Based on new experimental data of linear and nonlinear spectroscopic investigations of LHC2 complexes, both the energy transfer and energy relaxation of excitons were studied in the limiting cases of strong pigment-pigment and pigment-protein interactions, respectively. Consequences of the structural basis and the dominance of strong pigment-pigment interactions in monomers were independently established by different optical measurements. In this model, the energy relaxation of excitons was determined by dynamical processes of exciton interactions with the radiation fíeld and the long-wave protein vibrations, respectively, in particular with the mode having the wave number of 43 cm'f