5.4.1 Control and Coordination

What is phototropism?

The response of a plant to light.

What is gravitropism (or geotropism)?

The response of a plant to gravity.

What does positive phototropism mean?

The plant grows towards the light source.

What is the role of auxin in shoots?

Auxin moves to the shaded side, stimulates cells to grow more, making the shoot bend towards light.

Why is positive phototropism beneficial?

It allows plants to receive more light, increasing photosynthesis rate.

What is negative gravitropism?

When shoots grow away from gravity because auxin stimulates growth on the lower side.

Why is negative gravitropism beneficial to shoots?

It helps shoots grow upwards, where light is stronger.

What is positive gravitropism?

When roots grow towards gravity because auxin is less on the lower side, so the upper side grows more.

Why is positive gravitropism beneficial to roots?

It allows roots to grow downwards into soil for water, minerals and stability.

How can you investigate phototropism in seedlings?

Place seedlings in a cardboard box with light from one side.

How can you investigate gravitropism in seedlings?

Attach seedlings in a petri dish to a wall to observe growth direction.

What is the role of gibberellins?

They stimulate seed germination.

What is the role of ethene?

It controls cell division and ripening of fruits.