Gibberellins and cytokinins

The idea

Gibberellins, like auxins, help in the growth of the stem; cytokinins promote cell division and are present in greater concentration in areas of rapid cell division, such as fruits and seeds.

Busy places

In a growing fruit or seed, cells are dividing quickly. Many new cells are being made.

Which hormone do you think is found in greater amounts where cells divide rapidly?

• Cytokinins
• Gibberellins
• Abscisic acid

Two growth hormones

Sort each fact under the right hormone.

Growth in two ways

Gibberellins help the stem grow, as auxins do. Cytokinins help by making cells divide, so they are plentiful where cells divide fast.

Gibberellins, like auxins, help in the growth of the stem. Cytokinins promote cell division and are present in greater concentration in areas of rapid cell division, such as fruits and seeds.

Notes

Gibberellins, like auxins, help in the growth of the stem; cytokinins promote cell division and are in greater concentration in areas of rapid cell division, such as fruits and seeds.

Check yourself

Which hormone, like auxin, helps in the growth of the stem?

What do cytokinins promote?

Where are cytokinins found in greater concentration?

• Cytokinins. Cytokinins promote cell division.
• Gibberellins — correct. Yes!
• Abscisic acid. Abscisic acid inhibits growth.
• Wilting of leaves. Wilting is among the effects of abscisic acid.
• Bending of roots away from light. Roots bend away from light in phototropism. Cytokinins promote cell division.
• Cell division — correct. Yes!
• In areas of rapid cell division, such as fruits and seeds — correct. Yes!
• Only at the shoot tip, where auxin is made. The book says cytokinins are in greater concentration in areas of rapid cell division, such as fruits and seeds.
• In leaves that are wilting. Wilting is an effect of abscisic acid. Cytokinins are plentiful where cells divide rapidly.