Breaks, splits. Glue with Elmer's Glue-All and hold in place with clamps, or wrap with thread or light cord until glue sets. For further reinforcement, when glue is dry, wrap neatly with heavy cotton thread (see fishing rod) and brush on varnish.
Another way you can sometimes reinforce bamboo is to insert in the hole in the bamboo a wood dowel of approximately the same diameter as the hole. Coat the dowel first with glue.