23 / 116
Starting to Grow
The signal for the embryo to start
growing is water. When water makes
it through the seed coat, the embryo
and the cotyledons soak it up. The
cotyledons swell. The embryo starts to
grow. The swelling cotyledons break
open the seed coat so that more water
can get in. This is called germination.
It is the first step in seed growth.
Soon the embryo starts to develop structures. The first structure to
come out of the seed is the
root
. The root usually comes first because the
root brings water and
nutrients
into the plant. Then the stem and first
leaves
come out. The stem gives the plant support as it grows.
The baby plant is now a seedling. The cotyledons stay attached to the
seedling. The seedling is using the food stored in the cotyledons to
grow. As soon as the seedling gets its first leaves, it can make its own food.
By that time the seedling has used most of the food in the cotyledons.
The germination process is the same for most seeds. The thing that
changes from seed to seed is how long it takes for the seed to germinate.
Some seeds can germinate right away. Other seeds take years to
germinate. Why the difference?
Germinated seeds
Bean seedlings
23