ULTRADIAN MOVEMENTS OF SHOOTS OF 2 SPECIES OF SOYBEANS GLYCINE SOJA (SIEB. AND ZUCC.) AND GLYCINE-MAX (L.) MERR

Circumnutation movements of shoot tips of two species of soybean were studied. Shoot tips of Glycine soja (Sieb. and Zucc.) moved in a count erclockwise direction with a mean period (+/-SD) of 108 +/- 9 minutes when the shoots were not handled prior to monitoring (n = 17). Effects of mechanical stress or stimulation (thigmomorphogenesis) resulted in the lengthening of the mean period by 15% when shoot lengths were mea sured (handled) prior to monitoring movements (124 +/- 18 minutes, n = 49) or handled and restaked prior to monitoring movements (124 +/- 14 minutes, n = 11). Shoot tips of G. max cultivars moved counterclockwi se, and, depending on the cultivar, periods ranged from 112 minutes to 133 minutes, with an overall average period of 124 +/- 21 minutes (n = 21). This period was identical to the mean period of comparably hand led G. soja shoot tips. Amplitudes for the four G. max cultivars were much smaller (0.12 cm to 1.43 cm) than for G. soja (2.9-8.7 cm). Facto rs that may have contributed to differences in rhythm characteristics between species and among cultivars included the presence of a disting uishable bending zone in G. soja, but not in G. max, and morphological features associated with shoot development.