Chapter 30

Explain the role of the cork cambium in woody plants.

In woody plants, the cork cambium is the outermost lateral meristem; it produces new cells towards the interior, which enables the plant to increase in girth. The cork cambium also produces cork cells towards the exterior, which protect the plant from physical damage while reducing water loss.

What is the function of lenticels?

In woody stems, lenticels allow internal cells to exchange gases with the outside atmosphere.

What type of meristem is found only in monocots, such as lawn grasses? Explain how this type of meristematic tissue is beneficial in lawn grasses that are mowed each week.

Lawn grasses and other monocots have an intercalary meristem, which is a region of meristematic tissue at the base of the leaf blade. This is beneficial to the plant because it can continue to grow even when the tip of the plant is removed by grazing or mowing.

compare the structure and function of xylem to that of phloem.

Xylem is made up tracheids and vessel elements, which are cells that transport water and dissolved minerals and that are dead at maturity. Phloem is made up of sieve-tube cells and companion cells, which transport carbohydrates and are alive at maturity.

Leaflets are a characteristic of ________ leaves. alternate whorled compound opposite

compound

Secondary growth in stems is usually seen in ________. monocots dicots both monocots and dicots neither monocots nor dicots

dicots

Compare a tap root system with a fibrous root system. For each type, name a plant that provides a food in the human diet. Which type of root system is found in monocots? Which type of root system is found in dicots?

A tap root system has a single main root that grows down. A fibrous root system forms a dense network of roots that is closer to the soil surface. An example of a tap root system is a carrot. Grasses such as wheat, rice, and corn are examples of fibrous root systems. Fibrous root systems are found in monocots; tap root systems are found in dicots.

What are the major benefits of gravitropism for a germinating seedling?

Gravitropism will allow roots to dig deep into the soil to find water and minerals, whereas the seedling will grow towards light to enable photosynthesis.

Which of the following is the major site of photosynthesis? apical meristem ground tissue xylem cells phloem cells

Ground tissue

Besides the age of a tree, what additional information can annual rings reveal?

Annual rings can also indicate the climate conditions that prevailed during each growing season.

Give two examples of modified stems and explain how each example benefits the plant.

Answers will vary. Rhizomes, stolons, and runners can give rise to new plants. Corms, tubers, and bulbs can also produce new plants and can store food. Tendrils help a plant to climb, while thorns discourage herbivores.

The primary growth of a plant is due to the action of the ________. lateral meristem vascular cambium apical meristem cork cambium

Apical meristem

Plant regions of continuous growth are made up of ________. dermal tissue vascular tissue meristematic tissue permanent tissue

Meristematic tissue

How do dicots differ from monocots in terms of leaf structure?

Monocots have leaves with parallel venation, and dicots have leaves with reticulate, net-like venation.

Which of the following statements is false? Negative water potential draws water into the root hairs. Cohesion and adhesion draw water up the xylem. Transpiration draws water from the leaf. Negative water potential draws water into the root hairs. Cohesion and adhesion draw water up the phloem. Transpiration draws water from the leaf. Water potential decreases from the roots to the top of the plant. Water enters the plants through root hairs and exits through stoma.

Negative water potential draws water into the root hairs. Vohesion and adhesion draw water up the phloem. Transpiration draws water from the leaf.

Fruit and vegetable storage facilities are usually refrigerated and well ventilated. Why are these conditions advantageous?

Refrigeration slows chemical reactions, including fruit maturation. Ventilation removes the ethylene gas that speeds up fruit ripening.

Describe the roles played by stomata and guard cells. What would happen to a plant if these cells did not function correctly?

Stomata allow gases to enter and exit the plant. Guard cells regulate the opening and closing of stomata. If these cells did not function correctly, a plant could not get the carbon dioxide needed for photosynthesis, nor could it release the oxygen produced by photosynthesis.

The process of bulk flow transports fluids in a plant. Describe the two main bulk flow processes.

The process of bulk flow moves water up the xylem and moves photosynthates (solutes) up and down the phloem.

What might happen to a root if the pericycle disappeared?

The root would not be able to produce lateral roots.

Describe an example of a plant with leaves that are adapted to cold temperatures.

Conifers such as spruce, fir, and pine have needle-shaped leaves with sunken stomata, helping to reduce water loss.

When stomata open, what occurs? Water vapor is lost to the external environment, increasing the rate of transpiration. Water vapor is lost to the external environment, decreasing the rate of transpiration. Water vapor enters the spaces in the mesophyll, increasing the rate of transpiration. Water vapor enters the spaces in the mesophyll, increasing the rate of transpiration.

Water vapor is lost to the external environment, increasing the rate of transpiration

Positive water potential is placed on the left side of the tube by increasing Ψp such that the water level rises on the right side. Could you equalize the water level on each side of the tube by adding solute, and if so, how?

Yes, you can equalize the water level by adding the solute to the left side of the tube such that water moves toward the left until the water levels are equal.

A decrease in the level of which hormone releases seeds from dormancy? abscisic acid cytokinin ethylene gibberellic acid

abscisic acid

A mutant plant has roots that grow in all directions. Which of the following organelles would you expect to be missing in the cell? mitochondria amyloplast chloroplast nucleus

amyloplast

The ________ forces selective uptake of minerals in the root. pericycle epidermis endodermis root cap

endodermis

Roots that enable a plant to grow on another plant are called ________. epiphytic roots prop roots adventitious roots aerial roots

epiphytic roots

After buying green bananas or unripe avocadoes, they can be kept in a brown bag to ripen. The hormone released by the fruit and trapped in the bag is probably: abscisic acid cytokinin ethylene gibberellic acid

ethylene

Which of the following is an example of secondary growth? increase in length increase in thickness or girth increase in root hairs increase in leaf number

increase in thickness or girth

Cells of the ________ contain chloroplasts. epidermis vascular tissue stomata mesophyll

mesophyll

Stem regions at which leaves are attached are called ________. trichomes lenticels nodes internodes

nodes

Which of the following cell types forms most of the inside of a plant? meristem cells collenchyma cells sclerenchyma cells parenchyma cells

parenchyma cells

The stalk of a leaf is known as the ________. petiole lamina stipule rachis

petiole

The main photoreceptor that triggers phototropism is a ________. phytochrome cryptochrome phototropin carotenoid

phototropin

Which cells are responsible for the movement of photosynthates through a plant? tracheids, vessel elements tracheids, companion cells vessel elements, companion cells sieve-tube elements, companion cells

sieve-tube elements, companion cells

Which of the following is most likely to be found in a desert environment? broad leaves to capture sunlight spines instead of leaves needle-like leaves wide, flat leaves that can float

spines instead of leaves

A seedling germinating under a stone grows at an angle away from the stone and upward. This response to touch is called ________. gravitropism thigmonasty thigmotropism skototropism

thigmotropism

Tracheids, vessel elements, sieve-tube cells, and companion cells are components of ________. vascular tissue meristematic tissue ground tissue dermal tissue

vascular tissue

Newly-formed root cells begin to form different cell types in the ________. zone of elongation zone of maturation root meristem zone of cell division

zone of cell division

Which layers of the stem are made of parenchyma cells? cortex and pith epidermis sclerenchyma epidermis and cortex.

The cortex, pith, and epidermis are made of parenchyma cells

Stomata close in response to bacterial infection. Why is this response a mechanism of defense for the plant? Which hormone is most likely to mediate this response?

To prevent further entry of pathogens, stomata close, even if they restrict entry of CO2. Some pathogens secrete virulence factors that inhibit the closing of stomata. Abscisic acid is the stress hormone responsible for inducing closing of stomata.