds and 11 hours 25minutes, respectively.
4) The circadian rhythm of tangential strain on the surface of the inner bark in constant permanent darkness was 29 hours 50 minutes. In this case, the lighting and dark considerable period were 14 hours 56 minutes 40 seconds and 14 hours 53 minutes 20 seconds, respectively.
5) The circadian rhythm of tangential strain on the surface of the inner bark in constant permanent light shortened from 24 hours and that in constant permanent darkness lengthened from 24 hours. The time difference between the circadian rhythm of tangential strain on the surface of the inner bark in constant permanent darkne ss was 6 hours 51 minutes 40 seconds.
6) The amplitude of diurnal fluctuation of tangential strain on the surface of the inner bark in constant perma nent light was the almost double of that in constant permanent darkness.
7) In constant permanent light, the circadian time, which divided a period for 24 hours equally, of tangential strain on the surface of the inner bark was 12 hours 04 minutes 21 seconds and 11 hours 55 minutes 39 seconds for the lighting and darkness considerable period, respectively. In constant permanent darkness, the circa dian time of tangential strain on the surface of the inner bark was 12 hours 12 minutes and 11 hours 48 minu tes for the lighting and darkness considerable period, respectively.
8) In natural light, the circadian time of tangential train on the surface of the surface of the inner bark was 12 hours 11 minutes and 11 hours 49 minutes for the lighting and darkness considerable period, repectively, and the darkness considerable period. This tendency was same with the results in artificial light as mentioned above. Namely, it seemed memorize the period of naturl light which lived before under the artificial light.
10) For the circadian rhythm of tangential strain on the inner bark under the stificial light, the period that was similar to the natural light was that in constant permanent light quantitavely, and was that in constant permanent darkness qualitatively.