Review for Midterm #1: Plants
Exam content
The exam will cover all the lecture material up to and including Lecture 9 (secondary growth,
Monday Feb. 6). The textbook and lab manual are supplemental and will not be tested
directly. (This review handout is not comprehensive, just an outline!)
Exam format
The test will last for fifty minutes (6:10 – 7:00 p.m.) and contain approximately 33 questions
for a total of 99 points (14% of your total grade). All questions will be multiple-choice with
one best answer and will be entered on a Scantron. The test is closed-book and closed-notes.
Calculators and other devices not allowed - you need only a #2 pencil and your brain!
For last-minute questions
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Attend Dr. Feldman’s review session on Wednesday, 2/22, at 6 pm in 1 Pimentel.
Go to GSI office hours in 2013 VLSB: Amber 11-12 W and 12-1 F; Brian TBA. You
can also go to any other GSI’s office hours throughout the week.
E-mail your GSI: Amber akerrl@lberkeley.edu or Brian bobbitworml@lberkeley.edu.
Visit the class webpage for posted questions and answers:
http://ist-socrates.berkeley.edu/~akerr/bio1b/questions-plants.html.
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Evolution of fungi, algae, and plants
- Fungi, algae, plants and animals are all eukaryotes (cells with a nucleus).
- Fungi are NOT closely related to plants. Plants have cellulose in their cell walls,
whereas fungi have chitin, indicating that they are more closely related to animals.
- Green algae are the direct ancestors of plants.
- Algae are not plants, but protists (a loosely defined group of mostly microscopic
eukaryotes)
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Fungi and their life cycles
- Fungi are decomposers, excreting enzymes to break down dead organic matter.
- Their bodies are made of up filaments called hyphae. All the hyphae together are
called a mycelium. Most of the mycelium is below-ground.
- Fungi have a variety of life cycles but do not have alternation of generations.
- A common life cycle is as follows:
o haploid (n) hyphae of different mating types fuse, resulting in a dikaryotic phase
(2 haploid nuclei per cell, designated n + n).
o These dikaryotic nuclei fuse to make to make diploid cells (2n), and soon undergo
meiosis to produce spores (n), which disperse and form new haploid hyphae.
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plants.usda.gov/gallery
Bio 1B Sections 105/106
February 21, 2006
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Fungi are important in human food (e.g. bread, wine) and medicine (e.g. penicillin).
A lichen is a symbiosis between an alga (which provides energy through
photosynthesis) and a fungus (which provides structure and takes up nutrients).
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Algae and their life cycles
- Algae have diverse life cycles, sometimes including alternation of generations (algae
are thought to have “invented” A of G, and given rise to land plants).
- Main types of algae: green, red, brown, diatoms, dinoflagellates.
- Green, red, and brown algae can be single- or multicellular. The multicellular ones
are what we call “seaweeds.”
- Dinoflagellates cause toxic red tides which can kill fish and people.
- Diatoms are single-celled organisms with hard shells (-> diatomaceous earth).
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Alternation of generations: basic ideas
- Multicellular haploid generation (gametophyte) alternates with multicellular diploid
generation (sporophyte). These phases must be multicellular.
o Gametophytes produce haploid gametes (egg and sperm) that fuse to become
a diploid sporophyte. The fusion of haploid nuclei is called “fertilization.”
o Sporophytes produce haploid spores by meiosis. Each spore develops into a
new gametophyte on its own. (A spore does not fuse with another spore).
- In early land plants, the gametophyte was the dominant generation. But there was a
trend for the gametophyte to get smaller while the sporophyte got bigger. Now, in
most modern plants, the sporophyte is the dominant generation.
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Bryophyte life cycle
- Includes mosses, liverworts, hornworts. Similar to earliest land plants.
- Unique among living plants because of dominant gametophyte, dependent sporophyte
- Non-vascular -> cannot grow very tall, need damp environment
- Flagellated sperm need water to swim to egg
- Sporophyte sends out spores from tall stalk which drift on wind
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Fern life cycle
- Ferns were the first vascular plants, meaning they have water-conducting tissue.
- Unique because of independent gametophyte, independent sporophyte
- Gametophyte is tiny and fragile but photosynthetic. Sporophyte emerges from it.
- Like in bryophytes, sperm are flagellated and must swim to archegonia. Still
dependent on water for reproduction.
- No seeds. Ferns reproduce by spores from clusters of sporangia (called sori) on their
leaves (called sporophylls).
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Gymnosperm life cycle
- Gymnosperms were the first seed plants. Name means “naked seed.”
- Gymnosperms still have megasporangia (on female cones) and microsporangia (on
male cones), but rather than releasing spores, the parent sporophyte retains the spores
until they turn into gametophytes. (This is the biggest difference between ferns and
gymnosperms.)
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Because they are protected by the sporophyte, gametophytes of gymnosperms are
very small:
o male = pollen; has 5-10 cells. Sends sperm nuclei to egg through pollen tube.
o female = ~2000 cells, inside ovule. It nourishes the developing sporophyte.
The function of the seed (= mature ovule) is to retain and protect the female
gametophyte and the developing embryo (sporophyte). It is covered by a seed coat
derived from the parent sporophyte.
Seeds are located on scales of female cones (= strobili), exposed to outside world.
The invention of pollen to transport the male gamete to the female gamete meant that
gymnosperms no longer needed wet environments to reproduce.
After pollination, fertilization may be delayed by a year or more, to wait for the
female gametophyte to germinate and produce the egg.
Gymnosperms are wind-pollinated. This is their main method of long-distance
dispersal.
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Angiosperm life cycle
- Major new innovations: flowers (to attract animal pollinators) and fruits (to protect
the seed and aid in seed dispersal).
- Flower parts: sepals, petals, carpels (stigma + style + ovary), stamens (anther +
filament). The ovary protects the seeds, unlike naked seeds of gymnosperms.
- Fruit is usually derived from wall of mature ovary.
- Gametophytes even more reduced than in gymnosperms:
o male = pollen (2 cells when immature, 3 cells when mature);
o female = “embryo sac” (7 cells + 8 nuclei).
- Pollen tube must grow very long to penetrate protective barrier of sporophyte tissue.
- Double fertilization: 1 sperm fertilizes egg, 1 sperm fertilizes 2 polar nuclei 
triploid endosperm.
- Endosperm nourishes growing embryo. Endosperm can be solid or liquid.
- In some angiosperms, the endosperm is absorbed into special structures of the embryo
called cotyledons (see below). The part of the embryo below the cotyledon is the
hypocotyl; above is the epicotyl.
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Monocots and eudicots
- The two major groups of angiosperms.
- Eudicot embryos have 2 cotyledons (“seed leaves”), which often absorb endosperm.
- Eudicots usually have net-like veins, floral parts in 4’s or 5’s, and taproots.
- Eudicots have secondary growth. Their vascular bundles are arranged in a ring.
- Examples of eudicots: violet, oak tree, bean, rose.
- Monocots usually have parallel veins, floral parts in 3’s, and adventitious roots that
arise from the stem.
- Monocots do not have secondary growth. Their vascular bundles are scattered.
- Monocot embryos have 1 cotyledon. It does not absorb endosperm.
- Coleoptile = special cap-like structure, protects shoot apex of monocot embryos.
- Examples of monocots: grass, corn, palm tree, orchid, lily.
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Primary growth of plant body
- Primary growth occurs at apical meristems (shoot and root), at tips of plant.
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Behind an apical meristem (which is a zone of rapid cell division) there is a zone of
cell elongation and then a zone of cell differentiation.
Shoot apical meristem produces leaf primordia ( leaves) and bud primordia (
axillary buds  branches).
Nodes (where leaves come out) alternate with internodes. Axillary buds produced are
produced at axil, where leaf intersects stem.
Leaves and stems can be very modified. E.g. onion bulb = leaves, modified for
storage. Potato = underground stem, modified for storage. Tendril = leaf modified
for grasping. Many other examples.
Plant structures are often arranged in spirals according to the Fibonacci series (1, 2, 3,
5, 8, 13, 21...) For example, pineapple scales are often arranged in two interlocking
spirals, 8 spirals in one direction and 13 in the other.
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Cell types
- Parenchyma = “parent tissue” = basic tissue which carries out photosynthesis, fills in
gaps, stores starch, etc. The “default tissue.”
- Palisade parenchyma is in upper half of leaf; spongy parenchyma underneath.
- Collenchyma = “glue tissue” = tough, stretchy, provides support. Celery strings.
- Sclerenchyma = “hard tissue” = rigid support. May be dead when functional.
- Two types of sclerenchyma cells are fibers (long) and sclereids (round).
- Lignin is the substance which makes sclerenchyma tough.
- Some cells, e.g. stomata, are too specialized to fit into any of these cell types.
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Tissue types
- Three main types: dermal tissue, ground tissue, vascular tissue.
- Dermal tissue (“skin”) forms from protoderm and becomes epidermis.
o Epidermis is covered by a waxy layer called cuticle.
o It contains stomata (pores), each consisting of a pair of guard cells, which
exchange gas for photosynthesis. Stomata are usually on leaf’s lower surface.
o Leaf hairs, root hairs, and cotton fibers are special types of epidermal cells.
- Vascular tissue (transport) forms from procambium and becomes:
o xylem (toward inside of stem / top of leaf; transports water)
 Made up of vessels (only in angiosperms) and smaller tracheids.
 Xylem is dead when functional.
o phloem (toward outside of stem / bottom of leaf; transports sugars)
 Made up of sieve tube members and companion cells.
 Phloem is alive when functional.
- Ground tissue is everything else (does photosynthesis, fills in spaces, etc.)
- One tissue type can contain multiple cell types.
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Primary structure of stems and roots
- Stems, from outside to inside: epidermis, cortex, phloem, xylem, pith
- Roots, from outside to inside:
epidermis, cortex, endodermis (contains Casparian strip), pericycle, phloem, xylem.
- In roots, all the vascular tissue is contained in a central “vascular cylinder” to control
entry of water and solutes.
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The Casparian strip contains a waxy substance called suberin, which prevents water
and solutes from leaking between the endodermis cells. See text p. 744 for details.
The pericycle gives rise to lateral roots.
The root cap senses gravity using organelles called amyloplasts, which contain heavy
starch grains.
Secondary growth
- Caused by lateral meristems, chiefly the vascular cambium (also cork cambium).
- All plants have primary growth. But secondary growth only occurs in gymnosperms
and some eudicots, not monocots. Monocots can increase in girth through three other
mechanisms: (1) cell enlargement; (2) adventitious roots; (3) retention of leaf bases.
- Vascular cambium is located in between xylem and phloem. It produces secondary
xylem to the inside and secondary phloem to the outside
- Secondary xylem accumulates, but secondary phloem is ripped apart by expanding
xylem and keeps falling off.
- By definition, everything inside the vascular cambium is wood, and everything
outside is bark.
- Cork cambium arises in the secondary phloem and produces cork, a thick waxy tissue
that provides protection and insulation.
- Because the phloem keeps falling off, cork cambia must keep re-forming in the
phloem, closer to the inside. When a new cork cambium produces cork, it kills
everything to the outside of it, because cork cuts off supply of water and nutrients.
- In temperate trees, annual rings are formed in secondary xylem. This is because
large, light-colored cells are produced as soon as conditions become favorable in the
spring, and then the cells gradually get smaller and darker as the year goes on.
Other topics from the Plants section of Bio 1B:
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Plant growth substances
Control of flowering
Water relations
Mineral nutrition
These will not be covered on the midterm, but will be emphasized on the final. A separate review
sheet will be handed out later.
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