Temperature/light dependent development of selective resistance to photoinhibition of photosystem I.
Exposure of winter rye leaves grown at 20 degrees C and an irradiance of either 50 or 250 micromol m(-2) s(-1) to high light stress (1600 micromol m(-2) s(-1), 4 h) at 5 degrees C resulted in photoinhibition of PSI measured in vivo as a 34% and 31% decrease in deltaA820/A820 (P700+). The same effect was registered in plants grown at 5 degrees C and 50 micromol m(-2) s(-1). This was accompanied by a parallel degradation of the PsaA/PsaB heterodimer, increase of the intersystem e- pool size as well as inhibition of PSII photochemistry measured as Fv/Fm. Surprisingly, plants acclimated to high light (800 micromol m(-2) s(-1)) or to 5 degrees C and moderate light (250 micromol m(-2) s(-1)) were fully resistant to photoinhibition of PSI and did not exhibit any measurable changes at the level of PSI heterodimer abundance and intersystem e- pool size, although PSII photochemistry was reduced to 66% and 64% respectively. Thus, we show for the first time that PSI, unlike PSII, becomes completely resistant to photoinhibition when plants are acclimated to either 20 degrees C/800 micromol m(-2) s(-1) or 5 degrees C/250 micromol m(-2) s(-1) as a response to growth at elevated excitation pressure. The role of temperature/light dependent acclimation in the induction of selective tolerance to PSI photoinactivation is discussed.
Department of Plant Sciences, University of Western Ontario, London, Canada.
A G
AG
Ivanov
R M
RM
Morgan
G R
GR
Gray
M Y
MY
Velitchkova
N P
NP
Huner
D002736:Chloroplasts; D004578:Electron Spin Resonance Spectroscopy; D007425:Intracellular Membranes; D008027:Light; D008565:Membrane Proteins / Q000032:analysis; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000528:radiation effects*; D045331:Photosystem I Protein Complex; D018515:Plant Leaves; D011836:Radiation Tolerance; D012434:Secale / Q000254:growth & development* / Q000528:radiation effects; D013055:Spectrophotometry, Infrared; D013696:Temperature
D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; C089909:photosystem I, psaB subunit