Roots, Stems and Leaves
Chapter 23
Biology – Miller • Levine
Specialized Tissue in Plants
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The three organs of a plant are the roots, stems
and leaves
The three tissue systems of a plant are dermal
tissue, vascular tissue, and ground tissue
A special type of tissue called meristematic
tissue is the only plant tissue that can produce
new cells by mitosis
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Found in the tips of shoots and roots
Dermal Tissue
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The outer covering of a plant
Consists of a single layer of epidermal cells
Cuticle – a waxy layer that often covers the
epidermis
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Provides protection against water loss & injury
May include specialized structures such as root
hairs and guard cells
Vascular Tissue
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Transports water and
nutrients throughout the
plant
Xylem – transports
water; composed of
dead cells
Phloem – transports
nutrients; composed of
living cells called sieve
tube elements
Ground Tissue
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Lies between the dermal and
vascular tissues
Parenchyma – has thin cell walls
and large central vacuoles
Collenchyma – has strong, flexible
cell walls and is found in larger
plants
Sclerenchyma – has extremely
thick, rigid cells walls
Roots
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Types of roots:
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Taproot - A thick primary root that grows long and
is found mainly in dicots
Fibrous roots – branch extensively and are found
mainly in monocots
Root Structure & Growth
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Root hairs – tiny projections from the
epidermis that increases the surface area for
absorption of water
Cortex – layer of ground tissue
Endodermis – layer of tissue that encloses the
vascular tissue
Root cap – protects the root as it forces its
way through the soil
Root Structure & Function
Root Function
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Anchor a plant in
the ground
Absorb water and
dissolved nutrients
from the soil
Stem Function & Types
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Three important functions:
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Produce leaves, branches and flowers
Hold leaves up in the sunlight
Transport substances between roots and leaves
Two types:
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Monocot – has vascular bundles that contain the
xylem & phloem scattered randomly
Dicot – have vascular bundles organized in a
ringlike pattern
Monocots and Dicots
Stem Structures
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Nodes – where
leaves are attached
Internodes – regions
between the nodes
Buds – contain
undeveloped tissue
that can produce new
stems and leaves
Leaf Structure
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Blade – thin,
flattened section
Petiole – thin stalk
that attaches the leaf
to the stem
Veins – contain the
xylem and phloem
Leaf Structure
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Palisade mesophyll – tightly packed cells that
absorb light
Spongy mesophyll – loosely packed cells with
air spaces
Stomata – pore-like openings for taking in
CO2 and releasing O2
Guard cells – cells that open and close the
stomata
Leaf Structure
Leaf Functions
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Photosynthesis – takes place in the mesophyll
cells of the leaf
Transpiration – the loss of water from a plant
through its leaves (helps to pull water up from
the roots)
Gas exchange – taking in carbon dioxide and
releasing oxygen