Abstract

Exposure of control (non-hardened) Arabidopsis leaves for 2 h at high irradiance at 5 degreesC resulted in a 55% decrease in photosystem II (PSII) photochemical efficiency as indicated by FcFm. In contrast, cold-acclimated leaves exposed to the same conditions showed only a 22degreesC decrease in FupsilonFm. Thermoluminescence was used to assess the possible role(s) of PSII recombination events in this differential resistance to photoinhibition. Thermoluminescence measurements of PSH revealed that S(2)QA(-) recombination was shifted to higher temperatures, whereas the characteristic temperature of the S(2)Q(B)(-) recombination was shifted to lower temperatures in cold-acclimated plants. These shifts in recombination temperatures indicate higher activation energy for the S(2)Q(A)(-) redox, pair and lower activation energy for the S(2)Q(B) redoxpair. This results in an increase in the free-energy gap between P680(+)Q(A)(-) and P680(+)Pheo(-) and a narrowing of the free energy gap between primary and secondary electron-accepting quinones in PSH electron acceptors. We propose that these effects result in an increased population of reduced primary electron-accepting quinone in PSII, facilitating non-radiative P680(+)QA(-) radical pair recombination. Enhanced reaction center quenching was confirmed using in vivo chlorophyll fluorescence-quenching analysis. The enhanced dissipation of excess light energy within the reaction center of PSII, in part, accounts for the observed increase in resistance to high-light stress in cold-acclimated Arabidopsis plants.

Published in

Plant Physiology
2003, Volume: 132, number: 4, pages: 2144-2151
Publisher: AMER SOC PLANT BIOLOGISTS

UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.1104/pp.103.022939

Permanent link to this page (URI)

https://res.slu.se/id/publ/76359