1. Plants Colonized Land

3. Land plants evolved from green algae
Green algae called charophyceans are the closest relatives of land plants

4. Morphological and Biochemical Evidence
Land plants share key traits only with charophyceans:
Peroxisome enzymes
Structure of flagellated sperm
Chlorophyll A

5. Viridiplantae
Streptophyta
Plantae
Red algae
Chlorophytes
Charophyceans
Embryophytes
Ancestral alga

9. Derived Traits of Plants
Five key traits appear in nearly all land plants but are absent in the green algae:
Apical meristems
Alternation of generations
Walled spores produced in sporangia-aexual reproduction
Multicellular gametangia-gamete producing structures
Multicellular dependent embryos

10. Apical Meristems Apical Meristem of shoot Developing leaves
Root
100 µm
100 µm

11. Alternation of Generations
Haploid multicellular
organism (gametophyte)
Mitosis
Mitosis
Spores
Gametes
MEIOSIS
FERTILIZATION
Zygote
Mitosis
Diploid multicellular
organism (sporophyte)

12. The Origin and Diversification of Plants
Fossil evidence indicates that plants were on land at least 475 million years ago
Fossilized spores and tissues have been extracted from 475-million-year-old rocks

13. Fossilized spores. Unlike the spores of most living plants, which are single grains, these spores found in Oman are in groups of four (left; one hidden) and two (right).
Fossilized sporophyte tissue. The spores were embedded in tissue that appears to be from plants.

15. Seedless vascular plants Origin of vascular plants
Land plants
Vascular plants
Bryophytes
Seedless vascular plants
Seed plants
Gymno-
sperms
Angio-
sperms
Liverworts
Hornworts
Mosses
Lycophytes
Pterophytes
Charophyceans
Origin of seed plants
(about 360 mya)
Origin of vascular plants
(about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga

16. The life cycles of mosses and other bryophytes are dominated by the gametophyte stage
Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants:
Liverworts, phylum Hepatophyta
Hornworts, phylum Anthocerophyta
Mosses, phylum Bryophyta

17. Bryophyte Gametophytes
In all three bryophyte phyla, gametophytes are larger and longer-living than sporophytes
Sporophytes are typically present only part of the time
Animation: Moss Life Cycle

18. Bryophyte gametophytes
Produce flagellated sperm in antheridia
Produce ova in archegonia
Generally form ground-hugging carpets and are at most only a few cells thick
Some mosses have conducting tissues in the center of their “stems” and may grow vertically

19. Bryophyte Sporophytes
Grow out of archegonia
Are the smallest and simplest of all extant plant groups
Consist of a foot, a seta, and a sporangium
Hornwort and moss sporophytes have stomata

20. MOSS SPOROPHYTE

21. MOSS GAMETOPHYTE

22. LE 29-9d
Polytrichum
commune,
hairy cap
moss
Sporophyte
Gametophyte

23. Walled Spores Produced in Sporangia Multicellular Gametangia
Dependent Embryos
Longitudinal section of
Sphagnum sporangium (LM)
Archegonium
with egg
Female gametophyte
Spores
Embryo
Maternal
tissue
Sporangium
2 µm
10 µm
Sporophyte
Male gametophyte
Antheridium
with sperm
Gametophyte
Wall
ingrowths
Placental
transfer
cell
Sporophyte and sporangium
of Sphagnum (a moss)
Archegonia and antheridia
of Marchantia (a liverwort)

24. Raindrop
Key
Male
gametophyte
Haploid (n)
Sperm
Diploid (2n)
Spores develop into
threadlike protonemata.
“Bud”
A sperm swims through a film of moisture to an archegonium and fertilizes the egg.
Antheridia
The haploid protonemata produce “buds” that grow into gametophytes.
Most mosses have separate male and female gametophytes, with antheridia and archegonia, respectively.
Protonemata
“Bud”
Egg
Spores
Gametophore
Female
gametophyte
Archegonia
Meiosis occurs and haploid spores develop in the sporangium of the sporophyte. When the sporangium lid pops off, the peristome “teeth” regulate gradual release of the spores.
Rhizoid
Peristome
Sporangium
The sporophyte grows a long stalk, or seta, that emerges from the archegonium.
FERTILIZATION
MEIOSIS
(within archegonium)
Seta
Calyptra
Capsule
(sporangium)
Zygote
Mature
sporophytes
Foot
Embryo
Archegonium
The diploid zygote develops into a sporophyte embryo within the archegonium.
Young
sporophyte
Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte.
Capsule with
peristome (SEM)
Female
gametophytes

25. LIVERWORT STRUCTURE

26. GEMMA CUPS

27. Marchantia polymorpha, a “thalloid” liverwort
LE 29-9a
Gametophore of
female gametophyte
500 µm
Foot
Seta
Sporangium
Marchantia polymorpha,
a “thalloid” liverwort
Marchantia sporophyte (LM)

28. Ecological and Economic Importance of Mosses
Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat
Sphagnum plays an important role in the Earth’s carbon cycle

29. LE 29-10 A peat bog. Gametophyte Sporangium at tip of sporophyte
Living
photo-
synthetic
cells
Dead water-
storing cells
100 µm
Closeup of Sphagnum.
Note the “leafy”
Gametophytes and their offspring, the sporophytes.
Sphagnum “leaf” (LM). The combination of living photosynthetic cells and dead water-storing cells gives the moss its spongy quality.
“Tolland Man,” a bog mummy dating from 405–100 B.C. The acidic, oxygen-poor conditions produced by Sphagnum can preserve human or animal bodies for thousands of years.

30. Ferns and other seedless vascular plants formed the first forests
Bryophytes and bryophyte-like plants were the prevalent vegetation during the first 100 million years of plant evolution
Vascular plants began to diversify during the Carboniferous period
Vascular plants dominate most landscapes today

31. Origins and Traits of Vascular Plants
Fossils of the forerunners of vascular plants date back about 420 million years
, branching sporophytes
They lacked other derived These early tiny plants had independent traits of vascular plants

32. Life Cycles with Dominant Sporophytes
In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in the familiar leafy fern
The gametophytes are tiny plants that grow on or below the soil surface
Animation: Fern Life Cycle

33. LE 29-12 Key Haploid (n) Diploid (2n) Antheridium Spore Young
gametophyte
Antheridium
MEIOSIS
Sporangium
Sperm
Archegonium
Egg
New
sporophyte
Sporangium
Mature
sporophyte
Zygote
FERTILIZATION
Sorus
Gametophyte
Fiddlehead

34. Transport in Xylem and Phloem
Vascular plants have two types of vascular tissue: xylem and phloem
Xylem conducts most of the water and minerals and includes dead cells called tracheids
Phloem consists of living cells and distributes sugars, amino acids, and other organic products

35. Evolution of Roots Roots are organs that anchor vascular plants
They enable vascular plants to absorb water and nutrients from the soil
Roots may have evolved from subterranean stems

36. Evolution of Leaves
Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy that is used for photosynthesis

37. Leaves are categorized by two types:
Microphylls, leaves with a single vein
Megaphylls, leaves with a highly branched vascular system
According to one model of evolution, microphylls evolved first, as outgrowths of stems

38. LE 29-13
Vascular tissue
Microphylls
Megaphylls

39. Sporophylls and Spore Variations
Sporophylls are modified leaves with sporangia
Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual gametophyte
All seed plants and some seedless vascular plants are heterosporous, having two types of spores that give rise to male and female gametophytes

41. Classification of Seedless Vascular Plants
There are two phyla of seedless vascular plants:
Lycophyta includes club mosses, spike mosses, and quillworts
Pterophyta includes ferns, horsetails, and whisk ferns and their relatives

42. LE 29-14a
Selaginella apoda,
a spike moss

43. LE 29-14b
Isoetes
gunnii,
a quillwort

44. Diphasiastrum tristachyum, a club moss
LE 29-14c
Strobili
(clusters of
sporophyllis)
Diphasiastrum tristachyum, a club moss

45. LE 29-14d
Psilotum
nudum,
a whisk
fern

46. Equisetum arvense, field horsetail Vegetative stem Strobilus on
LE 29-14e
Equisetum
arvense,
field
horsetail
Vegetative stem
Strobilus on
fertile stem

47. Athyrium filix-femina, lady fern
LE 29-14f
Athyrium filix-femina, lady fern

48. Phylum Pterophyta: Ferns, Horsetails, and Whisk Ferns and Relatives
Ferns are the most diverse seedless vascular plants, with more than 12,000 species
They are most diverse in the tropics but also thrive in temperate forests
Some species are even adapted to arid climates

49. The Significance of Seedless Vascular Plants
The ancestors of modern lycophytes, horsetails, and ferns grew to great heights during the Carboniferous, forming the first forests
These forests may have helped produce the global cooling at the end of the Carboniferous period
The decaying plants of these Carboniferous forests eventually became coal

51. FERNS VS GYMNOSPERMS Ferns vs Gymnosperms 1. Two types of spores
a. Megaspores-origin of female gametophyte
1. Zygote
2. Embryo-sporophyte
b. Microspores-origin of male gametophytes
1. Pollen tube/pollen
2. Separate gametophytes-Separate sexes
3. Gametophyte much more reduced
a. No chlorophyll/Not free living
4. No flagella on sperm
5. Young embryo house within seed
a. Protects embryo / Embryo self sufficient
b. Nutrients from seed to grow

52. GYMNOSPERMS- conifers, cycads, ginkgoes Name means "naked seed"
A. General characteristics
1. Lack separate gametophyte generation
2. Heterosporous
3. Develop seed-no spreading spores
a. Contains egg that comes from megaspore
b. Contains embryo after fertilization
4. Have pollen
a. Microspore turns into pollen
b. Develops pollen tube to remove the necessity of water for fertilization-enters thru micropyle of seed

53. a. Aids in dispersal-wind-water-insects-etc
5. Adaptive importance of pollen and seed
a. Aids in dispersal-wind-water-insects-etc
b. Protects embryonic plant from drying out
c. Protects embryo`s food store from predators or parasites
d. Food storage analogous to yolk of egg
6. They have no flowers, they have cones
a. Staminate cones-male cones that release pollen
b. Ovulate cones-female cones that produce egg-ovules
B. Development of secondary growth
1. Cell division occurs in regions around periphery
2. Conducting tissues multiplied into cylindrical zone
3. Enables increase in diameter of plant/tree-like height