Cytokinins in Plants: Cell Division and Anti-Aging

1. What is the primary cellular process stimulated by the presence of cytokinins?

Cytokinesis (cell division)

Photolysis of water

Glycolysis

DNA denaturation

Apoptosis

If "cytokinesis" refers to the physical division of a cell's cytoplasm into two daughter cells, then the hormone named after this process must be its primary stimulator.

Explanation

If "cytokinesis" refers to the physical division of a cell's cytoplasm into two daughter cells, then the hormone named after this process must be its primary stimulator.

2. The primary role of cytokinins in plants is to accelerate the process of leaf senescence (aging).

True

False

If senescence is the biological process of aging and tissue death, and if cytokinins are known to keep leaves green and functional for longer, then they delay senescence rather than accelerate it.

Explanation

If senescence is the biological process of aging and tissue death, and if cytokinins are known to keep leaves green and functional for longer, then they delay senescence rather than accelerate it.

3. While auxins are mostly produced in the shoot tips, the majority of ______ are produced in the actively growing roots.

If a plant needs to signal the shoots about root health and growth, then it produces hormones in the roots to travel upward.

Explanation

If a plant needs to signal the shoots about root health and growth, then it produces hormones in the roots to travel upward.

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4. How do cytokinins in plants typically travel from the roots to the rest of the organism?

Through the xylem in the transpiration stream

Through the phloem using active transport

By diffusing through the air as a gas

By jumping from cell to cell via plasmodesmata only

They do not move from their site of production

If these hormones are produced in the roots and must reach the leaves and stems, then they must use the plant's plumbing. If they follow the upward flow of water and minerals, then they travel through the xylem.

Explanation

If these hormones are produced in the roots and must reach the leaves and stems, then they must use the plant's plumbing. If they follow the upward flow of water and minerals, then they travel through the xylem.

5. When scientists use tissue culture to grow new plants, what occurs when the ratio of cytokinins to auxins is very high?

Shoot buds begin to form

The culture remains a callus

Roots grow aggressively

Cell division stops

The plant enters dormancy

If auxin promotes root formation and cytokinins in plants promote shoot formation, then a high cytokinin-to-auxin ratio will specifically trigger the development of stems and leaves.

Explanation

If auxin promotes root formation and cytokinins in plants promote shoot formation, then a high cytokinin-to-auxin ratio will specifically trigger the development of stems and leaves.

6. One way that cytokinins in plants affect growth is by antagonizing apical dominance to promote lateral bud growth.

True

False

If apical dominance (caused by auxin) keeps side branches from growing, then an opposing hormone is needed to break that control. If cytokinins stimulate axillary buds, then they are the antagonist to auxin in this process.

Explanation

If apical dominance (caused by auxin) keeps side branches from growing, then an opposing hormone is needed to break that control. If cytokinins stimulate axillary buds, then they are the antagonist to auxin in this process.

7. The first naturally occurring cytokinin to be identified and isolated from corn is known as ______.

If researchers found a specific chemical in "Zea mays" (corn) that stimulated cell division, then they named that compound Zeatin.

Explanation

If researchers found a specific chemical in "Zea mays" (corn) that stimulated cell division, then they named that compound Zeatin.

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8. In the context of cytokinins in plants, what is "nutrient mobilization"?

The ability of the hormone to pull sugar and amino acids toward a specific leaf

The process of roots absorbing salt

The movement of water out of the stomata

The breakdown of starch into glucose

The storage of energy in the vacuole

If a leaf has a high concentration of cytokinins, then it acts as a "sink" that draws nutrients from other parts of the plant. If it pulls these resources to itself, then it can stay healthy even when the rest of the plant is stressed.

Explanation

If a leaf has a high concentration of cytokinins, then it acts as a "sink" that draws nutrients from other parts of the plant. If it pulls these resources to itself, then it can stay healthy even when the rest of the plant is stressed.

9. Which of the following are recognized physiological effects of cytokinins in plants?

Delaying leaf senescence

Promoting chloroplast maturation

Stimulating lateral bud growth

Increasing fruit ripening speed

Inhibiting cell division

If cytokinins maintain tissue youth, then they delay aging and help chloroplasts develop. If they oppose the main tip's control, then they help side buds grow; however, they do not ripen fruit or stop division.

Explanation

If cytokinins maintain tissue youth, then they delay aging and help chloroplasts develop. If they oppose the main tip's control, then they help side buds grow; however, they do not ripen fruit or stop division.

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10. The effect of cytokinins in plants is often dependent on the presence and concentration of auxins.

True

False

If these two hormones work together to control the cell cycle and organ development, then the absolute amount of one matters less than the relative ratio between both.

Explanation

If these two hormones work together to control the cell cycle and organ development, then the absolute amount of one matters less than the relative ratio between both.

11. Which enzyme's activity is often inhibited by cytokinins to help prevent the breakdown of chlorophyll?

Chlorophyllase

DNA Polymerase

RuBisCO

ATP Synthase

Amylase

If chlorophyllase is the enzyme responsible for destroying green pigment during aging, and if cytokinins keep leaves green, then the hormone must block or reduce the activity of chlorophyllase.

Explanation

If chlorophyllase is the enzyme responsible for destroying green pigment during aging, and if cytokinins keep leaves green, then the hormone must block or reduce the activity of chlorophyllase.

12. If a mass of undifferentiated plant cells, called a ______, is treated with equal parts auxin and cytokinin, it will continue to divide without forming organs.

If the hormone signals for roots and shoots are perfectly balanced, then the cells receive the "divide" instruction but no "specialize" instruction. If they remain unspecialized, then the mass is called a callus.

Explanation

If the hormone signals for roots and shoots are perfectly balanced, then the cells receive the "divide" instruction but no "specialize" instruction. If they remain unspecialized, then the mass is called a callus.

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13. Which of the following describe the chemical structure of most cytokinins in plants?

They are derivatives of adenine

They contain a nitrogenous base ring

They are long-chain fatty acids

They are gaseous hydrocarbons

They often have side chains attached to the N6 position

If cytokinins are modified versions of the DNA base adenine, then they are nitrogen-heavy rings with specific side chains; they are not fats or gases like ethylene.

Explanation

If cytokinins are modified versions of the DNA base adenine, then they are nitrogen-heavy rings with specific side chains; they are not fats or gases like ethylene.

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14. Why do florists sometimes spray cut flowers with a solution containing cytokinins in plants?

To extend the shelf life of the flowers by delaying wilting

To make the flowers change color

To prevent the flowers from ever blooming

To make the stems turn into roots

To kill any bacteria on the petals

If cytokinins prevent the degradation of proteins and chlorophyll, then they stop the "death" signal in harvested plants. If death is delayed, then the flowers remain fresh and colorful for the customer longer.

Explanation

If cytokinins prevent the degradation of proteins and chlorophyll, then they stop the "death" signal in harvested plants. If death is delayed, then the flowers remain fresh and colorful for the customer longer.

15. Cytokinins in plants primarily regulate the G2 to M-phase transition of the cell cycle.

True

False

If cell division requires specific checkpoints to be passed, then hormones must act on the molecular machinery of those checkpoints. If cytokinins trigger the start of mitosis, then they act on the transition to the M-phase.

Explanation

If cell division requires specific checkpoints to be passed, then hormones must act on the molecular machinery of those checkpoints. If cytokinins trigger the start of mitosis, then they act on the transition to the M-phase.

16. The movement of ______ through the plant is considered "acropetal," meaning it moves from the base toward the apex.

If a hormone is carried in the xylem from the roots up to the leaves, then its direction of travel is acropetal (upward).

Explanation

If a hormone is carried in the xylem from the roots up to the leaves, then its direction of travel is acropetal (upward).

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17. What is the likely result of a mutation that prevents a plant from producing any cytokinins?

The plant would be severely stunted and unable to maintain shoot meristems

The plant would grow into a giant tree

The plant would have no roots but many leaves

The plant would ripen its fruit too early

The plant would become a fungus

If cytokinins are required for the cell division that builds the stem and leaves, then a total lack of the hormone will stop growth. If growth stops at the tips, then the plant remains a dwarf or dies.

Explanation

If cytokinins are required for the cell division that builds the stem and leaves, then a total lack of the hormone will stop growth. If growth stops at the tips, then the plant remains a dwarf or dies.

18. In what ways do cytokinins in plants interact with the environment?

They help regulate the opening and closing of stomata

They assist in the response to light (photomorphogenesis)

They help the plant resist certain pathogens

They allow the plant to sense gravity in the roots

They increase the amount of sugar in the soil

If cytokinins are involved in general cell health and light signaling, then they help the plant adjust its pores and growth to the sun and fight off infections; however, they do not manage root gravity or soil sugar.

Explanation

If cytokinins are involved in general cell health and light signaling, then they help the plant adjust its pores and growth to the sun and fight off infections; however, they do not manage root gravity or soil sugar.

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19. Some bacteria and fungi can produce cytokinins to manipulate the growth of the host plant.

True

False

If a pathogen wants to create a "nutrient sink" to feed itself, then it can secrete cytokinins into the plant tissue. If the tissue grows into a tumor or remains unnaturally green (green islands), then the pathogen has successfully hijacked the plant's hormones.

Explanation

If a pathogen wants to create a "nutrient sink" to feed itself, then it can secrete cytokinins into the plant tissue. If the tissue grows into a tumor or remains unnaturally green (green islands), then the pathogen has successfully hijacked the plant's hormones.

20. Finalizing the logic of cytokinins in plants: If auxins promote "elongation," then cytokinins primarily promote ______.

Proliferation

Evaporation

Hibernation

Dehydration

Fossilization

If elongation means making existing cells longer, then proliferation means making more cells through division. If cytokinins trigger cytokinesis, then their primary contribution to growth is cell proliferation.

Explanation

If elongation means making existing cells longer, then proliferation means making more cells through division. If cytokinins trigger cytokinesis, then their primary contribution to growth is cell proliferation.

The Fountain of Youth: Cytokinins in Plants

1. What is the primary cellular process stimulated by the presence of cytokinins?

2.

What first name or nickname would you like us to use?

2. The primary role of cytokinins in plants is to accelerate the process of leaf senescence (aging).

3. While auxins are mostly produced in the shoot tips, the majority of ______ are produced in the actively growing roots.

4. How do cytokinins in plants typically travel from the roots to the rest of the organism?

5. When scientists use tissue culture to grow new plants, what occurs when the ratio of cytokinins to auxins is very high?

6. One way that cytokinins in plants affect growth is by antagonizing apical dominance to promote lateral bud growth.

7. The first naturally occurring cytokinin to be identified and isolated from corn is known as ______.

8. In the context of cytokinins in plants, what is "nutrient mobilization"?

9. Which of the following are recognized physiological effects of cytokinins in plants?

10. The effect of cytokinins in plants is often dependent on the presence and concentration of auxins.

11. Which enzyme's activity is often inhibited by cytokinins to help prevent the breakdown of chlorophyll?

12. If a mass of undifferentiated plant cells, called a ______, is treated with equal parts auxin and cytokinin, it will continue to divide without forming organs.

13. Which of the following describe the chemical structure of most cytokinins in plants?

14. Why do florists sometimes spray cut flowers with a solution containing cytokinins in plants?

15. Cytokinins in plants primarily regulate the G2 to M-phase transition of the cell cycle.

16. The movement of ______ through the plant is considered "acropetal," meaning it moves from the base toward the apex.

17. What is the likely result of a mutation that prevents a plant from producing any cytokinins?

18. In what ways do cytokinins in plants interact with the environment?

19. Some bacteria and fungi can produce cytokinins to manipulate the growth of the host plant.

20. Finalizing the logic of cytokinins in plants: If auxins promote "elongation," then cytokinins primarily promote ______.