Plant Structure
And Growth
The Plant Body is
Composed of Cells and
Tissues
•Tissue systems (Like Organs)
–made up of tissues
•Made up of cells
Plant Tissue Systems
• ____________________
photosynthesis
storage
support
• ____________________
conduction
support
• ___________________
Covering
Dermal Tissue System
• Epidermis
– Single layer, tightly packed cells
– Complex Tissue – Does different
things in different areas (roots vs.
leaves)
– usually transparent
– secretes cuticle
• ___________ –
– replaces epidermis in woody plants
– protection
• ____________
– Tap Root
– Lateral Roots
• ____________
– Stems
• Nodes (leaves
are attached)
• Internodes
– Leaves
• blades
• petioles
– Buds
Plant
Systems
• Terminal
(apical)
• Axillary
Plant Growth
• ______________ Tissue
–generates cells for new
growth (like stem cells in
animals)
•apical meristems
•lateral meristems
Apical Meristems
• increases length called primary
growth
–___________ - gives rise
to dermal tissue
–________________gives rise to ground tissue
–_____________ - gives
rise to vascular tissue
Lateral Meristems
• increases girth called secondary
growth
–__________________produces secondary xylem and
secondary phloem
–______________- produces
cork (outer most layer of bark)
Pine Tree w/ 8 Cotyledons!
The Root System
• Functions
– anchor plant
– absorb minerals, water and
nutrients
– store food
• Systems
– ____________ - one large root
with smaller lateral roots (dicots)
– ____________- threadlike roots
(monocots)
Root Tissue
• Protoderm - gives rise to the
epidermis
• Ground Meristem
– Cortex (external to vascular
tissue)
• Procambium - gives rise to the
_______ (the vascular tissue of a
root or stem)
– xylem and phloem
– may include pith (parenchyma
cells surrounded by vascular
tissue)
Dicot Root vs. Monocot
Modified Roots
• Food Storage
– carrots, sweet
potatoes, yams
• Water Storage
– pumpkin family
• Propagative
Roots
– cherries, pears
• Pnematophores
– mangroves
• Aerial Roots
– orchids
• Buttress Roots
– tropical trees
• Haustoria
– dodder
Shoot
System
Stems (Primary Growth)
• Protoderm - gives rise to the
epidermis
• Procambium - gives rise to the
stele
– xylem and phloem in vascular
bundles
•dicots - found in ring
•monocots - scattered
throughout
– includes “pith” in dicots
• Ground Meristem
– Cortex
____________
– stele (vascular tissue)
divided into strands in
stems and leaves
Sclerenchyma
cells
Phloem
Xylem
Dicot Stem Vs. Monocot (35.16)
How can you tell root from stem?
Stems (Secondary Growth)
• Occurs to increase girth
(thickness)
– Vascular Cambium
• produces secondary xylem and
secondary phloem
– Cork Cambium
• produces cork and phelloderm
(thin layer of parenchyma cells)
• together these structures are called
periderm (Cork Cambium, cork,
phelloderm)
Secondary Growth
Derivative
Vascular cambium
Secondary
Growth of
a Stem
• Pith
• Primary
Xylem
• Secondary
Xylem
(wood)
• Vascular
Cambium
Periderm
Secondary Growth of a
Stem (Inside to Outside)
• Secondary
Phloem
• Primary
Phloem
• Cortex
• Phelloderm
• Cork Cambium
• Cork (outer
layer of bark)
Older, inner layers
of 2° Xylem – no
longer transport
water
Younger, outer
layers of 2°
Xylem still
function in
transport
All tissue
outside
vascular
cambium
Missing cortex and phelloderm!
___________ (Early) growth
occurs more
quickly. Cells are large and thin
walled and have less strength.
Summerwood (Late) growth
occurs more slowly. Cells are
thicker, more dense, and stronger.
Modified Stems
• __________ - horizontal
stems above the ground
(strawberries)
• Rhizomes - horizontal
stems below the ground
(Irises)
• Tubers - swollen areas of
rhizomes or stolons
(Potatoes)
• Bulbs & Corms - vertical
shoots under ground
(onions, garlic w/ mod
storage leaves)
• _____________ cactus pads
Leaf Structure
Leaves
• Epidermis
– __________ - openings on
underside of leaf
– Guard Cells - surround stomata
– Cuticle - waxy coating excreted
by epidermis
• Mesophyll - middle of leaf
– ___________ - photosynthesis
– Spongy layer - gas exchange
Modified Leaves
• ___________attachment
• Bracts –modified
leaves that
surround a group
of flowers
• Spines protection
• Storage Leaves
- succulents
Uptake of
Nutrients
_______________
cultures used to
determine which
chemical elements are
essential.
17 essential elements
needed by all plants
Soil
• Develops from weathered
rocks
– Anchors plants
– Provides water
– Provides dissolved minerals
Soil Texture
• Pertains to sizes of soil
particles
– includes the following:
• sands (0.02 - 2 mm)
• silt (0.002 - 0.02 mm)
• clay (less than 0.002 mm)
Control Systems in
Plants
Plant Hormones
• Coordinates growth
• Coordinates development
• Coordinates responses to
environmental stimuli
Auxins
• Stimulates stem elongation
• Stimulates root growth
• Stimulates differentiation and
branching
• Stimulates development of
fruit
• Stimulates apical dominance
• Stimulates phototropism and
gravitropism
Auxin Control
• Auxin stimulates
growth
• Auxin block on
right causes cells
to elongate and
the plant bends
left
• Auxin block on left
causes cells to
elongate the the
plant bends right
Acid Growth
•
•
•
•
Proton pump stimulated by auxin lower pH of wall
H+ activates Enzyme
Enzyme breaks hydrogen bonds in cellulose
Wall takes up water and elongates
Auxin Others
• Promotes secondary
growth by stimulating
vascular cambium and
secondary xylem
• Promotes adventitious
root at the base of a cut
stem
• Promotes fruit growth
without pollination
(seedless tomatoes)
Cytokinins
• Works with Auxin:
– more cytokinin - shoot buds
develop
– more auxin - roots develop
• Stimulates germination
• Delays Senescence
Gibberellins
• Promotes seed and bud
germination
• Promotes stem elongation
• Promotes leaf growth
• Stimulates flowering and
fruits
– (with auxin)
Ethylene
• Promotes fruit ripening
• Controls Abscission (causes
leaf loss)
Phytochromes
• Function as photoreceptors / red (660nm) to
far red (730nm)
• Activates kinases (regulatory proteins)
Red vs. Far Red Response
Why plants are
important?
• Food!
• Humans have domesticated plants for
13,000 years.
• ____ of all the calories consumed by
humans come from six crops: Wheat,
Rice, Maize, Potatoes, Cassava, and
Sweet Potatoes.
• Also, we use plants to feed cattle, 5-7kg
to produce 1 kg of beef.
Pyramid of Net
Productivity
Plants remove CO2
•_____ of all US
Prescription Drugs
contain one or more
active ingredients from
plants.
•____ earth’s species
will become extinct
within the next 100
years (larger than the
Permian or Cretaceous)
•Only 5,000 of 290,000
species have been
studied.
•3-4 species per hour,
27,000 per year!
Cinchona tree
• Bark contains
__________
• Grows in the
Andes in peru
• Used since the
early 1600’s to
treat malaria
Aspirin
• Acetylsalicylic acid or ASA
• Dates back to 3000 B.C.
• Greek Physician Hippocrates
prescribed it.
• From _____________ and
other Salicylate-rich plants
(leaves and bark)
• Scientists at Bayer began
investigating acetylsalicylic
acid as a less-irritating
replacement for standard
common salicylate medicines.
By 1899, Bayer named it this
Aspirin
Ecology
Hadley Cells
Biomes
Coriolis Effect
Charles Darwin
• Differential
Reproductive
Success Adaptation
• 1859 Origin of
Species.
• Romanes –
Neodarwinism
& The Modern
Synthesis
(Genetics)
Evolution in the Lab
Allopatric Speciation
Sympatric Speciation
Hugo De Vries
• Evening Primrose
Need to know to
here now!