  Phycobilisomes, the light-harvesting antennas of cyanobacteria, can adapt to
a wide range of environments thanks to a composition and function response to
stress conditions. We study how structural changes influence excitation
transfer in these super-complexes. Specifically, we show the influence of the
rod length on the photon absorption and subsequent excitation transport to the
core. Despite the fact that the efficiency of individual disks on the rod
decreases with increasing rod length, we find an optimal length for which the
average rod efficiency is maximal. Combining this study with experimental
structural measurements, we propose models for the arrangement of the
phycobiliproteins inside the thylakoid membranes, evaluate the importance of
rod length, and predict the corresponding transport properties for different
cyanobacterial species. This analysis, which links the functional and
structural properties of full phycobilisome complexes, thus provides further
rationals to help resolving their exact structure.
