Chlorophyll Metabolism in Etiolated Gherkin Seedlings I. Photoinhibition of Chlorophyll Accumulation

Abstract

Abstract. Cotyledons of etiolated gherkin seedlings do not turn green upon transfer to high intensity red light (about 25 W/m2). A pre‐irradiation with high intensity red light has an after‐effect as chlorophyll accumulation during a subsequent exposure to white light (20 W/m2) is inhibited. The capacity of protochlorophyll regeneration during a dark period depends on the length of a previous light period but is hardly affected by the light intensity. At high intensity light the rate of protochlorophyll regeneration, which also depends on the length of the foregoing irradiation, is lower than that at low intensity light only during the first 1.5h of the light period. It is concluded that high intensity red light inhibits chlorophyll accumulation mainly by photo‐bleaching of chlorophyll. The after‐effect is the result of a photooxidation which may lead to photo‐bleaching of newly formed chlorophyll in relatively low intensity light. Photoinhibition of chlorophyll accumulation is accompanied by a disturbed development of etioplasts into chloroplasts.

Ribulose bisphosphate carboxylase capacity and chlorophyll content in developing seedlings of Chenopodium rubrum L. growing under light of different qualities and fluence rates

“…Pf~ has a stabilizing action on Chl in light [35] and Chl might thus be protected from photobleaching. It was repeatedly observed that under higher irradiances Chl is lost due to photobleaching [28,34,14,45] ; R especially favours photodestruction of Chl [15] as well as decreasing the capacity of P Chl Ode) biosynthesis at later stages of development [42]. Photobleaching might be involved under high R during the first hours of irradiations (Fig.…”