AP Biology Chapter 23

Plants most likely detect gravity by sensing the direction in which some components respond to gravity. A mutant plant has roots that grow in all directions. Which organelle would you expect to be missing in the cell?

Specialized amyloplasts are involved in sensing gravity

If a gardener trims leaves off of the stem of a rose, which part of the leaf is cut?

The petiole.

Where is the vascular cambium located in an established woody plant?

The vascular cambium divides, adding both to the secondary phloem and secondary xylem. So the vascular cambium is located between the secondary xylem and the secondary phloem.

A technician is preparing microscope slides that will display the different stages of mitosis from root samples. He compares sections from several areas of the root. Which statement is the best prediction of his observation? A The technician will see mostly mitotic cells in the root cap. B The technician will observe mitotic figures in the meristematic tissue below the cap. C The technician will observe cell division in the elongation zone. D The technician will see that most mitotic cells are in the maturation zone.

(B). The technician will observe mitotic figures in the meristematic tissue above the cap. The meristematic tissue in the root is located above the root cap and contains mitotic cells.

Some weeds are anchored by taproots. They cause problems to gardeners because they are —

difficult to pull up because their taproots penetrate deep into the soil

Modified organs are part of survival strategies of plants. Which plant has a flattened, photosynthetic stem that could be mistaken for a leaf? A Fern B Cactus C Potato D Iris

(B). A cactus has evolved to conserve water in a dry environment. It can have leaves that are modified as spines, providing protection and conserving water.

A carrot is an example of a taproot. Which option can also be classified as a taproot? A The large network of superficial roots of a cactus B A dandelion anchored by a long main root that penetrates deep into the soil C A banyan tree's system of roots that dangle from the branches D A round organ that stores carbohydrates

(B). A taproot is a long, main root that penetrates deep into the soil.

Which adaptation is most likely to be found in a desert environment? A Broad leaves to capture sunlight B Spines instead of leaves C Needle-like leaves D Wide, flat leaves that can float

(B). Plants that live in desert areas tend to have reduced or modified leaves to conserve water. Some have spines that serve a defensive function while also reducing water loss compared to larger leaves.

Scientists are cataloguing slides of plant cross-sections. They are interested in finding examples of secondary growth. Which example contributes to secondary growth? A Apical meristem, which contributes to increase in length B Vascular cambium, which contributes to increase in thickness or girth C Root region, which shows an increase in root hairs D Stems, which show an increase in number of leaves

(B). Vascular cambium contributes to increases of girth in a plant, meaning that it produces secondary growth. Primary growth would result in an increase in length.

Which of the following best describes a fibrous root system? A Covers a limited surface and contains few roots B Consists of a single main root with adjacent smaller roots C Covers a large area and contains an extensive network of roots D Contains several major, interconnected roots

(C). A fibrous root system is relatively shallow, covers a large area, and contains an extensive network of roots.

Students are sketching diagrams of the reproductive system of angiosperms for a plant anatomy class. These lists describe diagrams made by four students. Which diagram represents the reproductive system correctly? A Hair roots, lateral roots, and taproot B Stem, branches, and leaves C Flowers and fruit D Leaves, petioles, and branches

(C). Flowers and fruit are reproductive organs of plants. Flowers produce pollen that pollinators can transport to other flowers so that sperm from the pollen can fertilize the ovule. The seed develops within fruit, which aids in dispersal.

Solute potential decreases when solutes are added to a cell. The consequence is to draw water into the cell. Which term corresponds to solute potential? A Water potential B Pressure potential C Osmotic potential D Negative potential

(C). Osmotic potential corresponds to solute potential and influences water movement in and out of the cell.

A lab teacher wants to demonstrate thigmotropic behavior of a plant. Which experiment is the best choice? A Roots growing downward B A Venus flytrap snapping on an insect C A seedling germinating under a stone and growing upward and away from the stone D A plant growing toward a shaded area

(C). Thigmotropism is a response to physical contact, so a seedling that grows away from a stone is the best example.

If the concentration of solute increases in a cell, the water potential will blank_____ inside the cell and water will move blank_____ the cell. A increase; out of B increase; into C decrease; into D decrease; out of

(C). Water potential becomes more negative as more solute molecules bind water molecules. Osmotic pressure increases in the cell and water moves into the cell.

In an experiment to release seeds from dormancy, several hormones were applied to seeds and germination rates were computed. The plates are as follows. A Abscisic Acid B Cytokinin C Ethylene D Gibberellic Acid Which plate likely showed the highest rate of germination?

(D). Gibberellic acid can trigger germination.

On a field trip, students collect a few samples to analyze back in their classroom. One student picks a blade of grass in the field and identifies it as a dicot leaf, but his partner thinks it is a monocot. Which explanation supports his partner's opinion? A The leaf displays a thin lamina. B There is no petiole. C The margins are serrated. D The venation is parallel.

(D). Monocots have parallel veins while dicots have network patterns of veins. If your lab partner identified the grass as a dicot but the leaves were parallel, then that would be a good reason to disagree and to argue that the grass was a monocot.

Analyzing cross-sections of different parts of a plant in a plant anatomy class, students categorized the most frequently encountered types of cells in plant tissues. Which student gave the most accurate report? A Student A reported that meristematic cells were the most abundant. B Student B tallied mostly collenchyma cells. C Student C noticed mostly sclerenchyma cells. D Student D observed that parenchyma cells were the most abundant.

(D). Parenchyma cells are the most common tissue type. Student D observed that parenchyma cells were the most abundant.

A lab teacher wants to demonstrate thigmonastic behavior of a plant. Which experiment is the best choice? A Observe flowering of a plant after a brief red light irradiation in the middle of a dark period. B Observe whether seedlings bend towards blue light. C Observe whether a tree grows bent in the direction of the prevailing wind. D Touch the plant Mimosa pudica and observe the closing of the leaflets.

(D). Thigmonastic behavior occurs when plants respond to touch, so touching a mimosa plant and observing the closing of the leaflets is the best example.

Students are sketching diagrams of the shoot system of angiosperms for a plant anatomy class. These lists describe diagrams made by four students. Which diagram represents the shoot system incorrectly? A Leaves, stem, fruit, flowers B Stem, fruit, leaves, branches C Flowers, leaves, branches, stem D Stem, hair roots, leaves, flowers, branches

(D). While leaves, stem, fruit, flowers, and branches are all part of the shoot system, hair roots are associated with roots and part of the root system even when above ground.

Plant scientists are interested in isolating meristematic tissue for an experiment. They sample several regions of a plant. Which sample is most likely to contain meristematic tissue?

A region of actively dividing cells located at the tip of an onion root is most likely to contain meristematic tissue, which contributes to the lengthening of the root.

Many forms of modified organs exist in plants. What is a rhizome?

A rhizome is a modified horizontal stem that grows underground.

While examining the stump of a recently cut tree, you count four thick rings alternating with four rings that are much narrower and appear denser. From this observation, you should conclude that the tree is —

Four years old, because secondary xylem grows only in the spring and fall of each year

A pulse of radioactive carbon dioxide is provided to isolated leaves. In which tissue would you expect to see radioactive glucose appear first?

Glucose, produced from G3P from the Calvin cycle or light independent reactions, appears first in the cells which have chloroplasts.

A plant biologist is examining sections of plant tissue under the microscope. The slides are not labeled and the biologist is interested in simple tissues. Which slide is a sample of a simple tissue?

A tissue sample from parenchyma showing only one type of cell is a sample of a simple tissue.

You picked leaves while on a hike. One specimen appears to show an opposite arrangement. On closer inspection, you notice that those are not leaves, but leaflets attached to a midrib vein. What type of leaf arrangement are you observing?

Leaflets are attached to a midrib vein represent a pinnately compound leaf.

Multiple leaves attached to the same node are fairly unusual. One example is found on the macadamia nut tree. The leaf arrangement in the macadamia tree is best characterized as —

Macadamia nut tree leaves are attached to the same node, making a whorled leaf arrangement.

A student examines a plant part and concludes that it is part of a stem. The presence of blank_____ fully justifies the student's conclusion.

Nodes and internodes are part of the stem. Leaves grow from nodes and internodes make up the space between nodes.

Ethylene promotes the fall of leaves by triggering the death of cells and abscission. What region of the leaf responds to ethylene?

Petioles attach leaves to stems; ethylene must affect them to cause leaves to fall.

In environments where light is scarce, some plants grow on other plants to reach light. Which root system would best support this mode of life?

Plants growing on other plants would function best with epiphytic roots in the air (allowing them to be farther from the ground).

Red light converts phytochrome red (Pr) to —

Red light converts Pr to Pfr, which absorbs far red light.

A lab technician is looking for a slide that shows an example of permanent tissue. Which slide is the best choice?

Secondary xylem is permanent because the cells have die after reaching maturity, leaving the tissue permanently in place.

Dendrochronology is the science of dating the age of a tree by counting the annual rings in a tree trunk. If scientists are determining the age of a tree by dendrochronology, what tissue are they looking at?

Secondary xylem is the tissue that contains rings. It is produced during the year but differs according to the season.

A section of buttercup root is stained with iodine, which stains starch blue. Where would you expect to find the blue granules indicative of starch?

Starch may be stored in parenchymal cells within the cortex.

Sudan Red dye stains primarily waxy, hydrophobic material. A root is soaked in Sudan Red and analyzed for stain retention. What is a scientist observing sections of the root under a microscope likely to see?

The Casparian strip will show the deepest coloring because it is made of waxes, which are hydrophobic and would be stained by Sudan Red.

A pulse of sugars labeled with a fluorescent dye is supplied to leaves of young plants. After a brief interval, tissue sections are obtained from the plant and examined under the fluorescence microscope. Tissues are scored for the presence of fluorescence and ranked from very high to low fluorescence. Which cells would contain the most fluorescence?

The most fluorescence would occur in sieve elements are they are involved in sugar transport.

What is the structure that connects the leaf to the stem?

The petiole is the structure that connects the leaf to the stem at the node.

An herbicide causes roots to shrivel and die. What is the most direct consequence for a plant treated with the herbicide?

The plant will dry out because water is not reaching all its organs.

Sugars produced in the leaf are distributed throughout the plant body. An experimenter supplies plants with a pulse of radiolabeled carbon dioxide in a control chamber. The movement of radioactively labeled sugar is monitored in the plant by analyzing different cells' content over time. Where will the radiolabeled sugar appear immediately after detection in the leaf cells?

The radiolabeled sugar would appear in sieve-tube elements and companion cells because these are involved in sugar transport.

Plants have many light responses, including photosynthesis, photoperiodism, and phototropism (growing toward a light source). Specific wavelengths of light absorbed by different photoreceptors trigger responses. Research shows that plants bend toward blue light. Even mutant plants that lack carotenoids will bend toward blue light. The photoreceptor is likely —

Because bending occurs even when carotenoids are absent, phototropin is responsible.

Gravitropism is plant growth in response to gravity. A dahlia stem is toppled by the wind and is lying on the ground. After a few days, you would likely notice that —

Because the stem is sensitive to gravity, it will grow upward, away from the ground.

One of the major concepts of biology is that form follows function. If that is so, what can be deduced from the shape and location of the root cap?

The root cap covers the tip of the root to provide protection.

Which region of a plant is most likely to contribute to an increase in its length?

The root elongates at the tip.

Students are asked to sort tissue slides into simple and complex tissues. How should they recognize a complex tissue through the microscope?

Complex tissue has a variety of cell types that fulfill different functions. The cells have strikingly different appearances because they fulfill different functions.

What is a protection against microbial pathogens?

Cutin and suberin found on the surface serve as protection against microbes, helping to form a barrier.

What does the dermal tissue of a plant provide for the plant?

Dermal tissue is the outer layer, which provides protection for the plant.

A horticulture student is classifying plants as dicots or monocots according to their leaf structure. How is a dicot leaf recognizable?

Dicot leaves have veins in networks

Plant flowering is an example of photoperiodism, the response to the length of nights or periods of darkness. A plant that responds to short nights followed by increasingly longer nights will most likely flower in —

During autumn, nights are increasingly longer. So this type of plant is likely to flower in autumn.

Green bananas or unripe avocadoes can be kept in a brown bag to ripen faster. What hormone is involved?

Ethylene is a gas that becomes trapped by the brown bag and stimulates fruit ripening.

In the collection of a botanical garden, plants are classified according to the environments in which they thrive. What plant would have large leaves covered with a thick upper cuticle and wide flat blades, and possess large air spaces (chambers) within its mesophyll tissue? A A water lily floating on water B A pine tree growing in the cold and dry taiga C A cactus growing in a hot, sunny, and dry environment D An orchid hanging from a tree in a tropical forest

(A). A water lily would have waxy upper cuticle to repel water and keep the stomata open, large air chambers/spaces and wide blades to help it float.

Plants can modify their water potential by opening and closing their stomata to modulate the rate of respiration according to environmental conditions. Which environmental condition would cause the stomata to close? A Increased temperature B High oxygen concentration C High relative humidity D High light levels

(A). Warm temperatures accelerate the loss of water from the leaves. When the stomata close, water loss is prevented, although photosynthesis is also inhibited by a lack of carbon dioxide intake.

Many secondary alkaloids are poisonous to the nervous system. What organisms are targeted by the alkaloids? A Bacteria B Herbivores C Fungi D Viruses

(B). Herbivores are animals that eat plants, so they have nervous systems that can be poisoned

Plants regulate their internal water potential by opening and closing stomata. Which events take place when stomata open?

When stomata open, water vapor is lost to the external environment and transpiration rates increase.

Circadian rhythm refers to a pattern of behavior that recurs on a daily schedule in the absence of an external stimulus. Flowers open and close according to a circadian rhythm. If a plant is transferred to a dark environment, what will happen?

Without cues from the environment, flowers will open and close at approximately the same time every day.

A branch of celery is soaked in a glass of water containing food dye. Soon, the tough fibers in celery branch are colored. What tissue do the tough fibers contain?

Xylem transports water and solutes.

While using a microscope to observe a stem section stained with a dye that binds lignin, a student notices that some cells with thick cell walls and large hollow centers are preferentially stained. He concludes that those cells belong to the —

vascular tissue

Selective uptake of minerals in the root is measured and the results are analyzed. If you analyze the data, what should you see?

The endodermis is a selective barrier for minerals that are taken up through the root because the Casparian strip forces water to pass through the endoderm, where selectivity takes place.

You are measuring the effect of a new fertilizer on the growth of lawns. Which tissue should be the target of the fertilizer?

The intercalary meristem is typically the zone in grasses where elongation of the shoot and leaves takes place.

Scientists label cells in the lateral meristem of a sapling with a dye to follow the developmental fate of the cells. After several weeks, sections are prepared from the sapling and observed under the microscope. Which tissues are most likely to be stained by the dye that was injected into the lateral meristem?

The lateral meristem produces secondary xylem that increases the girth of the stem, so the dye would appear in secondary xylem.

Which physical component of the total water potential cannot be manipulated by the plant because it represents the interaction between water and hydrophilic molecules lining the vessels and tracheids?

The matric potential reaches zero when seeds take up water and therefore cannot be manipulated by plants and is ignored in well-watered stems.

Chlorophyll, the primary photosynthetic pigment, emits light in the red region of the visible spectrum. The presence of chlorophyll correlates with photosynthetic capacity. Under a fluorescent microscope, what part of a leaf would fluoresce in the red region of the spectrum?

The mesophyll is the main site of photosynthesis.

A student reported vascular tissue while inspecting a cross-section of a plant stem under the microscope. Which cells would allow the student to identify vascular tissue?

Vascular tissue contains xylem (which consists of tracheids, vessel elements, and xylem parenchyma) and phloem (which consists of sieve-tube cells, companion cells, phloem parenchyma, and phloem fibers).