Chloroplast Biogenesis 81: Transient Formation of Divinyl Chlorophyll a Following a 2.5 ms Light Flash Treatment of Etiolated Cucumber Cotyledons

Abstract

Abstract— The possible conversion of nascent divinyl (DV) chloro‐phyllide a (Chlide a) to DV chlorophyll a (Chi a during the early stages of greening in a dark divinyl‐light divinyl‐light/dark divinyl (DDV‐LDV‐LDDV) plant species was investigated. Etiolated cucumber cotyledons (Cucu‐mis sativus L.) were subjected to a 2.5 ms light flash followed by darkness. The DV and monovinyl (MV) components of the protochlorophyllide a (Pchlide a), Chlide a, Pchlide a ester and Chi a pools were monitored quantitatively by high‐resolution spectrofluorometry, immediately following the light treatments and after various periods in darkness. The light treatment photoconverted DV and MV Pchlide a to DV and MV Chlide a. Some photoconversion of MV Pchlide a ester to MV Chi a also appeared to take place. A sharp rise in the level of DV Chi a following the light treatment could not be accounted for by photoconversion of DV Pchlide a ester. It must have arisen by rapid esterification of nascent DV Chlide a. After illumination, the level of DV Chi a rose for 5 s and then declined. The implications of the transient rise and fall of DV Chi a content following illumination to the Chi a biosynthetic heterogeneity is discussed.