Carolus Linnaeus - late 18thC Species Plantarum 1753 Systems Naturae 1767 - (24) major categories of...

Carolus Linnaeus - late 18thC

Species Plantarum 1753

Systems Naturae 1767

- (24) major categories of plants (Divisions)

- (23) vascular (Phanerogams);

- (1) non-vascular & vascular (Cryptogams)

K: Plantae - Ordovician - Non-vascular - Silurian - Vascular

Continental Positions During Early Plant Evolution

Vascular Plants - The Tracheophytes

• 1. Have specialized cell type for conducting water - tracheids (early xylem tissue). Also has specialized cell type for conducting sugar - seive cells (phloem tissue).

• 2. Lignin in xylem for rigid structural support.

• 3. A branching, independent sporophyte.

Vascular Plants - The Tracheophytes

Vascular Plants - The Tracheophytes(300 mya)

• Non-seed Tracheophytes - haloid & diploid generations totally independent

• - spores most prominent resting state

Rhyniophyta - the earliest Tracheophytes(extinct by Devonian Period 400 mya)

• 1. Simple vascular system (xylem &

• phloem) in stem.

• 2. “Leaves” flattened scales - no

• vascular tissue.

• 3. No roots - but rhizomes.

• 4. Dichotomous stem branching.

• 5. Aerial branches and sporangia at

• branch tips.

• 6. Spores were in groups of four (?)

• tetrads - indicate meiosis

• plant body - a sporophyte (2n)

• spores - (n) ---> gameophyte (n)-->

• sexual reproduction--> sporophyte (2n)

• (fossil)

Lignier’s Hypothesis (1903)How Roots Evolved from Stems

• ancestoral form --->

Evolution of Leaves• Leaf - a flattened photosynthetic structure emerging from the stem and

possessing true vascular tissue.

• Probably evolved from sterile sporangia.

Evolution of Leaves• Leaf - a flattened photosynthetic structure emerging from the stem and

possessing true vascular tissue.

• Complex leaves arose as photosynthetic tissue developed between complex branching patterns

HomosporyThe Most Primitive Spore Process

• one type of spore; one type of gametophyte

HeterosporyThe Most Advanced Spore Process

• two types of spores; two types of gametophytes

• heterospory probably evloved several times

K: Plantae Div: LycophytaG: Lycopodium “ground pines”

• 1. Leaves small and sessile; no ligule

• at base.

• 2. Stems with aerial branches and

• rhizomes; dichotomous branching.

• 3. Branch roots originate deep within

• main root.

• 4. Mainly perennial.

• 5. Low growing in temperate forest or

• epiphyte in Tropical forest.

• 6. Homosporous.


• Plectostele - dissected xylem

• with phloem branches in

• between.– Xylem - all tracheids.

– Phloem - all seive cells

• Epidermis - contains stomata.


• Plectostele -

• Always a layer of parenchyma cells between xylem and phloem.


• Plectostele - dissected xylem

• with phloem branches in

• between.– Xylem - all tracheids.

– Phloem - all seive cells

– mucilaginous canal

• Epidermis - contains stomata.

• Exarch Stele -


• A. Exarch Stele -

• B. Mesarch Stele

• C. Endarch Stele


• Sexual Reproduction:

• sporophyte (2n) ---- meiosis ---->

•

• ------> spores (n) --> gametophyte (n) --> antheridia (n) & archegonia (n)• (homospores)

• antheridium ----> sperms (n)

• -- fertilization --> zygote (2n) --> sporophyte (2n)

• Archegonium ----> egg (n)


•


• Sexual Reproduction:

• sporophyte (2n) ---- meiosis ---->

• ------> spores (n) --> gametophyte (n) --> antheridia (n) & archegonia (n)

• antheridium ----> sperms (n)

• -- fertilization --> zygote (2n) --> sporophyte (2n)

• Archegonium ----> egg (n)


• MALE GAMETOPHYTE:

• Antheridia (n) on crown.• Embedded (like Anthoceratophyta)

• Biflagellated sperms (n)

• FEMALE GAMETOPHYTE looks much the same.

•


•


• • strobilus (2n) -• stem with short

• internodes and fertile• appendages

• sporophyll (2n)

• sporangium (2n)

• spores (n)

• • l


• sporophyll & sporangium

• adaxial view

•

•


•


• gemmae or bulbils (2n)

• (asexual reproduction)

• axial sporophylls

•

•

• g

K: Plantae Div: LycophytaG: Selaginella “ground pines”

• Mainly in tropical areas

•

• g


• 1. Herbaceous: perennial.

• 2. Ligulate* leaves; microphyllous; spirally or alternately arranged.

• 3. Abundant branching.

• 4. Some vessels* in xylem.

•

• g


• 1. Herbaceous: perennial.

• 2. Ligulate*leaves; microphyllous; spirally or alternately arranged.

• 3. Abundant branching.

• 4. Some vessels* in xylem.

• 5. Strobilus composed of sporophylls each bearing a single sporangium

• on the adaxial surface.

• 6. Heterosporous* reproduction.

•

• g


• 6. Heterosporous* reproduction.

• Strobilus (2n) --> microsporophylls (2n) --> microsporangium (2n) -->

• megasporophylls (2n) --> megasporangium (2n) -->

• meiosis

• microsporangium (2n) --> microsporocytes (2n) ---------------> microspores (n)

• megasporangium (2n) --> (4) megasporocytes (2n) ----------> (4) megaspores (n)

•

• g


• meiosis

• microsporangium (2n) --> microsporocytes (2n) ---------------> microspores (n)

• megasporangium (2n) --> (4) megasporocytes (2n) ----------> (4) megaspores (n)

• --> microspores (n) --> male gametophytes (n), antheridium --> sperms (n)

• --> (4) megaspores (n) --> female gametophytes (n), archegonium --> egg (n)

• dioecious

•

• triradiate

• walls -->

• g


• fertilization - -> zygote (2n) --> adult sporophyte (2n)


• fertilization - -> zygote (2n) --> adult sporophyte (2n)


•

•

• g

K: Plantae Div: LycophytaG: Isoetes “quillworts”

• 1. Quill-like leaves spirally attached to a corm; microphyllus and ligulate.

• Corm - thickened underground stem. Nodes very close together.

• Lacunae --->

•


• 1. Quill-like leaves spirally attached to a corm; microphyllus and ligulate.• Corm - thickened underground stem. Nodes very close together. • 2. Each leaf has 4 lacunae; stomata in epidermis. *• 3. Some seive cells lack nucleus at maturity - plasmodesmata with adjacent • cells. • 4. Stem and root protostelic.• 5. Xylem consists of large numbers of parenchyma cells with few tracheids. *• 6. Delicate roots grow from base of corm (rhizophores); stele bound by• well defined endodermis*; have root caps.

• •


• 7. Heterosporous.• 8. Every leaf of Isoetes is potential a sporophyll; per season - • sterile leaves 1st; then megasporophylls; then microsporophylls.

• --> 1 million microspores; 50 - -> 300 megaspores.

• •


• Sporangium massive > 7mm.

• Velum - covering over sporangium.

• Trabecula - strands of sterile tissue extending from the sporangial wall.

• Tapetum - innermost layer of the sporangial wall. Indistinguishable.

•

•


• meiosis (all spores set free)

• microsporangium (2n) ---------> microspores (n) --> male gametophyte (n)

• megasporangium (2n) --------> megaspores (n) --> female gametophyte (n)

• male gametophyte (n) --> antheridium (4 sperms) multiflatelated

• female gametophyte (n) --> archegonium (1 egg)

• *further reduction of

• gametophyte!*

• colorless, saprophytic

•

•


• male gametophyte (n) --> antheridium (4 sperms)• female gametophyte (n) --> archegonium (1 egg) • *further reduction of • gametophyte!*

• colorless, saprophytic

• no suspensor

• 1 embryo develops• from each gametophyte

• •


• No suspensor; delayed development

• of the stem.

•

•

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Carolus Linnaeus - late 18thC Species Plantarum 1753 Systems Naturae 1767 - (24) major categories of...

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