Photosynthesis takes place in the mesophyll cells and, in C4 plants, in the bundle sheath cells of the leaf (see Figure 8.16). The products of photosynthesis (primarily carbohydrates) diffuse to the nearest small vein, where they are actively transported into sieve tube elements.
Substances in the phloem move from sources to sinks. A source is an organ (such as a mature leaf or a storage root) that produces (by photosynthesis or by digestion of stored reserves) more sugars than it requires. A sink is an organ (such as a root, a flower, a developing fruit or tuber, or an immature leaf) that consumes sugars for its own growth and storage needs. Sugars (primarily sucrose), amino acids, some
Question: Are organic solutes translocated in the xylem or in the phloem?
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