The transition from protostele to siphonostele reflects an evolutionary shift in the vascular architecture of plants. A protostele has a solid core of xylem surrounded by phloem, typical of early vascular plants and young dicot roots. A siphonostele introduces a central pith (parenchyma), with vascular tissue forming a ring around it—an adaptation linked to increased organ size and secondary growth.

In dicot roots, this transition is not commonly observed as a developmental sequence but is interpreted as an evolutionary trend from simpler to more complex stelar types across plant lineages. Classic references include Esau’s Plant Anatomy and Beck’s An Introduction to Plant Structure and Development.

Dr. Adrian Leonard Mociulschi