Recent Topics Posters
Florez, Ana Marcela , Wurdack, Kenneth .
Comparative ontogeny of compound leaves: deciphering the enigmatic 3-parted leaf of the bishopwood tree (Bischofia; Phyllanthaceae).
Compound leaves have convergently evolved many times in angiosperms but few comparative studies have been done on their origin and development. Based on leaf architecture, there are three main compound leaf types: pinnate, palmate, and ternate. Pinnate forms have leaflets attached along an elongate axis; palmate have more than three leaflets attached at a single point; and ternate are 3-parted (trifoliate) from a single point. The origins of ternate leaves are unclear without phylogenetic hypotheses and closely related pinnate or palmate taxa from which to determine the direction of any changes. For example, ternate leaves might be derived by reductions from pinnate or palmate forms. There also have been suggestions that ternate leaves might even represent a different pattern of development. The origins of compound leaves can be revealed through their early ontogeny and the study of mutant leaves. This study focuses on the bishop tree (Bischofia javanica), the only compound-leaved Phyllanthaceae (formerly part of Euphorbiaceae s.l.), which has an unusual, slightly asymmetrical, ternate leaf with small domatia and theoid teeth. A pinnate derivation was previously proposed, based on limited 5-foliolate leaf mutants. The structure and development of Bischofia leaves was examined with SEM and histological observations of young shoot tips, and compared with the early ontogeny of other taxa (i.e., ternate Rhus aromatica, Staphylea trifolia, and Staphylea holocarpa and palmate Joannesia princeps). In Bischofia and Staphylea holocarpa , mutant mature leaves were found with mixed multi-leaflet pinnate and palmate forms. Development of extra leaflets in the latter taxon was acropetal in the manner of pinnate leaves. The leaves of Bischofia showed no further axis growth after the near simultaneous initiation of the lateral leaflets. Laminar domatia in Bischofia did not reveal any secretory regions that might indicate a reward for the mites they putatively house.
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1 - Universidad Industrial de Santander, Botany, Bucaramanga, Santander, Colombia
2 - Smithsonian Institution, Botany Department, PO Box 37012, NMNH, MRC-166, Washington, DC, 20013-7012, USA
Presentation Type: Recent Topics Poster
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM