•
•
•
•
•
AUTOTROPHIC
MULTICELLULAR
EUKARYOTIC
MOST TERRESTRIAL
CELL WALLS OF
CELLULOSE
• Dominant group on land
based on weight
• DIVERSE!! Range from
2mm to 100m tall!!
Evidence for a phylogenetic connection
between land plants and charophyceans
• Rosette cellulose
synthesizing complexes
(vs. linear)
• Enzymes in
peroxisomes (minimize
photorespiration)
• Structure of sperm
• Certain details of cell
division
• DNA & RNA sequences
are more similar
Differences between plants and
algae
1. Apical meristem
• Localized regions of cell division
• Increases length of plant body to maximize
exposure to sun and water
• Produces primary tissues
• Location: tips of shoots and roots
2. Multicellular, dependent embryo’s
• Embryo receives sugars, amino acids, and other
nutrients from maternal tissue
3. Alternation of generations
4. Walled spores produced in sporangia
• Sporopellin  polymer
that makes spores very
tough and resistant to
harsh conditions
• All 4 major plant groups
produce spores
5. Multicellular gametangia
• All gametophyte forms of
bryophytes,
pteridophytes, and
gymnosperms produce
their gametes within
multicellular organs
called gametangia
• Female archegonia 
produces 1 egg
Male  antheridia 
produces many sperm
– Sperm cells have flagella to
swim through water to eggs
WHAT OBSTACLES
DID PLANTS HAVE TO
OVERCOME TO LIVE
ON LAND?
• DRYING OUT - CUTICLE
& STOMATA
• MEANS OF
REPRODUCTION
• MEANS OF GETTING
WATER AND NUTRIENTS
KINGDOM
PLANTAE
NONVASCULAR
VASCULAR
DIVISION
BRYOPHYTA
DIVISION
TRACHEOPHYTA
MOSSES
LIVERWORTS
FERNS
SEED PLANTS
Nonvascular plants
hornwort
• PRIMITIVE:
AMONG THE 1st
LAND PLANTS
• NONVASCULAR
• NO TRUE ROOT
SYSTEM: HABITAT?
• NO VASCULAR
TISSUE: SIZE?
• SIZE LIMITED
BECAUSE SPERM
MUST SWIM TO
FERTILIZE EGGS
Bryophytes
• Consists of 3 phyla:
– Hepatophyta
– Anthocerophyta
– Bryophyta
• The gametophyte is the
dominant generation
• Nonvascular: grow close to
ground anchored by rhizoids
• Sporophytes disperse
enormous numbers of spores
• Benefits:
– Habitats
– used as soil conditioner and
packing plant roots during
shipment (absorbs 20x H 0),
– Carbon reservoirs (stabilizes
CO and thus climate),
2
2
– important soil builders,
– prevent erosion,
– peat moss grows in bogs or ponds
and used for fuel, mulch, etc.
Vascular plants
(seedless)
Roots
•
Water enters the root
hairs through the
vascular tissue, which
consists of
– Xylem, the waterconducting tissue
– Phloem, the tissue
that conducts food
throughout the plant
Transpiration
Xylem sap (water and
dissolved minerals from soil)
travel up inside a plant
Water vapor is lost from leaves
When water evaporates, the forces of cohesion
and adhesion create tension
Tension causes water molecules from the xylem
to be drawn out into the leaf to replace the water
that has evaporated
This, in turn, increases tension on the water
molecules immediately below them in the
xylem
This causes water to move towards the leaves,
and so on
•
Transpiration relies on
– The sun to cause evaporation
– Hydrogen bonding
•
Plants can modify the rate of transpiration
by regulating stomata size
Seedles Vascular
Plants
• Whisk ferns  no
roots or leaves, “living
fossils”, DNA
sequences place them
with ferns
• Horsetails  Genus
Equisetum, only 15
extant species, marshy
habitats
• Ferns  Most diverse
& widespread, 12,000
sp.
h
Vascular plants (seeds)
• Gymnosperms
• Angiosperms
Gymnosperms
• Ovules and Seeds develop on the
surfaces of specialized leaves called
sporophylls
• Four Phyla
– Ginkgophyta (Ginkgo)
– Cycadophyta (Cycads)
– Gnetophyta (Gnetophytes)
– Coniferophyta (Conifers)
Phylum Ginkgophyta
• Ginkgo biloba is
the only extant
species
• Believed to
improve memory
Phylum Cycadophyta
• Resemble palms (which are angiosperms)
Phylum Gnetophyta
• Three genera that are very different in
appearance
– Welwitschia
– Gnetum
– Ephedra
Phylum Coniferophyta
• Cone bearing
• Pines, firs, spruces, yews, junipers,
cedars, cypresses, redwoods and larches
Gymnosperm Life Cycle
Angiosperms
• Flowering plants
– (flowers and fruits)
• Two main classes
– Monocots
– Dicots
Roots
•
The root system
functions to absorb
water and minerals
from the soil
–
Monocot roots
tend to be fibrous
and spread out
obtain water
quickly
–
Dicots usually
have a single
taproot that goes
deeper in the soil
Plant Reproduction
• Pollination is the transfer of
pollen to the stigma of a
carpel
• Pollen grains grow tubes
down through the stigma
• When pollen tube reaches
the ovules, sperm are
released
• Fertilization occurs
• Pollination occurs by many
means such as by wind,
insects, and other animals
• Petals are adaptations to
facilitate pollination
– Small petals: windpollinated grasses
– Large, colorful petals full
of nectar: insectpollinated plants
Plant Reproduction
• Flowers are the sexual
organs of angiosperms
– Contain both male
and female
reproductive organs
– Make both male and
female gametes
Female reproductive organs:
Carpel – entire reproductive structure
Style – tube to ovules
Ovary – hold ovules
Ovules – contain female gametes
Stigma – where pollen lands
Male reproductive organs:
Stamen – entire reproductive structure
Filaments – support for anther
Anthers – produces pollen
Pollen – contain male gametes
Plant
Reproduction
• When the pollen tube
reaches the ovule, two
sperm are released in
double fertilization
– One sperm fertilizes the
egg and becomes the
embryo
– The other fuses with
two nuclei in the ovule
to become endosperm
(food for developing
embryo)
• Successful fertilization
triggers development of
fruit (the ovary)
Life Cycle of Angiosperms
The Right Plant for the Place:
Water Relations
• Plant growth is influenced by
– Chemical nature of soil
– Light availability
– Length of growing season (time from
last frost in spring to first frost in fall)
– Amount of water available for plant…
• Plants can respond to different
environmental signals in a surprising
number of ways
Tropisms
(directional growth)
• Roots have positive
gravitropism – they
grow toward gravity
source
– This ensure good
exposure to water
• Stems have negative
gravitropism – they
grow away from gravity
source
– This ensures good
exposure to light
http://vimeo.com/7608720
Tropisms
• Phototropism is
directional growth
toward light
– Can be seen in
houseplants on
windowsills
• Thigmotropism is a
plant’s response to
touch
– Vining plants show this
when they grow around
stakes
•
http://www.youtube.com/watch?
v=ZWB9UtIUizg
Plant hormones regulate
a plant’s internal
environment and control
its response to
environmental conditions
Hormones
• Auxin causes cells to expand
in a main stem and inhibits
growth of axillary buds on
sides of stem
• This is apical dominance –
tendency for plant apex (top
bud) to grow faster than lower
buds
• Apical dominance increases
height and leaf area of plant
but limits bushiness and flower
and fruit production
• Gardeners try to reduce apical
dominance by pruning
• When apical bud is pruned
branch formation is promoted
while auxin levels are reduced
auxin
gibberellin
cytokinin
ethylene
The Role of the
Consumer
• Consumer demand for
meat also fuels
unsustainable farming
practices
– Animals fed fieldgrown grain in
“factory farms”
– Leads to highly
inefficient use of
grains versus using
grain to feed humans
directly
USDA figures indicate
animal waste from meat
industry is 130 times that
from U.S. human population
Freedom from Pest Damage
•
•
•
•
Farmers can lose up to 40% of
crop every year to pests
Pesticide are chemicals that kill
insect, fungal and bacterial
pests
Pesticide use hasn’t
considerably reduced loss of
crops to pests, but have allow
farmers to plant monocultures
– Single crops in large areas
– Very efficient
Monocultures are very sensitive
to pest outbreaks
– Farmers can lose entire
crop
•
Farmers also use cultural
control to minimize pest
populations
– Crop rotation – moves
plants away from pests
– Polyculture – plant many
crop plants together to
reduce amount of loss to
pests
• Some bacteria can “fix”
nitrogen into a form that
plants can use (nitrogenfixing bacteria)
– Nodules form on roots
– House bacteria and
supply with food
– Excess nitrogen is
released into soil
• Crop rotation can replace
nitrogen into the soil
– Legumes – have
nitrogen-fixing bacteria
– Rotate with grains –
nitrogen consuming
plants
Nutrients and
Soil
Designing Better Plans:
Hybrids and Genetic
Engineering
• Using DNA technology
• Genetically modifying
plant genes
– Pest-resistant corn
– Ripen-on-demand
tomatoes
• Many questions remain
about genetically
modified organisms
(GMOs), however