THE PHOTOINHIBITION OF GROWTH IN ETIOLATED STEM SEGMENTS. III. FAR‐RED REVERSIBILITY OF BLUE LIGHT EFFECTS IN PISUM

Abstract

Bertsch, Walter F. (Yale U., New Haven, Conn.) The photoinhibition of growth in etiolated stem segments. III. Far‐red reversibility of blue light effects in Pisum. Amer. Jour. Bot. 50(8):754–760. Illus. 1963.—Etiolated pea stem segments were used to study the relationship between blue light effects and the red, far‐red reversible photoinhibition of growth. The irradiation periods were too short to give an appreciable effect of high‐energy, nonreversible photoreactions. Filters which were used to isolate blue light are specified, contaminations by other wavelengths being extremely small. It was found that photoinhibitions due to uncontaminated blue light were reversible by subsequent far‐red irradiation, regardless of whether a broad band of blue wavelengths, or the 4358‐A emission line of mercury, was used. Blue light (4800 A) was about 0.3‐1% as effective as red (6600 A) light. Changes in the incubation medium caused the same changes in photosensitivity to blue as to red irradiations. These observations are presented as evidence supporting the hypothesis that the pigment moiety of phytochrome absorbs blue light.