Stems:
STRUCTURE
& FUNCTION
Workbook 23.3
Stem Structure & Function
1. What are the three main functions of stems?
Stems produce organs (leaves, flowers), hold leaves
up to sun, and transport materials throughout plant
2. What is an example of a stem that conducts
photosynthesis and stores water?
Desert cactus stem
3. What is a node?
Where leaves are attached to the stem
4. What kind of plant tissue does a
bud contain?
Apical meristem - area of rapidly dividing
cells [GROWTH!]
5. What does a vascular bundle
contain?
Xylem (carries water) and phloem (carries
sugars)
Stem cross-section
Notice how the vascular bundles are arranged
VASCULAR BUNDLES
GROUND
TISSUE
EPIDERMIS
CORTEX
PITH
COMPARE & CONTRAST CHART
STRUCTURE OF MONOCOT STEMS AND DICOT STEMS
SIMILARITIES
COMPOSED OF VASCULAR
TISSUE, GROUND TISSUE,
AND EPIDERMAL TISSUE
VASCULAR TISSUES ARE IN
VASCULAR BUNDLES
DIFFERENCES
IN MONOCOTS, VASCULAR
BUNDLES ARE SCATTERED
IN DICOTS, VASCULAR
BUNDLES ARE ARRANGED
IN A RING
Growth of Stems – True or False
8. Plants grow in a way that is the same as the way
animals grow.
False – DIFFERENT FROM
9. The # of legs an animal will have is predetermined, but
the # of branches a plant will have is not predetermined.
True
10. Primary growth of stems is the result of elongation of
cells produced in the ground tissue
False – APICAL MERISTEM
11. The increasing thickness of stems and roots in dicots
and gymnosperms is called new growth
False – SECONDARY
12. Secondary growth is common in monocots
False - RARE
13. Dicots can grow to great heights because the increase
in width supports the weight.
True
14. Vascular cambium forms between the xylem and
phloem of the vascular bundles
True
15. In conifers and dicots, secondary growth takes place
in stems and roots called vascular cambium and cork
cambium
False - MERISTEMS
16. The inner layers of a stem are produced by cork
cambium
False – OUTER COVERING
17. Stems become thicker because the cambium
produces new layers of vascular tissue each year
True
SECONARY GROWTH (WIDTH)
PRIMARY
PHLOEM
SECONDARY
PHLOEM
BARK
WOOD
PRIMARY
XYLEM
SECONDARY
XYLEM
19. Most of what we call “wood” is made up of
layers of SECONDARY
xylem.
20. The dark wood that no longer conducts
water is called HEARTWOOD
.
21. The wood that is active in fluid transport is
called SAPWOOD
.
22. The lighter wood in tree rings contains LARGER
cells with thin cell walls compared with the cells
in darker wood.
23. Alternating layers of light wood and dark
wood are used to estimate a tree’s AGE .
FORMATION OF WOOD & BARK
WOOD
BARK
CORK
CORK
CAMBIUM
HEARTWOOD
PHLOEM
SAPWOOD
VASCULAR
CAMBIUM
Apply the Big Idea
• “Girdling” is a term that refers to removing the bark of a tree
in a complete ring around the trunk or a branch. Predict the
effect that girdling will have on a tree.
Girdling will eventually cause parts of the tree above the injury
to die. Because…
- Phloem vessels are cut, so no sugars/nutrients can travel up
- Photosynthesis occurring in the leaves will not be able to send
sugars to the roots for food
- Cork cambium will be gone and unable to replace bark which
prevents tree from losing water