Chapter 8 Lesson 2 & 3: Plant Responses & Reproduction

Which of the following is not an environmental stimuli plants respond to?

• Light

• Wind

• Gravity

• Touch

Answer explanation

Plants respond to various environmental stimuli, including light, gravity, and touch. However, while wind can affect plants, it is not a direct stimulus they respond to in the same way as the other options.

A response that results in a plant growth toward or away from a stimulus.

• Tropism

• Auxins

• Stimuli

• Cytokininis

Answer explanation

Tropism refers to the growth response of plants toward or away from stimuli, such as light or gravity. This makes it the correct answer, as it directly describes the phenomenon of plant movement in response to environmental factors.

Which type of tropism is being described?

When touched, the leaves of a Mimosa pudica quickly fold up.

• Phototropism

• Hydrotropism

• Thigmotropism

• Gravitropism

Answer explanation

The rapid folding of Mimosa pudica leaves when touched is an example of thigmotropism, which is a plant's response to mechanical stimuli. This distinguishes it from other tropisms like phototropism (light) or gravitropism (gravity).

Which type of tropism is being described?

A sunflower will turn its head to faced the direction of the sun.

• Phototropism

• Hydrotropism

• Thigmotropism

• Gravitropism

Answer explanation

The sunflower's ability to turn towards the sun is an example of phototropism, which is the growth response of a plant to light. This behavior helps maximize light absorption for photosynthesis.

Which type of tropism is being described?

The stem of a plant grows upward and their roots grow downwards.

• Phototropism

• Hydrotropism

• Thigmotropism

• Gravitropism

Answer explanation

The described growth patterns of the stem upward and roots downward are due to gravitropism, which is the plant's response to gravity. Stems exhibit negative gravitropism (growing against gravity), while roots show positive gravitropism (growing with gravity).

Which type of tropism is being described?

The roots of a plant will grows towards an area in the soil with more water.

• Phototropism

• Hydrotropism

• Thigmotropism

• Gravitropism

Answer explanation

The roots growing towards an area with more water is an example of hydrotropism, which is the plant's response to moisture gradients in the soil. This distinguishes it from phototropism (light), thigmotropism (touch), and gravitropism (gravity).

Which type of tropism is being described?

Some plants flower in response to the amount of darkness they are exposed to.

• Phototropism

• Hydrotropism

• Photoperiodism

• Thigmotropism

Answer explanation

The question describes how some plants flower based on darkness exposure, which is a characteristic of photoperiodism. This term refers to the response of plants to the length of day and night, influencing flowering.

Plants that flower when exposed to less than 10 - 12 hours of darkness are called. . .

• Short-day plants

• Day-neutral plants

• Long-day plants

• Photoperiodism

Answer explanation

Plants that flower with less than 10-12 hours of darkness are known as short-day plants, not long-day plants. Long-day plants require more than 12 hours of light to flower.

Which type of plant hormone is being described?

Placing a ripe banana in a paper bag containing unripe avocados.

• Gibberelins

• Ethylene

• Auxin

• Cytokinins

Answer explanation

The ripe banana emits ethylene, a plant hormone that promotes ripening. Placing it with unripe avocados accelerates their ripening process due to ethylene's effects, making 'Ethylene' the correct answer.

Which type of plant hormone is being described?

Applying this to an outdoor plant to drastically increase the growth of its stem.

• Gibberllins

• Ethylene

• Auxin

• Cytokinins

Answer explanation

Gibberellins are plant hormones that promote stem elongation and growth. Applying gibberellins to an outdoor plant significantly increases its stem growth, making it the correct choice for this question.