What constitutes a plant?What constitutes a plant?

29-30: Kingdom Plantae29-30: Kingdom Plantae

What are the reproductive trends in plants?What are the reproductive trends in plants?

What are the evolutionary trends in plants?What are the evolutionary trends in plants?

The Netherlands

What constitutes a plant?

Plants are:Plants are:MulticellularMulticellularEukaryotesEukaryotesPhotosynthetic autotrophsPhotosynthetic autotrophs

Algae may also have these characteristics. Algae may also have these characteristics. Plants appear to have developed from algae.Plants appear to have developed from algae.

Other features that plants and algae have in common:Other features that plants and algae have in common:Presence of chrolophyll b as an accessory pigmentPresence of chrolophyll b as an accessory pigmentCellulose cell wallsCellulose cell wallsStarch as storage product of surplus carbohydratesStarch as storage product of surplus carbohydrates

Plants occur both on land and in water. Algae only in the presence Plants occur both on land and in water. Algae only in the presence of water.of water.

29.4 Where is the line dividing land plants from algae?

Three possible plant kingdoms?

Embryophytes: Plants with embryos

Figure 29.7 Some highlights of plant evolution

1. Walled spores toughened by sporopollenin

2. Multicellular, dependent embryos

3. Apical meristems (root, shoot)

4. Presence of a waxy cuticle

[See book p. 602-603]

29.5. Walled spores produced in sporangia.

Spores are haploid reproductive cells that can grow into gametophytes (n) by mitosis. Sporopollenin makes the walls of spores very tough and protects them against dehydration

Multicellular, dependent embryos

Develop from zygotes that are retained within tissue from the female parent

29.5. Apical meristem

Figure 35.18. Leaf anatomy (incl. waxy cuticle)

Figure 3.3 Vascular tissue – support against gravity and transport system in plants

Xylem: Water conducting cells

PhloemCambium

Lignin: Hard material embedded in cellulose cell walls for structural support

Figure 29.5 Alternation of generations: a generalized scheme

A hypothetical mechanism for the origin of alternation of generations in the ancestor of plants

Figure 29.7 Some highlights of plant evolution

Table 29.1Ten Phyla (Divisions) of Extant Plants (Embryophytes)

Figure 29.3 CharophyceansThe closest algal relatives of land plants

Chara (top), Coleochaete orbicularis (bottom)

29.4

Chara

Figure 29.7 Some highlights of plant evolution

29.9. Bryophytes

Liverworts

MossesHornworts

Figure 29.8 The life cycle of a moss (Polytrichum)

Figure 29.8 The life cycle of a moss (Polytrichum)

Moss life cycle

protonemasporangium

archegonium

spores

gametophyte sporophyte

Marchantia, a liverwort

Gametangia: Archegonium of Marchantia (left), Anteridium of a hornwort (right)

A moss sporangium with a “spore-shaker” tip

Bryophytes

Liverworts

MossesHornworts

Sphagnum, or peat moss: Peat bog in Oneida County, Wisconsin (top), close-up of Sphagnum (bottom left), Sphagnum "leaf" (bottom right)

A peat moss bog in Norway

Carbon reservoir may help stabilize global atmospheric CO2

29.11. More than 2000-year old bog mummy preserved in acid, oxygen poor Sphagnum wetlands

29.11. Peat, partially decayed organic material, harvested from peat moss (Sphagnum) wetlands. Decomposition is slow due to cold temperatures, acid conditions and little oxygen.

Figure 29.7 Some highlights of plant evolution

Xylem cells in angiosperms (see also Fig 35.10)

Lignin

Seedless Vascular plants- Ferns

Figure 29.16 Lycophyta and Pterophyta. Artist’s conception of a Carboniferous forest based on fossil evidence (some 350 million yrs B.P.)

29.15. Lycophytes: club "moss" (top left), many are epiphytesPterophytes: whisk fern (top right), horsetail (bottom left), fern (bottom right)

Lycophyta

Pterophyta

strobulus

Figure 29.13 The life cycle of a fern

Figure 29.13 The life cycle of a fern

Life cycle of a fern: mature fern

Life cycle of a fern: sorus

Life cycle of a fern: sporangium

Life cycle of a fern: mature sporangium

Life cycle of a fern: germinating

Life cycle of a fern: gametophyte

Life cycle of a fern: sporophytes

29.15. Lycophytes: club "moss" (top left)Pterophytes: whisk fern (top right), horsetail (bottom left), fern (bottom right)

Lycophyta

Pterophyta

Figure 29.13 The life cycle of a fern

Heterospory: The sporophyte has two types of sporangia that produce two types of spores, which develop into either female or male

unisexual gametophytes.

Spores:• Megaspore, developing into a female gametophyte, which will produce an egg

• Microspore, developing into a smaller male gametophyte, which produces sperm

Which of the following is TRUE of seedless vascular plants?

A. They produce many spores, which are really the same as seeds.

B. Seedless vascular plants are all heterosporous.

C. Whole forests were dominated by large, vascular seedless plants more than 300 million years ago.

D. The few seedless vascular plants still living are large and rare.

E. None of the above are true. Vascular plants never form seeds.

Chapter 29 –Review (p. 616)

• Concept 29.1. Land plants evolved from green algae

• Concept 29.2. Mosses and other non-vascular plants have life cycles dominated by gametophytes

• Concept 29.3. Ferns and other seedless vascular plants were the first plants to grow tall