Question: secondary xylem and phloem in dicot stems are produced by
[{'answer': 'the vascular cambium', 'provenance': [{'wikipedia_id': '227675', 'title': 'Vascular cambium', 'start_paragraph_id': 1, 'start_character': 708, 'end_paragraph_id': 1, 'end_character': 728, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]