Journal Article

Pericarp development and fruit structure in borassoid palms (Arecaceae–Coryphoideae–Borasseae)

Mikhail S. Romanov, Alexey V. F. Ch. Bobrov, D. Siril A. Wijesundara and Ekaterina S. Romanova

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 108, issue 8, pages 1489-1502
Published in print December 2011 | ISSN: 0305-7364
Published online August 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcr148
Pericarp development and fruit structure in borassoid palms (Arecaceae–Coryphoideae–Borasseae)

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

The Borasseae form a highly supported monophyletic clade in the Arecaceae–Coryphoideae. The fruits of Coryphoideae are small, drupaceous with specialized anatomical structure of the pericarp and berries. The large fruits of borassoid palms contain massive pyrenes, which develop from the middle zone of the mesocarp. The pericarp structure and mode of its development in Borasseae are similar to those of Eugeissona and Nypa. A developmental carpological study of borassoid palms will allow us to describe the process of pericarp development and reveal the diagnostic fruit features of borassoid palms, determine the morphogenetic fruit type in Borasseae genera, and describe similarities in fruit structure and pericarp development with other groups of palms.

Methods

The pericarp anatomy was studied during development with light microscopy based on the anatomical sections of fruits of all eight Borasseae genera.

Key Results

The following general features of pericarp structure in Borasseae were revealed: (1) differentiation of the pericarp starts at early developmental stages; (2) the exocarp is represented by a specialized epidermis; (3) the mesocarp is extremely multilayered and is differentiated into several topographical zones – a peripheral parenchymatous zone(s) with scattered sclerenchymatous elements and vascular bundles, a middle zone (the stony pyrene comprising networks of elongated sclereids and vascular bundles) and an inner parenchymatous zone(s); (4) differentiation and growth of the pyrene tissue starts at early developmental stages and ends long before maturation of the seed; (5) the inner parenchymatous zone(s) of the mesocarp is dramatically compressed by the mature seed; (6) the endocarp (unspecialized epidermis) is not involved in pyrene formation; and (7) the spermoderm is multilayered in Hyphaeninae and obliterated in Lataniinae.

Conclusions

The fruits of Borasseae are pyrenaria of Latania-type. This type of pericarp differentiation is also found only in Eugeissona and Nypa. The fruits of other Coryphoideae dramatically differ from Borasseae by the pericarp anatomical structure and the mode of its development.

Keywords: Fruit development; pericarp anatomy; mesocarpic pyrene; unspecialized endocarp; Borasseae; pyrenarium of Latania-type

Journal Article.  7563 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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