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

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2

7

4

1

3

5 4

6 6

Monocot stem c. s. (e.g. corn): 1. epidermis, 2. ground tissue (parenchyma), 3. primary

phloem, 4. primary xylem, 5. bundle sheath

1 2

3 4

5

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Corn stem model: 1. epidermis, 2. ground tissue (parenchyma), 3. primary phloem, 4.

primary xylem, 5. bundle sheath

1

2 3 4 5

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Corn stem model: 1. epidermis, 2. ground tissue (parenchyma), 3. primary phloem, 4.

primary xylem, 5. bundle sheath

1

2

3

4

5

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Young, dicot stem of alfalfa (Medicago sativa) c.s.:

epidermis

cortex:

- collenchyma

- parenchyma

vascular bundle:

- primary phloem

- cambium

- primary xylem

pith ray

pith

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Herbaceous stem model – dicot - a few centimeters below the growing point Stems - Internal © KPU.ca/Hort

epidermis

cortex:

- collenchyma

- parenchyma

vascular bundle:

- primary phloem:

(sclerenchyma)

(sieve tubes)

- cambium

- primary xylem

pith ray

pith

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 © KPU.ca/Hort

Monocot Dicot

Primary growth

secondary growth

Woody stem model

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Outer bark or periderm

(cork cells, cork cambium,

phelloderm or “live cork”)

secondary

phloem

secondary xylem (wood)

primary

xylem

pith

vascular cambium

Woody stem c.s. (e.g. Tilia): cork cells, cork cambium, phelloderm, cortex, primary phloem,

secondary phloem (sp), vascular cambium (vc), secondary xylem (sx), primary xylem (px), pith (p) Stems - Internal © KPU.ca/Hort

vc

sx

px

p

sp

Hardwood - secondary xylem of a dicot (e.g. oak): vessels (v), tracheids (t), ray cells (r),

sclerenchyma fibers (s).

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r

v

v

v

t

r

t

Softwood – secondary xylem of a conifer (e.g. pine): tracheids (t), resin duct cells (c), ray cells (r)

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t t

t

r

r