Plant Growth
Way too much information
for a single presentation…
Plant Growth Outline
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Indeterminate growth
Determinate growth
Plant Hormones
Shoot apical meristem (and shoot tip), hormones
Root apical meristem (and root tip), hormones
Lateral Buds / Nodes
Cambium ring/Secondary growth
Two types of growth
Indeterminate and Determinate
Indeterminate Growth
• Animals = maximum size
& shape
• Plants = no maximum
size or shape
• Able to keep growing all
their lives
• Limited by resources
Indeterminate Growth
• If injured, plants can
grow more:
– Branches
– Leaves
– Roots
• Being bigger means
being more
susceptible to:
– Disease
– Pests
– Weather & Gravity
Determinate Growth
• Maximum size and
shape
• Certain parts of the plant
have determinate
growth:
– Leaves
– Flowers
– Fruit
• Cannot heal/fix these
when injured
Indeterminate vs. Determinate
Growth
Hormones
All growth is influenced by hormones
Hormones Influence Growth
• Auxin
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Associated with (root) growth
Cell elongation
Keeps leaves from dropping
Apical meristem (not lateral buds)
Hormones Influence Growth
• Cytokinin
– Associated with (stem) growth
– Cell division
– Lateral bud growth
Hormones Influence Growth
• Ethylene
– Gas that encourages fruiting/ripening
Hormones Influence Growth
• Abscisic Acid
– Shoot dormancy
Hormones Influence Growth
• Gibberellic Acid
– Stem elongation and division
Meristems
The tips of the root and the shoot
Shoot Apical Meristem
• At the tip of the shoot
• Growing tip can turn into
any type of tissue
• Hormone-controlled
• Makes hormones that
keep lateral buds from
growing
Shoot Tip Anatomy
• Cell Division
• Elongation
• Differentiation
– Dermal tissue
– Ground tissue
– Vascular tissue
Getting plants to fill out…
Root Apical Meristem
• At the tip of the root
• Growing tip can turn into
any type of tissue
• Hormone-controlled
Root Tip Anatomy
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Root Cap (protection)
Cell Division
Elongation
Differentiation
– Dermal tissue
– Ground tissue
– Vascular tissue
Growth is Hormone Controlled
Growth is Hormone Controlled
Cytokinin
Auxin
• What’s in the
rooting powder we
use in the
greenhouse?
– Auxin
– Cytokinin
Growth is
Hormone-Controlled
Lateral Bud/Nodes
• Next to leaf
• Could become meristem
• Hormone-Controlled
Lateral Bud/Node
Secondary Growth
Plants getting wider
Secondary Growth
• Stems getting fatter
– Woody tissue
• Only some plants can do this!
Vascular Bundles
• Scattered in the stem
• In a ring in the stem
If the stem gets fatter…
• It needs more xylem and phloem to support the
new tissue
• Vascular Bundles in a RING only!
Vascular Cambium
Also called the Lateral Meristem
• Between the Xylem and Phloem
• Xylem is ALWAYS on the inside
• Phloem is ALWAYS on the outside
Secondary Growth
• Cambium produces more xylem on the inside
(DEAD thick walled-cells)
• More phloem on the outside (slightly alive)
• Tree bark is actually old, dead PHLOEM
• Neato!
Tree rings
• In the spring/summer cambium makes big cells
since it is growing fast
• In the fall cambium makes smaller cells since it
is growing slowly
• Change in cell size throughout time is seen as a
ring…
Tree rings
Size of Rings
• You can tell the climate of an area using tree
rings…
• “Good” years are really wide because the tree
grew fast in the spring and summer.
• When plants grow at a steady rate all year there
are NO TREE RINGS!
Plant Growth Outline
•
•
•
•
•
•
•
Indeterminate growth
Determinate growth
Plant Hormones
Shoot apical meristem (and shoot tip), hormones
Root apical meristem (and root tip), hormones
Lateral Buds / Nodes
Cambium ring/Secondary growth
The End