title: PHOTOSYSTEM I AS THE KERNEL OF THE PHOTOSYNTHETIC MACHINERY OF LEAVES: KINETICS AND CONTROL OF ELECTRON TRANSPORT UNDER NORMAL AND STRESS CONDITIONS
reg no: ETF5236
project type: Estonian Science Foundation research grant
subject: 1.5. Biophysics
1.6. Physical, Analytical and Inorganic Chemistry
2.7. Biotechnology, Food and Drink Technology
status: completed
institution: University of Tartu
head of project: Agu Laisk
duration: 01.01.2002 - 31.12.2005
description: Hypothesis: Photosystem I and the related e-/H+ transporting complexes Cytochrome b6f, plastocyanin, ferredoxin, NADP(H), PGA-kinase and Glyceraldehyde-dehydrogenase, as well as ATP synthase form a supercomplex (defined as PSI-unit) that handles e- and H+ preferentially in its own limits, without complete equilibration with the bulk stroma pools reducing (NADPH) and assimilatory (ATP) power. The maximum photosynthetic capacity of a leaf is determined by the density of PSI-units. Long-term acclimation of leaf photosynthesis to environmental conditions involves changes in the density of PSI-units per leaf area.
Methods: Using a rapid-response system for the measurement of leaf CO2 uptake, O2 evolution, and 820 nm absorbance, kinetics and regulation of electron transport on the donor and acceptor side of photosystem I are investigated under normal and stress conditions. The data are analysed to detect the pool sizes of PSI itself, e- carriers and ATP. If the pools of e- carriers and ATP are close to the pool of PSI, it will support (but probably not prove) the hypothesis. If the pools are much bigger than the PSI pool, the result will disprove the hypothesis.
The project will help to explain factors and processes limiting the rate of photosynthesis in leaves. Plant photosynthesis is the cornerstone of future alternative energetics.

project group
no name institution position  
1.Irina BicheleTU, IMCBresearcher 
2.Hillar EichelmannTU, IMCBresearcher 
3.Agu LaiskTartu University, Faculty of Biology and Geographyprofessor 
4.Vello OjaTU, IMCBsen researcher 
5.Evi PaduTU, IMCBass. professor 
6.Bahtijor RasulovTU, IMCBresearcher