Introduction to Plants

Figure 29.1

Charophytes

Figure 29.2

ANCESTRALALGA

Red algae

Chlorophytes

Charophytes

Embryophytes

Virid

iplan

taeStrep

top

hyta

Plan

tae

Relationship between algae and land plants

Green Algae & Plants: shared traits

• Chlorophyll A & B• Cell walls of cellulos• Starch as polysaccharide for storage

30 nm

Charophytes as closest relatives

Shared traits w/ land plants• Protien rings on cell membrane to make cellulose• Similar sperm (assymetrical arranged flagella)• Phragmoplasts (microtubule arrangement during mitosis)• Nuclear and chloroplast DNA similarities• Some charophytes protect zygote w/ in gametophyte

Derived Traits of Plants• Five key traits appear in nearly all land plants

but are absent in the charophytes– Alternation of (heteromophic) generations – Multicellular, dependent embryos– Walled spores produced in sporangia– Multicellular gametangia– Apical meristems – Cuticle– Stomata (except liverworts)

Figure 29.3a

Alternation of generations

Gametophyte(n)

Gamete fromanother plant

Mitosis

GameteSpore

Mitosis

Mitosis

Zygote

Sporophyte(2n)

Key

Haploid (n)

Diploid (2n)

n

n

n

n

2n

MEIOSIS FERTILIZATION

Figure 29.3b

Multicellular, dependent embryos

Embryo (LM) and placental transfer cell (TEM)of Marchantia (a liverwort)

Embryo

Maternaltissue

Wallingrowths

Placentaltransfer cell

(blue outline)

10 µm2 µm

Figure 29.3c

Walled spores produced in sporangia

Sporophytes and sporangia of Sphagnum (a moss)

Spores

Sporangium

Longitudinal section of Sphagnum sporangium (LM)

Sporophyte

Gametophyte

Figure 29.3d

Multicellular gametangia

Femalegametophyte

Archegonia,each with anegg (yellow)

Antheridia(brown),containing sperm

Malegametophyte

Archegonia and antheridia of Marchantia (a liverwort)

Figure 29.3e

Apical meristems

Apical meristemof root

Apical meristemof shoot

Developingleaves

Root Shoot

Apical meristems of plant roots and shoots100 µm 100 µm

Figure 29.5

ANCESTRALGREENALGA Origin of land plants

Origin of vascular plants

Origin of extantseed plants

Liverworts

Mosses

Hornworts

Lycophytes (club mosses,spike mosses, quillworts)

Monilophytes (ferns,horsetails, whisk ferns)

Gymnosperms

Angiosperms

Lan

d p

lants

Vascu

lar plan

ts

No

nvascu

larp

lants

(bryo

ph

ytes)

Seed

lessvascu

larp

lants

Seed

plan

ts

500 450 400 350 300 50 0Millions of years ago (mya)

1

2

3

Plant Diversity:- non-vascular- seedless vascular- seed (but no flowers)- flowering plants (seed + flowers)

Table 29.1

Challenges of dry land

• Dryness/relative lack of water• Gravity (need for support)

Nonvascular plants (24,000 species)

Liverworts, hornworts, & mosses

Nonvascular plants1. Gameptophyte dominant2. Dependent sporophyte3. Flagellated sperm

– Consequences on reproduction?

4. Environment found?5. Non vascular tissue

– Size?– Environment found?

Figure 29.6

Key

Haploid (n)Diploid (2n)

Protonemata(n)

“Bud”

Sperm

Malegametophyte (n)

Antheridia

GametophoreSporedispersal

Spores

Peristome

Egg

Archegonia

Rhizoid

Sporangium

SetaCapsule(sporangium)

FootMature

sporophytes

MEIOSIS

Embryo

Zygote(2n)

FERTILIZATION(within archegonium)

Archegonium

Youngsporophyte(2n)

Capsule withperistome (LM)

2 m

m

“Bud”

Femalegametophyte (n)

Femalegametophyte

Animation: Moss Life Cycle

Figure 29.6a

Capsule with peristome (LM)

2 m

m

Figure 29.9

(a) Peat being harvested from a peatland (b) “Tollund Man,” a bog mummy datingfrom 405–100 B.C.E.

Seedless Vascular Plants• Ferns, club mosses, horsetails, wiskferns, etc..

Monilophytes (Phylum Monilophyta)

Strobilus onfertile stem

Vegetativestem

Athyrium filix-femina,lady fern

Equisetum telmateia,giant horsetail

Psilotum nudum,a whisk fern

4 cm

3 cm

25 c

m

Figure 29.13a

Seedless Vascular Plants: Lycophytes (Phylum Lycophyta)

Isoetesgunnii,a quillwortSelaginella

moellendorffii,a spike moss

Diphasiastrum tristachyum,a club moss

Strobili(clusters ofsporophylls)

2.5 cm

1 cm

Seedless Vascular Plants

• Sprophyte dominant– Independent gametophyte

• Flagellated sperm– Impact on reproduction

• Vascular Tissue– Transport– Support

Promotes increase in size

Vascular Tissue

• Xylem– Transports water and minerals (nutrients from

soil)– Provides support

• Phloem– Transports sugars

True roots, stems, & leavesRoots:• Length via apical meristem• Contain vascular tissues• Anchor and absorb

Leaves• Specialized for photosynthesis• Microphylls—single vein (of vascular tissue)• Megaphylls—multiple veins (of vascular tissue)• Sporophylls—leaves that create/house sporangia

Figure 29.14

Horsetail Fern

Seed plants: gymnosperms + angiosperms

Seed plant developments• Pollen

– Distribution (w/o water) and protection of sperm– Non-flagellated sperm

• Ovule = megasporangium– Contains egg– Retained w/ in parent tissue– After fertilization develops into seed

Seed

• From ovule• Contains embryo (young sporophyte)• Nutrients for embryo• Protects and disperses embryo• Important food source for animals, supported

evolution of faster, larger, more intelligent organisms.

Figure 30.3-3Immatureovulate cone

Integument (2n)

Megaspore (n)

Spore wall

Megasporangium(2n)

Pollengrain (n)Micropyle

(a) Unfertilized ovule (b) Fertilized ovule

Malegametophyte (n)

Pollen tube

Dischargedsperm nucleus(n)

Egg nucleus(n)

Femalegametophyte (n)

Seed coat

Sporewall

Foodsupply(n)

Embryo (2n)

(c) Gymnosperm seed

Figure 30.UN05

Five Derived Traits of Seed Plants

Reducedgametophytes

Heterospory

Ovules

Pollen

Seeds

Malegametophyte

Femalegametophyte

Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)

Microspore (gives rise toa male gametophyte)

Megaspore (gives rise toa female gametophyte)

Ovule(gymnosperm)

Integument (2n)

Megaspore (n)

Megasporangium (2n)

Pollen grains make waterunnecessary for fertilization

Seeds: survivebetter thanunprotectedspores, can betransportedlong distances

Seed coat

Food supply

Embryo

Flowering Plants (angiosperms)

Dog rose (Rosa canina), a wild rose

Angiosperm developments

• Flowers– Promote effective, targeted reproduction– Transfer of sperm to egg– Attract w/ sight and smell– Reward w/ food (pollen and/or nectar)

• Fruit– Protects and disperses seed more effectively

Tomato

Ruby grapefruit

Nectarine

Hazelnut

Milkweed

▼

▼

▼

▼

▼

Figure 30.11c

Seeds within berries and otheredible fruits are often dispersedin animal feces. The barbs of cockleburs facilitate

seed dispersal by allowing the fruitsto “hitchhike” on animals.

Angiosperm Diversity: monocots v. dicots

Embryos Leaf venation Stems

MonocotCharacteristics

Onecotyledon

Veins usuallyparallel

Vascular tissuescattered

Root systemusually fibrous(no main root)

Pollen grainwith oneopening

Floral organsusually inmultiplesof three

Floral organsusually in

multiples offour or five

Pollen grainwith threeopenings

Taproot(main root)

usually present

Vascular tissueusually arranged

in ring

Veins usuallynetlike

Twocotyledons

EudicotCharacteristics

Roots Pollen Flowers

Figure 30.2PLANT GROUP

Seed plants (gymnosperms and angiosperms)

Reduced (usually microscopic), dependent onsurrounding sporophyte tissue for nutrition

Dominant

Gymnosperm Angiosperm

Microscopic femalegametophytes (n)inside ovulate cone

Microscopic femalegametophytes (n)inside these partsof flowers

Microscopicmalegametophytes(n) inside pollencone

Microscopicmalegametophytes(n) inside these partsof flowers

Sporophyte(2n)

Dominant

Sporophyte(2n)

Reduced, dependenton gametophyte fornutrition

Gametophyte(n)

Example

Sporophyte

DominantGametophyte

Mosses and othernonvascular plants

Ferns andother seedlessvascular plants

Reduced,Independent(photosyntheticand free-living)

Gametophyte(n)

Sporophyte (2n) Sporophyte (2n)