Phytochrome Modifies Blue-light-induced Electrical Changes in Corn Coleoptiles

Abstract

Unilateral blue ligt administered to corn coleoptile segments produces no alteration of transem potenffal on the light side, and only a small and slow hyperpolarizaton on the dak side. Red light causes a 5-15 millivolt depolarization in cels on the light side causes and somewhat smaller effects on the dark side. Blue given after red causes a rapid hyperpolarization on both sides of the coleoptile. The effect of the potentiating red preirradiation is probably due to phytochrome, being largely abolished by far-red given after red, but before the blue light. The effect of prior red irradiation decays in the dark, showing a half-time of about 45 minutes at room temperature. This rapid cooperativity between phytochrome and the phototropic pigment may indicate a common locale, possibly in a membrane.

Electrical Changes in the Apical Cell of the Fern Gametophyte during Irradiation with Photomorphogenetically Active Light

“…The rapidity and magnitude of these electrical changes are similar to those previously observed in algal cells (18) and grass coleoptiles (13,14), reinforcing the concept that the early consequences of photoreception involve the membranes of the cell.…”

“…Cells were observed and impaled under green light (peak wavelength 548 nm) obtained by passing light from a 15-w tungsten filament lamp through a combination of absorbance and interference filters (14). The intensity of light at the level of the tissue was 0.020 w m2.…”

Ion channels and the transduction of light signals

“…The early suggestion that phytochrome exerts its effects by first altering the permeability of the plasma membrane to ions ( Hendricks & Borthwick 1967) received promising support from subsequent demonstrations of red‐light‐induced changes in membrane potential ( Newman & Briggs 1972; Racusen & Galston 1980; Racusen & Galston 1983), and the curious Tanada effect ( Tanada 1967). Not a great deal has been learned in the meantime about phytochrome‐mediated effects on transport processes at the plasma membrane, despite their potential importance as primary transducing steps.…”

Interactions of green or red light with blue light on the dark closure of Albizzia pinnules

“…This system seems to be tied in some manner to phytochrome so that Hght (red and green) probably absorbed by phytochrome results in augmenting the action of the blue-only-absorbing photoreceptor. Since the action of this photoreceptor is not negated by green Hght even at high photon fluence rates of green, it is distinctly different from "heliochrome" which is very sensitive to low irradiances of green Hght, Perhaps this blue-only-absorbing photoreceptor (could be more than one) is the same as the one whose action has been reported by several investigators to be enhanced by red Hght (Chon andBriggs 1966, Racusen andGalston 1980), Under high irradiances in the blue region, "he-Hochrome" could be absorbing more blue Hght and begin to exert its influence. This likelihood is indicated by the data showing that under such conditions some of the delaying effects of blue irradiation are negated by low photon fluence rates of green Hght -but not by those of red Hght -just as in the case of far-red irradiation.…”