Question 1

What caterpillar saliva-based chemical stimulates a corn plant to release an alarm signal?

Accepted Answer

Volicitin is a caterpillar saliva-based chemical that stimulates a corn plant to release an alarm signal, which attracts predators of the caterpillars to the area. Florigen is a hormone responsible for flowering in plants, methyl salicylate and salicylic acid are both compounds involved in plant defense mechanisms, and salicin is a natural pain reliever found in willow bark.

Question 2

Which of the following is TRUE of the relationship between the phytochrome system and the biological clock of plants?

Accepted Answer

The phytochrome system detects light and uses this information to reset the biological clock of plants. This allows the plant to properly regulate its growth, development, and reproduction in response to changes in the environment.

Question 3

Plants that flower in the United States only in the early spring (when nights are long)are ________ plants.

Accepted Answer

Plants that flower in the spring when nights are long have a photoperiod requirement of short days. These plants are therefore called short-day plants.

Question 4

Leaves of the Venus fly trap and other sensitive plants move quickly due to:

Accepted Answer

The movement of leaves in the Venus fly trap and other sensitive plants is due to an electrical stimulus and rapid diffusion of ions. When an insect touches the sensitive trigger hairs on the Venus fly trap, it triggers an electrical signal that causes the plant to rapidly release ions, leading to a change in turgor pressure and resulting in the movement of the trap leaves. This movement is not caused by reduced permeability to potassium ions, muscle-like plant cells, or hormones.

Question 5

Which pigment is responsible for the phototropism responses of plants?

Accepted Answer

Phytochrome is responsible for the phototropism responses of plants. Phytochrome is a pigment that is sensitive to light and plays a crucial role in regulating plant growth and development. When a plant is exposed to light, phytochrome triggers a cascade of cellular responses that result in the plant bending towards the light source.

Question 6

The process of aging is called:

Accepted Answer

Senescence is the scientific term for the process of aging, while maturation refers more specifically to the process of becoming fully grown or developed. Elongation refers to the process of lengthening, usually in plants. Abscission is the process of shedding or dropping plant parts or fruits, such as leaves or flowers. Death refers to the permanent cessation of all vital functions, and is not necessarily a part of the aging process.

Question 7

Willow trees and many other plants produce ________, from which aspirin is made.

Accepted Answer

Willow trees and many other plants produce salicylic acid, which is the precursor to aspirin. Aspirin is synthesized from salicylic acid through acetylation.

Question 8

At night, when little red light is available to the plants in an area:

Accepted Answer

In the absence of red light, Pfr is converted to Pr. This is because Pfr undergoes a slow thermal conversion to Pr in the dark. Therefore, in the absence of red light, the concentration of Pr increases at the expense of Pfr.

Question 9

If a storm breaks off the top of a tree, within a year or two, one of the lower branches will grow upward and become the new tree top, while inhibiting other branches from doing the same. This is an example of:

Accepted Answer

This process is known as apical dominance, where the growth of the apical meristem (topmost growing point) inhibits the growth of lower lateral branches. When the apical meristem is damaged or removed, the lateral branches are released from inhibition and can start to grow upward to become the new leader.

Question 10

Short-day plants flower only if:

Accepted Answer

Short-day plants require longer periods of uninterrupted darkness to flower, which is specific to each species.

Question 11

The phytochrome that is active and absorbs far-red light is:

Accepted Answer

Phytochrome that absorbs far-red light is in the Pfr state, so the correct answer is B. Pr is the inactive form of phytochrome that absorbs red light. Pa and Pe are not forms of phytochrome.

Question 12

Plants that flower in Canada in August and in the United States in July (when nights are short)are ________ plants.

Accepted Answer

Long-day plants flower when nights are short, as they require longer daylight periods to initiate flowering.

Question 13

Senescence in plants usually involves:

Accepted Answer

Senescence in plants involves the formation of an abscission layer, which is a layer of cells that separates the plant from the leaf or fruit being shed.

Question 14

If a plant is living under conditions that limit root growth, shoot growth is:

Accepted Answer

When root growth is limited, less cytokinin is produced, which is a hormone that promotes shoot growth. Therefore, shoot growth is also limited.

Question 15

Some plants under attack by insects can communicate this information to other parts of the same plant and to nearby plants via:

Accepted Answer

Plants can release chemicals called volatile organic compounds (VOCs) into the air when they are being attacked by insects. These VOCs can serve as a warning signal to nearby plants, allowing them to prepare for a potential attack by producing their own defensive chemicals. Additionally, the same plant can also communicate this information to other parts of itself through the same chemical signaling system.

Question 16

The phytochrome Pr:

Accepted Answer

The answer of The phytochrome Pr:
...

Question 17

What happens to phytochromes after several days of dark, rainy weather?

Accepted Answer

After several days of dark, rainy weather, Pfr is converted to Pr. This is because Pfr is the active form of phytochrome that is formed when Pr absorbs red light. Without light, Pfr gradually reverts back to its inactive form Pr over time.

Question 18

A new type of strawberry plant produces fruit in the late spring, throughout the summer, and into the fall. It is a(n)________ plant.

Accepted Answer

Day-neutral plants are not affected by the length of daylight and can produce fruit at any time of the year. This matches the description of the new strawberry plant that produces fruit in the late spring, throughout the summer, and into the fall.

Question 19

________ plants bloom only when the duration of uninterrupted darkness is shorter than a critical length.

Accepted Answer

Long-day plants bloom only when the duration of uninterrupted darkness is shorter than a critical length.

Question 20

Which environmental factor is most significant for flowering?

Accepted Answer

Day length, also known as photoperiod, is the most significant environmental factor for flowering in many plant species. This is because plants use photoperiod as a cue to determine the time of year and adjust their flowering accordingly. For example, long-day plants only flower when the days are longer than a certain threshold, while short-day plants only flower when the days are shorter than a certain threshold. Temperature, water availability, nitrogen availability, and light intensity can also affect flowering, but to a lesser degree than photoperiod.

Quiz 45: Plant Responses to the Environment