Download From Seed to Plant and Back 15-18

LESSON 5
W I S C O N S I N FA S T P L A N T S : B E G I N N I N G
THE
CYCLE
From Seed to
Adult Plant—and Back
These tiny Wisconsin Fast Plants seeds look rather insignificant compared to this bean
seed. But the plants that result from each type of seed are quite impressive, not to
mention nutritious.
Take a look at some Fast Plants seeds. They are
so tiny! They’re hard and appear to be dry. In
fact, they don’t even look like they are alive.
How does one of these small seeds turn into a
plant?
The process by which a seed becomes a plant
is called “germination.” Because germination
normally takes place underground, we do not
see it happen. All we see is the exciting result—
a tiny green plant emerging from the soil.
But suppose you had x-ray vision and could
follow each step of what happens underneath
the soil as a seed germinates. Here is what you
would see.
Right after planting, a bean seed would look
pretty much like it did before you placed it in
the soil. That’s because the seed is in a dor-
mant—or inactive—stage. Protected by its
tough seed coat, the seed can withstand
extremely hot and cold temperatures. Some
varieties of seeds can remain dormant for years.
A dormant seed may look lifeless, but inside,
it’s a different story. Inside the seed is an
embryo, which contains the tiny beginnings of a
root, a stem, and leaves. These will become the
major parts of the mature plant. An important
food-storing tissue called “endosperm” surrounds the embryo. Also contained in the seed
are one or more seed leaves, called “cotyledons.” The seeds of some plants only have one
cotyledon. These plants are called “monocotyledons,” or monocots for short. Other plants,
whose seeds contain two cotyledons, are called
“dicotyledons,” or dicots.
(continued)
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LESSON 5
W I S C O N S I N FA S T P L A N T S : B E G I N N I N G
Monocot seeds, which include
cereal grains, wheat, rice, and
corn, use energy from the
endosperm to nourish the developing embryo and germinating
seedling. Their cotyledon never
emerges from the soil. Dicot
seeds, such as bean and Fast
Plants seeds, transfer energy from
the endosperm to the cotyledons.
These cotyledons emerge from
the soil with the stem and continue to provide energy for the
developing plant.
After the bean seed has been
underground for a while, it
begins to absorb water and gets
larger. This happens faster when
the ground is warm.
Finally, the process of germination begins. A root emerges
from the seed. This root, called
the “primary root,” grows downward. It forms an anchor for the
developing plant. Tiny root hairs
and secondary roots form. Root
hairs are microscopic, fingerlike
extensions of the outer cells of
the roots that give the root more
surface area through which
water and minerals may enter
the plant.
Meanwhile, there is further
activity in the seed. Water,
which comes in through the root
hairs, causes the tightly packed
cells in the tiny young stem to
elongate. This causes the stem to
push upward. The cotyledons,
which are at the top of the stem,
are dragged upward through the
soil until they poke through its
surface. As the seed leaves sense
light, they expand.
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Leaves
Embryo
Seed coat
Cotyledons
(seed leaves)
Notice the seed coat, cotyledons, and embryo of this bean seed.
No matter what position the seed is
in, the roots will still grow downward.
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In bean plants, the cotyledons provide the
energy for germination and emergence from the
soil. As soon as the true leaves form and begin
to function, the cotyledons wither and die. In
Fast Plants, the cotyledons also supply energy
for germination and emergence, but upon emergence, they expand, turn green, and gather
energy from the sun for further growth until
true leaves form to take on that role.
As the bean plant grows, it develops more
leaves and its root system matures. The plant
now is able to get the nutrients it needs from
the soil, water, and air. It can also manufacture
its own food in its leaves in a process called
photosynthesis.
The plant eventually matures and flowers.
The flowers are pollinated, fertilization occurs,
and seeds develop. As the flowers wither, a fruit
develops. The fruit provides a protective covering, which supports the development of the
seeds, and aids in their dispersal. When these
fruits decay, their seeds are left behind. Many
are eaten by animals; some mold. But others
survive, and given proper conditions, will germinate and grow—and the life cycle begins
again. !
W I S C O N S I N FA S T P L A N T S : B E G I N N I N G
THE
CYCLE
Three stages in the development of a young bean plant
© 1998 WILLY A. VERHEULPEN
LESSON 5
If you plant a seed and it does
not germinate, what could be
the reason? Sometimes, when
the soil is over-watered, the
seed does not get enough
oxygen. Occasionally, a seed
doesn’t germinate because it
is too cold or it doesn’t get
enough water. More often than
not, though, if a seed does
not germinate, a fungus is the
culprit, as you can see in this
photograph.
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LESSON 5
W I S C O N S I N FA S T P L A N T S : B E G I N N I N G
THE
CYCLE
The bean plant is looking more like an adult
each day.
Soon, the seeds will fall from the ripened seed pods and the cycle
will begin again.
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LESSON 5
W I S C O N S I N FA S T P L A N T S : B E G I N N I N G
THE
CYCLE
Table 5.1 Wisconsin Fast Plants Maintenance Chart
Directions This table gives directions for tasks that your group must perform during the development of your Fast Plants in addition to ensuring that the plants receive a constant supply of light
and nutrient solution.
Day 1
Sow Fast Plants
seeds.
2
3
4
Plants should
have sprouted.
If not, start over.
5
6
7
Thin growing
system to six
plants.
8
9
Flower buds
begin to appear.
10
11
12
13
Begin
pollinating Fast
Plants flowers.
14
Continue
pollinating
flowers.
15
Continue
pollinating
flowers.
16
Continue
pollinating
flowers.
17
Last day for
pollinating
flowers. Cut off
unopened buds.
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Remove nutrient
solution from
reservoirs.
36
37
38
39
40
Harvest your
seeds. Set
them up for
germination.
41
42
43
Observe the
stem and leaf
color of the
growing sprouts.
44
45
46
47
48
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