Chapter 32: Plant Responses

What are the main stimuli that affect animal behavior?

Loud noise, Hunger, Pain

List some common animal responses to stimuli.

Movement, Production of Enzymes, Hormones and Feeding

What stimuli affect plant responses?

Light, Gravity, Water

What are some common plant responses to stimuli?

Growth, Flowering, Fruit Formation

What is required for responses in both plants and animals?

A chemical or hormonal system.

What additional systems do animals have for response?

A nerve and sense organ system, and a method of movement.

What role does light play in plant growth?

Provides energy for photosynthesis and is needed for chlorophyll production.

How does day length affect plants?

It plays a role in causing plants to flower and influences fruit and seed formation, dormancy, and germination.

What is phototropism?

A change in growth of a plant in response to light, usually from one direction.

Define geotropism.

Change in growth of a plant in response to gravity.

What are auxins?

Growth promoters made in shoot tips, young leaves, and seeds that stimulate stem elongation, root growth, and fruit development.

What happens when the apical bud of a plant is intact?

Auxin produced in the tip inhibits lateral buds and side branching.

What is the effect of IAA on roots at low and high concentrations?

At low concentrations, IAA promotes root growth; at high concentrations, it promotes stem growth.

Explain the mechanism of phototropism.

IAA produced in meristems diffuses to the shaded side of a stem, causing cells to elongate and the stem bends towards light.

What is ethene and its primary function?

A growth inhibitor gas that ripens fruits and stimulates leaves to fall in autumn.

What do heat-shock proteins do in plants?

They help maintain the shape of other proteins when temperatures rise above 40°C.

What are phytoalexins?

Stress proteins produced by plants in response to microorganisms that damage the pathogen and stimulate local plant defenses.