Chloride Availability Affects the Malate Content and its Control by the Circadian Clock in Pulvini of Phaseolus coccineus L

In soil-grown 3-to 4-weeks-old Phaseolus coccineus L. plants the chloride content changed antagonistically in the extensor and flexor of the laminar pulvinus during the circadian leaf movement in continuous light. This is as expected for an osmoticum involved in the volume changes of pulvinar cells. H ow ever, the malate content of extensor and flexor cells was not altered in a circadian manner. Furthermore, during light/dark cycles the malate content in both, extensor and flexor, was higher in the light than in the dark. This indicates that malate was not used in the osmotic motor of leaf movement and that its level was not controlled by the circadian clock in 3-to 4-weeks-old soil-grown plants. When leaves were cut from 14-days-old soil-grown plants and cultured in distilled water the pulvini were depleted of chloride and the malate content was increased. In these chloride de­ prived leaves malate, and to a lesser extent citrate (about 1/10 of malate), changed antagonistically in a circadian manner in the extensor and flexor, indicating that these organic anions were now involved in the osmotic motor and under the control of the circadian clock. The similar properties of pulvinar and stomatal movements of starch-containing guard-cells are evident: in both cases, depending on the availability of chloride, CL- and/or organic anions are used for the compensation of the electrical charge of K+.

Action of gibberellic acid in effecting phase shifts of the circadian leaf-movement rhythm of a cotton plant, Gossypium hirsutum

Pulses of gibberellic acid (GA3) offered at various phases of circadian leaf-movement rhythms in the cotton plant, Gossypium hirsutum, effected advance phase shifts of varying magnitude. Neither the quality nor the amount of these phase shifts was altered by the background illumination, suggesting an apparent absence of synergistic action of the light and gibberellic acid.