Abstract Detail

Anatomy and Morphology

Smith, Annika [1], Struwe, Lena [2], Stenn, Kurt [3], Soltis, Douglas [4], Soltis, Pamela [4].

How many ways are there to make a nectar spur? Studies in the nasturtiums (Tropaeolum).

Nectar spurs have evolved numerous times across the angiosperms, but the morphological, developmental, and genetic underpinnings of nectar spurs vary among clades. The organ from which the spurs develop varies from clade to clade: in some species, they develop from sepals, and in others from petals, or a combination of the two. The development of nectar spurs in the nasturtiums (Tropaeolum) has been controversial, with assertions that the spurs develop from the receptacle at the base of the flower or from the sepal tissue alone. If the nectar spur of Tropaeolum develops from the receptacle (i.e., relatively undifferentiated stem and basal flower tissues), it would put Tropaeolum in the unique position of possibly having the only known receptacle-derived nectar spur in the flowering plants. To uncover the developmental origin of the spur of Tropaeolum, we employed both paraffin sectioning and whole-mount histology techniques in five species of Tropaeolum: one from Tropaeolum sect. Tropaeolum and four from Tropaeolum sect. Chilensia, representing a variety of spur morphologies. We investigated patterns of stele vasculature and cell division from multiple floral developmental stages and various levels within individual flowers to see the origin of vascular traces associated with the spurs, the relative order of developmental stages for different flower organs, and glands and surface structures at the anatomical level. Permanent sections and whole-mounts were photographed through microscopes and used to recreate spur development and anatomy in both temporal and 3-dimensional spatial scales. Results to date indicate that the nectar spurs of Tropaeolum are unique within the angiosperms in both their position and development.

1 - University of Florida, Florida Museum of Natural History, 1659 Museum Rd., Gainesville, Florida, 32611, USA
2 - Rutgers University, Ecology, Evolution, & Natural Resources, 237 Foran Hall, 59 Dudley Road, New Brunswick, NJ, 08901, United States
3 - Rutgers University, Ecology, Evolution, & Natural Resources, 237 Foran Hall, 59 Dudley Road, New Brunswick, NJ, 08901, USA
4 - Florida Museum of Natural History, University of Florida, 1659 Museum Road, Gainesville, Florida, 32611, USA

Keywords:
Tropaeolum
floral evolution
anatomy
morphology
Histology
nectar spur.

Presentation Type: Oral Paper
Session: AM1, Anatomy and Morphology I
Location: San Ignacio/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 10:30 AM
Number: AM1007
Abstract ID:950
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award