Question: where do primary xylem and phloem originate?
Answer: During primary plant grow, xylem and phloem originate from the procambium meristem. Protoxylem and protophloem originate first at both the embryonary and postembryonary stages, but they are progressively replaced by metaxylem and metaphloem, which are the mature vascular system in organs that only show primary grow.