Question 1

Which plant hormone is primarily responsible for inducing stomatal closure during drought stress, and what is the physiological effect of this response?

Accepted Answer

Abscisic acid; reduces water loss by closing stomata

Question 2

A plant is exposed to high salt concentrations in the soil. Which of the following best describes the plant's cellular response to maintain water uptake?

Accepted Answer

Increase the production of solutes in root cells to decrease water potential ($$\Psi)$$

Question 3

Which of the following best explains why roots exhibit positive gravitropism while shoots exhibit negative gravitropism?

Accepted Answer

Auxin accumulates on the lower side of roots, inhibiting cell elongation, while in shoots, auxin promotes elongation on the lower side

Question 4

A plant growing in a windy environment develops a shorter, thicker stem. This is an example of:

Accepted Answer

Thigmomorphogenesis

Question 5

Which of the following is a rapid, touch-induced response in plants such as Mimosa pudica, and what is the underlying mechanism?

Accepted Answer

Thigmonasty; rapid loss of turgor pressure in pulvini due to ion flux

Question 6

During flooding, plant roots experience oxygen deprivation. What hormone is produced in response, and what is its effect?

Accepted Answer

Ethylene; induces apoptosis to form air tubes

Question 7

Which of the following best describes the function of heat-shock proteins in plants under heat stress?

Accepted Answer

They guide protein folding and prevent denaturation

Question 8

How do plants compensate for decreased membrane fluidity during cold stress?

Accepted Answer

By increasing the proportion of unsaturated fatty acids in membranes

Question 9

A plant is infected by a pathogen but does not develop disease symptoms because it recognizes the pathogen's avirulence (avr) gene product. What is the name of this recognition system, and what is the typical downstream response?

Accepted Answer

Gene-for-gene recognition; hypersensitive response and systemic acquired resistance

Question 10

Which of the following is NOT a typical function of phytoalexins produced during the hypersensitive response?

Accepted Answer

Enhance pathogen reproduction

Question 11

Systemic acquired resistance (SAR) in plants is most closely associated with which signaling molecule, and what is its effect?

Accepted Answer

Salicylic acid; triggers long-lasting, systemic defense gene expression

Question 12

Which of the following is a primary metabolite, and which is a secondary metabolite involved in plant defense?

Accepted Answer

Amino acid; terpene

Question 13

A tomato plant is genetically modified to block jasmonic acid signaling (OPRN3-RNAi). What is the most likely consequence when the plant is attacked by insect herbivores?

Accepted Answer

Decreased resistance to insects due to impaired induced defense responses

Question 14

Which of the following is a mechanical defense against insect herbivory in plants?

Accepted Answer

Trichomes on leaf surfaces

Question 15

How do volatile organic compounds (VOCs) released by plants in response to herbivory benefit the plant?

Accepted Answer

They attract parasitoids and predators of the herbivores

Question 16

Which of the following best describes the process of thigmotropism?

Accepted Answer

Growth in response to touch, such as vines coiling around a support

Question 17

A plant cell loses turgor pressure rapidly after mechanical stimulation. Which ions and molecules are primarily involved in this process?

Accepted Answer

Unloading of $$\mathrm{K^+}$$ and sugars into the apoplast, followed by water loss

Question 18

Which of the following is the first line of defense against plant pathogens?

Accepted Answer

Epidermis and periderm (bark)

Question 19

What is the main function of antifreeze proteins in plants exposed to freezing temperatures?

Accepted Answer

Prevent the growth of ice crystals in cell walls and intercellular spaces

Question 20

Which of the following best explains why plants increase their root:shoot ratio during drought stress?

Accepted Answer

To enhance water uptake by allocating more resources to root growth

Plant Responses to Environmental Stimuli and Stress

Study Guide - Practice Questions

Study Guide - Flashcards