Exercise 10:
Primary Growth
of Stem
Introduction
Stems play an integral part in the
growth of plants, acting as the link
between the roots and the rest of
the plant
2
Functions of the Stem
Supports the Leaves
Conducts Water and
Dissolved Mineral Salts
Upward
3
Functions of the Stem
Transport Food
Materials Downwards
Vegetative
Reproduction and
Storage
4
Objective
1.
Identify the
external and
internal parts of
the primary
tissues of the
stem
5
Objective
2.
Differentiate
the monocot
and dicot stem
and the
herbaceous
and young
woody stems
6
Objective
3.
Relate the parts
of the stems
with the
functions
7
Materials
Equipment, Plant Specimens, and
Prepared Slides Used in the
Laboratory Activity
8
Equipment
Microscope
9
Plant Specimens
Bambusa (Bamboo)
Coleus (Mayana)
Hibiscus (Gumamela)
Nerium (Adelfa)
10
Prepared Slides
 Coleus or Elodea Shoot
Tip







Zea mays (corn)
Commelina (alikbangon)
Helianthus sp.
Ranunculus sp.
Tilia sp.
Hibiscus sp.
Aristolochia sp
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Guide Questions
EXTERNAL PARTS OF THE STEM
12
External Parts of the Stem
Monocot
Herbaceous Dicot
Woody Dicot
13
External Parts of the Stem
Monocot
Herbaceous Dicot
Woody Dicot
14
External Parts of the Stem
Bases of
Comparison
Coleus
Nerium or
Hibiscus
Bamboo
Branches
present
present
present
Nodes
present
present
present
Internodes
present
present
present
Lenticels
absent
present
absent
Leaf Scars
present
present
present
Terminal Buds
present
present
present
Axillary Buds
present
present
present
green
brown
green
smooth and supple
to touch
rough/bumpy
smooth
Color
Texture
15
‘’
Can you differentiate a
monocot plant from a
dicot plant just by
looking at the stem?
How?
One main feature are
the lenticels present
only in mature dicot
stems.
16
‘’
What advantage would
herbaceous stems have
over woody stems?
Herbaceous stems
grow faster and have
photosynthetic stems.
17
‘’
What advantage would
woody stems have over
herbaceous stems?
Woody stems counteract gravity so they can
grow taller than
herbaceous plants.
18
‘’
What important
functions do nodes
have in a plant?
Nodes contain the buds
and leaves.
19
‘’
What is the function of
the lenticels? Do all
stems have lenticels?
Lenticels function for
gas exchange. Not all
stems have lenticels as
only mature dicot
stems have lenticels.
20
‘’
What develops at the
axils of leaves?
Bud primordium
develops at the axils of
leaves.
21
‘’
Are the internodes of
the plants you
examined of the same
length? Give possible
reasons for the
similarities or
differences in internode
lengths among the
plants that you
examined.
22
Guide Questions
SHOOT TIP
23
II. The Shoot Tip
▣ Coleus and Elodea shoot tip
24
‘’
Where would you find
older leaves on a stem,
near the tip or near the
lower part?
They are near the lower
parts of the stem.
25
‘’
Why are the tips of
some plants usually
used as vegetables (e.g.
kamote tops, kangkong
tops, etc.)? Why are the
lower parts not edible?
The newer parts are
edible while the lower
parts are not because
the lower parts are
older.
26
‘’
What feature in the
terminal bud make it
the most active part of
the stem?
It is mitotic with its
meristems that
continually produce
leaves as necessary
27
Guide Questions
PRIMARY TISSUES AND INTERNAL
STRUCTURE OF THE STEM
28
Primary Tissues and Internal Structures
Feature
Vascular bundle
arrangement
Vascular cambium
Monocot
Vascular bundles
are scattered
Herbaceous Dicot
Vascular bundles
tapered to the center
Young Woody
Dicot
Vascular bundles
arranged in a ring
Absent
Present
Present
Specific supporting
structures or tissues
Outer Cortex
(Collenchymal)
Outer Cortex
(Collenchymal)
Outer Cortex
(Collenchymal)
Filler tissues
Ground Tissue
Ground Tissue
Ground Tissue
Parenchymal Tissue
Parenchymal Tissue
Parenchymal Tissue
Storage tissues
29
Primary Tissues and Internal Structures
Epidermis
Ground Tissue
Vascular Bundle
Bundle Sheath
Xylem
Phloem
30
Primary Tissues and Internal Structures
▣ Monocot Stem (Zea mays)
31
Primary Tissues and Internal Structures
Epidermis
Cortex
Phloem
Vascular Cambium
Xylem
Pith
32
Primary Tissues and Internal Structures
▣ Herbaceous Young Dicot Stem (Tilia sp. or
Ranunculus sp.)
33
Primary Tissues and Internal Structures
Bundle Cap Fibers
Fascicular Cambium
Pith
Xylem
Interfascicular cambium
Phloem
Cortex
Epidermis
34
Primary Tissues and Internal Structures
▣ Herbaceous Young Dicot Stem (Aristolochia
sp.)
35
Guide Questions
TRICHOMES
36
Trichomes
▣ Glandular
37
Trichomes
▣ Scale
38
Trichomes
▣ Stellate
39
Trichomes
▣ Bristle
40
Trichomes
▣ Peltate
41
Trichomes
▣ Branched
42
Guide Questions
MODIFIED STEMS
43
Modified Stems
Cladophyll
Tendril
44
Modified Stems
Stolon
Tuber
45
Modified Stems
Bulb (Tunicate)
Bulb (Scaly)
46
Modified Stems
Rhizome
Corm
47
‘’
What makes
herbaceous plants
more valuable to
people as a food source
than woody plants?
Herbaceous plants
function better as a
food source since
woody plants are
heavily lignified.
48
‘’
Are axillary buds also
present in monocots?
Give proof of your
answer.
Yes as monocots also
produce lateral shoots
or branches which is
proof of axillary buds.
49
‘’
Is the formation of leaf
primordia and stem
tissues orderly or
random?
They are orderly.
50
Thanks!
Any questions?
51