Transcript Features of Land Plants

UNIT 6
Chapter 29: Plant Diversity I
Chapter 30: Plant Diversity II
Chapter 31: Fungi
Chapter 35: Plant Structure & Growth
Types of Land Plants


Plants are: multicellular, eukaryotic,
photosynthetic autotrophs
Four MAIN groups of land plants exist:
– Bryophytes: seedless, non-vascular
– Pteridophytes: seedless, vascular
– Gymnosperms: seeded, non-flowering
– Angiosperms: seeded, flowering

Vascular plants possess vessels (tubes)
for transport of water and nutrients
Features of Land Plants

Main characteristics of the four groups of
land plants:
– Meristems

Regions located at specific places from which
new growth occurs
– Apical, lateral
– Multicellular embryos dependent on the
parent plant

Embryo is retained by parent; provides
nutrients
– Alternation of
generations

Two multicellular
body forms
alternate
– Sporophyte: 2n,
produces n spores
by meiosis
– Gametophyte: n,
come together to
form 2n zygote
– Sporangia that produce spores

Organs on the sporophyte that produce spores
– Megasporangia: produce megaspores,
becomes female gametophyte = produces
egg
– Microsporangia: produces microspores,
becomes male gametophyte = produces
sperm
 Spores
will be released into air
– Gametangia that produce gametes
 Organs
on gametophyte that produce
gametes
– Archegonium: female gametangium produces a
single haploid egg
– Antheridia: male gametangia that produce many
haploid sperm
Other Features of Land
Plants


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Many land plants possess a cuticle, a
waxy layer on leaves to prevent water
loss and infection
Stomata, present mostly on the leaves
allow for gas exchange and evaporation
of water
Vascular tissue transports water and
nutrients (except bryophytes)
– Xylem: transport of water and nutrients
from roots

Xylem is “dead” at maturity – only cell wall
remains
– Phloem: distribution of sugars, amino acids
and other organic molecules

Phloem is living tissue
END
Seeds

A seed is a sporophyte embryo with its
own food supply in a protective coat
– Seed plants (gymnosperms and
angiosperms) retain their spores

Microspores develop into pollen
– Carried off by wind or animals
– Pollen carry sperm (1 or 2) to ultimately
pollinate an egg

Sperm are unflagellated
Gymnosperms


Modern gymnosperms appeared
~350mya
Gymnosperms reflect 3 major
changes in the evolution of
plants
– Increasing dominance of the
sporophyte
– Seeds resistant enough for
dispersal
– Pollen

Conifers are the most common group of
gymnosperms
– Most have male and female cones on the
same plant
Smaller pollen cones produce microspores
which develop into male gametophytes =
pollen
 Larger ovulate cones make megaspores that
develop into female gametophytes

– Seeds typically dispersed by wind

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Most conifers are evergreen (vs.
deciduous) and photosynthesize all year
Needles are modified leaves adapted to
dry conditions
– Most have thick cuticles


Most lumber and paper comes from
conifers (xylem tissue)
Conifers are among the oldest and
largest organisms on earth
Angiosperms

Angiosperms have existed for ~130my
– Categorized into two groups: monocots and
dicots
– ~250,000 known species

The flower is the most significant
evolutionary adaptation found in
angiosperms
– Reproductive structure

Animals (esp. insects) often used to transfer
pollen
Angiosperms – The Flower

Flowers are
modified shoots
with four types of
modified leaves
called whorls
– Sepals, petals,
stamens, carpels
Female – carpel
 Male – stamen

Angiosperms – The Fruit

A fruit is a mature ovary
– After fertilization, ovary wall thickens to
form fruit
– Protect dormant seeds and aid in dispersal

Various modifications exist to aid in
dispersal
– Ex. Dandelions and maples use wind
– Many angiosperms use animals for
dispersal

Edible fruits eaten and passed unharmed (along
with fertilizer)

Three main
fruit types
exist
Plants & Humans


All animals ultimately depend on plants,
either for oxygen or for food
Angiosperms provide virtually all of our
food (~12 species)
– Fruits, vegetables, grasses (corn, wheat,
rice)

Diversity in plants is a non-renewable
resource
– Human growth vs. plants


Many plant (and animal) species go
extinct as forests are cut down for
agriculture
Ethical concerns are not the only issue
– Food, building materials, medicines

Only about 2%
of the 250,000
known plant
species have
been studied
– More than
25% of
prescription
drugs are
isolated from
plants
END
Fungi

Fungi are (usually) multicellular,
eukaryotic, non-vascular, heterotrophic
and possess a cell wall made of chitin



Acquire nutrients by secreting exoenzymes
and absorbing nutrients
Act as decomposers, mutualistic symbionts
and parasites
Mycorrhizae are mutualistic associations
between plant roots and fungi

Fungus increases surface area for
absorption by plant roots


Fungus provides
minerals from soil to
plant; plant provides
organic nutrients
Almost all vascular
plants have a
mycorrhizae

Plant growth is
often stunted
without mycorrhizae
END
Plant Anatomy
 Plants have three basic organs: roots, shoots
and leaves
 Angiosperms have most features in common,
but a few major features distinguish the
monocots from the dicots
 A basic
plant
Plant Tissue Systems
 There are three main
types of tissues found
in plants: ground,
dermal and vascular

All types are found
throughout the plant

Dermal
 Covers outer surface
of plant
 Extends to create
root hairs
 Secretes cuticle

Vascular (xylem)
 Tracheids are
individual units of
xylem

Vascular (phloem)
 Organic material
moves through
chains of cells called
sieve-tube members

Ground
 Neither dermal nor vascular
 Photosynthesis, storage and support
 The three tissue types are made up of
three major cell types

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Parenchyma: (living) sieve-tube members,
photosynthesis, storage
Collenchyma: (living) support young parts
of plant
Sclerenchyma: (dead) thick cell walls,
tracheids, support & transport
Growth & Development
 Most plants grow and develop throughout
their lifetime – indeterminate growth


Growth: increase in mass due to cell division
Development: changes that elaborate an
organism’s body
 Plant life cycles vary based on when they are
capable of reproduction

Germination  flowering  seed production
 death

Annual, biennial, perennial
 Meristems are
regions of
embryonic cells


Apical: increase in
plant’s
length/height –
primary growth
Lateral: increase in
plant’s width –
secondary growth
Leaf Anatomy
 Leaf epidermis comprised
of tightly packed cells

Stomata: tiny pores found
in the epidermis flanked
by guard cells

Water pressure in guard
cells control stomata
opening/closing

Mesophyll is ground tissue
sandwiched in between two
epidermal layers

O2 and CO2 circulate in the
spaces in the parenchyma

Vascular tissue is
continuous with that of the
stem
END