IAA and Plant Tropisms

This tutorial on A-level biology covers the concepts of taxes, kinesis, and tropisms. It begins by defining stimulus, taxes, and kinesis, explaining how organisms respond to stimuli. The tutorial then delves into tropisms, focusing on gravitropism and phototropism, and how plants respond to stimuli using indole acetic acid (IAA). The role of IAA in plant growth and response is discussed, along with evidence supporting its involvement in tropism. The tutorial concludes with a recap of the key points covered.

What is the primary focus of this tutorial?

• A-Level Biology

• A-Level Physics

• A-Level Mathematics

• A-Level Chemistry

How is a taxis different from a kinesis?

• Taxis is non-directional, kinesis is directional

• Taxis is directional, kinesis is non-directional

• Both are directional

• Both are non-directional

Which of the following best describes a stimulus?

• A type of plant hormone

• A growth response in plants

• A change in the internal or external environment

• A constant environmental condition

What is positive phototropism?

• Growth away from light

• Growth towards light

• Growth away from gravity

• Growth towards gravity

Which type of tropism involves growth in response to gravity?

• Thigmotropism

• Phototropism

• Hydrotropism

• Gravitropism

What role does indole acetic acid (IAA) play in plant growth?

• It stimulates growth in shoots and inhibits growth in roots

• It inhibits growth in shoots

• It stimulates growth in roots

• It has no effect on plant growth

How does IAA affect phototropism?

• IAA moves to the sunny side of the plant

• IAA moves to the shaded side of the plant

• IAA is evenly distributed in the plant

• IAA moves to the root tips

What happens when the shoot tip is removed or covered?

• Tropism is prevented

• Tropism is enhanced

• IAA concentration increases

• IAA concentration decreases

What evidence supports the role of IAA in tropism?

• Preventing IAA movement inhibits tropism

• IAA is not involved in tropism

• IAA is found in the root tips

• IAA movement is not necessary for tropism

What is the main chemical involved in plant tropisms discussed in the tutorial?

• Indole Acetic Acid (IAA)

• Cytokinin

• Ethylene

• Gibberellin