AP Biology : Plant Functions
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Example Question #71 : Plant Biology
Which of the following nutrients is most likely to be abundant in soil?
Phosphorus
Oxygen
Hydrogen
Carbon
Iron
Iron
There are many necessary nutrients involved in plant development. The nutrients are used in different quantities and are grouped accordingly in two categories: micronutrients and macronutrients. Micronutrients, such as iron, are important to healthy plant growth but are used in small quantities. Macronutrients, such as oxygen, carbon, hydrogen, and phosphorus, are also used for healthy plant growth but are used in the greatest quantities.
As a result, the macronutrients are more likely to become depleted in the soil as the plant absorbs them, while the micronutrients remain abundant. Iron, as a micronutrient, is more likely to be abundant in soil than any of the macronutrients.
Example Question #22 : Plant Biology
Perishable fruit is often picked before it is ripe. This hard, unripe fruit is easier to transport as it is less likely to bruise or spoil while in transit. Once fruit reaches its destination, it can be sprayed with a plant hormone that will promote its rapid ripening. What hormone is most likely used for this function?
Abscisic acid (ABA)
Gibberellins
Ethylene
Cytokinins
Ethylene
Ethylene gas promotes fruit ripening; in a classic example of a positive feedback loop, ripe fruit causes the production of more ethylene gas, which promotes more fruit ripening (this is the origin of the phrase "one bad apple spoils the bunch!")
Cytokinins stimulate cell division and cytokinesis, and they can delay senescence (deterioration due to age, as in the case of cells). Gibberellins promote cell growth, and also promote stem and leaf elongation. Abscisic acid (ABA) promotes seed dormancy, inhibits plant growth, and closes plant stomata during water shortages.
Example Question #23 : Plant Biology
Which of the following is not true of auxins, a class of plant hormones?
Indoleacetic acid (IAA) is a natural auxin
They promote fruit ripening, which triggers the production of more auxins
They are responsible for phototropism—plants' tendency to grow toward light sources
They enhance apical dominance, which promotes plants' upward growth, as opposed to lateral growth
They promote fruit ripening, which triggers the production of more auxins
Auxins play a number of crucial roles in plant growth, behavior, and development. They were the first major class of plant hormone to be discovered and are present in all parts of a plant in varying concentrations. Some of their more notable functions include causing phototropism, enhancing apical dominance, and softening the cell wall to stimulate cell elongation and growth. Indoleacetic acid (IAA) is a naturally occurring auxin, though some synthetic auxins are used as weed killers.
Ethylene gas is a plant hormone that promotes fruit ripening in a positive feedback loop. Ripe fruit produces more ethylene gas, which promotes more fruit ripening, and so on. It is not a kind of auxin.
Example Question #12 : Plant Biology
What is the function of lateral meristems?
Provide nutrients to apical meristems
Provide secondary growth in woody plants
Stimulate root hair growth
Maintain water homeostasis
Provide secondary growth in woody plants
In addition to growing in height, woody plants also grow in thickness. This is the function of lateral meristems. Lateral meristems are comprised of the vascular cambrium, and by cork cambrium that form vascular cylinders. The vascular cambrium adds layers of secondary xylem and phloem (wood), whereas the cork cambrium replaces the outer epidermis with a thicker and tougher layer called periderm.
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