Final answer:
Seeds can be either a source or a sink, depending on the plant's stage of development and the season. When a seed is a source, it produces sugars that are transported to other parts of the plant. When a seed is a sink, it receives and stores sugars from other parts of the plant.
Step-by-step explanation:
Seeds can be either a source or a sink, depending on the plant's stage of development and the season. When a seed is a source, it means that it is producing photosynthates (sugars) that are being transported to other parts of the plant via the phloem. For example, during vegetative growth, sugars produced in leaves are directed to shoots and leaves. On the other hand, when a seed is a sink, it means that it is receiving and storing sugars from other parts of the plant. This commonly occurs during reproductive development when sugars are directed to seeds and fruits for storage.