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Abstract Detail



Developmental and Structural Section

Budke, Jessica M. [1].

Comparative cuticle development in morphologically divergent mosses of the Funariaceae.

The ability to minimize water loss was critical for the evolution and survival of plants in terrestrial environments. On aerial organs water loss is decreased by the cuticle, layers of cutins and waxes that cover and permeate the epidermal cells. The cuticle has been retained and elaborated across all major plant lineages, including bryophytes, which points toward their functional importance in highly divergent taxa. Cuticles are present on both the gametophyte and sporophyte phases of bryophytes. In mosses, a cap of maternal gametophyte tissue (the calyptra) covers the apex of the offspring sporophyte during early development. The calyptra has a multilayered cuticle that is significantly thicker than the cuticle on other maternal gametophyte tissues, indicating an increased maternal investment in the calyptra. Experimental removal of the calyptra cuticle reveals that this structure functions to protect the immature sporophyte from dehydration stress. This study undertakes a comparative developmental analysis of the moss cuticle in closely related taxa to determine the relationship between the maternal investment in the calyptra and sporophyte height. Calyptra and sporophytes from four morphologically diverse taxa in the Funariaceae (Aphanorrhegma serratum, Physcomitrellopsis africana, Physcomitrium pyriforme, Funaria hygrometrica) were collected from laboratory-grown populations at two developmental stages (pre- and post-capsule expansion). Tissues were embedded, sectioned, and then examined using transmission electron microscopy (TEM). Thickness of the cuticle layers were measured from three epidermal cells per organ for each individual and compared statistically. All four of these Funariaceae species have cuticles consisting of multiple layers that are present on both the calyptra and sporophyte at both developmental stages. Young sporophytes have relatively thin cuticles that do not thicken until late during capsule expansion. This is contrasted with the maternal gametophyte calyptra, in which all four taxa produce a mature cuticle early during sporophyte development that persists through capsule expansion. Taller sporophytes have both larger calyptra and thicker calyptra cuticles. Species with taller sporophytes also have specialized thickenings of the cuticular layer (cuticular pegs) at the regions of the anticlinal cell walls, where higher pectin levels may contribute to increased water loss through these areas. Increasing levels of maternal investment in the calyptra correspond with taller sporophytes, which may be driven by taller sporophytes experiencing higher levels of dehydration stress. These observations add further support to the hypothesis that the calyptra cuticle functions to protect the sporophyte apex from dehydration during early development.


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1 - University Of California - Davis, Department Of Plant Biology, One Shields Avenue, Davis, CA, 95616, USA

Keywords:
Bryophyte
calyptra
comparative development
cuticle
cuticular pegs
dehydration stress
Electron Microscopy
Funariaceae
maternal investment
sporophyte protection.

Presentation Type: Oral Paper:Papers for Sections
Session: 76
Location: Salon 11/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 3:45 PM
Number: 76001
Abstract ID:699
Candidate for Awards:None


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