Book 29, Question 29
Why does a sprouting bean stem poke up in a hook shape?
A young stem pushes through soil, which could scrape the delicate leaves.
So the stem bends into a hook and pulls the leaves up behind it, with the tough bend taking the rubbing. Once the hook reaches light, it straightens and the leaves open. Many seedlings use this trick. It's a bit like pulling a rope through a tunnel.