Question 7
What actually throws the seeds when a rubber or okra fruit bursts?
The right answer is the one marked above.
Tension that has built up in the drying pericarp. The wall dries unevenly and stores energy like a stretched spring; when it splits, that energy throws the seeds several metres.
Touch, wetting and drying are the three triggers that release the tension — they are not three separate mechanisms, and none of them is the source of the force. The plant paid for the throw when it built the fruit.