Question 1

Auxin is the only plant hormone known to be transported in a polar manner.

Accepted Answer

Auxin is unique among plant hormones because it is transported directionally from cell to cell, a process known as polar auxin transport.

Question 2

In roots, a substance transported in a basipetal direction is transported toward the root tip.

Accepted Answer

In roots, basipetal transport refers to movement toward the base or away from the root tip, typically toward the stem.

Question 3

Recent evidence indicates that auxin does not directly inhibit the growth of lateral buds.

Accepted Answer

Auxin primarily promotes apical dominance by inhibiting lateral bud growth indirectly through the synthesis of other hormones like strigolactones and cytokinins.

Question 4

Which of the following statements about second messengers is FALSE?

Accepted Answer

Protein kinase is not a second messenger; it is an enzyme that is activated by second messengers to phosphorylate target proteins.

Question 5

The weed killer 2,4-D is a synthetic cytokinin.

Accepted Answer

2,4-D is a synthetic auxin, not a cytokinin. Cytokinins are a different class of plant hormones.

Question 6

Gibberellins promote fruit development in some species in which auxin does not.

Accepted Answer

Gibberellins can promote fruit development in certain plant species where auxin alone is not effective, as they can stimulate cell division and elongation, leading to fruit growth.

Question 7

Application of cytokinin inhibits the growth of lateral buds.

Accepted Answer

Cytokinins promote the growth of lateral buds by stimulating cell division and overcoming apical dominance.

Question 8

The transport of auxin can be nonpolar as well as polar.

Accepted Answer

Auxin transport can be both polar, moving in a specific direction, and nonpolar, moving in various directions, depending on the plant's needs and environmental conditions.

Question 9

One of the principal roles of abscisic acid is in leaf, flower, and fruit abscission.

Accepted Answer

Abscisic acid primarily regulates plant stress responses and seed dormancy, not abscission. Ethylene is the hormone mainly responsible for abscission.

Question 10

Mutants of Arabidopsis that lack brassinosteroids have leaves that are smaller and have fewer cells than the wild-type.

Accepted Answer

Brassinosteroids are plant hormones that promote cell expansion and division. Mutants lacking these hormones exhibit reduced growth, resulting in smaller leaves with fewer cells compared to the wild-type.

Question 11

In climacteric fruits, there is a large increase in cellular respiration during ripening.

Accepted Answer

Climacteric fruits experience a significant rise in ethylene production and respiration rate during ripening, which is a characteristic feature of their ripening process.

Question 12

Cytokinins are synthesized in roots and transported in the xylem to other parts of the plant.

Accepted Answer

Cytokinins are primarily synthesized in the roots and then transported through the xylem to other parts of the plant where they promote cell division and growth.

Question 13

Rice plants grow rapidly and become spindly due to the presence of gibberellic acid produced by a fungus.

Accepted Answer

Gibberellic acid is a plant hormone that promotes growth and elongation of cells, and it can be produced by certain fungi, leading to rapid and spindly growth in rice plants.

Question 14

In the ABA-induced closing of stomata, the following ion fluxes occur across guard cell plasma membranes: first calcium ions flow ______, then anions flow ______, and finally potassium ions flow ______.

Accepted Answer

In the ABA-induced closing of stomata, calcium ions flow into the guard cells, triggering the release of anions out of the cells, followed by the efflux of potassium ions, leading to stomatal closure.

Question 15

An excised leaf floated in a kinetin solution will remain green longer than a leaf floated in water.

Accepted Answer

Kinetin is a type of cytokinin, a plant hormone that promotes cell division and delays senescence (aging) in leaves, helping them remain green longer compared to leaves in water.

Question 16

Salicylic acid regulates thermogenesis in members of the arum family.

Accepted Answer

Salicylic acid is known to play a role in regulating thermogenesis in some plants, including members of the arum family, by influencing the metabolic processes that generate heat.

Question 17

Plant hormones usually act alone and only occasionally "cross-talk."

Accepted Answer

Plant hormones often interact with each other in a process known as "cross-talk," which allows them to coordinate complex responses to environmental stimuli and developmental processes.

Question 18

Jasmonic acid has a structure similar to aspirin.

Accepted Answer

Jasmonic acid and aspirin have different chemical structures; jasmonic acid is a plant hormone derived from fatty acids, while aspirin is a synthetic compound derived from salicylic acid.

Question 19

If you cut the tip off a bean plant, the lateral buds will stop developing.

Accepted Answer

Cutting the tip off a bean plant, a process known as "topping," typically encourages the growth of lateral buds, not stops it. This is because the removal of the apical bud reduces apical dominance, allowing lateral buds to grow more freely.

Question 20

Ethylene stimulates internodal elongation of rice plants that are submerged during monsoon flooding.

Accepted Answer

Ethylene is a plant hormone that accumulates in submerged conditions, promoting internodal elongation in rice to help the plant reach the water surface for better access to oxygen and light.

Quiz 27: Regulating Growth and Development: the Plant Hormones