Investigations Into the Effects of Light and Darkness on Chlorophyll Biosynthesis in Angiosperms (Monovinyl, Divinyl Protochlorophyllide)
Carey, Edward Ewing
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https://hdl.handle.net/2142/72624
Description
Title
Investigations Into the Effects of Light and Darkness on Chlorophyll Biosynthesis in Angiosperms (Monovinyl, Divinyl Protochlorophyllide)
Author(s)
Carey, Edward Ewing
Issue Date
1985
Department of Study
Horticulture
Discipline
Horticulture
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Plant Physiology
Abstract
Three separate studies were undertaken.
In the first study, changes in the monovinyl (MV) and divinyl (DV) protochlorophyllide (Pchlide) contents of photoperiodically grown seedlings of nine dicotyledonous and four monocotyledonous species were followed during periods of darkness and light. DV Pchlide was predominant in all species at the end of a 14 hour light period. During a 10 h dark period, MV Pchlide accumulated in all species. In some species DV Pchlide also accumulated, while in others its levels fell. When plants were placed in the light at the end of the dark period, Pchlide levels fell, due to photoconversion to Chlorophyllide a. In light, DV Pchlide returned to predominance. Thus, there was a differential contribution of MV and DV Pchlide to Chlorophyll biosynthesis.
In the second study, the MV and DV Pchlid biosynthetic capabilities of whole maize, barley and cucumber seedling tissues, and of etiochloroplasts isolated from them were studied. It was found that light and darkness had similar effects on Pchlide biosynthesis in etiochloroplasts in vitro and in vivo. These effects were similar to those observed in the previous study on photoperiodically grown seedlings--ie. maize synthesized mainly MV Pchlide, and cucumber synthesized both MV and DV Pchlide in darkness. Thus, species-dependent differences in the effects of darkness and light on Pchlide biosynthesis were present very early in plastid greening. Furthermore, isolated plastids possessed the ability to respond to the light and dark stimuli. The in vitro maize and barley systems developed in this work may prove to be useful in determining the biochemical basis of the effects of light and darkness on Pchlide biosynthesis.
In the third study, a ('14)C ALA labelling experiment using photoperiodically grown bean leaves, produced preliminary evidence of dark biosynthesis of a putative reaction center chlorophyll.
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