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PLANT STRUCTURE
AND FUNCTION
Copyright © 2009 Pearson Education, Inc.
Evolution and types of plants
 Since the earth was
once covered in water,
plants had to make
three adaptations to
survive on land
 The ability to prevent
water loss
 The ability to reproduce
in the absence of water
 The ability to absorb
and transport nutrients
 Plants can be placed
under two groups
 Vascular- having true
roots, leaves, and stems
 Ex. ferns, conifers,
flowering plants
 Nonvascular- not having
true roots, leaves, and
stems
 Ex. mosses, liverworts,
hornworts
Vascular Plants can be divided into two groups
Seedless Plants
 Made up of ferns and
plants closely associated
with ferns
Seed Plants
 Two types of seed plants
 Gymnosperms- which
includes pine trees,
produce seeds that are not
encased in fruit
 Angiosperms- aka
flowering plants, produce
seeds within a protective
fruit
The two main groups of angiosperms are the
monocots and the dicots
 Monocots
– One cotyledon
– Parallel leaf venation
– Scattered vascular bundles
– Flower parts in 3s or multiples of 3
– Fibrous roots
The two main groups of angiosperms are the
monocots and the eudicots
 Dicots- aka eudicots
– Two cotyledons
– Branched leaf venation
– Ring of vascular bundles
– Flower parts in 4s or 5s (or multiples)
– Taproot system
A typical plant body contains three basic organs:
roots, stems, and leaves
 Plants absorb water and minerals from soil through
roots
 Plants absorb the sun’s energy and carbon dioxide
from the air through shoots (stems and leaves)
 Plant roots depend on shoots for carbohydrates
produced via photosynthesis
 Plant shoots depend on roots for water and minerals
Copyright © 2009 Pearson Education, Inc.
A typical plant body contains three basic organs:
roots, stems, and leaves
 Plant roots
– Anchor plant
– Absorb water and nutrients
– Store food
 Plant shoots
– Stems, leaves, and reproductive
structures
– Stems provide support
– Leaves carry out photosynthesis
Copyright © 2009 Pearson Education, Inc.
Terminal bud
Leaf
Shoot
system
Blade
Flower
Petiole
Axillary bud
Stem
Node
Internode
Root
hairs
Root
hair
Taproot
Root
system
Epidermal cell
Many plants have modified roots, stems, and
leaves
 Modifications of plant parts are adaptations for
various functions
– Food or water storage
– Asexual reproduction
– Protection
– Climbing
– Photosynthesis
Copyright © 2009 Pearson Education, Inc.
Many plants have modified roots, stems, and
leaves
 Root modifications
– Food storage
– Examples include carrots & potatoes
Many plants have modified roots, stems, and
leaves
 Stem modifications
– Runners (allow for
asexual reproduction)
Many plants have modified roots, stems, and
leaves
 Leaf modifications
– Climbing
– tendril
– Example: pea plants
– Protection
– Thorns or spines
– Example: Cactus spine
Plant cells and tissues are diverse in structure and
function
 Plants cells have three
structures that
distinguish them from
animals cells
– Chloroplasts used in
photosynthesis
– A large, fluid-filled
vacuole
– A cell wall composed
of cellulose
PLANT GROWTH
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Primary growth
Plants are categorized based on how long they live
– Annuals complete their life cycle in one year
– Biennials complete their life cycle in two years
– Perennials live for many years
Copyright © 2009 Pearson Education, Inc.
Primary growth
allows roots
to push downward
through the
soil and shoots to
grow upward
Terminal bud
Axillary buds
Arrows =
direction
of growth
Root
tips
Secondary growth increases the girth of woody plants
Year 1
Early Spring
Year 1
Late Summer
Year 2
Late Summer
Secondary growth increases the girth of woody
plants
 Cork cambium produces
the outer bark
Copyright © 2009 Pearson Education, Inc.
Secondary growth increases the girth of woody
plants
 Wood annual rings show when new growth starts
each year.
 Sapwood (transport)- functional, lighter-colored wood
near the outside of the trunk
 Heartwood (storage)- the darker wood at the center of
the trunk
Secondary growth increases the girth of woody
plants
 Xylem- transports water
 Phloem- transports food