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Transcript
Plant Structure and Growth
Overview
Lifecycles
– Annual, biennial, perennial
Basic Plant parts
Plant cell walls, simple tissue types
Plant growth:
–
–
–
–
–
Meristems
Primary Tissues
Primary growth – apical meristems
Secondary growth – lateral meristem
Secondary tissues
Flowering Plant Lifecycles
• Annual – germinates, flowers set seeds and
dies in one growing season
• Biennial- germinates grows first season,
storing up energy underground. Second
spring plant use energy to quickly bloom
(bolting) set seed and die.
• Perennial grows for several seasons until
mature, Blooms and sets seed for years.
bolting
Basic Plant Parts
• Shoot system: photosynthesis,
reproduction
– Stems with nodes
– Leaves - axilliary bud at base of each
– Flowers and fruits (cones in gymnosperms)
• Root system ; Anchors plant; Storage
organs; absorption of water and
nutrients.
– Roots, root hairs
– Mycorrhizae
– Nitrogen fixing bacteria
Angiosperm Diversity
BASAL ANGIOSPERMS
Amborella trichopoda
Star anise (Illicium
floridanum)
Water lily (Nymphaea
“Rene Gerard”)
MAGNOLIIDS
Southern magnolia (Magnolia
grandiflora)
Eudicots
Monocots
Magnoliids
Star anise
and relatives
Water lilies
Amborella
HYPOTHETICAL TREE OF FLOWERING PLANTS
MONOCOTS
EUDICOTS
Monocot
Characteristics
Orchid
(Lemboglossum
rossii)
Eudicot
Characteristics
California
poppy
(Eschscholzia
californica)
Embryos
One cotyledon
Two cotyledons
Leaf
venation
Veins usually
parallel
Pygmy date palm
(Phoenix roebelenii)
Pyrenean oak
(Quercus
pyrenaica)
Veins usually
netlike
Stems
Lily (Lilium
“Enchantment”)
Vascular tissue
usually arranged
in ring
Vascular tissue
scattered
Root
Barley (Hordeum vulgare),
a grass
Root system
Usually fibrous
(no main root)
Dog rose (Rosa canina), a wild rose
Taproot (main root)
usually present
Pollen
Pollen grain with
one opening
Pea (Lathyrus nervosus,
Lord Anson’s blue pea),
a legume
Pollen grain with
three openings
Flowers
Anther
Stigma
Filament
Ovary
Floral organs
usually in
multiples of three
Floral organs usually
in multiples of
four or five
Zucchini (Cucurbita
Pepo), female
(left) and male flowers
Fig.
35.2
Simple Plant Tissue Types
• Tissues- cells with a common structure and
function and specialized connections.
• Parenchyma- Soft, rounded cells with thin
primary cell walls, air spaces between cells
– Many are Totipotent Cells- undifferentiated that
can still divide
– Some are specialized: chlorenchyma, phloem
• Collenchyma- irregularly thicken primary cell
wall, no air spaces. Elastic support.
• Sclerenchyma – rigid secondary cell wall.
May have no cytoplasm left: Wood, Xylem,
vessels, fibers, tracheids. Also seed coat.
Fig
35.11
Xylem
•
•
•
•
•
•
•
•
Sclerenchyma
Dead at maturity
Hollow
Grows to size
first then makes
secondary cell
wall
Tracheids
Vessel elements
Secondary xylem
is true wood.
Conducts water
from roots to leaf
Young Xylem
• We’ll go over
different types in
lab
Phloem
• Transports sugar solution from source to sink.
• Parenchyma-Living tissue, uses active
transport.
• Sieve tube members and companions cells
Plant Tissues comprise Organs
• Dermal tissues cover the plant
– Epidermis, stomata, trichomes, bark
• Vascular Tissues transport materials
– Xylem carries water
– Phloem carries sugar solution
• Ground Tissues – metabolic functions, growth
– Meristems, photosynthesis, storage
• Organs-groups of tissues forming a larger
structure, with a common structure and
function.
Fig 35.7
Plant cell wall structure
• Adjoining cells held together by middle
lamella (polysaccharides of pectin)
• Cells first make thin, flexible primary cell
walls.
• Plant cells can still enlarge / divide with
primary cell wall.
• Some cells lay down three rigid secondary
cell wall layers with ligin inside primary cell
wall.
• Plasmodesmata connect cytoplasm between
neighboring cells through cell walls.
Fig 6.28
Cell Elongation
• How cellulose microfibrils are laid down
determine the direct of elongation.
• Elongation takes place when a cell only
has primary cell wall.
• Once proper size and shape is attained,
secondary cell wall material is added
inside the primary cell wall.
Plane of Cell division
• Determines the cell
shape
Plane of symmetry
Plant Growth
• Indeterminate growth
• Primary growth: cells derived from the apical
meristems (both root and shoot).
– Makes the plant grow taller and roots deeper.
– Makes leaves, flowers fruits
• Secondary Growth: cells derived from the
lateral meristems.
– Adds girth to plant
– Vascular cambium makes secondary xylem
(wood) and secondary phloem.
– Cork cambium adds to bark
• Meristems- localized areas of cell divisions
– Plants grow in zones, not all over whole organism
Fig. 35.12
Fig. 35.17
Apical Meristem
• Divides cells that form primary
meristem tissues
– Protoderm – further divides to
make dermal layers
– Procambium – divides to form
xylem and phloem, residual layer
becomes vascular cambium
– Ground Meristem – forms pith
and cortex
• Plants grow like building a
brick wall- add bricks at top
(primary growth), then add
girth to sides (secondary
growth).
Primary growth
• Herbaceous – no true wood
• May have tough parts –
Collenchyma or
Sclerenchyma.
• All cells derived from apical
meristem
• Forms separate vascular
bundles in stem.
• You fall madly in love with you’re a lab mate
in 131 – and hand in hand you both carve you
initials 4 feet off the ground on the Bishop
Pine (Pinus muricata) in the turn-around by
the LS building.
• The Bishop Pine grows 3 feet a year.
• Two years later you return to DVC after
finishing up at UC Santa Cruz in Organismal
Biology to visit you old favorite Biology
instructor.
• How far off the ground are your initials then?
Secondary Growth
• In Ferns, Gymnosperms and Eudicots, not in
monocots
• Vascular cambium layer begins to form.
– Divides off more cells.
– Cells to the inside become secondary xylem
(wood) Cells to outside become secondary
phloem.
• Adds girth, pushing outer layer farther out.
• Parenchyma in phloem rays fill-in space
until cork cambium starts making bark.
Fig. 35.20
Annular growth rings
• In temperate or wet /dry seasonal zones
• In spring new growth use a lot of water,
xylem cells grow very large (early
wood).
• Under water stress late in the season
xylem cells very narrow (late wood).
• Evidence of past climates, period of
drought.
Monocot and Eu-dicot
• Monocots do not have secondary
growth.
– Palm trees, bamboo - not true wood!!
• We’ll compare anatomical variation
between these groups in lab
– Learn differences between monocot , dicot
anatomy of leaves, stems, roots.