Download ch. 22- 25 : the plants

Kingdom: Plants
Non-Vascular Plants
Vascular Plants
1. No tubes (roots, stems, or leaves) to carry
water
2. Carry water/materials via osmosis/diffusion
3. All need water to reproduce
1. Vascular tissue (true roots, stems...)
a. xylem
-dead tubular cells
-transport water upwards
b. phloem
-living tubular cells
-transports surags down
from leaves
Example: Bryophyta (Moss)
Without Seeds
With Seeds
Psilophyta: whisk fern
Lycophyta: club moss
Sphenophyta: horse tail
Pterophyta: ferns
Gymnosperms (cones)
Cycadophyta: palm tree-like
Gnetophyta: shrubby vine
Ginkophyta: ginko
Coniferophyta: pine fur
Monocots
-1 seed leaf
-parallel veins
-examples: grasses,
lilies
Angiosperms (flowering)
Anthophyta: fruit trees
Dicots
-2 seed leaves
-branching veins
-examples: shrubs,
trees
CH. 22- 25 : THE PLANTS
Ch. 22 : "The Importance of Plants
I. Plants As Food
-Of the more than 350,000 plant species, people use at least 10,000
species for food."
FOOD CROPS
-cereals
-root crops
-legumes
-fruits, vegetables and nuts
-spices, herbs, and flavorings
NONFOOD USES OF PLANTS
-medicinal- quinine. aspirin, taxol, echinacea, etc.
-clothing and fabric dyes
-fuels
-anti-erosion
-fertilizers- crop rotation
PLANT ECOLOGY
-food chain - producers
-oxygen supply
-plant-animal interactions
-harmful plants
Ch. 23: Plant Evolution and Classification
1st land plants----> simple structure; probably evolved from green algae (Chlorophytes)
Advantages to living on land:
-light more available
-CO2 more available at the time = no other competing life forms (until about 430 mya)
Problems with living on land- must evolve protective features to live on land
-preventing water loss
-reproducing by seeds and spores
-transporting materials throughout body
I. EARLY LAND PLANTS: The Bryophytes
-includes mosses and liverworts
-"nonvascular" = no transport of materials up and down stem, therefore must remain
small, low to the ground; must have
-direct contact with H2O
-lack true roots, stems and leaves
-anchor with rootlike hairs called "rhizoids"
-require H2O for reproduction (sperm swims to egg)
-Undergo "Alternation of Generations"
-gametes produced in sex structures: archegonia (female) & antheridia (male)
-spores produced in sacs called "sporangia" (contained in capsules at plant's tip)
-Gametophyte is the dominant stage
Gametophyte (N) -->(mitosis)-->gametes--(N+N)-->Sporophyte (2N)-->(meiosis)-->
spores(N)--->Gametophyte (N) ---> produces N gametes ---> etc..
II. TRACHEOPHYTES: the first vascular plants
-Have a true vascular system and conducting system for water, food, and minerals
-xylem: conducts water and ions from roots to leaves
-Conducting elements of xylem are called Tracheids & Vessel members
-phloem: carries dissolved sugar and other products of photosynthesis from the
leaves to the nonphotosynthetic cells of the plant.
-Conducting elements of phloem called Sieve Cells (Sieve-tube members)
-Have true leaves, roots, stems
-Have support: lignins and fibrous materials
A. The Seedless Plants: ferns, horsetails, club mosses
1. Phylum Pterophyta: the Ferns (~335 myo); dominant during the Carboniferous
period...important to us because many were compressed
into fossil fuels
-have a dominant sporophyte stage
-reproductive spores, instead of seeds (on sori)
B. The Seed Plants
-~300 myo; includes most "modern" plants
-have a dominant sporophyte stage
-reproduce using pollen (sperm) traveling to egg (ovum) on cones or flowers,
which results in SEEDS
1. VASCULAR SEED PLANTS: dominant today
a. 2 Groups:
1. Gymnosperms "naked seeds"
-~350 million years old
-about 700 species today
-do not have flowers as reproductive structures
a. Division Cycadophyta: cycads
b. Division Ginkgophyta: ginkgos
c. Division Coniferophyta: cone-bearing trees,
evergreens, pines; have reduced-sized leaves
= needles (water conservation)
d. Division Gnetophyta: some desert plants, like Ephedra
2. Angiosperms "flowering plants"
-~135 million years old
-about 240,000 species today
-have flowers as reproductive structures
-cotyledon: the embryonic seed leaf
-Two Classes: Monocots, Dicots
a. DICOTS
-Single embryonic seed leaf
-Dicots contain vascular bundles in the stem in the
form of a ring
-Leaves have a network-like venation in dicots (also
usually broad, wide leaves)
-Dicots have a taproot system (main central root)
-Dicots have flowers in groups of 4 or 5 petals
b. MONOCOTS
-Single embryonic seed leaf
-Monocot leaves are tapered w/ parallel venation
-Monocots have a fibrous root system (close to
surface)
-Vascular bundles are scattered in a monocot stem
-Monocots have flowers w/ groups of 3 petals
Ch. 23: Plant Structure and Function
I. Plant Body: Cells and Tissues
-Cells of angiosperm embryo differentiate early in development into 3 distinct
tissues (Specialized Plant cells: mostly parenchyma, with specialized
support cells of collenchyma and sclerenchyma)
A. parenchyma: cells which occur in all 3 tissue systems, usually
photosynthesis, elongated, loosely packed, thin, flexible
cell walls
B. collenchyma: primary wall (in cells) thickened at corners, irregular
shapes, provide support
C. sclerenchyma: 2 types, support and strengthen the plant, thick, even
cell walls, dead cells provide framework for additional
cells
1. fibers- elongated, elastic strands or bundles associated with the
vascular tissue
2. sclereids- form hard outer covering of seeds, nuts, and fruit stones
a. Dermal Tissue: forms the outside covering of plants
-epidermis
-cuticle
-cork
-bark
-stomata
b. Ground tissue: for storage, metabolism and support. Mostly
parenchyma, with specialized support cells of
collenchyma and sclerenchyma
c. Vascular tissue: phloem and xylem consists of special
conducting cells, along with support fibers
i. Phloem: conducts sucrose from leaves to roots
-sieve tubes: vertical column of sieve tube
members joined by their end walls
-sieve plates: end walls, with openings between
the members
-companion cells: specialized parenchyma
associated with sieve tube members;
responsible for secretion of substances
in / out of sieve tube members
ii. Xylem: conducts water & minerals from roots to leaves
made up of tracheids & vessel members
secondary walls supported with Lignin, dead
at maturity
-. Tracheids: long, thin cells that overlap one
another at their tapered ends
-. Vessels: larger, more effective conductors
**Meristems: growing regions where cells divide
II. ROOTS
A. Functions:
1. Anchorage
2. Absorption of minerals and water from soil
3. Food storage- any extra carbohydrates (sugars) the plant makes that it
doesn't convert into energy, get changed into starches
and stored in tissues.
B. Patterns of Root Growth
1. Primary Root: 1st root growing from a plant, thick, tend to grow
downward into water table
2. Secondary Roots: long, thin, lateral roots that spread out over great
distances, tend to be more shallow
a. Root Growth (depth and width (spread)) depends upon soil
composition and water availability
b. Taproot: dicot primary root; gives rise to lateral (or branch) roots;
grows downward into the earth
c. Fibrous root: Secondary roots that are shallower; far-reaching, v
vertical migration outward
d. Adventitious roots: specialized; in monocots they develop from
primary root; short-lived, develops from base of stem
a) aerial: produced from above ground structures (ivy)
b) prop: (corn) above ground, from stem in some, tips bend
upward for O2
C. Root Structure: (dermal, ground, and vascular tissue)
1. Epidermis: encloses entire surface of young root; for absorption and
protection of internal tissues
2. Root hairs: fine, tubular outgrowths to increase surface area
3. Cortex: cells which occupy the most volume in young root
4. Parenchyma cells: lack chloroplasts, many air spaces (hold O2 from
soil for all respiration)
5. Endodermis: innermost layer, no air spaces
6. Casparian Strip: waxy band, not permeable to water, which encircles
each endodermal cell (within a wall); purpose is to
regulate passage of substances into rest of plant
7. Root cap: tip of root that helps root burrow into ground
D. The Vascular Cylinder
-xylem, phloem
-surrounded by the pericycle
-branch roots arise from pericycle (layer surrounding xylem and phloem)
-Pith: soft, central core of ground tissue in some monocots
E. Primary Root Growth (diagram)
-embryonic root = "radicle"
1. 3 sections:
a. Zone of differention
b. Zone of elongation
c. Zone of cell division (meristematic)
F. The Uptake of Minerals
1. Minerals: naturally occurring substances transported in water thru xylem
a. some are single elements, some are compounds
b. there are over 92 diff. elements found in soil O2; Si; Al; Fe
2. Macronutrients: % of dry plant wt. (0.5- 4%)
3. Micronutrients: ppm
4. Mineral Requirements of Plants: 16 essential- C, H, O, P, K, N, S, Ca,
Fe, Mg, Mo, B, Cu, Mn, Zn, Cl
III. STEMS
A. Functions:
1.
2.
3.
4.
Transportation of food
Transportation of water and minerals
Food storage
Supports leaves (holds them upward and outward to capture max sun)
B. Stem Structure
1. Typically, there are two types of stems
a. Herbaceous (soft, flexible)
b. Woody (hard, supportive)
C. Primary Growth
1. In both dicots and monocots
2. First stage of growth
3. "shoot" includes all above ground structures
a. cell division (occurs at meristems)
b. cell elongation
c. cell differentiation
4. Exterior: dermal tissue forms on outside surface = epidermis;
stomata; waxy cuticle
5. Interior
a. Pith: ground tissue inside of vascular tissue
b. Cortex: ground tissue that lies outside vascular tissue
c. Cambium: layer of immature tissue between vascular bundle
D. Secondary Growth
1. In dicots
2. In woody plants; increases thickness of trunks, stems, branches, & roots
3. Exterior
a. Cork Cambium: forms from the cortex to repair tearing and
stretching of epidermis during growth; keeps moving inward as
epidermis is added.
b. Bark: thickened, hardened epidermal layers
4. Interior:
a. Vascular Cambium: thin, cylindrical sheath of tissue below xylem
and phloem. Adds xylem to inside and phloem to outside by cell
division
E. Wood: mostly dead xylem, parenchymal cells
1. Heartwood: as tree grows older, parenchyma on outside dies
2. Sapwood: live xylem (tracheids & vessels), conduct water & minerals
3. Bark: dead, protective outer layer of cork and phloem
F. Stem Patterns (diagrams)
G. Stem / Shoot Growth:
1.
2.
3.
4.
5.
Nodes
Internodes
Axil- where bud joins stem
Lateral buds- remain dormant until after growth of internodes
Apical buds- ("terminal" bud) develops first; called "Apical dominance"
6. Leaves: blade, vein, petiole
H. Vegetative Reproduction, propagation
1. Horizontal stems:
a. bulbs- onions
b. runners, stolons: above ground (strawberries, hanging plants)
c. rhizomes, tubers: below ground (potatoes, grasses)
d. advantage: produces clones; lower mortality, connected to
parent plant (as opposed to seedlings)
2. Develop from unfertilized seeds: "parthenogenesis" (dandelions)
3. Stem Cuttings - (willow)
4. Grafting - (fruit trees)
IV. LEAVES
-Leaves compromise between 2 evolutionary pressures:
1. must expose max. photosynthetic surface to light
2. must conserve water while providing openings for gas exchange (CO2 --> O2)
-parenchyma: photosynthetic cells
1. palisade: long, columnar cells where most photo. takes place
2. spongy: irreg. shape, loosely packed, fill with gases and water vapor
-mesophyll (middle parenchymal layers) is enclosed by epidermis and cuticle
-cuticle: formed by cutin (waxy) secreted by epidermal cells
-vein: xylem/phloem bundles (venation: monocots= parallel / dicots = network)
-stomata (stoma): openings in epidermis (more on underside) to allow for gas exchange
-guard cells: open /close stoma (90% water lost through here)
A. The Movement of Water and Minerals
1. Transpiration: the loss of water from the plant body; accounts for almost
90% of loss; also serves to cool the atmosphere.
2. The Uptake of Water:
a. Root cells contain high [conc.] of solutes, soil H2O will enter by osmosis
b. Root Pressure: sufficient to move H2O a little way up the stem (xylem
takes H2O the rest of the way up)
c. Xylem: pressure is negative (< atmospheric) which draws H2O in and up
d. Cohesion-Tension Theory of Upward Transport:
i. In the Leaf:
-transpiration: water evaporates (via stomata) molecule-bymolecule = decrease in water potential of leaf cells
-cohesion- polar water molecules stick to each other (upward)
-adhesion- tendency of water molecules to be attracted to
other substances (like the sides of vessels)
this pulling action causes a negative pressure in
xylem
-hydrogen bonds (h-bonds) in water
-water potential in leaf draws molecules in (attached by Hbonds)
-small diameter of vessels (xylem vessels and tracheids)
prevent air bubbles
3. Factors Affecting Transpiration
a. Temperature: rate doubles for every 10 degree C rise
b. Humidity: more H2O in air, the less is lost from leaf
c. Air Currents: wind blows away H2O on leaf surfaces (leaf hairs- create a
layer of still air on leaf surface)
d. Opening & closing of Stomata: most important
e. Surface Area of Leaves: surface area increase = increased water loss
4. The Mechanism of Stomatal Movement
a. stomatal movement is controlled by Turgor Pressure and K+ ions in
their two guard cells
b. when guard cells are turgid, they bow outward and open
c. Turgor: due to osmotic movement of H2O in/out of guard cells
5. Adaptation of Plants to Dry Environments
a. example: succulents
i. cacti- thick cuticle, sunken stomates, needles (instead of leaves)
ii. evergreens- pines, needles have reduced surface area to
decrease water loss
6. The Movement of Sugars
a. Translocation: movement of sugars(sucrose) down plant (from leaves)
is through Phloem (sieve tubes and companion cells)
b. Aphids: (small, sap-sucking insects) can tap into phloem with piercing
mouthparts
c. Phloem: located just inside the bark of trees (sap carrier) - "girdling"
d. The Pressure-Flow Hypothesis: the solutes move in solutions that, in
turn, move because of differences in water potential caused by
concentration gradients of sugar.
Ch. 24: Plant Reproduction
I. Sexual Reproduction: The Flower
-Most flowers consist of four sets of parts: the sepals, petals, stamens, carpels
A. sepal: the outermost part; green leaf-like parts which enclose and
protect the developing flower bud
B. petals: they "advertise" the flower and attract insects, birds, etc.
C. stamen: male parts; consists of a filament and anther; produce pollen,
the immature male gametophyte
D. pistil: female part; innermost structures; consists of stigma, style, ovary
note: this is sometimes called the CARPEL
E. Dioecious: some species have male and female parts on different
flowers; examples: mistletoe, holly (aka "imperfect" flowers)
F. Monoecious: some species have both male and female parts on their
flowers; xamples: corn, squash, oaks, birches (aka "perfect"
flowers)
II. Pollen
-when released from the anther, it usually consists of three haploid cells (2 sperm
and 1 larger "tube cell"), each with a haploid nucleus (total of 3 nuclei)
the tube cells is enclosed by a protective wall of the pollen grain
III. Fertilization
A. Development of Seeds (single fertilization)
1. (male gamete) pollen grain (2 sperm & 1 tube cell) is travels from a flower
2. the pollen grain lands on the sticky stigma of a carpel, germinates and
pollen tube grows down through the style to the ovule inside the ovary
3. there may be competition between grains to get to the ovule
4. the pollen tube, produced by the tube nucleus, releases the 2 sperm
nuclei into the ovary thru which only ONE sperm nucleus enters egg
5. fusion of sperm nuclei with egg nuclei forms a zygote (2N) which
undergoes mitosis and becomes a "polarized" ball of cells (enclosed
within the female ovary)
**Polarization: one end of the ball of cells is destined to become a root, the
other, the leaves.
B. "Double Fertilization"
1. (male gamete) pollen grain (2 sperm & 1 tube cell) is travels from a flower
2. the pollen grain lands on the sticky stigma of a carpel, germinates and
pollen tube grows down through the style to the ovule inside the ovary
3. the pollen tube, produced by the tube nucleus, releases the TWO sperm
nuclei into the ovary
4. one sperm nucleus fuses with the egg nucleus to form a diploid zygote
5. the 2nd sperm nucleus unites with the central cell in the egg (which has
two polar nuclei) to form a 3N cell. This will become the special tissue
called "endosperm" which will surround and nourish the embryo.
-2N zygote undergoes mitotic division to become a plant embryo
-3N endosperm provides stored food for the embryo (starchy)
IV. The Embryo
-Zygote divides mitotically and begins to differentiate (develop specific tissues)
-Embryo will take on its characteristics = "morphogenesis"
-As the embryo matures, growth of new cells is restricted to apical meristems
V. The Seed and the Fruit
A. Seed consists of:
1. embryo (fertilized egg)
2. endosperm (stored food)
3. seed coat (develops from integuments of the ovule)
-At the same time, FRUIT develops from the wall of the ovary
-As seeds form (and fruit) stamen and petals may fall off, ovary
becomes enlarged and fleshy
B. Types of Fruit- mature, ripened ovary of an angiosperm, which contains
the seeds
1. Simple: most diversity; soft, dry, and fleshy; develops from one carpel
a. fleshy- most single berries, drupes (pitted-peach), pomes
(multiple seeds, core -apple), hesperidium (leathery skin
that is easy to remove-orange), etc…
b. dry- nuts, etc.
i. dehiscent: wall breaks open to disperse seeds; "achenes"
like milkweed
ii. indehiscent: seeds remain within wall when ripe (nuts)
2. Aggregate: (raspberry, strawberry) from multiple carpels
3. Multiple: carpels of more than one flower fuse (pineapple, fig)
V. Asexual reproduction ---> "vegetative propagation" (ex: grafting, bulbs, etc.)
VI. Adaptations to Seasonal Change
A. Dormancy and the Life Cycle
1. Seed Dormancy- seed coat inhibits (worn away gradually) or there is a
chemical inhibitor (changes with amt. of light or water)
B. Growth Patterns
1. Annuals- entire growing season = life cycle
a. vegetative plant--> flowers--> seed
b. All vegetative plant organs die in winter, but seeds remain (highly
resistant) to carry on next growing season
c. These are usually herbaceous plants
2. Biennials- period from seed germination to seed formation spans 2
growing seasons (usually root plants like carrots, sugar
beets)
3. Perennials- vegetative structures persist year after year (usually woody
plants)
Ch. 25: Plant Responses
I. Plant Hormones and the Regulation of Growth
A. hormone: chemical substance produced in one tissue that exerts influence
on specific areas (tissues)
1. may stimulate or inhibit growth of various regions
2. may interact with one another
3. Examples of hormone groups:
a. Auxins
b. Cytokinins
c. Ethylene
d. Abscisic Acid
e. Gibberellins
a. Auxins- mainly IAA (indolacetic acid)
i. Produced in shoot, distributed down to roots
ii. Too much causes INHIBITION of growth and branching
iii. Needed for fruit development (as well as apical growth and root development)
iv. Commercial uses: more fruits/plant, seedless fruits, larger fruits, delayed fruit
drop (riper)
b. Cytokinins- example: Zeatin
i. Causes cell division; found in seed endosperms, meristems, fruits, roots
ii. Increases rate of protein synthesis
iii. Can reverse auxin inhibition
iv. Prevents leaf aging
c. Ethylene: C2H4
i. Gaseous hormone, simple hydrocarbon
ii. Made in cell membranes of plants, bacteria, fungi
iii. Causes- fruit ripening (improved color/flavor in citrus)
iv. Regulates leaf drop (abscission)
H2C=CH2
d. Abscisic Acid- (ABA)
i. Present in seeds to maintain dormancy
ii. Preserves buds (dormancy)
e. Gibberellins- (GA) > 70 kinds
i. Affect cell elongation
ii. Can cause hyperelongation of stems; "bolting" and "flowering"
iii. Can also induce cellular differentiation
iv. Immature seeds have high [GA]
II. Plant Movements
A. Tropism: a growth response of a plant part toward (+) or away (-) from an
external stimulus that determines the direction of movement
1. Phototropism: young seedlings will bend toward a single light source
a. Plant tip bending caused by a redistribution of auxin from light side
to dark side of plant
B. Geotropism: Movements of roots toward center of earth
1. + = "positive geotropism" (roots; grow down "with" gravity)
2. - = "negative geotropism" (shoots; grow upward, "against" gravity)
this response is determined by hormones
C. Thigmotropism: response to contact (touch)
D. Chemotropism or Hydrotropism: respond to chemicals or water (respectively)
E. Nastic Movements: plants movements that occur in response to
environmental stimulus BUT that are independent of the direction of the
stimulus (ex: closing of Mimosa leaves as response to touch; Venus flytrap)
III. Photoperiodism
-response to relative periods of light and dark (flowering, etc.)
-seasonal changes = differences in growth rates, etc.
-not really a function of temperature, but more of DAY LENGTH
How do plants know? A pigment called phytochrome
Two forms of Phytochrome: red-light sensitive (Pr) and far-red-light sensitive (Pfr)
-Pr absorbs red light (660nm) during sunny hours and is converted to Pfr
-At night, Pfr is slowly coverted back to Pr
-Scientists think that the ratio of Pr to Pfr is a chemical means of measuring
day length
-The changing proportions of these two chemicals are what may trigger
hormonal release and flowering
Vernalization: some plants must be exposed to cold temp. before they will flower
(turnips, beets, carrots)
Abscission: leaf drop, stimulated by short-day, or lack of water