In a dicot root, the vascular cambium originates from which combination of tissues?
1. Conjunctive tissue between xylem and phloem, and tissue internal to endodermis
2. Cortical cells adjacent to endodermis, and pith cells in the centre of the stele
3. Pericycle cells lying below the protoxylem, and parenchyma between xylem and phloem
4. Medullary rays between vascular bundles, and cells derived from procambium