Question 1

What are the sites of highest ethylene production in plants?

Accepted Answer

Ripening fruits are the primary sites of ethylene production in plants, as ethylene is a key hormone involved in the ripening process.

Question 2

Which of the following plant responses requires integration of auxin, cytokinin, and strigolactone?

Accepted Answer

Apical dominance, the phenomenon where the main, central stem of the plant grows more vigorously than the other side shoots, is regulated by a complex interaction of hormones including auxin, cytokinin, and strigolactone. Auxin promotes apical dominance, cytokinin promotes lateral bud growth (thus opposing auxin's effect), and strigolactones inhibit growth of lateral buds, reinforcing the effect of auxin.

Question 3

Which of the following is an evolutionary adaptation for a plant growing in darkness?

Accepted Answer

C

Question 4

The following steps occur during a plant's response to drought stress.
I. ABA accumulates in the leaves
II. stomata close
III. transpiration decreases
IV. guard cell potassium channels open
Which of the following places the steps in the correct sequence to represent the acquisition of drought tolerance in the plant?

Accepted Answer

ABA accumulates in the leaves (I), leading to the opening of guard cell potassium channels (IV), which causes stomata to close (II), and subsequently, transpiration decreases (III).

Question 5

Which of the following statements best summarizes the acid growth hypothesis in an actively growing shoot?

Accepted Answer

The acid growth hypothesis suggests that auxin (a plant hormone) stimulates proton pumps in the plasma membrane, not the tonoplast, to pump hydrogen ions (H+) into the cell wall. This acidification of the cell wall region lowers the pH, which activates expansins and other enzymes that break hydrogen bonds between cellulose fibers, making the cell walls more flexible and allowing for cell expansion.

Question 6

Which of the following can be involved in the mechanism of plant hormone function?
I. altering the expression of genes
II. modifying the permeability of the plasma membrane
III. modifying the structure of the nuclear envelope

Accepted Answer

Plant hormones can function by altering the expression of genes and modifying the permeability of the plasma membrane, but there is no direct evidence that they modify the structure of the nuclear envelope.

Question 7

In an experiment investigating phototropism, pieces of shoot apices were applied to small blocks of agar with light shining from one side only. The apices were either partly or completely divided in two with a barrier that also divided the blocks. The figure summarizes the results of the experiment. Numbers indicate the percent of auxin moving from the apex into the agar segment below it.  Which of the following hypotheses is best supported by the data?

Accepted Answer

The answer of In an experiment investigating phototropism, pieces of...

Question 8

You want to alter the shape of a growing plant, causing it to bend by applying auxin to one side of the stem. Application at which of the following positions, A, B, C, or D would produce the greatest bending?

Accepted Answer

The answer of You want to alter the shape of...

Question 9

Which of the following hormones primarily function(s) to regulate plant cell division?

Accepted Answer

Cytokinins are the hormones that primarily regulate plant cell division by promoting cytokinesis in plant roots and shoots.

Question 10

Which of the following describes a difference between hormonal regulation in plants compared to animals?

Accepted Answer

Plants do not have specific organs dedicated to hormone production like animals do. Instead, plant hormones can be produced in almost any part of a plant, including roots, stems, leaves, and fruits. This contrasts with animals, where hormones are typically produced in specialized glands.

Question 11

Which of the following plant parts elongate in response to etiolation during seedling germination?
I. Roots
II. Hypocotyl
III. Internodes
IV. Leaves

Accepted Answer

Etiolation is a process in plants grown in partial or complete absence of light, characterized by long, weak stems, and smaller leaves due to elongation of cells. This phenomenon is most notably observed in the hypcotyl and internodes, which elongate to push the seedling upwards towards the light.

Question 12

What are the primary sites of auxin (IAA) production in plants?

Accepted Answer

Auxin (IAA) is primarily produced in the shoot apical meristem and young leaves, where it plays a crucial role in regulating plant growth and development by promoting cell elongation.

Question 13

Corn seeds were germinated on two petri dishes of agar containing a colored pH indicator. The dishes were placed on edge with the seedling oriented either vertically (A) or horizontally (B). After 24-hours growth, the plates appeared as in C and D. Dark areas in D indicate lower pH.  Which of the following statements is supported using the data?

Accepted Answer

The answer of Corn seeds were germinated on two petri...

Question 14

Which of the following is the correct sequence of events that takes place during the plant responses to internal and external signals?

Accepted Answer

The correct sequence of events in plant responses to signals is reception (where the plant detects a stimulus), transduction (the process of converting the stimulus into a form that can bring about a response), and response (the plant's reaction to the stimulus).

Question 15

Which of the following detects light during de-etiolation (greening) of a tomato plant?

Accepted Answer

Phytochromes are the photoreceptors in plants that detect light and initiate the de-etiolation (greening) process, leading to changes in plant growth and development in response to light.

Question 16

Which one of the following hormones stimulate(s) rapid stem elongation (straight growth) and pollen tube growth?

Accepted Answer

Gibberellins are known to stimulate rapid stem elongation and pollen tube growth, among other functions. They play a crucial role in various aspects of plant growth and development, including seed germination, stem elongation, and flowering.

Question 17

Auxins frequently interact with other plant hormones to cause a particular process. Which of the following processes is attributed ONLY to auxin?

Accepted Answer

Phototropism, the growth of a plant in response to a light stimulus, is attributed solely to auxin. Auxin is distributed unevenly in a plant when exposed to light, causing the plant to grow towards the light. This process does not directly involve other hormones.

Question 18

Unlike animal hormones, plant hormones can have multiple functions depending on which of the following factors?
I. site of action
II. concentration
III. developmental stage
IV. chronological age

Accepted Answer

Plant hormones can have multiple functions depending on the site of action, concentration, and developmental stage. These factors influence how the hormones interact with plant tissues and trigger different responses. Chronological age is not typically a direct factor in determining hormone function.

Question 19

You have a small tree in your yard that is the height that you want it, but does not have as many branches as you want. Which of the following pruning strategies will trigger increased branching?

Accepted Answer

Cutting off the tips of the main shoots (apical dominance) encourages lateral growth because it removes the dominant growth point which suppresses the growth of side branches. This allows the buds on the sides of the branches to grow and form new branches.

Question 20

Four physiological events that occur during de-etiolation (greening) of plants are listed below.
I. detection of light signal
II. activation of phytochrome
III. activation of specific protein kinase1
IV. formation of de-etiolation response protein
Which of the following lists these events in the correct order?

Accepted Answer

The correct sequence for de-etiolation in plants starts with the detection of light signal (I), followed by the activation of phytochrome (II), which then activates specific protein kinases (III), leading to the formation of de-etiolation response proteins (IV).

Quiz 39: Plant Signals and Behavior