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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