Chapters 22-25
Plants
Characteristics
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Eukaryotes
Multicellular
Cell walls of cellulose
Carry out photosynthesis using pigments
chlorophyll a and b
 Life cycle
 Gametophyte (1N) > gametes (1N) > fertilization >
zygote > sporophyte (2N) > meiosis > spores (1N) >
mitosis > gametophyte
 Evolved from green algae
3 Types of Tissues
 Dermal tissue – outer covering
 In leaves covered by cuticle – waxy layer
 Vascular tissue – conducts nutrients through plant
 Xylem – conducts water
 Composed of dead cells called tracheids and vessel
elements that act as pipes.
 Phloem – conducts food
 Composed of sieve tube elements – contain openings
to allow sugars through
 Also, companion cells – surround for support
 Ground tissue – btw others
 Parenchyma – site of most photosynthesis
 Collenchyma – flexible walls, help support – celery
 Sclerenchyma – thick, rigid, strong
Structure I
 Roots – underground organs that absorb
water and minerals, anchors, prevents
erosion
 2 types
 Taproot – 1 main root – carrots
 Fibrous roots – many similar
branches
 Structure
 Epidermis – outer layer
 Covered in root hairs – increase
surface area for absorption
 Cortex – middle – ground tissue
 Endodermis – inner
 Aka vascular cylinder
 Contains xylem & phloem
 Root cap – covers apical meristem
Structure II
 Leaves – bundles of photosynthetic
vascular tissue
 Structure
 Blades – flattened section
 Petiole – attaches to stem
 Specialized ground tissue
 Palisade mesophyll – absorbs light
 Spongy mesophyll – connects to the outside via
stomata (openings) to allow carbon dioxide in and
oxygen out
 Guard cells – control opening/closing of stomata
 Functions
 Photosynthesis
 Transpiration – loss of water through leaves
 Gas exchange
Structure III
 Stem
 3 functions
 Produce leaves, branches, & flowers
 Hold leaves up to sunlight
 Transport substances between roots and leaves
 Structure
 Nodes – where leaves attach
 Internode – region btw nodes
 Buds – at nodes – tissue that can produce new
stems and leaves
 Primary growth – occurs in meristematic tissue at the
apical meristem – increase in length
 Secondary growth – increase in width
 Occurs in lateral meristematic tissue – vascular
cambium & cork cambium
Classification I
 Bryophytes
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3 phyla
Vascular tissue absent – results in small size
Flagellated sperm - must stay close to water
No true roots or leaves
Gametophyte - dominant life cycle
Ex. Mosses, liverworts, hornworts
Classification II
 Pteridophytes
 2 phyla
 Vascular tissue
present
 Appearance of true
roots & leaves
 Sporophyte – now
the dominant life
cycle
 Ex. Ferns, club
mosses, horsetails
Classification III
 Gymnosperms
 Appearance of seeds (embryo
of a plant encased in a
protective covering with a food
supply) which are produced in
cones - plants were able to
reproduce without water
 Male gametophyte – pollen
 Ex. Gnetophytes, Cycads,
Ginkgoes
 Conifers – pine, juniper, spruce
 Aka evergreens
Classification IV
 Angiosperms
 Aka flowering plants
 Cotyledons – embryonic seed leaves
 Monocots – 1 seed leaf, parallel veins
 Vascular bundles in stem are scattered
 Dicots – 2 seed leaves, branched veins
 Vascular bundles in stem are arranged in a ring
 May be subdivided based on stem characteristics
 Woody or Herbaceous
 Life spans
 Annuals - complete a life cycle 1 year
 Biennials - complete a life cycle in 2 years
 Perennials - live for more than 2 years
Alternation of Generations
 Gametophyte (1N) > gametes (1N) >
fertilization > zygote (2N) > sporophyte (2N)
> meiosis > spores (1N) > gametophyte
 Gymnosperms
 Gametophytes are found in cones
 Pollen cones – male
 Ovulate cones – female
 Pollen is carried by wind from male to
female
Alternation of Generations
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Angiosperms
 Gametophytes are found in flowers
 Structure
 Sepals - outermost petals – green – enclose bud before opening
 Petals - brightly colored – attract pollinators
 Stamen
 Filament - thin stalk
 Anther - produce male gametophytes (pollen)
 Pistil
 Aka carpel
 Stigma - top – sticky
 Style – stalk
 Ovary - contains female gametophytes – becomes fruit
 Life cycle – Double Fertilization
 Pollen sticks to stigma
 Pollen tube forms and grows down style to ovary
 1 sperm fertilizes egg = embryo
 A 2nd sperm joins with other cells to form the endosperm (food
supply)
Angiosperm life cycle
Flowers
 Sepal
 Petals
 Stamen
 Anther
 Filament
 Carpel
 Stigma
 Style
 Ovary
Pollination
Seed Dispersal
 May be dispersed by wind, water, or
animals
 May remain dormant until conditions are
right
 Germination – early stage of growth
Plant Hormones
 Hormone – chemical substance that control’s a plants
growth, development, and responses
 Target cell – part affected by a particular hormone
 Auxins cause:
 Phototropism – growth toward light
 Gravitropism – causes branches to grow up and
roots to grow down
 Apical dominance - delays the appearance of new
lateral buds (which grow into side branches)
 Cytokinins - stimulate cell division, growth of lateral
buds, and sprouting
 Gibbreellins - promotes overall growth
 Ethylene - stimulates fruits to ripen
Plant responses
 Tropisms – response to an external stiumulus
 Types
 Gravitropism - response to gravity
 Phototropism - response to light
 Thigmotropism – slower changes in growth
in response to touch
 Vines
 Rapid responses – quick movement in
response to touch
 Mimosa, venus fly trap
Photoperiodism
 Timing of seasonal activities
 Phytochrome - pigment responsible
 Short-day plants - flower when days are
short
 Ex. Poinsettias
 Long-day plants - flower when days are
long
 Dormancy - period when growth/activity
decrease or stop
 Usually during winter for deciduous plants