Phytochrome Controlled Nyctinasty in Albizzia Julibrissin. Ii. Potassium Flux as a Basis for Leaflet Movement

Satter, Ruth L.; Marinoff, Philip; Galston, Arthur W.

doi:10.1002/j.1537-2197.1970.tb09891.x

Cited by 89 publications

(111 citation statements)

References 18 publications

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“…These early events might involve control of ion movements. In Samanea and Albizzia, K+ (13)(14)(15), Cl- (17), and transmembrane potential (10) are regulated by phytochrome and high intensity white light, the latter possibly acting via the same blue absorbing flavoprotein that appears to regulate rhythmic phasing in Neurospora (7,11). A blue absorbing pigment regulates leaflet opening in Albizzia (2,6) and probably in Samanea (3).…”

Section: Discussionmentioning

confidence: 99%

Circadian Rhythmicity in Excised Samanea Pulvini

Simón

Satter²,

Galston³

1976

Plant Physiol.

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pulvini received R and the other FR in all experiments comparing these two light treatments. Light sources for phytochrome photoconversion (R = 3-or 5-min exposure at 2.2 J m-2, 600 to 690 nm, and FR = 1.5-min exposure at 9 J m-2, 710 to 750 nm) and the dim green light used during the measurements and experimental manipulations are described in reference 15. The beginning of the dark period, DD = 0, coincides with the regular lights off signal. RESULTSExcised pulvini incubated in H20 during DD oscillate for only one cycle before the rhythm damps in the open position (18). R or FR administered at regular intervals (Fig. 1) permit the rhythm to persist for two to three cycles, although the amplitude of the oscillations and R-FR differences tend to decrease with time, and oscillations cease after 72 hr darkness. Since sucrose is required for sustained rhythmicity in DD (18), all pulvini were supplied with 50 mm sucrose in the remaining experiments. As will become apparent (see Figs. 5 and 6), R and FR have very different effects on the phase, period, and amplitude of the movement, when sucrose is available.Two types of experiments were performed. To investigate phase response, one R or FR light pulse was presented at different times of the rhythm. To test for rhythmic entrainment, pulses of R or FR light were presented every 24 hr. In all cases, the effects of light treatments were compared to free running dark controls.Phase Shifting with One Red Light Flash. The effects of R presented at 25 different times during a long dark cycle were analyzed; Figure 2 indicates the results of eight such treatments, while Figure 3 compares the effects of all 25 treatments. One R pulse presented during the second two-thirds of pulvinal opening or the first half of closure reduces the duration of the next cycle, thereby producing a phase advance, while one pulse presented during the second half of pulvinal closure, or the first third of the opening movement increases the duration of the next cycle, thereby causing a phase delay. R presented at the middle of closure has no effect on the phase; we have designated this as the ZPST.Phase and Amplitude Response Curves. The amount-of phase shift was determined by comparing the time of the first maximum after the R light treatment with that of the same maximum in the dark control. R produces a maximum phase shift of about 12 hr when presented during pulvinal opening, 12 hr from ZPST. The amount of phase shift depends primarily upon the interval between the light pulse and ZPST and is remarkably independent of the cycle in which the R treatment is presented, except for the first 8 hr of DD. R at this time is much less effective than if presented at an equivalent part of a later cycle, as also reported in other plants (5,22

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Section: Discussionmentioning

confidence: 99%

Circadian Rhythmicity in Excised Samanea Pulvini

Simón

Satter²,

Galston³

1976

Plant Physiol.

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“…There is some evidence that phytochrome is a membrane protein (3), and that it exerts its effects by regulating the ionic permeability, and, consequently, the electrical potential of some cell membranes (4,5). We postulated that this regulation could be made possible by differences in membrane conductance induced by the two forms of phytochrome, and thus designed experiments to test this hypothesis (6).…”

Section: Far-red Lightmentioning

confidence: 99%

Photoreversible Conductance Changes Induced by Phytochrome in Model Lipid Membranes

Roux

Yguerabide²

1973

Proc. Natl. Acad. Sci. U.S.A.

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The plant protein phytochrome induces photoreversible conductance changes when added to a black lipid membrane made from oxidized cholesterol. The conductance of the phytochrome-modified membrane is increased by red-light illumination but is decreased by illumination with far-red light. Denatured phytochrome does not affect the conductance of the model membrane.Phytochrome is a widely distributed plant chromoprotein that mediates many developmental changes triggered by light (1, 2). It has two spectrally different forms that can be reversibly interconverted by irradiation with light of the appropriate wavelength: The red-absorbing form, Pr (Xmax 667 nm), and the far-red-absorbing form, Pfr (Xmax 725 nm). The interconversion of the two forms can be described by the scheme: red light PrPfr. far-red lightThere is some evidence that phytochrome is a membrane protein (3), and that it exerts its effects by regulating the ionic permeability, and, consequently, the electrical potential of some cell membranes (4, 5). We postulated that this regulation could be made possible by differences in membrane conductance induced by the two forms of phytochrome, and thus designed experiments to test this hypothesis (6). Here we present the initial results of our studies in which we have attempted to incorporate phytochrome into a model membrane to determine whether Pr and Pfr can differently affect the ionic permeability of a bimolecular lipid membrane.The model membrane that we used was developed by Mueller, Rudin, and coworkers (7). It can be made from various lipids, including phospholipids, and has a conformation and other properties similar to the bilayer regions of biological membranes. The membrane is formed between two aqueous compartments, thus allowing its electrical properties to be readily measured by standard techniques of electrophysiology. The effects of proteins on ionic permeability can be tested by incorporating them into the membrane. The very high resistance of the pure lipid membrane (109-10°1 _-cm2) provides an ideal system for detection of small changes in conductance, such as have been reported after the incorporation in the bilayer of low amounts of a protein called excitability-inducing material (EIM) (8). MATERIALS AND METHODSThe experimental arrangement for forming and studying the membrane is shown in Fig. 1. The membrane was made across a 0.7-mm hole on the side of a 6-ml Teflon cup that was partially immersed in and filled with a solution of 0.1 M KCl, buffered at pH 7 with 5 mM histidine chloride. The temperature of the system was maintained between 250 and 270.

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“…Extensor cells swell as the pulvinus opens in the daytime, and the oppositely positioned flexor cells swell as the pulvinus closes at night. The turgor pressure changes responsible for the swelling and shrinking are caused by uptake and release of large amounts of solutes, chiefly K and Cl (Samanea [21]; Albizzia julibrissin [22]; Phaseolus [11,14]). These ion fluxes may be driven by an outwardly directed H+ pump (10).…”

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confidence: 99%