Reversible inactivation of PSII reaction centers and the dissociation of LHC II from PSII complex in soybean leaves

Both PS II photochemical efficiency (F-v/F-m) and the low-temperature fluor escence parameter F-685/F-735 declined in soybean leaves after 3 h of stron g light treatment. These two parameters returned to the fully dark-adapted level within 3 h in the dark, and NaF markedly inhibited these recovery pro cesses. After sucrose gradient centrifugation of thylakoid membranes, the a mount of LHC II from the strong light-treated leaves decreased in lower gre en layers and increased in upper green ones, but the distribution of LHC II in both stacked and unstacked thylakoid membranes did not change when comp ared with that of the fully dark-adapted leaves. When soybean leaves were i lluminated with weak red light, F-685/735 decreased while F-735 kept at alm ost the same level as control leaves in the dark. Based on the above result s, it is concluded that: (1) partial reversible inactivation of PS II in so ybean leaves is closely related to the dissociation of LHC If from the PS I I complex; and (2) the detached LHC II does not migrate from the stacked me mbranes to the unstacked membrane regions. (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.