The World of Plants in 41
Minutes
Kingdom Plantae
–All are multicellular, nonmotile, autotrophic
eukaryotes
–Their cell walls are made from cellulose
–Plants carry out photosynthesis using
chlorophyll a and b
–Plants store their carbohydrates as starch
–Alternation of Generations - Reproduce
sexually by alternating between gametophyte (n)
and sporophyte (2n) generations.
–Some plants have vascular tissue
(tracheophytes) and some have none
(bryophytes)
–Mosses, ferns, gymnosperms, angiosperms
Fig. 29-7
1 Origin of land plants (about 475 mya)
2 Origin of vascular plants (about 420 mya)
3 Origin of extant seed plants (about 305 mya)
Hornworts
1
Mosses
Pterophytes (ferns,
horsetails, whisk ferns)
3
Angiosperms
450
400
350
300
Millions of years ago (mya)
50
0
Seed plants
Gymnosperms
Vascular plants
2
Seedless
vascular
plants
Lycophytes (club mosses,
spike mosses, quillworts)
500
Land plants
ANCESTRAL
GREEN
ALGA
Nonvascular
plants
(bryophytes)
Liverworts
Nonvascular plants (bryophytes)
Seedless vascular plants
Gymnosperms
Angiosperms
Morphological and Molecular
Evidence
• Many characteristics of
land plants also appear
in a variety of algal
clades, mainly algae
• However, land plants
share four key traits
only with charophytes:
– Rose-shaped complexes
for cellulose synthesis
– Peroxisome enzymes
– Structure of flagellated
sperm
– Formation of a
phragmoplast
Chara species, a pond organism
5 mm
Coleochaete orbicularis, a
disk-shaped charophyte that
also lives in ponds (LM)
Bryophytes
• Bryophytes
– Bryophytes are
primitive plants that lack
vascular tissue
– They must live in moist
environments because
they have no roots or
xylem and must absorb
water by diffusion
– Bryophytes are tiny
because they lack the
lignin-fortified tissue
necessary to support
tall plants on land
– Mosses are an example
Tracheophytes
• Tracheophytes
– Tracheophytes have
transport vessels, xylem
and phloem
– They include ancient
seedless plants, like
ferns, that reproduce by
spores
– They include modern
plants that reproduce by
seeds
– Those with seeds are
further subdivided into
gymnosperms and
angiosperms
Gymnosperms
– Gymnosperms
are conifers, the
cone-bearing
plants.
– Needle shape,
cuticle, stomates
in the stomatal
crypts help to
conserve water
loss
– Cedars,
sequoias,
redwoods, pines,
yews and
junipers
Angiosperms
– Flowering
plants,
anthophyta
– Most diverse
and plentiful
plants on
earth
– Principle
differences
between
Monocots and
Eudicots
Alternation of Generations and
Multicellular, Dependent Embryos
• Plants alternate between two
multicellular stages, a
reproductive cycle called
alternation of generations
• The gametophyte is haploid
and produces haploid
gametes by mitosis
• Fusion of the gametes gives
rise to the diploid
sporophyte, which produces
haploid spores by meiosis
• The diploid embryo is retained
within the tissue of the female
gametophyte
• Nutrients are transferred from
parent to embryo through
placental transfer cells
• Land plants are called
embryophytes because of the
dependency of the embryo on
the parent
Fig. 29-5a
Gametophyte
(n)
Mitosis
n
n
Spore
Gamete from
another plant
Mitosis
n
n
Gamete
MEIOSIS
FERTILIZATION
2n
Mitosis
Sporophyte
(2n)
Alternation of generations
Zygote
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
• Water-conducting cells are
strengthened by lignin and
provide structural support
• Increased height was an
evolutionary advantage
• Phloem consists of living cells and
distributes sugars, amino acids,
and other organic products
• Sugar-Conducting Cells of the
Phloem
• Sieve-tube elements are alive at
functional maturity, though they
lack organelles
• Sieve plates are the porous end
walls that allow fluid to flow
between cells along the sieve tube
• Each sieve-tube element has a
companion cell whose nucleus
and ribosomes serve both cells
Fig. 35-10d
Vessel
Tracheids
100 µm
XYLEM
Pits
Tracheids and vessels
(colorized SEM)
Perforation
plate
Vessel
element
Vessel elements, with
perforated end walls
Tracheids
Fig. 35-10e
Sieve-tube elements:
longitudinal view (LM)
3 µm
Sieve plate
Sieve-tube element (left)
and companion cell:
cross section (TEM)
Companion
cells
Sieve-tube
elements
PHLOEM
Plasmodesma
Sieve
plate
30 µm
10 µm
Nucleus of
companion
cells
Sieve-tube elements:
longitudinal view
Sieve plate with pores (SEM)
Plant Growth: Meristems generate
cells for new organs
• Apical meristems
– Are located at the
tips of roots and in
buds of shoots.
– Sites of cell
division that allow
plants to grow in
length (primary
growth)
• Lateral
meristems
– results in growth
which thickens the
shoots and roots
(secondary
growth)
Primary Growth
lengthens roots
and shoots
• Zone of cell
division
– Includes apical
meristem
– New cells produces
– Root cap is located
in root
Cortex
Vascular cylinder
Epidermis
Key
to labels
Dermal
Root hair
Zone of
differentiation
Ground
Vascular
Zone of
elongation
• Zone of elongation
– Elongation of cells
• Zone of maturation
Apical
meristem
– Cell differentiation
– Cell become
functionally mature
Root cap
100 µm
Zone of cell
division
Angiosperms
Nonvascular plants (bryophytes)
• Angiosperms
are seed
plants with
reproductive
structures
called flowers
and fruits
• They are the
most
widespread
and diverse of
all plants
Seedless vascular plants
Gymnosperms
Angiosperms
Fig. 30-7
Stigma
Stamen
Anther
Carpel
Style
Filament
Ovary
Petal
Sepal
Ovule
Video: Flower Blooming (time lapse)
Fruits
• A fruit typically consists of a mature
ovary but can also include other flower
parts
• Fruits protect seeds and aid in their
dispersal
• Mature fruits can be either fleshy or dry
Animation: Fruit Development
Fig. 30-8
Tomato
Ruby grapefruit
Nectarine
Hazelnut
Milkweed
Fig. 30-9
Wings
Seeds within berries
Barbs
• A pollen grain that has
landed on a stigma
germinates and the
pollen tube of the
male gametophyte
grows down to the
ovary
• The ovule is entered
by a pore called the
micropyle
• Double fertilization
occurs when the pollen
tube discharges two
sperm into the female
gametophyte within an
ovule
Fig. 30-10-4
Key
Haploid (n)
Diploid (2n)
Mature flower on
sporophyte plant
(2n)
Microsporangium
Microsporocytes (2n)
Anther
MEIOSIS
Ovule (2n) Microspore
(n)
Ovary
Germinating
seed
MEIOSIS
Megasporangium
(2n)
Embryo (2n)
Endosperm (3n)
Seed
Seed coat (2n)
Nucleus of
developing
endosperm
(3n)
Male gametophyte
(in pollen grain)
Pollen
(n)
grains
Stigma
Pollen
tube
Megaspore
(n)
Antipodal cells
Female gametophyte Central cell
(embryo sac)
Synergids
Egg (n)
Generative cell
Tube cell
Sperm
Style
Pollen
tube
Sperm
(n)
FERTILIZATION
Zygote (2n)
Egg
nucleus (n)
Discharged sperm nuclei (n)
Fig. 30-13n
Monocot
Characteristics
Eudicot
Characteristics
Embryos
Two cotyledons
One cotyledon
Leaf
venation
Veins usually
parallel
Veins usually
netlike
Stems
Vascular tissue
scattered
Vascular tissue
usually arranged
in ring
Fig. 30-13o
Monocot
Characteristics
Eudicot
Characteristics
Roots
Taproot (main root)
usually present
Root system
usually fibrous
(no main root)
Pollen
Pollen grain with
one opening
Pollen grain with
three openings
Flowers
Floral organs
usually in
multiples of three
Floral organs usually
in multiples of
four or five
Vegetative Propegation
Types of Veg.
Propagation
Description
Examples
Bulbs
Short Stems
Underground
Horizontal Stems
above ground
Onions
Underground
Stems
Cut a stem and
attach it to a
closely related
plant
Potatoes
Runners
Tubers
Grafting
Strawberries
Seedless Oranges
Tropical Tropisms
tropism – turning response to a
stimulus
Phototropism
Refers to how plants respond to
light
Gravitropism
Refers to how plants respond to
gravity
Thigmotropism Refers to how plants respond to
touch (IVY, strangler trees
Auxins
Responses are initiated by
hormones. Major plant hormones
belong to the class AUXINS
Table 39-1