Download Seed Emergence and Turgor Pressure

Seed Emergence and
Turgor Pressure
How plants overcome forces to grow.
Seed Emergence
• What is it?
– It is the process of plants emerging from the seed
and out of the ground.
Click on picture for video.
Forces
• Plants must overcome many forces to grow.
– How must they overcome gravity?
– How must they overcome friction?
Gravity
• Plants know how to grow based one many
things, one is gravity.
• The shoots grow up against gravity, or
negative geotropism
• The roots grow down towards the pull of
gravity, or positive geotropism
Friction
• As the seed emerged from the soil, friction pulls
against the seed as it passes by.
• The plant has to keep pushing to emerge from
the soil.
• The cotyledon will protect the new leaves as they
push from the soil as well as provide nutrients.
• If the plant does not have a cotyledon it will have
the leaves wrapped tightly around each other,
this provides additional protection and helps
reduce friction.
Forces
• See if you can identify the forces in this video.
• Also, once the plant has emerged see if you
can something happen to the leaves.
Turgor Pressure
• This is what allows plants to wilt
Turgor Pressure
• Plants have a large central vacuole in the
middle of the cell that holds water
– This is similar to a large water balloon
Large central vacuole
Turgor Pressure
• The large central vacuole can hold different
amounts of water, it can be full or empty
• The amount of water in the vacuole depends
on the amount of water the plant has gotten.
• The vacuole helps to hold the cell up
– When it is empty the cell will not be stiff and not
stand up straight.
Turgor Pressure
• If the cell cannot stand up it will be bend to
one side or the other allowing the plant to
wilt.
Click on picture for video.