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.