What factors determine the point on the surface of an apparently homogenous potato at which a new sprout bursts forth?
• The clue is in the word "apparent". A potato tuber is not just an amorphous lump of dinner, but a modified stem. "Stem" in botany is a technical term - it is a structure that has polarity (an apex and a base), grows leaves out of its sides, and has a bud in the angle, or axil, between the stem and each leaf or branch.
The tuber differs from a typical stem in many respects. First, it originates as a swelling at the tip of another special stem, called a stolon, which is itself unusual in that it grows downwards into the soil instead of upwards into the air, and which later withers, leaving a scar.
Second, it is packed with starch, which is why we eat potato tubers, ...
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