Rhynia lacks roots. This early Devonian vascular plant featured rhizomes, rhizoids for anchorage, and terminal sporangia, but true roots were absent in its simple body plan.

Question Solution

The correct answer is Root. Rhynia, a fossil rhyniophyte from the Rhynie chert (410-400 MYA), represents primitive vascular plants without differentiated roots, relying instead on basal rhizoids for absorption.

Option Analysis

• Root: Correct. Absent entirely; Rhynia had no true roots with root caps or meristems, marking its primitive status among tracheophytes.

• Rhizome: Incorrect. Present as horizontal underground stems producing upright aerial shoots dichotomously; essential for vegetative spread.​

• Rhizoids: Incorrect. Multicellular, basal structures on rhizomes for anchorage and limited absorption, analogous to bryophyte rhizoids.​

• Sporangia: Incorrect. Terminal on dichotomously branched aerial shoots; homosporous with dehiscent walls containing isomorphic spores.

Introduction to Part Missing in Rhynia

The part missing in Rhynia is roots, defining this as one of the earliest vascular land plants from Scotland’s Rhynie chert. Without true roots, Rhynia relied on rhizomes and rhizoids, showcasing primitive tracheophyte evolution. Botany students study this for understanding root origins.

Rhynia Morphology Overview

Rhynia gwynne-vaughani (20 cm tall) and R. major (50 cm) had leafless, dichotomously branching aerial shoots from creeping rhizomes. No vascular cambium or leaves; simple protostele with tracheids present.

Why No Roots?

Primitive condition: Rhizoids sufficed for anchorage/absorption in moist habitats. True roots evolved later in lycophytes/ferns. Rhizomes handled horizontal growth; sporangia ensured reproduction.

Key Features Present

• Rhizome: Underground, protostelic, produces shoots/rhizoids.

• Rhizoids: Unicellular/multicellular basal anchors.

• Sporangia: Terminal, homosporous for gametophyte alternation.
  This rootless design highlights early land plant adaptations.