Title: P700 oxidation and energy transfer in normal maize and in carotenoid-deficient mutants
Abstract: 1. Particles enriched in System 1 and 2, respectively, were prepared by digitonin fragmentation of chloroplasts from normal maize and from mutants which accumulate lycopene or ζ-carotene instead of the normal carotenoids and which have a reduced chlorophyll content. Although both mutants had a relatively high carotenoid content in relation to chlorophyll, the System-1 particles showed about the same carotenoid to chlorophyll ratio as particles from normal maize. Particles from the lycopene mutant showed approximately a normal ratio of light harvesting to reaction center chlorophyll (P700). In the ζ-carotene mutants the amount of light harvesting chlorophyll was somewhat reduced, both in relation to the number of System-1 reaction centers and to the amount of protein. 2. Action spectra for P700 oxidation indicate a 30–50% efficiency of energy transfer from carotenoids to chlorophyll in System-1 particles of normal maize, increasing with increasing chloroplast development during greening. With the lycopene mutant the transfer efficiency was 30–50%. In the ζ-carotene mutant the transfer efficiency from ζ-carotene was estimated to be somewhat higher. The quantum efficiencies for P700 oxidation for light absorbed by chlorophyll a by System-1 particles from mutant maize were about twice as low as for normal maize. 3. With normal maize, after prior etiolation, the formation of functional System-1 reaction centers lags behind the synthesis of chlorophyll in the early phases of greening. Approximately at the time of beginning of granum formation, when about 20% of the chlorophyll had been synthesized, the ratio of chlorophyll to P700 and the distribution of chlorophyll between the two pigment systems was found to reach a constant value, suggesting a close relation between the regulatory mechanisms for these phenomena and the development of the photosynthetic membrane system.
Publication Year: 1970
Publication Date: 1970-01-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 25
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