Question 1

Which of the following best describes the process of signal transduction in plant cells?

Accepted Answer

The conversion of a sensory signal into a cellular response via a phosphorylation cascade and second messengers.

Question 2

A plant is exposed to blue light. Which of the following is the correct sequence of events that leads to the opening of stomata?

Accepted Answer

Phototropin is activated, the proton pump builds up an electrochemical gradient, K+ and Cl- enter, water follows by osmosis, and the cells swell, opening the pores.

Question 3

Which hormone is primarily responsible for closing stomata during drought stress, and what is its main effect?

Accepted Answer

Abscisic acid; closes stomata to reduce water loss.

Question 4

A seedling grown in the dark exhibits elongated stems and small, pale leaves. This phenomenon is best explained by which process?

Accepted Answer

Etiolation

Question 5

Which of the following best explains how statoliths contribute to gravitropism in plant roots?

Accepted Answer

Statoliths settle at the bottom of the cell, putting pressure on the membrane and creating an auxin gradient that directs root growth.

Question 6

A plant is exposed to red light followed by far-red light. What is the likely effect on seed germination, and why?

Accepted Answer

Germination is inhibited because far-red light converts phytochrome back to its inactive form.

Question 7

Which of the following best describes the role of jasmonic acid (JA) in plant defense?

Accepted Answer

JA stimulates the production of proteinase inhibitors that block digestive enzymes in herbivores.

Question 8

A researcher exposes a plant to wind and observes that it grows shorter and sturdier. Which response is being demonstrated?

Accepted Answer

Thigmomorphogenesis

Question 9

Which of the following is a correct statement about systemic acquired resistance (SAR) in plants?

Accepted Answer

SAR involves the production of salicylic acid, which signals uninfected tissues to activate defense genes.

Question 10

Which of the following best explains the difference between long-day and short-day plants in terms of photoperiodism?

Accepted Answer

Long-day plants flower when nights are shorter than a critical length; short-day plants flower when nights are longer.

Question 11

A mutation in the gene encoding the FT protein (Florigen) would most likely affect which plant process?

Accepted Answer

Flowering time in response to photoperiod

Question 12

Which of the following is an example of a plant's mechanical barrier against herbivores?

Accepted Answer

Thick cuticle or thorns

Question 13

Which hormone is most directly involved in apical dominance, and what is its effect?

Accepted Answer

Auxin; inhibits the growth of lateral buds

Question 14

A plant is attacked by a pathogen and rapidly produces salicylic acid. What is the most likely outcome?

Accepted Answer

The plant will activate systemic acquired resistance, protecting uninfected tissues.

Question 15

Which of the following best describes the process of thigmonasty?

Accepted Answer

Non-directional, rapid movement in response to touch

Question 16

A plant is exposed to a herbivore attack. Which of the following is a likely sequence of events in the plant's defense response?

Accepted Answer

Production of jasmonic acid, activation of proteinase inhibitors, and disruption of herbivore digestion

Question 17

Which of the following best explains the role of second messengers in plant signal transduction?

Accepted Answer

They relay and amplify the signal from the receptor to target molecules inside the cell.

Question 18

A plant's leaves close rapidly when touched. Which process is responsible for this movement, and what is the underlying mechanism?

Accepted Answer

Thigmonasty; rapid, non-directional movement due to changes in turgor pressure

Question 19

Which of the following best describes the function of proteinase inhibitors in plant defense?

Accepted Answer

They block the digestive enzymes of herbivores, causing the herbivores to become sick.

Plant Responses to Environmental Stimuli and Defense Mechanisms

Study Guide - Practice Questions

Study Guide - Flashcards