Question 1

Which of the following best describes the process of thigmomorphogenesis in plants?

Accepted Answer

Adaptive changes in plant form due to mechanical disturbance, such as wind or touch.

Question 2

A plant is exposed to drought conditions. Which hormone is primarily responsible for inducing stomatal closure to reduce water loss?

Accepted Answer

Abscisic acid

Question 3

What is the main function of statoliths in plant cells?

Accepted Answer

They detect gravity, allowing roots and shoots to orient their growth.

Question 4

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

Accepted Answer

Auxin accumulates on the lower side of the root, inhibiting cell elongation and causing the root to bend downward.

Question 5

A plant leaf rapidly folds after being touched. Which process and cellular mechanism are primarily responsible for this response?

Accepted Answer

Thigmonasty; rapid loss of turgor pressure due to K$$^+$$ and sugar efflux

Question 6

During flooding, how do plants adapt to oxygen deprivation in their roots?

Accepted Answer

By producing ethylene, which induces apoptosis and forms air tubes for oxygen transport

Question 7

Salt stress in soil primarily affects plants by:

Accepted Answer

Decreasing the water potential ($$\Psi) of $$the soil, making water uptake more difficult

Question 8

Which of the following is a correct statement about heat-shock proteins in plants?

Accepted Answer

They guide protein folding and help prevent protein denaturation during heat stress.

Question 9

A plant is exposed to freezing temperatures. Which adaptation helps prevent cellular damage from ice crystal formation?

Accepted Answer

Synthesis of antifreeze proteins

Question 10

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

Accepted Answer

The epidermis and periderm (bark)

Question 11

Gene-for-gene recognition in plant immunity involves:

Accepted Answer

A plant R protein recognizing a pathogen avr gene product, triggering defense responses

Question 12

Which of the following is NOT a function of phytoalexins?

Accepted Answer

Guiding protein folding during heat stress

Question 13

Systemic acquired resistance (SAR) in plants is most closely associated with which signaling molecule?

Accepted Answer

Salicylic acid

Question 14

Which of the following is a secondary metabolite involved in plant defense against herbivores?

Accepted Answer

Alkaloids

Question 15

A tomato plant with blocked jasmonic acid signaling (OPRN3-RNAi) would most likely:

Accepted Answer

Show decreased resistance to insect herbivores

Question 16

Which of the following best describes the role of volatile organic compounds (VOCs) in plant defense?

Accepted Answer

They attract parasitoids and predators of herbivores, and warn nearby plants.

Question 17

A plant exposed to repeated mechanical disturbance (such as wind) is likely to:

Accepted Answer

Exhibit thigmomorphogenesis, resulting in shorter and sturdier growth.

Question 18

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

Accepted Answer

Formation of trichomes on leaf surfaces

Question 19

Which of the following best explains why plants alter their lipid composition in response to cold stress?

Accepted Answer

To increase the proportion of unsaturated fatty acids, maintaining membrane fluidity at low temperatures.

Question 20

A plant is attacked by a caterpillar. Which sequence of events best describes the induced defense response?

Accepted Answer

Mechanical damage → jasmonic acid signaling → transcriptional changes → emission of VOCs → attraction of parasitoid wasps

Plant Responses to Environmental Stimuli and Stress

Study Guide - Practice Questions