Action and Interaction of Red and Far-Red Radiation on Lipoxidase Metabolism of Squash Seedlings

Publisher Website
Google Scholar
Abstract
Lipoxidase, in the cotyledons of squash (Cucurbita moscata) seedlings grown in the dark, reached its peak activity on the 5th day and then declined to its lowest activity on the 8th day. Under continous irradiation, the rate of enzyme disappearance was accelerated by red (655 m[mu]) and was retarded by far-red (735 m[mu]) radiation. Acceleration of enzyme disappearance caused by red light was reversed repeatedly by far-red light in seedlings that received in initial exposure to red radiation. These responses were independent of the duration of irradiation at each of the alternating wavebands. No change was observed when the white light was administered either 24 hr. before or 24 hr. after the red, far-red treatment. The lipoxidase system of the seedlings given an initial exposure to far-red radiation also responded reversibly to alternating far-red, red extended exposure to far-red radiation also responded reversibly to alternating far-red, red extended exposures, but it failed to respond reversibly when short exposures were employed. Similarly, no change occurred in these seedlings when either pre- or post-treatment with the white light was applied. The capacity of lipoxidase to act reversibly depends primarily on the duration of exposure and on the kind of light (red or far-red) to which the seedlings were exposed initially. In spite of these variations, lipoxidase metabolism can be considered an additional biochemical manifestation of red, far-red reaction that operates in the photomorphogenesis of plants.