Integrative Biology 335:
Systematics of Plants
Monocots

Announcements:

Your Final Lab Exam will be held on Tuesday, April 29 (in lab) and on Wednesday, April 30 (in lecture). Coverage is comprehensive, but with greater emphasis on the last half of the course. This exam is worth 15% of your final grade.

Laboratory Review, Sunday April 27, in lab, Time TBA. Clark will have more information on this. On Monday, April 30th, we will have a review of slides in lecture.

The Final Lecture Exam is Friday, May 2 in the EVENING, 7:00—10:00 pm.

Your Fifth Lecture Assignment, which was handed out on April 11, is due in lecture on Wednesday, April 23.

How many persons would like a lecture review session on Reading Day, Thursday, May 1? Perhaps 9:00—11:00 am?

"Dicotyledons" and Monocotyledons: an example of paraphyly

The "dicots" do not form a monophyletic group (they do not contain all the descendants of their common ancestor). They are rejected as a formal group in phylogenetic classification systems. Basically, it's difficult to circumscribe the "dicots" without including the monocots. Some "dicots" are more similar to monocots than they are to other "dicots." The "dicots" are paraphyletic (that is, they contain some, but not all, descendants of the most recent common ancestor of that group), whereas the monocots can be defined by several synapomorphies.

Cladogram from Judd et al. (2007) showing relationships among some major groups of flowering plants.

Phylogeny of the monocots and their allies, according to APG II (2003)

The six monocot families we will cover this semester and their ordinal placements:
Araceae (Alismatales)
Iridaceae and Orchidaceae (Asparagales)
Liliaceae (Liliales)
Arecaceae (Arecales)
Poaceae (Poales)

Comparison of Eudicot and Monocot Characteristics

Illustrations from Texas A&M

Genera and species:

10,000 genera and 176,000 species of eudicots (about 75% of all angiosperms)

2,800 genera and 58,000 species of monocots (about 22% of all angiosperms)

Cotyledons (the primary leaves of the embryo):

2 (rarely 1, 3 or 4) in dicots; usually develops above ground The possession of two cotyledons is an ancestral feature for all flowering plants and not an apomorphy for any group within.

1 (embryo undifferentiated in orchids) in monocots; usually develops below ground

Floral parts:

4-5 merous perianth in typical dicots (sometimes 3 or many)

3-merous perianth (usually) in monocots (also in dicot paleoherbs)

Floral Expression in major monocot and dicot lineages, from Texas A&M

Pollen grains:

tricolpate or a derived type (rarely monocolpate) in dicots (three furrows or apertures, but monocolpate in Magnolia group)

usually monocolpate in monocots (one furrow or pore)

This is referring to the depressed region in the pollen wall where the pollen tube emerges.

Leaf venation:

reticulate, with exceptions, in dicots

parallel, with exceptions, in monocots

Primary vascular bundle arrangement:

scattered in monocots and some dicots closely allied to them; no pith and no cortex

arranged in a ring in dicots; pith and cortex distinct

Secondary growth (true wood production):

usually present, from a vascular cambium, in dicots; also cork cambium

absent or not coming from a vascular cambium in monocots; no cork cambium

Mature root system:

either primary or adventitious, or both, in dicots

adventitious and fibrous, no taproots, in monocots and some dicots closely allied to them

Distribution of "woody" habit:

cosmopolitan in dicots

only tropical in monocots

Free vein endings:

common in dicots

rare in monocots

Above ground dormancy:

frequent in dicots

infrequent in monocots; essentially ever-growing

Monocot Families to be Studied this Term

Overview of Monocot Systematics and Characteristics from Texas A&M University. We will not use subclasses to separate monocot families.

See Digital Flowers for all families.

Arecaceae (or Palmae), the palm family
Araceae, the arum family
Liliaceae, the lily family
Iridaceae, the iris family
Orchidaceae, the orchid family
Poaceae (or Gramineae), the grass family