Fun with Science Club®


			After a damaging experience seaweed becomes stronger. Carrie Straight 05.14.01 Many plants have defenses against herbivores (the animals that eat them). Some plants have thorns, others have thickened leaves, and others just taste bad. But how do these plants create these defenses? Scientists from Canada wanted to look at this question with an ocean dwelling plant, seaweed (Ascophyllum nodosum). These scientists marked seaweed fronds (leaves) and later returned to each marked frond to measure the amount of damage done by herbivores. These systematic observations would tell the scientists what kind of damage natural herbivores did to the fronds. Herbivores damaged on all parts of the frond (stem?) including the central axis (the main vein that provides structural support and nutrients to the remainder of the frond). The fronds were more likely to break if herbivores damaged the central axis. The researchers randomly chose seaweed fronds and simulated herbivore damage. They simulated the damage by cutting areas of the central axis. Then they tested the frond strength and toughness after the damage and after a recovery period. To test strength, the scientists attached the frond to a machine that would measure how far the frond would bend before it broke. After testing the strength of the damaged fronds compared to the strength of undamaged fronds (controls), the researchers found that the previously damaged fronds were stronger and tougher than the controls. Somehow the damaged fronds became stronger.


			Lowell, Richard B., John H. Markham, and Kenneth H. Mann. 1991. Herbivore-like damage induces increased strength and toughness in a seaweed. Proceedings of the Royal Society of London Biological Sciences Series 243 (1306): 31-38.