Millia biflora UofAz
This pollen type is often used as an eclectic term for all
monolete - reticulate pollen grains. In fact, the systematics for the plant family
Liliaceae are complex, and many families have been split out of it.
Some of these have distinctive pollen, such as Allium (in the Alliaceae),
while other taxa retained in the Liliaceae do not have this morphology (Smilax is
inaperturate and verrucate, and Calochortus [above] is not reticulate), and several
other monocots have pollen that is monocolpate and reticulate (e.g.,
Agavaceae and Iridaceae).
Given the heterogeneity of the Liliaceae, recoginition of monolete - reticulate grains
to the genus level (or families split from Liliaceae) is possible, but these grains are
so rare as fossils, and the ecology of the group is so diverse, that the continued use
of this pollen type is likely.
In the broad sense, the Liliaceae contains over 3500 species worldwide, that are generally herbaceous
often with a "bulb" storage organ. The flowers are generally 6-parted, but Calochortus
(above) has 3 reduced petals. The leaves are generally long and parallel-veined, but many
exceptions exist (Asparagus!).
Pollen light micrograph:
Liliaceae pollen grains are generally 20 - 40 µm in long axis and monocolpate.
Generally the side of the grain opposite the colpus is narrow and somewhat angled -
like the sections of an orange.
The colpus generally extends fully to the end of the grain. The colpus may be very broad
and it may have an operculum, which may be ornamented (e.g. retuculate) or thin and
scabrate. Often the retuculum of the body is irregular. The reticulum may grade from
coarse on the side opposite the colpus to very thin (a margo) next to the colpus.
Also, very small lumina are present in the muri of some species.
Globular clumps of (exine?) "pollen kit" are visible clinging to the
surface of the pollen grains in both light and SEM specimens.
Perhaps the clumps are a characteristic of this pollen type.
Pollen scanning electron micrograph (SEM)
Liliaceae pollen generally appears the same in SEM and light-micrograph views.
Columella are sometimes (rarely) visible within the lumina of the pollen wall. TEM's
of the wall show a rounded tectum above short, thin columellae.
Production and Dispersal:
This insect pollinated family has low production and poor dispersal, but
the plants are so widespread that a few grains appear in most pollen counts.
Moderate. The grains are often broken in fossil preparations.
"Liliacidites" a monolete - reticulate pollen grain first appears in
the Jurassic, prompting the placement of monocots near the base of the Angiosperm
diversification (Traverse, 1988).
- Huyan, P. K-L. 1971. Etude de l'arrangement du pollen dans la tetrade chez
les Angiospermes sur la base de donnees cytologiques III. Le pollen trelete
du genere Dianella Lam. (Liliaceae). Beitr. Biol. Pflanzen 47: 277-286.
- Shoma, K. and Takahashi, M. 1982. Exine formation of Smilacina yesoensis
Fr. et Sav. and S. Japonica A. Gray (Liliaceae).
Science Reports Tohoku Univeristy 38: 165-172.
- Takahashi, M. and Shoma, K. 1979. Pollen wall formation and tapetum in
Disporum smilacinum A. Gray (Liliaceae). Science Reports Tohoku Univeristy 37: 273-281.
- Takahashi, M. and Shoma, K. 1982. Pollen morphology of the genus
Clintonia (Liliaceae). Science Reports Tohoku Univeristy 38: 157-164.
- Takahashi, M. and Shoma, K. 1983. Pollen morphology of the genus
Smilacina (Liliaceae). Science Reports Tohoku Univeristy 38: 191-218.
- Traverse, A. 1988. Paleopalynology. Allen & Unwin, Inc.
- Valio, I.F.M. and Labouriau, M.L. S., 1964. Pollen grains of plants of
the "Cerrado" - VII: Liliaceae subfamily Smilacoideae, and Loganaceae.
Rev. Brasil. BIol. 24: 119-126.
Owen Davis 5/02