Liguliflorae (Compositae)


Taraxacum officinale
© Caroline R. Dean


Taraxacum officinale
APMRU


Taraxacum officinale sp.
'Uppsala'

Plant:
"Liguliflorae" refers to a subfamily of the sunflower family (Asteraceae = nom. alt. Compositae) with a single tribe - the "Lactuceae (disc. Cichorieae)." Its flowers are unique in the family in being perfect (with both anthers and ovaries), each possesing ligules ("petals"), and typically having milky juice (latex). The traditional preference for "Liguliflorae" in palynology may stem from its usage in Faegri and Iversen (1st ed., 1950), because the word "Cichorieae" is used in the more comprehensive, but later publication by Wodehouse (1959). The Lactuceae is a cosmopolitan family of mostly herbs (the "lettuce tribe") including 75 genera and over 1500 species. Many of the North American species are weeds, such as dandelion (Taraxacum) and sow thistle (Sonchus).

Pollen light micrograph:
Sculpture fenestrate (lophate) and echinate. The fenestrae are large (1/4 grain diam.) windows in the pollen wall. The spines are typically arranged in single rows atop the tectum ridges, between the fenestrae. The number of fenestrae per grain varies from (none = 3) 9 to 15 (18).

Pollen scanning electron micrograph (SEM)
The APMRU image shows the germinal aperture, three per grain (presumably).

Production and Dispersal:
Production and dispersal is less than the wind-pollinated members of the sunflower family such as ragweed and sagebrush, but very high percentages of "Liguliflorae" pollen have been recorded, particularly in human-disturbed habitats in Europe and the USA (Davis and Mariscal, 1994).

Preservation:
Well preserved - thick walled. Also, the grain is easily recognized in a deteriorated state.

Fossil Occurrence:
Pollen of sunflower family is first recorded in the late Oligocene of North America and Europe, and Liguliflorae pollen appears in the the early Miocene of Europe, North America, and South America (Muller, 1981; Leopold 1969). However, the wide distribution of the sunflower family argues for an earlier origin, followed by a Oligocene-Miocene radiation.

References:
    Blackmore, S. 1984. Compositae - Lactuceae. Northwest Pollen Flora 32. Elsevier.

    Blackmore, S. 1986. The identification of taxonomic significance of lophate pollen in the Compositae. Canadian Journal of Botany,64:3101-3112.

    Carlquist, S. 1958 Anatomy and Systematic Position of Centaurodendron and Yunquea (Compositae). Brittonia 10: 78-93.

    Carter, A. 1964. The Genus Alvordia (Compositae) of Baja California Mexico. Proceedings of the California Academy of Sciences 30: 157-174.

    Davis, O.K. and Mariscal, B. 1994. A comparison of archeological palynology of Almeria, Spain, and coastal southern California, U.S.A. AASP Contribution Series. 29:75-82.

    Elsik, William C. and Tomb, A. Spencer. 1988. Fossil Compositae Pollen Morphotypes 21st Annual Meeting of The American Association of Stratigraphic Palynologists Inc.

    Faegri, K. and Iversen, J. 1950. Text-book of modern pollen analysis. Ejnar Munksgaard, Copenhagen.

    Hernandez, P.J. 1966 Notas palinologicas del Norte Argentino provincia Altoandina. I Compositae. Ameghiniana,4:305-347.

    Leopold, E.B. 1969. Late Cenozic palynology. pp. 377-438 IN: Tsuchdy, R.H. and Scott, R.A. 1969. Aspects of palynology. Wiley Interscience. Salgado-Labouriau, M.L. 1982 On cavities inspines of Compositae Pollen Grana 21: 97-102.

    Muller, J. 1981. Fossil pollen records of extant angiosperms. Botanical Review 47: 1-146.

    Salgado-Labouriau, M.L. 1982 Pollen Morphology of the Compositae of the Northern Andes. Pollen et Spores, vol.24, no.3-4

    Salgado-Ladourian, M.L. 1983 Key to the Compositae Pollen of the Northern Andes. Sociedad Venezolana de Ciencias Naturales

    Stebbins G.L. 1953. A new classification of the tribe Cichorieae, family Compositae. Madrono 12:65-81.

    Tomb, A.S. 1975 Pollen Morphology in Tribe Lactuceae (Compositae) Grana,15:79-89.

    Wodehouse, R.P. 1959. Pollen grains. Their structure, identification and significance in science and medicine. Hafner Publ., N.Y.

Links
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