Effects of Lanthanum and Ethylenediaminetetraacetate on Leaf Movements of Mimosa

Abstract

Lanthanum and ethylenediaminetetraacetate (EDTA) profoundly affect the rapid leaf movements of Mimosa pudica L. Lanthanum, which mimics calcium but does not penetrate the plasmalemma, inhibits the dosing response but does not affect reopening. A low concentration of EDTA retards the reopening process while a higher EDTA concentration prevents the dosing movement. There is evidence that the EDTA effects result from chelation of calcium ions rather than chelation of other cations. These results are discussed with regard to the role of calium in leaf movements.When the leaves of Mimosa are mechanically stimulated, the paired leaflets fold together (Fig. 1, A and B). This rapid response (seismonasty) requires less than 2 sec. After seismonastic closure the leaflets reopen within 30 min. These movements result from the bending of the pulvinules which join the leaflets to the rachilla. These bendings are caused by changes in the turgor of the motor cells of the pulvinule (1)(2)(3)20 MATERIALS AND METHODS Mimosa pudica L. plants were grown from cuttings in a University of California, Riverside greenhouse. Prior to use, plants were allowed to adjust to the laboratory environment for 48 hr. This "adaptation" period was indispensable; plants tested within the first several hr in the laboratory recovered from stimuli very slowly and the leaflet pairs did not completely reopen.Laboratory plants were illuminated with incandescent lamps for 15 hr/day and all experiments were performed within the first 5 hr of this illumination period. The effects of various test solutions were examined in two ways. In some experiments excised leaves had their petioles placed in vials containing distilled H20 (controls) or appropriate experimental solutions (Fig. 1A). In most of the experiments excised leaflet pairs were floated, adaxial surface up, on solutions in "spot plates" (Fig. 1B). For both types of experiments the samples were illuminated with incandescent lamps (6,500 lux) which were separated from the samples by heat shields. Both the whole leaves and the excised leaflet pairs could be stimulated with a dissecting probe. The angles between paired leaflets were measured before and after stimulation to the closest 10 degrees with a protractor. Each "point" in the graphs (Figs. 2-7) represents an average leaflet angle for four experiments. In each experiment, three leaves or three excised leaflet pairs received each treatment.Preliminary experiments indicated that distilled H20 and quarter-strength Hoagland solution produced identical results and distilled H20 was therefore chosen as the most appropriate control. Lanthanum chloride solutions (lanthanum nitrate yielded the same results) were adjusted to pH 6.5 with NaOH. Solutions of EDTA were adjusted to pH 7 with NaOH. All EDTA "wash-out" solutions were also adjusted to pH 7. The concentrations of the experimental solutions and the length of treatment time are given under "Results."For a description of the technique for the ultrastructural localization of lanthanum see Thomso...

Effects of Compounds Affecting Calcium Channels on Phytochrome- and Blue Pigment-Mediated Pulvinar Movements of Cassia fasciculata

“…On the basis that motility is inhibited by chelatants (EDTA and EGTA) (4,13,19) and promoted by the ionophore A 23187 (19), it can be supposed that calcium is involved in the regulation of leaf movements induced by variations in light conditions; in fact, fluxes of Ca2+ from the wall to the cellular interior have been reported during seismonastic movements of M. pudica (28). Until now, the mechanism of calcium mediation has not been clearly understood.…”

“…By contrast, it is suggested that calcium is not mobilized Since Ca2" is necessary to the response (4,19), it is postulated (28) that Ca2+ is taken from internal stores which may be the tannin vacuole and/or the endoplasmic reticulum. This can be achieved through involvement of the phosphatidylinositol pathway as described by Berridge and Irvine (2); this proposal is not unreasonable considering that the major metabolites of the phosphatidylinositol cycle have been separated from extracts of Samanea saman pulvini (14) and, furthermore, a short treatment with white light elicits a rapid change in the cycle components in these motor organs (15).…”

“…These movements, brought about by motor organs (pulvini), are not the result of growth processes but involve reversible turgor variations driven by ionic migrations, namely K+ and Cl-, in the cortical parenchyma cells of the pulvini (24). Furthermore, on the basis of the inhibitory effect induced by chelatants (EDTA and EGTA) (4,13,19) and the promotive effect induced by the ionophore A 23187 (19), calcium is hypothesized to intervene in the regulation of the pulvinar movements. Results presented previously (19,20) suggest that calmodulin could be implicated in some way.…”

Role of Calcium in Serine Transport into Tobacco Cells

“…9) indicates that the net transport of Ca2+ is small relative to Ca2+/Ca2+ exchange. (3,18) and animals (2). K+ was less effective in replacing surface-bound Ca24, as indicated by the total 'Ca2+ and the difference between water and CaCl2 at 10-min values.…”

Circadian rhythm leaf movement ofPhaseolus vulgarisand the role of calcium ions

“…11 Calcium is known as one of the ions involves in leaf movements. 12,13 Calcium uptake and transport from root to shoots take place through transpiration stream, 14 and its absorption and transport reported to be by passive diffusion and exchange reactions. 15,16 Sorooshzadeh et al 17 reported displacement of 45 Ca through leaf via mid-rib and secondary veins of soybean.…”