In translocation, sugar travels from a source to a sink. In a leafy plant in midsummer, which movement fits that description?
Explanation
A source is a part that releases sugar into the transport tissue, and in midsummer a lit leaf is doing exactly that, while a growing tip consumes what arrives and therefore acts as a sink. Reversing the pair puts the supply where the demand is, and a root in midsummer makes no sugar at all, so it cannot be the part that loads the tissue.