Stems
C9L3P4
Plant Organs
Stems
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The part of a plant that connects its roots to
its leaves is the stem.
Stems support branches and leaves,
and their vascular tissues transport water,
minerals, and food.
Plant stems are usually classified as either
herbaceous, which are usually soft and
green, or woody, which are stiff and
typically not green.
Types of stems
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Herbaceous stems
Woody stems
Herbaceous stems
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Softer, more flexible
type of stem
Supported by cell
walls and turgor
pressure
Woody plants often
begin as herbaceous
and then become
woody as the grow
older
Woody stems
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Hard and not very
felxible
Capable of
supporting a lot of
weight
Examples: trees
and shurbs
Stem Functions
manufacture,
support, and display
leaves
 conduct materials
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Monocot Stem
Dicot Stem
wood
a collection of layers of xylem that
have built up over several years
The oldest layer of
xylem is at the
center of the
woody plant part
newest layer is the
outermost layer
Kinds of Wood
Heartwood - dead xylem
cells that are often darker
 Sapwood - xylem that
conduct water and minerals
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Heartwood & Sapwood
Kinds of Wood
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Springwood - xylem cells that
develop early in the growing
season
Summerwood - small, thickwalled xylem cells that develop
later in the growing season
Springwood & Summerwood
Kinds of Wood
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Hardwood - comes primarily from
angiosperms (oaks, maples, walnut,
cherries)
Softwood - comes primarily from
gymnosperms (firs, pine, cedars,
spruce)
Hardwood
Softwood
Heartwood & Sapwood
bark
the outer
covering of
woody plant
parts(makes
new xylem
and phloem
cells)
cork
(the outer layer
of bark) tough,
thick-walled
cells forming
the outer layer
of bark in
woody plant
stems; made of
dead, thick-cell
walls
cork
heartwood
Annual
growth
ring
sapwood
(xylem)
phloem
cork
vascular
cambium
forms a tough,
water proof
coating that
keeps harmful
organisms out
and moisture
cork cambium
a layer of
living cells just
under the
dead cork
(produces new
cork cells)