Codium Branching

The Dead Man's Finger is a green alga that thrives deep under the sea. By the look of it, it almost looks like a sea sponge except that it is deep green and the branches have porous and firm texture to them. The deep green color is known as Codium green, which color was in use at the ancient Japanese royal court, called miru color.

The alga is peculiar in that at every node where it branches off, it branches off dichotomously. Indeed, it branches off at a certain angle at regular intervals. The branches are almost of the same thickness except for the root-most branch which is firmer and thicker. The regular patterns of the branches create the geometrical beauty of the alga. But how does it decide when to multiply or to branch off? The cells does not differentiate as in higher plants to meristem.

There could be hypotheses for the dichotomous branching of the alga. The signals to branch off could be the accumulation of chemical substances at the location of branching, or it could sense the gravity to know when to branch off. Both may be right. There are facts that support these hypotheses.

If you take a close look at the alga, you would notice a few things. At some individual, the root branch shows some different pattern from the other branches. It branches off multiple times at some nodes. While the rest of the alga branching patterns are same at every node, the conditions at root stem seem be different. Since the branches from those nodes are in different length and thickness, it seems to support the chemical theory that stimulate the branching which accumulates at the nodes.

On the other hands, the fact that when the branches are cut off, there seem to be no regrowth from the branch does seem to support the hypothesis that the branching occur at the further most location from the root. For those branches, there seems to be no elongation of stems between the nodes. The branches grow to a certain length then branches off.