plant morphologylockhartapbio.weebly.com/uploads/5/0/2/7/5027375/...plant morphology roots:...
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Plant Morphology Roots:
– Anchor plant in ground
– Draw up water – Can store carbs
Plant Morphology Stems:
– Provide support – Contain vascular tissues xylem and phloem
– Can be woody
Plant Morphology Leaves:
– Perform photosynthesis
– Can be modified into needles to conserve water
Plant Morphology Flowers:
– Contain reproductive organs
– Attract pollinators
– Are modified leaves
Major Divisions of Plants
Each division demonstrates
greater adaptations to life on land.
Division Bryophyta Mosses, liverworts, hornworts. Are non-vascular, meaning they
have no xylem or phloem. Have gametes produced in gametangia, located on the surface of the gametophyte.
Gametophyte is the dominant haploid stage of bryophytes.
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Characteristics of Bryophytes Antheridium: male gametangia
produces flagellated sperm. Archegonium: female
gametangia produces eggs. Resulting zygote grows into a
diploid structure attached to the gametophyte.
In mosses, this is a stalk with a capsule containing spores which can be carried by the wind.
Because of this, bryophytes must be small and live in wet environments.
Marchantia, sp.: A liverwort.
Division Tracheophyta
These are vascular plants, meaning they contain xylem and phloem.
They have true roots, stems and leaves.
However, some of these plants still reproduce with spores.
Class Pterophyta Include the ferns. Contain sporangia
known as sori on the underside of fern fronds.
Sori undergo meiosis and produce spores.
Seeds are then produced.
Production of seeds in ferns Two types of spores are present:
– Male spores (microspores) – Female spores (megaspores)
Microsporangia produce microspore mother cells. These become pollen grains.
The megasporangium produces a megaspore mother cell. This divides by meiosis to produce 4 haploid cells. One of these cells will become the egg cell (in angiosperms); in gymnosperms, 2 of them do.
Fertilization! When a pollen grain makes contact
with the megasporangium, the tube cell of the pollen grains directs the growth of a pollen tube.
The pollen tube provides a passage for the pollen grain to travel through the integuments surrounding the egg.
Fertilization of the egg by the sperm occurs.
The integuments become the seed coat.
Class Coniferophyta These are gymnosperms. Seeds are produced in
unprotected megaspores near the surface (cones).
Fertilization and seed development takes a long time—1 to 3 years.
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Naked seeds!
Gymnosperms: plants whose seeds have no outer covering to protect them
All conifers are gymnosperms.
What’s with naked seeds?
Two types of cones are produced: male and female.
Pollen cones are male and give off pollen.
A pollen grain is given off and lands on the female cone, and forms a pollen tube.
The pollen nucleus travels down the tube to the ovule.
A seed is formed from the fusion of the pollen nucleus with the ovule.
Class Anthophyta (Angiosperms)
These are the flowering plants.
Flowers are a major evolutionary development for several reasons.
Flowering plants Angiosperms
“Vessel Seed”: meaning there is some sort of covering for the seed,
usually a fruit.
Two categories of flowering
plants Monocots
Dicots
Monocots Monocot actually means monocotyledon, or “one seed leaf.”
Have leaves with parallel venation Flower parts are found in multiples of 3.
Tulips and lilies are good examples.
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Dicots Dicot comes from the word dicotyledon, meaning “two seed leaves.”
Have leaves that have net venation. Flower parts are in multiples of 4 or 5. Roses and maple trees are good examples.
Flowers! Attract pollinators. Protects ovules inside an
ovary. Ovary will develop into a
fruit, so that seeds can be dispersed by animals that eat it.
Generalized Flower
Plant Tissues
Ground tissues Dermal tissues
Vascular tissues
Ground Tissues Parenchyma: thin-walled cells
with various functions such as photosynthesis, storage and secretion. Most common.
Collenchyma: contain thick but flexible cell walls. Act in support functions.
Sclerenchyma: thicker cell walls than collenchyma. Also act as support.
Dermal Tissue Epidermis cells which cover the
outside of plant parts. Includes cells which make up
plant hair cells, guard cells, and stinging cells.
Portions of the plant exposed to air have epidermis which produces the cuticle.
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Vascular Tissue: Xylem
Xylem moves water and minerals from the roots to the leaves.
More about xylem Xylem cells contain both a
primary and a secondary cell wall.
Some xylem cells have pits, places where the secondary cell wall is absent.
Most xylem cells are dead at maturity.
More Xylem Two types of
xylem: – Tracheids – Vessel elements
Tracheids are long and tapered. Water passes from one tracheid to another through pits.
Vessel Elements Vessel elements are
shorter and wider than tracheids.
They are thought to be more advanced than tracheids due to their method of transporting water.
Vascular Tissue: Phloem
Phloem moves carbohydrates made in photosynthesis from the leaves to the stem, as well as all over the plant body.
More Phloem Made of cells called sieve tube elements. They form sieve tubes.
Unlike xylem, phloem cells are LIVING. Pores at the ends of sieve tube
elements form sieve plates, where the cytoplasm of neighboring cells makes contact with one another.
Sieve tubes are associated with companion cells. Companion cells are living parenchyma cells that lie next to sieve tube elements.
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Plant Structure
Roots Stems Leaves
Roots Anchor the
plant in the soil.
Absorb water and minerals.
Store carbs as glucose and starches. Carrots are a
type of root called a taproot.
Root hairs
Root hairs are tiny filaments that grow from each individual cell in the root.
They increase surface area for water absorption.
Stems Contain
vascular tissue, which conducts food and water around the plant.
Celery is a stem.
Leaves
Perform photosynthesis.
Leaves
Regulate water balance through transpiration.
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Leaves
Store carbohydrates in the form of glucose and starches.
Leaf Cross-Section