1
2
4
3
5
Monocot stem c. s. (e.g. corn): 1. epidermis, 2. ground tissue (parenchyma), 3. primary
phloem, 4. primary xylem, 5. bundle sheath
Stems - Internal
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1
2
3
45
Monocot stem c. s. (e.g. corn): 1. epidermis, 2. ground tissue (parenchyma), 3. primary
phloem, 4. primary xylem, 5. bundle sheath
Stems - Internal
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1
2
6
6
3
7
4
4
5
Dicot stem tip l.s. (Coleus): 1. leaf primordium, 2. apical meristem, 3. protoderm (produces
epidermis), 4. ground meristem (produces pith, cortex) 5. procambium (produces primary
xylem, primary phloem), 6. petiole of new leaf, 7. bud primordium
Stems - Internal
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Young, dicot stem of alfalfa (Medicago sativa) c.s.: epidermis, cortex (parenchyma,
collenchyma, vascular bundle (primary phloem, cambium, primary xylem), pith ray, pith
Stems - Internal
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A
B
C
Herbaceous stem model: A = primary phloem; B = primary xylem; C= pith
Stems - Internal
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A
B
C
Herbaceous stem model: A = epidermis; B = cortex; C= pith ray
Stems - Internal
© Kwantlen.ca/Horticulture
Primary growth
Monocot
Dicot
secondary growth
Comparison of young monocot and herbaceous dicot stem cross-sections: monocots have
scattered vascular bundles and no secondary growth; dicots have a ring of separate
vascular bundles that “grow together” and eventually have secondary growth
Stems - Internal
© Kwantlen.ca/Horticulture
A
B
C
Woody stem model: A = secondary phloem; B= vascular cambium; C= pith
Stems - Internal
© Kwantlen.ca/Horticulture
A
B
C
Woody stem model: A = Outer bark or periderm (cork cells, cork cambium, phelloderm or
“live cork”; B = secondary phloem; C= secondary xylem (wood)
Stems - Internal
© Kwantlen.ca/Horticulture
vc
sx
px
p
Woody stem c.s.: cork cells, cork cambium, phelloderm, cortex, primary phloem, secondary
phloem, vascular cambium, secondary xylem, primary xylem, pith
Stems - Internal
© Kwantlen.ca/Horticulture
Hardwood - secondary xylem of Angiosperms (e.g. oak): vessels, tracheids, ray cells,
sclerenchyma fibers
Stems - Internal
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Softwood – secondary xylem of Gymnosperms (e.g. pine): tracheids, resin duct cells, ray
cells
Stems - Internal
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B
A
C
Leaf Gap model: A = abscission zone; B = leaf trace; C= leaf gap
Stems - Internal
© Kwantlen.ca/Horticulture