title: STATE TRANSITIONS AND NONPHOTOCHEMICAL QUENCHING DURING A NUTRIENT-INDUCED FLUORESCENCE TRANSIENT IN PHOSPHORUS-STARVED DUNALIELLA TERTIOLECTA(1).
abstract: Assessments of nutrient-limitation in microalgae using chl a fluorescence have revealed that nitrogen and phosphorus depletion can be detected as a change in chl a fluorescence signal when nutrient-starved algae are resupplied with the limiting nutrient. This photokinetic phenomenon is known as a nutrient-induced fluorescence transient, or NIFT. Cultures of the unicellular marine chlorophyte Dunaliella tertiolecta Butcher were grown under phosphate starvation to investigate the photophysiological mechanism behind the NIFT response. A combination of low temperature (77 K) fluorescence, photosynthetic inhibitors, and nonphotochemical quenching analyses were used to determine that the NIFT response is associated with changes in energy distribution between PSI and PSII and light-stress-induced nonphotochemical quenching (NPQ). Previous studies point to state transitions as the likely mechanism behind the NIFT response; however, our results show that state transitions are not solely responsible for this phenomenon. This study shows that an interaction of at least two physiological processes is involved in the rapid quenching of chl a fluorescence observed in P-starved D. tertiolecta: (1) state transitions to provide the nutrient-deficient cell with metabolic energy for inorganic phosphate (Pi )-uptake and (2) energy-dependent quenching to allow the nutrient-stressed cell to avoid photodamage from excess light energy during nutrient uptake.
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Petrou
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: M A
authors.initials: MA
authors.lastname: Doblin
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: R A
authors.initials: RA
authors.lastname: Smith
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: P J
authors.initials: PJ
authors.lastname: Ralph
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Shelly
authors.affiliation: Institute for Water and Environmental Resource Management and Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, AustraliaSchool of Biological Sciences, PO Box 18, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Beardall
keywords: 77 K fluorescence; Dunaliella tertiolecta; NIFTs; nonphotochemical quenching; phosphorus starvation; state transitions