Overview of Green Plants

Bryophytes

1. Overview of Green Plants
Dr. B. K. Bramhe
Asstt. Professor Botany,
Govt. J.S.T.P.G. College Balaghat
Mob. [phone]
E mail – [email protected]

2. Overview of Green Plants
2

3. Overview of Green Plants
Chapter 30

4. 4
Defining Plants
•The kingdom Viridiplantae includes land
plants and green algae
–Red and brown algae are excluded
•The green algae split into two major clades
–Chlorophytes
–Charophytes
•Streptophyta includes the Charophytes
and all land plants
•All green plants arose from a single
species of freshwater algae

5. 5
Defining Plants

6. 6
Defining Plants
•Land plants have two major features
1.Protected embryos
2.Multicellular haploid and diploid phases

7. 7
Defining Plants
Adaptations to terrestrial life
•Evolution of leaves that increase
photosynthetic surface area
•Protection from desiccation by a waxy cuticle
and stomata
•Shift to a dominant vertical diploid generation

8. 8
Plant Life Cycles
•Humans have a diplontic life cycle
–Only the diploid stage is multicellular
Plants have a haplodiplontic life cycle
–Multicellular diploid stage = Sporophyte
–Multicellular haploid stage = Gametophyte
•Plants have an alternation of generation
–sporophyte → gametophyte → sporophyte → etc.

9. 9
Plant Life Cycles
•Sporophyte (2N) produces haploid spores
(N) by meiosis
•Spores (N) divide by mitosis producing the
gametophyte (N)
•Gametophyte (N) produces gametes (N) by
mitosis
•Gametes (N) fuse to form the diploid
sporophyte (2N)

10. 10
The General Plant Life Cycle
process
process
process

11. 11
Plant Life Cycles
As more complex plants evolved:
•Diploid stage (sporophyte) became the
dominant portion of the life cycle
•Gametophyte became more limited in size
•Sporophyte became nutritionally
independent

12. 12
Chlorophytes
•Chlorophytes, sister taxa of the Streptophytes,
are a diverse group including:
•Chlamydomonas
–Unicellular chlorophyte
with two flagella
–Have eyespots to direct
swimming
–Reproduces asexually as
well as sexually

13. 13
Chlorophytes
•Volvox
–Colonial chlorophyte
–Hollow sphere of
a single layer of
500-60,000 cells
–A few cells are
specialized for
reproduction

14. 14
Chlorophytes
•Ulva
–Multicellular chlorophyte
–True haplodiplontic life
cycle
–Gametophyte and
sporophyte have identical
appearance

15. 15
MITOSIS
Ulva life cycle

16. 16
Land plants
Charophytes
•Charophytes are green algae related to
land plants

17. 17
Charophytes
•Charales (300 species)
–Macroscopic
–Plant-like plasmodesmata
–Sister clade to land plants
•Choleocaetales (30 species)
–Microscopic
–Plant-like mitosis
–Next closest plant relatives

18. 18
Bryophytes
•Bryophytes are the closest living
descendants of the first land plants
–Called nontracheophytes because they lack
tracheids (specialized transport cells)
–Simple, but highly adapted to diverse terrestrial
environments
–Non-photosynthetic sporophyte is nutritionally
dependent on the gametophyte
–3 groups: liverworts, hornworts and mosses

19. 19
Bryophytes
•Liverworts (phylum Hepaticophyta)
–Have flattened gametophytes with liver-like
lobes
–Form gametangia
in umbrella-shaped
structures
–Also undergo
asexual
reproduction

20. 20
Bryophytes
•Hornworts (phylum Anthocerotophyta)
–Sporophyte has stomata
–Sporophyte is
photosynthetic
–Cells have a
single large
chloroplast

21. 21
Bryophytes
•Mosses (phylum Bryophyta)
–Gametophytes consist of small, leaflike
structures around a stemlike axis
–Anchored to substrate by rhizoids
–Multicellular gametangia form at the tips of
gametophytes
•Archegonia – Female gametangia
•Antheridia – Male gametangia
–Mosses withstand drought, but not air pollution

22. 22
Moss Reproduction

23. 23
Tracheophyte Plants
•Cooksonia, the first vascular land plant,
appeared about 420 MYA
–Only a few
centimeters tall
–No roots or leaves
–Homosporous
(spores are the
same size and
type)

24. 24
Tracheophyte Plants
•Vascular tissues are of two types
–Xylem – Conducts water and dissolved
minerals upward from the roots
•contains tracheids
–Phloem – Conducts sucrose and hormones
throughout the plant
•These enable enhanced height and size in
the tracheophytes
•Tracheophytes are also characterized by
the presence of a cuticle and stomata

25. 25
Tracheophyte Plants
•Vascular plants have gametophytes reduced
in size and complexity relative to sporophytes
•Seeds
–Highly-resistant structures that protect the plant
embryo
–Occur only in heterosporous plants
•Fruits in flowering plants add a layer of
protection to seeds
–Also attract animals that disperse seeds

26. 26
Tracheophytes
•Vascular plants (tracheophytes) include
seven extant phyla grouped in three clades
–Lycophytes (club mosses)
–Pterophytes (ferns and their relatives)
–Seed plants

27. 27
Lycophytes
•Club mosses are the earliest vascular
plants
–They lack seeds
–Superficially
resemble true
mosses but they
are not related
–Homosporous or
heterosporous

28. 28
Pterophytes
•The phylogenetic relationships among ferns
and their relatives is still being sorted out

29. 29
Pterophytes
•Whisk ferns
–Saprophyte consists of evenly forking green
stems without leaves or roots
–Some gametophytes
develop elements of
vascular tissue
–Often symbionts with
fungi

30. 30
Pterophytes
•Horsetails
–All 15 living species are homosporous
–Constitute a single genus, Equisetum
–Consist of ribbed,
jointed photosynthetic
stems that arise from
branching rhizomes
–High silica content in
stems made them
useful as “scouring
rushes”

31. 31
Pterophytes
•Ferns
–The most abundant group of seedless vascular
plants with about 11,000 species
–The conspicuous
sporophyte and much
smaller gametophyte
are both photosynthetic

32. 32
Pterophytes
•The fern life cycle differs from that of a moss
–Much greater development, independence and
dominance of the fern’s sporophyte
•Fern morphology
–Sporophytes have rhizomes
–Fronds (leaves) develop at the tip of the
rhizome as tightly rolled-up coils then uncoil and
expand

33. 33
Pterophytes
Uncoiled fronds are called “fiddleheads” and are a delicacy
among northern First Nation peoples

34. 34
Pterophytes

35. 35
Pterophytes
•Fern reproduction
–Most fern are homosporous
–Produce distinctive sporangia in clusters called
sori on the back of the fronds
–Diploid spore mother cells in sporangia produce
haploid spores by meiosis
–At maturity, the spores are catapulted by
snapping action

36. 36
Seed Plants
•Seed plants first appeared 305-465 MYA
–Evolved from spore-bearing plants known as
progymnosperms
•The seed represents an important advance
–Protects the embryo
–Easily dispersed
–Introduces a dormant phase in the life cycle

37. 37
Seed Plants
•Seed plants produce 2 kinds of gametophytes
–Male gametophytes
•Pollen grains
•Dispersed by wind or a pollinator
–Female gametophytes
•Develop within an ovule
•Enclosed within diploid sporophyte tissue

38. 38
•There are two types of seed plants
–Gymnosperms are plants with “naked seeds”
•Ovule is exposed on a scale at pollination
•All lack flowers and fruits of angiosperms
–Angiosperms are flowering plants
•Ovules are enclosed in diploid tissue at pollination
•The carpel (modified leaf) covers seeds and
develops into fruit
Seed Plants

39. 39
•There are four living groups
–Cycadophytes
–Gnetophytes
–Ginkgophytes
–Coniferophytes
Gymnosperms

40. 40
Gymnosperms
•Cycads (phylum Cycadophyta)
–Slow-growing gymnosperms of tropical and
subtropical regions
–Sporophytes resemble
palm trees
–Have largest sperm
cells of all organisms!

41. 41
Gymnosperms
•Gnetophytes (phylum Gnetophyta)
–Only gymnosperms with vessels in their xylem
–Contain three
(unusual) genera
•Welwitschia
•Gnetum
•Ephedra
–ephedrine can be
extracted from species
of this genus

42. 42
Gymnosperms
•Ginkgophytes (phylum Ginkgophyta)
–Only one living species remains
•Ginkgo biloba
–Dioecious
•Male and female
reproductive
structures form on
different trees

43. 43
•Conifers (phylum Coniferophyta) are the
largest gymnosperm phylum and include:
–Pines, spruces, firs, cedars and others
–Coastal redwood – Tallest tree
–Bristlecone pine – Oldest living tree
•Conifers are sources of important products
•Timber, paper, resin and taxol (anti-cancer)
Gymnosperms

44. 44
•Pines
–More than 100 species, all
in the Northern
hemisphere
–Produce tough needlelike
leaves in clusters
–Leaves have:
•Thick cuticle and recessed
stomata
•Canals into which cells
secrete resin
Gymnosperms

45. 45
Pine reproduction

46. 46
Angiosperms
•Angiosperm origins are a mystery
•The oldest known
angiosperm in the
fossil record is
Archaefructus
•The closest living
relative to the original
angiosperm is
Amborella

47. 47
Angiosperms

48. 48
Angiosperms
•Flower morphology
–Primordium develops into a bud at the end of
a stalk called the pedicel
–Pedicel expands at the tip to form a
receptacle, to which other parts attach
–Flower parts are organized in circles called
whorls

49. 49
Angiosperms
•Flower morphology
–Outermost whorl = Sepals
–Second whorl = Petals
–Third whorl = Stamens (androecium)
•Each stamen has a pollen-bearing anther and a
filament (stalk)
–Innermost whorl = Gynoecium
•Consists of one or more carpels that house the
female gametophyte

50. 50
Angiosperms
The ovary eventually develops into the plant’s fruit

51. 51
Angiosperm Reproduction

52. 52