Apical dominance and the importance of clonal integration to apical growth in the seagrass Syringodium filiforme

Abstract

The existence of apical dominance and the importance of clonal integration to apical growth in the seagrass Syringodium filiforme were examined using field and mesocosm experiments. In the field, apical dominance was observed with proliferative branching resulting from the removal of rhizome apical meristems (RAMs). Rhizome internode length and branching increased when plants grew from a dense meadow into a bare patch, providing further evidence for the existence of apical dominance in S. filiforme. The results of the experiments indicated that growth of the RAM is dependent on the translocation of resources from older ramets. Removing 3 shoots from a rhizome runner lead to a significant reduction in the growth of the RAM, and removing 6 shoots had a greater effect. Apical growth was more significantly affected by cutting the rhizome, with the lowest growth observed in clonal fragments comprised of a RAM and the 4 youngest ramets. We conclude that clonal integration is an important factor regulating the growth form and productivity of S. filiforme. These results have implications for damage assessment and restoration projects, and indicate that future studies of meadow structure and plant production should consider RAM health and branch formation along with individual ramet growth.