Xanthium Leaf Movements in Light and Dark

Abstract

Bunning suggested that circadian rhythms provide the basis for time measurement in the photoperiodic responses of plants (2)

The Participation of Two Rhythms in the Leaf Movements of Xanthium Plants Given Various Light-Dark Cycles

“…Four interpreted to be present by the epinastic movement that occurs about 16 hr after the beginning of the light period (9). This dip in the leaf position appears as dip A in the summary curves of Figure 2 and is clearly distinguishable in all but some of the LD 12:12 treatments (Ic and Id or 2c and 2d).…”

“…The presence of two distinct leaf movement rhythms, a "light-on" and a "light-off" rhythm, has been reported in Xanthium strumarium (9). The light-on rhythm, which is initiated by the onset of illumination, is characterized by an epinastic leaf curvature occurring 16 hr after the beginning of the light period and in continuous light approximately every 24 hr thereafter.…”

Two coupled oscillators: Simulations of the circadian pacemaker in mammalian activity rhythms

“…Aschoff, 1975). Various properties of insect eclosion rhythms (Engelmann, 1966) and of nyctinastic leaf movements (Engelmann & Honegger, 1967: Hoshizaki, Brest & Hamner, 1969 in different light-dark cycles have been interpreted as suggesting separate oscillating systems, one coupled to dawn and the other to dusk.…”

Rhythmic Leaf Movements in Biloxi Soybean and Their Relation to Flowering

“…It is, of course, possible that there are two separate clocks involved in the two responses we have been studying. In fact, the light-off, light-on rhythm that has been reported in the leaf movements of Xanthium (15) and in the flowering response of Pharbitis (23) might be an indication of a multiple clock system. Hastings (13) has discussed the possibilities and implications of one clock versus many clocks, and it does not seem worthwhile to detail that discussion.…”

“…Previous papers from our laboratory discussed the participation of a light-on and a light-off rhythm in the photoperiodic flowering response of Pharbitis (23) and in the leaf movements of Xanthilum (15). It should be noted that the present experiments were not designed to determine the presence or the effect of the light-on and light-off rhythms on the leaf movements or flowering in Biloxi soybeans.…”