The dependence of the low-temperature Q(y) absorption and nonphotochemical hole-burned spectra of the title complex (also known as the FMO complex) on pressure (less than or similar to 700 MPa) is reported. Pressure-induced structural changes of the complex were found to be elastic. The linear pressure shifts at 4.2 K for the principal absorption bands at 805, 814 and 825 nm are -0.08, -0.11, and -0.11 cm(-1)/MPa, respectively. Importantly, the 825 and 814 nm absorption profiles (shape, intensity) are independent of pressure. The results establish that, even at the highest values used, pressure has only a weak effect on the pairwise excitonic couplings of the bacteriochlorophyll (BChl) molecules, inhomogeneous broadening, and electron-phonon coupling. The pressure dependence of the Q, spectrum and zero-phonon holes (ZPH) burned in the 825 nm band can be rationalized in terms of dispersion interactions when BChl occupation numbers for the exciton levels are taken into account. These ZPH, which are assigned to the lowest level at 827 nm, carry a width of 0.6 cm(-1) at 4.2 K, which is independent of the pressure at which the hole is burned. This width is ascribed to dephasing, T-2 = 35 ps. Possible mechanisms for the dephasing are considered, and its pressure independence is discussed. Comparison of the Linear pressure shifts for the FMO complex against those of ether complexes suggests that pressure is a useful probe of strong coupling between BChl molecules.