UofA Pollen Grain of the Month
January, 2003

Olneya



Olneya tesota
Lee Sola

Olneya tesota
Olneya tesota
UofAz 991

Olneya tesota
Olneya tesota
UofAz

Olneya:
Ironwood (Olneya tesota) pollen is tricolporate with "roughened" (approaching reticulate) sculpturing. The pollen grain (ca. 37 (P) x 28 (E) µm) is rectangular in equatorial view and round in polar view. The furrows are narrow and straight, and the polar area is small. The furrows are flanked by broad sculptureless "margos." The large endopores are not visible in SEM micrographs, but are visible with careful LO analysis under transmitted light.

Plants:
Ironwood (Palofierro) trees are common in the Sonoran Desert. The plants are frost sensitive and occur (above the limit of cold air drainage) in the upper bajadas of desert basins in Arizona and eastern California at the northern limits of the plant's distribution. They bark of young branches is light, but mature stems are dark and furrowed. The leaves are pinnately compound, and the flowers are light purple. The wood is used for "ironwood carvings" - originally by the Seri Indians of western coastal Sonora, but now by commercial enterprises chiefly in the city of Hermosillo, Sonora.


Olneya tesota

Olneya tesota

Prosopis julifolra

Prosopis julifolra

Pollen light micrograph:
The rectangular outline and short straight furrows are distinctive, but LO analysis is often needed to distinguish the large endopore. This furrow in the thin area over the pore may be pinched, and the pore membrane may protrude. The "margo" is not obvious in light microscopy. Olneya grains area readily distinguished from Prosopis pollen (pollen-of-the-month Feb. 02) Mesquite's pollen is less rectangular; it has a larger polar area; it's furrows are broader, and it's endopore is smaller, surrounded by a annulus, and included within the edges of the furrow.

Pollen scanning electron micrograph (SEM)
The endopore is sometimes faintly visible.

Production and Dispersal:
Insect-pollinated ironwood has low production and poor dispersal, but the flowers are occasionally very abundant, and pollen abundances pf over 15% may be found in modern surface samples.

Preservation:
Good preservation.

Fossil Occurrence:
This branch of the Leguminosae (Fabaceae) is thought to have originated in the neotropics during the Neogene. However, there are no fossils records of the pollen older than Pleistocene, as far as I am aware.

References:
  • Lavin, M., Wojciechowski, M.F., Richman, A. Rotella, J., Sanderson, J.J., and Matos, A.B. 2001. Identifying Tertiary radiations of Fabaceae in the Greater Antilles: Alternatives to cladistic Vicariance analysis. Int. J. Plant Sci. (6 Supplemental)162: S53-S76.

Links
Owen Davis 11/02



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