Rhythmic Leaf Movements in Biloxi Soybean and Their Relation to Flowering

Abstract

The rhythmic leaf movement of Biloxi soybean (Glycine max) and its relationship to the rhythmic flowering response were studied. The movements of fully expanded trifoliate leaves were recorded with kymographs and time lapse photography in growth chambers. A comparison between the leaf movement rhythm and the rhythmic flowering response indicates that a high degree of similarity exists between the two rhythms. A definite relationship was shown to exist between the direction of the leaf movement and the photophil-photophobe phases of the rhythmic flowering response.Short light perturbations may affect flowering by interacting directly with the flowering process while not affecting the basic endogenous rhythm. Long light perturbations may affect flowering by phase shifting the basic endogenous rhythm. Thus, light perturbations appear to have a dual effect on the flowering response of Biloxi soybean. The hypothesis that both the flowering rhythm and the leaf movement rhythm are coupled to the same basic oscillator is supported by the similarity of the phase shifts induced in the two rhythms by identical light perturbations.

Analysis of clock gene homologs using unifoliolates as target organs in soybean (Glycine max)

“…Therefore, very young soybean plants with unexpanded leaves can be used as the target organs to analyze the mechanism of floral induction. Previous researchers usually employed the plants with trifoliolates opened to study soybean flowering (Brest et al, 1971;Carpenter and Hamner, 1963;Coulter and Hamner, 1965;Nanda and Hamner, 1959).…”

“…In those studies, researchers treated soybean plants with different photoperiods or lights such as red-and far-red light when the second (Carpenter and Hamner, 1963) or third (Brest et al, 1971;Coulter and Hamner, 1965;Nanda and Hamner, 1959) trifoliolate leaf was fully expanded, and then the total number of nodes was recorded when plants flowered (Carpenter and Hamner, 1964;Coulter and Hamner, 1965;Nanda and Hamner, 1959). Their results also showed that at least three photoinductive cycles, each consisting of a short light period and a long dark period, are required to produce floral primordia (Hamner, 1940;Nanda and Hamner, 1959).…”

A metabolic indicator of photoperiodic timing.

“…2 mean that the timing of the CO2 output maximum on NO3-medium follows that of the maximal sensitivity to a night interruption by about 3 hr, and that both respond to a change in the length of the light period in precisely the same way. These results thus confirm the conclusion tentatively (12) based only on the earlier flowering data obtained under nonskeleton photoperiods: the CO2 maximum here is an accurate indicator of the photoperiodic timing process.…”

“…Some means of following the crucial changes during induction itself would be valuable. Recognizing this problem, investigators of circadian timing in photoperiodism have used leaf movements as indicators of the effects of light and darkness, effects expressed in subsequent flowering responses (1)(2)(3). But (7), which possibly is more properly designated L. paucicostata (8), were maintained in continuous light (6).…”

“…On both nitrate and ammonium media, the maximum referred to is the second of the two daily peaks observable under schedules with main light periods shorter than about 8 hr and the only one remaining with longer light periods (6). In order to minimize temperature changes and direct light effects on CO2 flux, main light periods in all experiments were substituted by skeleton photoperiods in which 3 (11). No net CO2 uptake is observed at any time under these conditions, and the new fronds produced in them are yellow-white.…”