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Difference Between Protonema and Prothallus | Protonema vs Prothallus


Key Difference – Protonema vs Prothallus
 

Bryophytes and Pteridophytes are respectively non-vascular and vascular plants. Vascular plants contain xylem and phloem for the transportation of their nutrients. Therefore, bryophytes and pteridophytes differ in many ways including their life cycles. In Bryophyte life cycle, the dominant stage is the gametophyte, and in pteridophytes, the dominant stage is the sporophyte. Protonema and Prothallus are two types of gametophytes belonging to bryophytes’ and pteridophytes’ life cycles. The protonema is a filamentous threadlike structure while the prothallus is a heart-shaped structure with many rhizoids beneath it and contains both female and male reproductive units. This is the key difference between protonema and prothallus.

CONTENTS

1. Overview and Key Difference
2. What is Protonema
3. What is Prothallus
4. Similarities Between Protonema and Prothallus
5. Side by Side Comparison – Protonema vs Prothallus in Tabular Form
6. Summary

What is a Protonema?

In the context of mosses and liverworts life cycles, the protonema is a structure which appears as threads that developed during the very early stage. Protonema develops at the initiation of the moss development after the spore germination. Then through different sequential developments stages, the protonema develops into leafy shoots which are referred to as gametophores. The protonema is an algal-like filamentous structure. It is a characteristic feature of all mosses and many of the liverworts. In hornworts (a type of liverworts) the protonema stage is absent, and it is considered as an exceptional thing with consideration to the liverworts.

The protonema represents a typical gametophyte. A protonema develops through apical cell division. At the specific stage of this development cycle, phytohormone cytokinin influences the budding of three faced apical cells. The buds finally become gametophores. The gametophores are structures that mimic stems and leaves of bryophytes since they lack true stems and true leaves.