<abstract xmlns="http://www.w3.org/1999/xhtml">

<p>The extant plant genus Isoetes (Isoetaceae; lycophyte, quillwort) is important from an evolutionary point of view. Species of this heterosporous genus are small herbs (up to 50 centimeters) and exhibit some morphological, anatomical and embryological features of their Paleozoic arborescent lycopsid ancestors. The species Isoetes pantii produces three kinds of microspores (monolete, alete and trilete) and two types of trilete megaspores in one and the same heterosporangium. We attempt to associate these unusual functional megaspores with various Paleozoic spores described mainly from Devonian barinophytaleans such as Omniastrobus dawsonii, Barinophyton richardsonii, B. citrulliforme and Protobarinophyton pennsylvanicum. These have two kinds of spores in a sporangium and provide the first palynological evidence of heterospory at 405 Ma. The germination of microspores and megaspores and production of gametophytes within the heterosporangia of I. pantii corresponds with that of some of its Paleozoic ancestors. Retention of megaspores within heterosporangia and their germination in situ offers evidence that I. pantii exhibits the probable route of evolution of the seed habit. These observations support the hypothesis that a typical heterosporangium was the cradle for the evolution of heterospory.</p>
</abstract>

The extant plant genus Isoetes (Isoetaceae; lycophyte, quillwort) is important from an evolutionary point of view. Species of this heterosporous genus are small herbs (up to 50 centimeters) and exhibit some morphological, anatomical and embryological features of their Paleozoic arborescent lycopsid ancestors. The species Isoetes pantii produces three kinds of microspores (monolete, alete and trilete) and two types of trilete megaspores in one and the same heterosporangium. We attempt to associate these unusual functional megaspores with various Paleozoic spores described mainly from Devonian barinophytaleans such as Omniastrobus dawsonii, Barinophyton richardsonii, B. citrulliforme and Protobarinophyton pennsylvanicum. These have two kinds of spores in a sporangium and provide the first palynological evidence of heterospory at 405 Ma. The germination of microspores and megaspores and production of gametophytes within the heterosporangia of I. pantii corresponds with that of some of its Paleozoic ancestors. Retention of megaspores within heterosporangia and their germination in situ offers evidence that I. pantii exhibits the probable route of evolution of the seed habit. These observations support the hypothesis that a typical heterosporangium was the cradle for the evolution of heterospory.

Heterosporangia in <italic>Isoetes Pantii</italic> (Isoetaceae, Pteridophyta): Revealing the Beginnings of Heterospory and Recalling Paleozoic Ancestors?

Folia Musei rerum naturalium Bohemiae occidentalis. Geologica et Paleobiologica

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Heterosporangia in  (Isoetaceae, Pteridophyta): Revealing the Beginnings of Heterospory and Recalling Paleozoic Ancestors?

The extant plant genus Isoetes (Isoetaceae; lycophyte, quillwort) is important from an evolutionary point of view. Species of this heterosporous genus are...

Heterosporangia in Isoetes Pantii (Isoetaceae, Pteridophyta): Revealing the Beginnings of Heterospory and Recalling Paleozoic Ancestors?

Published Online: Apr 16, 2023

Page range: 11 - 26

DOI: https://doi.org/10.2478/fbgp-2022-0002

Keywords
heterospory, isoetaleans, barinophytes, gametophytes, Paleozoic

© 2022 Jiří Bek et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Heterosporangia in Isoetes Pantii (Isoetaceae, Pteridophyta): Revealing the Beginnings of Heterospory and Recalling Paleozoic Ancestors?

Published Online: Apr 16, 2023

Page range: 11 - 26

DOI: https://doi.org/10.2478/fbgp-2022-0002

Keywordsheterospory, isoetaleans, barinophytes, gametophytes, Paleozoic

© 2022 Jiří Bek et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
heterospory, isoetaleans, barinophytes, gametophytes, Paleozoic