AP Biology : Plant Biology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Xylem And Phloem

Which of the following are characteristics of companion cells in vascular plants?

Possible Answers:

They do not contain a nucleus

They do not contain a nucleus and are a specialized type of parenchyma cells

They have a large number of ribosomes and mitochondria

They have a large number of ribosomes and mitochondria and are a specialized type of parenchyma cells

Correct answer:

They have a large number of ribosomes and mitochondria and are a specialized type of parenchyma cells

Explanation:

Companion cells are a type of specialized parenchyma cells in vascular plants. They contain a large number of ribosomes and mitochondria and perform cellular functions for sieve-tube elements, which they are connected to by plasmodesmata.

Example Question #11 : Understanding Xylem And Phloem

Which of the following is true?

Possible Answers:

Phloem transports sugars, and dies at maturity

Xylem transports water and nutrients, and dies at maturity

Xylem transports water and nutrients, and does not have nuclei, ribosomes, and vacuoles at maturity

Phloem transports water and nutrients, and does not have nuclei, ribosomes, and vacuoles at maturity

Xylem transports sugars, and dies at maturity

Correct answer:

Xylem transports water and nutrients, and dies at maturity

Explanation:

Xylem are water-conducting cells that transport water and nutrients. They die at maturity and leave behind secondary walls. Phloem transports sugars through sieve-tube elements, but do not have nuclei, ribosomes, and vacuoles. However, phloem remains alive at maturity. 

Example Question #1 : Plant Structures

Of the following answer choices, which most accurately describes the mechanism that the stems of plants use to grow toward light?

Possible Answers:

Contractile cells on the light side of the stems dictate the growth toward light

Photosynthetic processes dictate the growth

The plant will grow away from other plants so as to minimize competition

Cells on the darker side of the stem elongate more than cells on the lighter side

The growth of the stem is determined by metabolic processes, which are stimulated by light striking the stems

Correct answer:

Cells on the darker side of the stem elongate more than cells on the lighter side

Explanation:

Plants grow so as to maximize the elongation of their stems as much as possible. Cells on the lighter side of the stem are already being provided with photosynthetic energy, while cells on the darker side are receiving less of this energy input. This causes the cells on the darker side to elongate toward the energy source. When one side of the stem is longer than the other, it causes a curve in the growth, resulting in a directionality of the growth of the stem.

Example Question #1 : Understanding Other Plant Macrostructures

Plant root systems can be generally categorized as either taproot systems or fibrous root systems. Which of the following is a characteristic of a fibrous root system?

Possible Answers:

Fibrous root systems are well adapted to soil where ground water is not close to the surface

Fibrous root systems do not penetrate deeply into the soil

Fibrous root systems consist of a series of roots that spread out from a major single root

Fibrous root systems usually penetrate deeply into the soil

Correct answer:

Fibrous root systems do not penetrate deeply into the soil

Explanation:

Fibrous root systems are common in seedless vascular plants and in most monocots, such as grasses. Many small roots grow from the stem of the plant and are considered adventitious (a term describing a plant organ that grows in an unusual location). 

Fibrous roots have no main root and do not penetrate deeply into the soil, usually penetrating only a few centimeters. As such, fibrous root systems are best adapted to shallow soil. This also helps prevent erosion, as the shallow, highly-branched roots hold the topsoil in place. 

Example Question #1 : Plant Structures

Which of the following is a type of stem?

Possible Answers:

Pith

Rhizomes

Lateral roots

Stele

Correct answer:

Rhizomes

Explanation:

Stems are one of the three basic plant organs, and consist of an alternating system of nodes (where leaves attach) and internodes (regions of the stem that span between nodes).

Some plants have evolved to have stems with additional functions, such as the ability to store food or to participate in asexual reproduction. These modified stems include rhizomes, bulbs, tubers and stolons.  

A rhizome is a horizontal shoot of the plant that grows just below the surface. Vertical shoots (and resulting leaves) grow from axillary buds on the rhizome. Examples of plants with rhizomes include irises, hops, and asparagus. 

Example Question #1 : Understanding Other Plant Macrostructures

Which of the following are true of the root cap?

Possible Answers:

It forms the outermost cuticle layer of the entire root

It contains xylem cells, which transport water to the leaves

It grows away from the pull of gravity

It contains a zone of elongation, which lengthens the root

It protects the tip of the plant and secretes mucilage

Correct answer:

It protects the tip of the plant and secretes mucilage

Explanation:

The root cap occurs on the end of any root. It protects the tip of a plant's root. Specifically, it protects the apical meristem of the plant, which lengthens the root and helps it grow. Also root cap secretes a polysaccharide slime called mucilage. The zone of elongation does occur in roots, but it is not contained to the root cap. The root cap grows towards the pull of gravity. The root cap occurs only on the tip of the root, not over the entire surface of the root. These cells only protect the root; they are not xylem cells, which function in transport of water and nutrients from the roots up to the leaves.

Example Question #1 : Understanding Other Plant Macrostructures

Which of the following is not a usually function of the roots of a plant?

Possible Answers:

Performance of photosynthesis

Storage of carbohydrates

Providing stability

Obtaining water and nutrients from the soil

None of these

Correct answer:

Performance of photosynthesis

Explanation:

Roots are usually underground and not exposed to sunlight, do not usually contain chlorophyll, thus they do not perform photosynthesis. However, roots do provide stabiity, obtain water and nutrients from the soil, and store carbohydrates.

Example Question #41 : Plant Structures

Which of the following best describes where parenchyma cells can be found in plants?

Possible Answers:

Stems

Roots

Leaves

All of these

Correct answer:

All of these

Explanation:

Parenchyma cells make up a type of ground tissue in plants. Parenchyma cells compose most of the soft tissues in plants including leaves, roots, stems, and seeds. The functions of parenchyma cells include photosynthesis, storage, and wound repair.

Example Question #1 : Understanding Other Plant Macrostructures

Which of the following is true regarding meristem tissue in plants?

Possible Answers:

It is present in areas of growth

It contains undifferentiated cells

All of these

There is a shoot and root apical meristem

Correct answer:

All of these

Explanation:

Meristem tissue contains undifferentiated cells and allows for plant growth. Apical meristems are found in areas of growth, which include the shoot and roots—cells in these tissues divide rapidly.

Example Question #1 : Understanding Other Plant Macrostructures

Which of the following best describes the location of the vascular cambium in plants?

Possible Answers:

Between the xylem and phloem 

None of these

In the tips of leaves

In the periderm

Correct answer:

Between the xylem and phloem 

Explanation:

The vascular cambium is a type of secondary meristem tissue located between the xylem and phloem of the stems and roots. Secondary meristem tissues are responsible for lateral growth; more specifically, the vascular cambium is responsible for secondary xylem and phloem development.

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