Apical Meristems
Read as a group:
Recall that meristemic cells (the unspecialized cells that divide enabling the plant to grow) are
located a) near the tips or the roots and shoots, and b) in the growing parts of the shoot, just
below the outside layer of the stem of woody plants.
Apical meristems: are the undifferentiated cells at the tips of the plants root and shoot; cells
divide to make the plant grow longer
Roots: There are 4 distinct zones of the growing tip of a root.
1.
2.
3.
4.
The root cap (which is not growing)
The meristem region of cell division
The region of elongation
The region of maturation
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When meristems first divide in the tips if a root, many of the cells begin to elongate
This makes the root longer and pushes its way through the soil (they can actually become
10X longer)
As they elongate they begin to specialize as dermal, ground, or vascular tissue depending
on their location.
Once they are matured they cannot grow or divide anymore
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Shoots: The apical meristems in shoots are located as buds at various regions of a stem.
Location: 1. At the very tip of the stem allowing the plant to grow longer upwards
2. At the different points along the stem allowing the plant to grow side branches
These buds contain meristem cells that will mature into stem, leaf, and flower tissue.
Activity:
1. Colour the root tip into its 4 regions. Take note of the region and recognize what the cells
look like in this region?
2. Label the shoot system with the following: apical meristem bud, lateral bud, leaf, and
new leaf.
Apical Meristems – enables the plant to grow longer
Vascular tissue
maturation
The only cell division in a root takes place in
the apical meristem. Then the cells elongate,
then differentiate into the various types of
tissue (dermal, ground, or vascular) and
finally they mature where they will not
longer grow or divide.
Apical meristems occur at
the tips of the stem to allow
the plant to grow longer
upwards, and lateral buds
can also occur on the stem
allowing the plant to grow
side branches. The bud will
mature into stem, leaf, or
flower tissue.
Lateral Meristems
Read as a group:
Recall that meristemic cells (the unspecialized cells that divide enabling the plant to grow) are
located a) near the tips or the roots and shoots, and b) in the growing parts of the shoot, just
below the outside layer of the stem of woody plants.
Lateral meristems: are the undifferentiated cells under the bark in the stems and roots of woody
plants; that divide enabling the plant to grow wider
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Lateral meristems form 2 cylinders, one inside of the other, that run the full length of the
shoots and roots.
As the plant grows in diameter, the outer lateral meristem produces new dermal tissue
called cork to replace the old epidermal tissue
The inner lateral meristem produces new phloem tissue on its outer surface and new
xylem tissue towards its interior.
Activity:
1. Look at the following diagram of a cross section of a tree. Fill in the blanks of the
statements below with the following words:
- Xylem
- Increase
- Age
- Phloem
- Lifespan
- Cork
- Non-woody
- Diameter
- Root
2. Take a look at the pictures of the tree trucks. Estimate the age of the trees by counting the
inner xylem rings.
Lateral Meristems – enables a woody plant to grow wider
Cork
Outer lateral meristem
(cork cambium)
Phloem
Inner lateral meristem
(vascular meristem)
Xylem rings
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The ____________ and the __________ form the bark of the tree, whereas the
____________ form rings of the inner part of the tree
The xylem keeps accumulating and causes the tree trunk to _____________in
____________ year after year
We can read the _______ of a tree because each year it grows there is a noticeable ring of
new xylem
Many plants (______________ plants) do not contain lateral meristems thus they cannot
grow thicker than their original _______ size and so they remain quite small and have a
shorter _______________ (approx. 1 year)
Estimate the age of the tree:
Age ______
Age ______
Vegetative Reproduction and Mass Producing Plants
Read as a group:
Vegetative reproduction is the process in which a plant produces genetically identical offspring
from its roots or its shoots.
In other words, it is when a plant produces a clone of itself.
Example: Strawberry plants reproduce by sending out shoots called runners across the surface of
the soil. When the meristems in the tips contact the ground they begin to grow into shoots and a
new plant develops.
Example: A cluster of poplar trees are actually clones from a single parent. The cluster is
actually not a bunch of trees but one tree with a bunch of stems. We can tell this because in the
fall they change color at the exact same time!
This process has been very useful to farmers, gardeners, and agricultural scientists because can
literally take a plant, cut it up and clone that plant many times over.
Tissue Culture Propagation: a method of growing many identical offspring by obtaining
individual plant cells from one parent, growing these cells into calluses, and then whole plants
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Cells from certain plant roots are grown in containers with special chemicals that
reverts them back into undifferentiated cells which begin to divide (like meristem
cells)
As they divide they form a clump called a callus
These calluses can be separated over and over again to produce a number of plants
These plants are genetically identical to the original parent plant
Activity:
1. Match the pictures with the correct definition.
2. As a group come up with 3 reasons why it is helpful to humans to use tissue culture
propagation.
Vegetative Reproduction and Mass Producing Plants
____ Vegetative reproduction
____ Mass production of plants
____ Leaf cutting produced all these shoots
____ Runners from a plant
____ Clones
____ Callus
____ New plant from a callus
____ Potatoes cut form spouts that can become a new potato plant
3 Reasons Why we Take Advantage of Tissue Culture Vegetative Reproduction
1.
2.
3.
Vegetative reproduction is the process in which a plant produces genetically identical offspring from its
roots or its shoots. In other words, it is when a plant produces a clone of itself.
Tissue Culture Propagation: a method of growing many identical offspring by obtaining individual
plant cells from one parent, growing these cells into calluses, and then whole plants