): 1. leaf primordium, 2. apical meristem, 3. protoderm ... - internal.pdfcomparison of young...

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 © KPU.ca/Hort

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

Stems - Internal © KPU.ca/Hort

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)

Stems - Internal © KPU.ca/Hort

t t

t

r

r