of the stipe) at low velocities (<0.2·m·s -1 ) and compaction of the crown (reduction in frontal area and change in shape) at higher velocities. Change in frontal area contributed more to drag reduction than change in drag coefficient. Drag coefficient and frontal area both decrease exponentially with increasing water velocity, and a mechanistic model of drag was developed with explicit functions to describe these changes. The model not only provides mechanistic parameters with which to compare reconfiguration among individuals and species, but also allows for more reliable predictions of drag at high, ecologically relevant water velocities.

Growth rates of branches of colonies of the gorgonian Pseudopterogorgia elisabethae were monitored for 2 years on a reef at San Salvador Island, Bahamas. Images of 261 colonies were made at 6-month intervals and colony and branch growth analyzed. Branch growth rates differed between colonies and between the time intervals in which the measurements were made. Colonies developed a plumelike morphology through a pattern of branch origination and determinate growth in which branch growth rates were greatest at the time the branch originated and branches seldom grew beyond a length of 8 cm. A small number of branches had greater growth rates, did not stop growing, and were sites for the origination of subsequent "generations" of branches. The rate of branch origination decreased with each generation of branching, and branch growth rates were lower on larger colonies, leading to determinate colony growth. Although colonial invertebrates like P. elisabethae grow through the addition of polyps, branches behave as modules with determinate growth. Colony form and size is generated by the iterative addition of branches.

Changing shape and reducing projected area in flow are two distinct strategies employed by flexible seaweeds to resist drag. Flexible reconfiguration contributes to the uncertainty of drag extrapolation, and researchers should use caution when predicting drag and dislodgement of seaweeds in the field.

Plant and animal biomechanists have much in common. Although their frame of reference differs, they think about the natural world in similar ways. While researchers studying animals might explore airflow around flapping wings, the actuation of muscles in arms and legs, or the material properties of spider silk, researchers studying plants might explore the flow of water around fluttering seaweeds, the grasping ability of climbing vines, or the material properties of wood. Here we summarize recent studies of plant biomechanics highlighting several current research themes in the field: expulsion of high-speed reproductive projectiles, generation of slow movements by shrinking and swelling cell walls, effects of ontogenetic shifts in mechanical properties of stems, flexible reconfiguration and material properties of seaweeds under crashing waves, and the development of botanically-inspired commercial products. Our hope is that this synopsis will resonate with both plant and animal biologists, encourage cross-pollination across disciplines, and promote fruitful interdisciplinary collaborations in the future.