Meristems and plant structure

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Meristems and plant structure
The plant body
Tissue systems
Meristems
Stems
Roots
Secondary thickening
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The plant body
leaf
A tomato plant
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Tissues
Tissues usually have cells that are specialized
for particular functions
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There is continuity of tissue systems through the
plant

Cells conduct water and nutrients and products of
photosynthesis
Cells protect the plant
The body of the plant. Tissues with different
functions ee.g., storage, support
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Function of apical meristems
Shoot apical meristem
activity at meristems
Actively dividing cells near the dome-shaped tip
new cells elongate and start to differentiate
into primary tissues
The apical meristems descendants divide, grow and
differentiate to form Protoderm
Ground meristem Procambium
new cells elongate and start to differentiate
into primary tissues
activity at meristems
Root apical meristem
Root cap
Fig. 29.4 p501
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Meristems- Tissues
Immature leaf
shoot apical meristem
procambrium
ground meristem
procambrium
protoderm
Fig. 29.11, p. 504
Meristems
Tissues
primary xylem
primary pholem
procambrium
cortex
pith
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What does a meristem look like?
Coleus
Apical meristem
Transverse section through the apical meristem
and newly forming leaves
Longitudinal section through the apical meristem
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Scanning electron microscope picture
Scanning electron microscope picture of
Myriophyllum apical meristem
The apical dome is usually convex or flat, as in
this example, and its surface is smooth.
Developing leaves cover the apex
 
Most recently budded leaves
Water-milfoil
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Coleus
Axilliary bud meristem
The axilliary meristem may develop into a
foliated branch.
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Do roots grow differently to shoots?
What is their problem?
What may it affect?
Is anything easier for roots rather than shoots?
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Root meristem and structure
Roots must force their way through the soil
Protection of the apical mersitem
Delayed initiation of the lateral meristems (not
shown in diagram)
Different requirements for support and water
collection and distribution
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Zea mays root apex
Zea mays root apex showing the junction between
root apex and the root cap
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Lateral root development in Zea mays
A meristem develops from parenchyma and the
lateral root grows out through the cortex
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Which is the most important function of a tree
trunk
support of branches and foliage,
conducting water, nutrients and sugars?
How might you find out?
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Stem thickening
Lateral meristems
Two lateral meristems in older stems and roots of
woody plants produce secondary growth that
results in an increase in diameter (whereas
apical meristems result in an increase in length).
thickening
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Secondary growth
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Cell divisions of the cambium
division
division
Fig. 29.22, p. 511
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Cells of vascular tissue
Fig. 29.8, p. 502
PHLOEM SIEVE TUBE
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Transverse section of Quercus rubra wood
vessel
EARLY WOOD
LATE WOOD
Fig. 29.25, p. 513
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Taking sections through a stem
Fig. 29.3, p. 501