Origin of the Taxaceae aril : evolutionary implications of seed-cone teratologies in Pseudotaxus chienii

Dörken, Veit; Nimsch, Hubertus; Rudall, Paula J.

Origin of the Taxaceae aril : evolutionary implications of seed-cone teratologies in Pseudotaxus chienii

Dateien

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Datum

2019

Autor:innen

Dörken, Veit

Nimsch, Hubertus

Rudall, Paula J.

Open Access-Veröffentlichung

Open Access Green

Sammlungen

Biologie

Publikationstyp

Zeitschriftenartikel

Publikationsstatus

Published

Erschienen in

Annals of Botany. 2019, 123(1), pp. 133-143. ISSN 0305-7364. eISSN 1095-8290. Available under: doi: 10.1093/aob/mcy150

Zusammenfassung

Background and Aims
Fleshy structures that promote biotic dispersal by ingestion have evolved many times in seed plants. Within the yew family Taxaceae sensu lato (six genera, including Cephalotaxus), it remains controversial whether the characteristic fleshy structure surrounding the seed is interpreted as a novel outgrowth of the base of the ovule (i.e. an aril) or a fleshy seed coat that is entirely derived from the integument (i.e. a sarcotesta). This paper presents a detailed study of both wild-type and teratological seed cones of Pseudotaxus chienii, including morphology, anatomy and ontogeny.

Methods
Wild-type and teratological seed cones were investigated with the classical paraffin technique and subsequent astrablue/safranin staining and scanning electron microscopy.

Key Results
The wild-type seed cone of Pseudotaxus possesses a fleshy white aril that is cup-like and not entirely fused to the seed. In the teratological seed cones investigated, the aril was bilobed and consisted of two free halves. In both wild-type and teratological cones, the aril was initiated as two lateral primordia in a transverse plane, but in wild-type cones the two primordia became extended into a ring primordium, which grew apically, leading to the cup-like shape. The teratological seed cones lacked a ring primordium and the two lateral aril lobes remained free throughout their entire ontogeny, alternating with the scale-like leaves inserted below them on the same branch; in some cases, these leaves also became fleshy.

Conclusions
Based on the ontogeny and arrangement of the two fleshy aril lobes in the teratological seed cones of Pseudotaxus, we suggest that the typical aril of Taxaceae could be readily interpreted as a fused pair of strongly swollen leaves rather than a modified integument. Our investigations of the cup-like aril of Pseudotaxus demonstrate a similarity not only with other Taxaceae but also with relatively distantly related conifers such as Phyllocladus (Podocarpaceae).

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

Schlagwörter

Aril, evolution, Pseudotaxus, seed cone, Taxaceae, teratology

Zitieren

ISO 690

DÖRKEN, Veit, Hubertus NIMSCH, Paula J. RUDALL, 2019. Origin of the Taxaceae aril : evolutionary implications of seed-cone teratologies in Pseudotaxus chienii. In: Annals of Botany. 2019, 123(1), pp. 133-143. ISSN 0305-7364. eISSN 1095-8290. Available under: doi: 10.1093/aob/mcy150

BibTex

@article{Dorken2019-01-01Origi-45624,
  year={2019},
  doi={10.1093/aob/mcy150},
  title={Origin of the Taxaceae aril : evolutionary implications of seed-cone teratologies in Pseudotaxus chienii},
  number={1},
  volume={123},
  issn={0305-7364},
  journal={Annals of Botany},
  pages={133--143},
  author={Dörken, Veit and Nimsch, Hubertus and Rudall, Paula J.}
}

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    <dcterms:abstract xml:lang="eng">Background and Aims&lt;br /&gt;Fleshy structures that promote biotic dispersal by ingestion have evolved many times in seed plants. Within the yew family Taxaceae sensu lato (six genera, including Cephalotaxus), it remains controversial whether the characteristic fleshy structure surrounding the seed is interpreted as a novel outgrowth of the base of the ovule (i.e. an aril) or a fleshy seed coat that is entirely derived from the integument (i.e. a sarcotesta). This paper presents a detailed study of both wild-type and teratological seed cones of Pseudotaxus chienii, including morphology, anatomy and ontogeny.&lt;br /&gt;&lt;br /&gt;Methods&lt;br /&gt;Wild-type and teratological seed cones were investigated with the classical paraffin technique and subsequent astrablue/safranin staining and scanning electron microscopy.&lt;br /&gt;&lt;br /&gt;Key Results&lt;br /&gt;The wild-type seed cone of Pseudotaxus possesses a fleshy white aril that is cup-like and not entirely fused to the seed. In the teratological seed cones investigated, the aril was bilobed and consisted of two free halves. In both wild-type and teratological cones, the aril was initiated as two lateral primordia in a transverse plane, but in wild-type cones the two primordia became extended into a ring primordium, which grew apically, leading to the cup-like shape. The teratological seed cones lacked a ring primordium and the two lateral aril lobes remained free throughout their entire ontogeny, alternating with the scale-like leaves inserted below them on the same branch; in some cases, these leaves also became fleshy.&lt;br /&gt;&lt;br /&gt;Conclusions&lt;br /&gt;Based on the ontogeny and arrangement of the two fleshy aril lobes in the teratological seed cones of Pseudotaxus, we suggest that the typical aril of Taxaceae could be readily interpreted as a fused pair of strongly swollen leaves rather than a modified integument. Our investigations of the cup-like aril of Pseudotaxus demonstrate a similarity not only with other Taxaceae but also with relatively distantly related conifers such as Phyllocladus (Podocarpaceae).</dcterms:abstract>
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