| MadSci Network: Botany |
Jewelweed (Impatiens capensis) is one of many plants that disperses its seeds by a phenomenon called explosive dehiscence. The pods split open with enough force to spew out the seeds far from the parent plant. Distances of more than two meters (6.5 feet!) have been recorded for this species (Schmitt at el. 1985). The world champion of explosive dehiscence is the tropical tree Hura crepitans, which can fling its seeds as far as 45 m (about 150 feet; Swaine and Beer 1977).
Interestingly, I couldn’t find a direct answer to your question in the scientific literature. As far as I could find, no one has tested to see which part of the jewelweed pod is most sensitive to touch. Schmitt et al. (1985) opened the pods by squeezing the base with forceps. They may have done some preliminary tests and found that this was the most sensitive part of the pod, but if so, they didn’t mention it in their paper. This could be a good experiment for you and your friends to try!
Literature Cited:
Schmitt, J., Ehrhardt, D., and D. Swartz. 1985. Differential dispersal of self-fertilized and outcrossed progeny in Jewelweed (Impatiens capensis). The American Naturalist 126: 570-575.
Swaine, M.D., and T. Beer. 1977. Explosive seed dispersal in Hura crepitans L. (Euphorbiaceae). New Phytologist 78: 695-708.
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