title: Hydrogen Photoevolution Indicates an Increase in the Antenna Size of Photosystem I in Chlamydobotrys stellata during Transition from Autotrophic to Photoheterotrophic Nutrition.
abstract: The changes in the light-harvesting antenna size of photosystem I were investigated in the green alga Chlamydobotrys stellata during transition from autotrophic to photoheterotrophic nutrition by measuring the light-saturation behavior of hydrogen evolution following single turnover flashes. It was found that during autotrophic-to-photoheterotrophic transition the antenna size of photosystem I increased from 180 to 250 chlorophyll. The chlorophyll (a + b)/P700 ratio decreased from 800 to 550. The electron transport of photosystem I measured from reduced 2,6-dichloro-phenolindophenol to methylviologen was accelerated 1.4 times. In the 77K fluorescence spectra, the photosystem II fluorescence yield was considerably lowered relative to the photosystem I fluorescence yield. It is suggested that the increased light-harvesting capacity and redistribution of absorbed excitation energy in favor of photosystem I is a response of photoheterotrophic algae to meet the ATP demand for acetate metabolism by efficient photosystem I cyclic electron transport when the noncyclic photophosphorylation is inhibited by CO(2) deficiency.
authors.affiliation: Institute of Soil Science and Photosynthesis, USSR Academy of Sciences, Pushchino 142292, Russia.
authors.forename: V A
authors.initials: VA
authors.lastname: Boichenko
authors.forename: W
authors.initials: W
authors.lastname: Wiessner
authors.forename: V V
authors.initials: VV
authors.lastname: Klimov
authors.forename: D
authors.initials: D
authors.lastname: Mende
authors.forename: S
authors.initials: S
authors.lastname: Demeter