Abstract Detail

Anatomy and Morphology

Stenn, Kurt [1], Struwe, Lena [2].

The colleters of Pentas (Rubiaceae: Gentianales): Morphology, anatomy, and search for their function.

Colleters make up a special type of glandular trichomes common to many members of the Gentianales (Apocynaceae, Gelsemiaceae, Gentianaceae, Loganiaceae, and Rubiaceae), as well as a few unrelated orders. Though described many times by botanical scholars the detailed morphogenesis and function of colleters is not fully understood. They appear in a variety of forms and organization of cell types and numbers. They are well-developed early in the formation of leaves, flowers, and vegetative nodes and often wither and disappear as the other organs develop. In some cases, like Potalia (Gentianaceae), they excrete very abundant resin in the young buds. In Pentas (Rubiaceae) and Calotropis (Apocynaceae) colleters are distinct, visible-by-the-eye, dark glandular hairs at the internodes between leaves. Because colleters are associated with developing leaves and flowers and because they often produce a sticky secretion, earlier investigators postulated that these structures served a protective function for developing structures from desiccation and/or predation. In this talk we report on our preliminary studies of the cellular biology of colleters and our attempts to define their functions. We chose to study the colleters of the horticultural species Pentas lanceolata (Rubiaceae) because it is readily available and its colleters are large.  Pentas colleters, each about 1–3 mm long, grow on its fimbriate interpetiolar stipules in clusters of two to six, usually four. Each colleter has a prominent dome, or head, consisting of a single layer of cuticle-covered, elongated cells. The colleter head is attached to a multicellular vascularized stalk. On its periphery at all levels are unicellular-uniseriate trichomes. The colleters are light-green at the most apical stem node but become white at the lower internodes. Later in development colleter heads become brown and necrotic, followed by senescence of the whole colleter structures at older nodes. Our preliminary colleter-ablation studies suggest that colleter growth and maturation are not controlled by the apical meristem and that intact colleters do not affect leaf formation or flower anthesis. Our current studies are testing for biome and/or hormonal influences on colleter development.

1 - Rutgers University, Dept of Ecology, Evolution, and Natural Resources, 237 Foran Hall, 59 Dudley Road, New Brunswick, NJ, 08901, US
2 - Rutgers University, Ecology, Evolution, & Natural Resources, 237 Foran Hall, 59 Dudley Road, New Brunswick, NJ, 08901, United States

Keywords:
Gentianales
anatomy
trichomes
morphology
development
Rubiaceae
Plant Structure-Function
Gentianaceae
Apocynaceae
colleters.

Presentation Type: Oral Paper
Session: AM1, Anatomy and Morphology I
Location: San Ignacio/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 11:00 AM
Number: AM1009
Abstract ID:692
Candidate for Awards:None