Above: Cladogram from Judd et al. (2008), Fig. 9.1 showing relationships among some major groups of flowering plants.
Monocots
Announcements:
Lecture Assignment 5 is due Monday, May 4th. Lecture Assignment 6 will be distributed on Monday and will be due May 11th.
The final lecture exam is on Thursday, May 14th, from 8 to 11 AM in this room. This exam will be comprehensive, but with emphasis on the last third of the course. It will be worth 20% of your final grade. There is a sample final exam in the back of your Class Notes (pp. 269-284) and the exam will be similar in style to what you saw in Lecture Exam 2. If there is interest, there will be a final lecture exam review (time and place TBA).
Final lab exam on Tuesday, May 5th (stations in lab) and Wednesday, May 6th (slides in lecture). Your final lab exam will also be comprehensive, but again with emphasis on the last half of the course. There will be a lab review on Sunday, May 3rd (time TBA) and I will review families in lecture on Monday, May 4th.
Text and Other Resources:
You are responsible for the following pertinent material presented in the Judd et al. (2008) textbook, Plant Systematics: A Phylogenetic Approach:
Some of the images linked to below were taken from our recommended text, Zomlefer, W.B. (1994), Guide to Flowering Plant Families, The University of North Carolina Press, Chapel Hill
See Digital Flowers for all of these families.
Course Objectives:
After studying this material you should be able to:
History of the Angiosperm Split
British naturalist, John Ray (1627-1705), in his NATURAL system of classification based on original observations of multiple characters of leaves, flowers and fruit, formally recognized two major subdivisions of flowering plants: dicotyledons or dicots (two cotyledons) and monocotyledons (one cotyledon), although the distinction between these two groups was likely apparent to Greek philosopher Theophrastus and was already noted by Saint Albertus Magnus (died ca. 1280).
Arthur Cronquist, in his PHYLETIC system of classification (1988), recognized these groups as Classes Magnoliopsida and Liliopsida.
Robert Thorne (1992) recognized them as Subclasses Dicotyledoneae and Monocotyledoneae.
These two groups of angiosperms have been distinguished traditionally by several morphological and anatomical characters (discussed below), but there are exceptions to most of them. Some dicot families are characterized by features common among the monocots, but rare or uncommon in most other dicots.
"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). Therefore, they are rejected as a formal group in phylogenetic classification systems. 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.
Above: Cladogram from Judd et al. (2008), Fig. 9.1 showing relationships among some major groups of flowering plants.
Synapomorphies for the monocots include:
Above: 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 (you are NOT required to know these):
Genera and species:
Cotyledons (the primary leaves of the embryo):
Floral parts:
Pollen grains:
Leaf venation:
Primary vascular bundle arrangement:
Secondary growth (true wood production):
Mature root system:
Distribution of "woody" habit:
Above ground dormancy:
Monocot Families
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.
Liliaceae (lily family)
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Left: Lilium flower. Middle: Erythronium flower. Right: Polygonatum flower.
The results of recent cladistic analyses, as well as your textbook, define both the order Liliales and the family Liliaceae quite narrowly. Many families traditionally considered within Liliales are now treated within the orders Dioscoreales, Asparagales and Liliales s.s. Cronquist (1981) placed most petaloid monocots (i.e., those with showy tepals and 6 stamens) into a broadly circumscribed Liliaceae. This group is clearly polyphyletic, and recently has been broken up into many segregate families, including Colchicaceae (Uvularia, bellwort), Smilacaceae (Smilax, greenbrier), Melanthiaceae (Trillium, wake-robin), Asparagaceae (Asparagus), Ruscaceae (Maianthemum, Polygonatum), Hyacinthaceae (Hyacinthus, Scilla), Alliaceae (Allium, onion and garlic), and Amaryllidaceae (daffodils). The taxonomy of this entire assemblage, however, is still quite problematic. In this class, we will stick with tradition (and simplicity!) and consider the entire group as comprising a broadly defined Liliaceae.
Araceae (arum family)
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Left: Leaves with reticulate venation rather than parallel venation. Middle: Spadix inflorescence with spathe from Aglaconema modestum. Right: Spadix and spathe in Jack-in-the-pulpit.
Calcium oxalate crystals (raphides) and associated chemicals cause irritation of the mouth and throat when eaten. However, after proper treatment, the irritating chemicals can be removed and the starchy corms eaten (taro). The traditionally related family Lemnaceae (duckweek family) is now included within Araceae and its members are considered highly modified (the spathe is represented by a membranous sheath or may be completely lacking).
Titan Arum, at Kew Gardens, the "world's largest unbranched inflorescence" on YouTube!
Read more about the titan arum (or corpse flower) on Wikipedia
Arecaceae or Palmae (palm family)
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Left: Pinnately compound leaves of palms. Middle: Male inflorescences (above) and female inflorescences (below). Right: A section of a coconut (drupe).
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The talipot palm (Corypha umbraculifera) is one of the largest palms in the world (25 m plus). It has large palmate leaves up to 5 m in diameter. It also bears the largest inflorescence of any plant (6-8 m long, and with millions of small flowers). Specifically, it has the largest branched inflorescence. It is also monocarpic (it flowers once when it is 30-80 years old, produces thousands of fruits, then dies).
An important video we should all watch describing how coconuts might be dispersed If you missed class today, be sure to watch this video.
Iridaceae (iris family)
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Left: Equitant leaves in Iris. Middle: Iris flower, showing the three petaloid styles. Right: Iris flower L.S., showing opposite sepals, stamens, and petaloid styles.
From Wikipedia. Saffron crocus. Saffron is a spice derived from the dried stigmas, and is the world's most expensive spice by weight. A pound of dry saffron (0.45 kg) requires 50,000 to 75,000 flowers, the equivalent of a football field's area of cultivation. Some forty hours of labour are needed to pick 150,000 flowers, and each flower can only contribute three stigmas!
Picking Saffron on YouTube! The stigmas have to be individually hand-picked when the flowers are fully opened.
Orchidaceae (orchid family)
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Left: Cattleya flower, zygomorphic and resupinate. Middle: Bletilla flower, showind details of the column. Right: pollinea from the Orchidaceae (also occurs in Asclepias).
The family is economically important because of its many ornamentals. Vanilla flavoring is extracted from the immature fruits (capsules) of Vanilla planifolia. Many orchids are very specialized, attracting only one or a few species as pollinators. The flowers are extremely varied in form and animal-mediated pollination mechanisms are diverse. Its dust-like seeds are wind dispersed and require a fungal symbiont to provide nutrition (the ovules do not develop until fertilization).
Poaceae or Gramineae (grass family)
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Left: A single spikelet from Festuca. Middle: Components of a spikelet inflorescence. Right: A single floret (with lemma removed).
Characters most important in identification include features of the spikelet (size, plane of compression, features of glumes, number of florets, presence of awns, and aggregation into secondary inflorescences).
About 70% of the world's farmland is planted in crop grasses, and over 50% of humanity's calories come from grasses (Judd et al., 2008). People have cultivated cereals for at least 10,000 years.
Twelve subfamilies are recognized as monophyletic based on molecular data (also many tribes). Your textbook discusses features of some of these families -- you are not required to know these subfamilies.
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