Botany
Spring 2008
Written by: Sue Kloss
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Angiosperms - Chapter 25
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I. Plants with an enclosed seed
A. Flowering plants today dominate the world’s vegetation
1. greatest biomass of most habitats is flowering plants
B. The defining angiosperm feature is enclosure of ovules within an ovary
C. In this text, Magnoliophyta is accepted as the name of flowering plant division
II. Mysterious origin of flowering plants
A. Flowering plants appear suddenly in the geologic record without a clear fossil history showing some transition
from other plant groups
1. Upland theory
2. Bond’s seeding hypothesis
III. Novel Features of the Angiosperm Life Cycle
A. (Fig. 25.7) Angiosperms and Gymnosperms both produce seeds but different in several life cycle features that
adapt flowering plants to life on land and conserve food reserves
1. Fig. 81 & 87 - coloring - flowering plants show greater reduction in gametophyte size and complexity
2. location of the ovule becomes hidden
3. fertilization involves 2 steps with double-fertilization rather than one
4. seed dispersal is improved by its enclosure within a fruit
IV. Division Magnoliophyta
A. object of classification is to divide flowering plants into groups that show historic evolutionary linkages classification should be phylogenetic
1. typically, Magnoliophyta is divided into two classes - Magnolipsida (dicots) and Liliopsida (monocots)
Fig. 88 - coloring
B. Phylogenetic Relationships are based on vegetative and reproductive traits - no fossil record, so inferences
are made, lots of disagreement among taxonomists
1. Bessey system found much favor in 20th century, still widely used
2. Besseys criteria - 26 criteria for determining evolutionary advancement e.g.
a. change from spiral to whorled arrangement
b. decreasing number of stamens and carpels
c. tendency for stamens and carpels to become attached to each other or to petals
3. Takhtajan, Cronquist, Thorne and Dahlgren expanded Besseys criteria to include wood anatomy
plant growth form, stomatal structure, pollination vectors, etc.
Takhtajan uses criteria to divide the Magnoliopsida into seven subclasses, and Liliopsida into 3
subclasses (Fig. 25.8)
a. new information from DNA analysis, protein structure are helping define primitive vs advanced
b. Fig. 25.8 will probably be revised at some point soon, but for now this is it
4. Subclass Magnolidae is the basis for both groups
C. Magnolidae is the most primitive subclass
1. subclass contains tropical and warm-temperate trees with simple leaves, pinnate venation, large
flowers with many stamens and pistils, and relatively simple wood anatomy; eg. Magnolia
2. other members of this subclass and close relative the Ranunculidae include: nutmeg, cinnamon,
sassafras, avocado, bay laurel, black pepper, water lily, pitcher plant, opium poppy, buttercup family
a. flowers of plants in these subclasses have regular symmetry, many separate parts and a
superior ovary; typically beetle pollinated
D. The Alismatedae and Arecidae are primitive monocots
1. Liliopsida diverged early from Magnoliidae
2. Most primitive Liliopsida are in the flowering rush family (Butomaceae) and the water plantain family,
herbaceous aquatic plants w/ vessels only in roots - Alismataceae - Arrowhead is an example Fig. 25.10),
both in subclass Alismatedae
3. the Arecidae is a more advanced subclass, Arecaceae is the largest family in this subclass
a. Arecaceae = palm family
b. unbranched trunk (wind resistance), terminal cluster of leaves, coconutlike fruit - edible
endosperm from huge seeds, oil pressed from dried coconut meat and cordage from stringy crust
c. sensitive to frost - if single SAM dies, tree dies.
d. also in Arecidae - duckweeds, philodendron, calla lily
4. palms are among the most important tropical families
E. The Liliidae are the most advance monocots
1. one line includes orchids, lilies and bromeliads - colorful flowers, highly coevolved with insect pollinators
2. the other line is grasses and sedges - small colorless flowers, wind pollinated
a. barley corn, rice, wheat, are family Poaceae (grass)
b. other families include pineapples, banana, Allium spp, ginger, Papyrus, tulips, lilies, iris
F. Hamamelidae and Rosidae are Primitive Dicots
1. Hamamelidae are small subclass of temperate zone woody plants, including important hardwoods of
eastern forests
a. sycamore
b. sweet gum
c. birch
d. alder
e. beech
f. oak
g. chestnut
2. Rosidae is the most diverse subclass of dicots; among the families are bean, eucalyptus, rose and
carrot
a. important for fruits, nuts, timber, ornamentals, spices, dyes and drugs
b. apples, oranges, cherry, plum mango, carrot, dill, clove, dogwood, holly, ivy, mangroves,
maple, indigo, rubber
G. The Caryopyllidae, Dilleniidae and Asteridae are advanced dicots
1. largest families in subclass Caryophyllidae includes ice plants, cacti, and beets
2. The Dilleniidae subclass has many families but only a few are large - heather, mulberry, mustard, elm
peonies, willows, violets, papaya, rhododendron
3. The Asteridae, the most advanced dicot subclass - large families include tomatoes, snapdragons,
mints and sunflowers; others are coffee, lavender, Penstemon, tobacco, olive
a. Advanced traits include irregular flower symmetry (a flower in which at least one member of at
least one whorl is different from other members of same whorl), inferior ovary, small flowers and
herbaceous habit
b. the largest of all flowering plant families is the sunflower family, the Asteraceae
V. Plant geography - describes the distribution of plant taxa
A. World’s flora is not uniform
B. Vegetation of a particular type of climate often looks similar wherever that climate recurs around the world, even
if plants at each location are unrelated taxonomically
C. Environmental conditions, genetic potential and isolation growing in a place combine to create unique and
bizarre vegetation found nowhere else in world
VI. Botanical Gardens
Lesson Objectives Ch. 25
1. Compare and contrast alternation of generations in angiosperms vs. gymnosperms.
2. Differentiate between pollination and germination
3. What is double fertilization and in what way is the process unique in angiosperms?
4. Explain how coevolution involves beneficial relationships for both angiosperms and their pollinators.
5. Compare the evolutionary advantages of gymnosperms vs angiosperms. Discuss importance of features of the life
cycle found only in angiosperms.
6. Why do you think wind pollinated plants do not have colorful flowers?
7. What hypothesis accounts for the lack of fossil evidence on angiosperm evolutionary origins? Explain it.
8. Explain what Bond’s seedling hypothesis is.
9. What characteristics are used to try to group plants into their taxonomic hierarchy and why?
10. Describe the 3 main groups of angiosperm plants, and briefly describe characteristics of each.
11. What are 2 important taxa of plants in each of the groups you listed in question 10?
12. What is plant biogeography?
13. What is the importance of botanical gardens?