Mastering Biology Chapter 32-Ickes

How big is the range of soil degradation observed between continents?

15%

Worldwide, about _____% of all fresh water is used for crop irrigation.

70-75

Which of the following allows plants to be selective about the molecules that enter the xylem?

A waxy barrier in the plant root.

Which continent likely represents the largest absolute land area experiencing degradation?

Asia

What is the physical barrier in the root that regulates the flow of water to xylem via cell walls?

Casparian strip

In roots the _____ forces water and solutes to pass through the plasma membranes of _____ cells before entering the _____.

Casparian strip ... endodermis ... xylem

Why was drip irrigation developed?

Drip irrigation uses less water than traditional methods.

A chemical element that a plant must obtain from the environment in order to grow and reproduce

Essential element

What happens to the xylem system during drought, when water is scarce?

Falling moisture levels in the leaf cause the guard cells to change shape, closing the stomata. This reduces water loss from the plant.

_____ cells are the cells that regulate the opening and closing of stomata, thus playing a role in regulating transpiration.

Guard

_____ bonds are responsible for the cohesion of water molecules.

Hydrogen

Which of the following would be the best way to determine if aphids must actively draw phloem sap into their digestive tract or if hydrostatic pressure in the phloem tube could force the sap into them?

Insert mouth parts removed from an aphid, without including the digestive tract, into phloem sap and see if sap keeps flowing through them.

Which of the following options best describes the mechanism that causes a stoma to open?

K+ enters the guard cells and water follows passively, making the cells turgid.

An element, such as carbon or calcium, that a plant must obtain in relatively large quantities

Macronutrient

An element, such as iron or copper, that a plant must obtain in relatively small quantities

Micronutrient

You conduct an experiment to learn more about how water moves within the plant body. You take a common houseplant and cut the stem off about one inch above the soil surface. Water begins collecting at the cut--in the stem stump--as if some force is pushing the water up through the roots and remaining stem. How could you best explain this observation?

Minerals, unable to move up to the leaves, are accumulating in the root, which causes water to rush in due to osmosis.

What are the macronutrients present in most commercial fertilizers?

Nitrogen, carbon and potassium

Commercial inorganic fertilizers have greatly increased agricultural productivity. Which of the following is an advantage of using inorganic rather than organic fertilizers?

Nutrients are released faster from inorganic fertilizers.

In an attempt to determine the source of a growing plant's mass, van Helmont planted a willow seedling in a pot of soil. After five years, the willow weighed 76.8 kg, and the soil had lost 0.06 kg of weight. Only water had been added to the pot. Which of the following conclusions should van Helmont have drawn?

Plants get all or almost all of their mass from a source other than soil.

Which of the following is NOT an essential plant micronutrient?

Potassium

Root pressure is positive pressure that helps to push water up out of the roots and into the aboveground plant. How is it formed?

Root cells bring mineral nutrients into the root using active transport. This sets up a concentration gradient that draws water into the root by osmosis.

How do root hairs aid in water uptake in roots?

Root hairs increase the surface area of a root, thus increasing the root's absorptive capacity.

Which of the following describes the correct order in which water moves through a plant and into the atmosphere?

Root, xylem, leaf cells, air space inside leaves, outside air.

For which continents is land degradation having the least impact on global grain production?

South America and Africa

In a sugar sink, such as a taproot, sugar is converted into _____.

Starch

The solute most abundant in phloem sap is _____.

Sugar

A gardener planted large, healthy flower bulbs in her garden. When spring arrived, green shoots emerged from the bulbs, and some of them, but not all, produced flowers. She decided to dig up a few bulbs that flowered and a few that didn't to see if she could see what the difference was. She was stunned to find that none of the bulbs looked healthy; they all appeared much smaller. What had happened?

The bulbs were a sugar source; sugars from them traveled up the phloem to the aboveground sugar sink.

Imagine that you spray a large, actively growing tree with a sealant that instantly seals off all of the stomata. What would happen in the xylem system?

The flow of xylem sap would stop, except for some minimal upward movement that might be generated by root pressure.

What is true of the guard cells shown in the right-hand panel of this figure? (Open stomata)

These cells are hypotonic to their immediate surroundings.

How do mineral ions get into the xylem cells of a plant root by way of the intracellular route?

They are taken up by root hair cells and transferred from cell to cell via plasmodesmata.

_____ provide(s) the major force for the movement of water and solutes from roots to leaves.

Transpiration

Xylem tissues create a system of very thin pipes that connect plant roots and leaves. Which option best describes the nature and function of xylem tissue?

Xylem is dead tissue. The pipes convey xylem sap from the roots to the leaves. Active transport is not important in moving xylem sap.

Which of the following is a difference between transport by xylem and transport by phloem?

Xylem sap moves up; phloem sap moves up or down.

In an apple tree that is producing sugars, sugar might flow from _____ to _____.

a leaf.... a developing apple

Which of the following studies is a meta-analysis?

a study that summarized research reports from many laboratories around the world indicating a relationship between a diet high in plants and colon cancer

At a sugar sink, sugar is removed from phloem by _____.

active transport

The sugar "sink" in roots is the result of

active transport of sugars from phloem to root cells.

Which of the following are important in breaking down organic material in fertile topsoil?

bacteria and fungi

The water pressure that pushes water and sugar from sugar source to sugar sink is referred to as _____.

bulk flow

_____ is responsible for the movement of sugars from leaves to taproots; _____ is responsible for the movements of sugar from taproots to leaves.

bulk flow....bulk flow

How do sugars move from one sieve-tube cell to the next?

by flowing along with water through perforations in the sieve plate

Which of the following essential macronutrients for plants is obtained directly from the air?

carbon

What is the source of most of a plant's dry mass?

carbon dioxide

A hot, dry summer will reduce crop yields in part because ?

carbon dioxide uptake is reduced by the stomata closing to prevent excessive water loss.

Which of the following lists the set of plant macronutrients that make up about 98% of a plant's dry weight?

carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus

Micronutrients function in plants mainly as?

cofactors in chemical reactions.

Which of the following terms describes water molecules sticking to other water molecules?

cohesion

What keeps the force of gravity from overcoming transpirational pull?

cohesion and adhesion of water molecules

Mineral nutrients _____.

contribute little to the weight of a plant About 95% of the weight of a plant is composed of material built from atmospheric CO2.

The last type of cell all water and solute molecules must pass through before they can enter the vascular system and move upward to the leaves is a(n) __________.

endodermal cell

Which of the following correctly lists the sequence of structures through which water passes into a root?

epidermis, cortex, endodermis, xylem

What is the main source of energy that moves water upward in the trunk of a tree?

evaporation of water by the sun

The continuum of spaces between cell walls of neighboring cells is the _____ route of water and solute transport from root hairs to xylem.

extracellular

Where do plants get most of their mass?

from carbon dioxide in the atmosphere

Soil layers are called _____.

horizons

What force is responsible for the cohesiveness of water?

hydrogen bonding between water molecules

"Smart" plants can reduce overuse of fertilizers by....

informing the grower of a nutrient deficiency before damage occurs.

a nutrient mixture that is composed of naturally-occuring or manufactured mineral compounds

inorganic fertilizer

The cytoplasmic continuum connecting neighboring cells is the _____ route of water and solute transport from root hairs to xylem.

intracellular

Topsoil __________.

is a mixture of rock fragments, living organisms, and humus

The loss of water from plants through transpiration

is an important part of the mechanism that pulls water from a plant's roots to its leaves.

If a plant's leaves are yellowing, it may be that the plant is deficient in the elements needed to make chlorophyll, which include _____.

magnesium

One of the differences between minerals found in natural fertilizers and minerals found in inorganic commercial fertilizers is __________.

minerals from natural fertilizers are released slowly

Fertilizers are usually enriched in _____.

nitrogen, phosphorus, and potassium

a nutrient mixture that is composed of chemically complex carbon-containing matter, such as compost

organic fertilizer

Which of the following is a macronutrient?

phosphorus

Generally speaking, fluids in plants are

pushed through phloem and pulled through xylem.

Sugar moves from leaves into the _____ of _____ by _____.

sieve-tube members ... phloem ... active transport

A small seed may grow into a very large tree. As the tree grows, it adds a great deal of mass. Where does most of this mass come from?

something in the air

Which of the following is a symptom of nitrogen deficiency?

stunted growth and yellow-green leaves

When referring to phloem transport, the "sink" in roots is created by _____.

the active transport of sugars from phloem to root cells

Guard cells actively open and close the stomata of leaves. What delicate internal balance do these guard cells control with their actions?

the balance between water uptake and gas exchange

When food is labeled 'organic' it means that _____.

the farmer grows food and processes it according to strict guidelines established and regulated by the USDA

The existence of a hydrostatic pressure gradient in phloem tubes can be accounted for by...

the loading of sugars into phloem at sources and removal of sugars at sinks.

Planting these transgenic crops periodically would be beneficial to the environment because

the plants would help clean accumulated salts deposited in the soil by irrigation.

Stomata open during the day in response to _____.

the uptake of K+ by guard cells

The loss of water from the leaves of plants is

transpiration

Water vapor moves out of leaves through open stomata. This process is known as _____.

transpiration

When considering the source-to-sink model of phloem transport, what plant structures can act as either a source or a sink depending on the season?

tubers and bulbs

A botanist discovered a mutant plant that is unable to produce the material that forms the Casparian strip. This plant is _____.

unable to control the amounts of water and solutes it absorbs

Compared to conventional agriculture, organic farming ......

uses fewer synthetic pesticides.

The rate of transpiration is expected to be greatest on a _____ day.

warm and dry

In the water relations of vascular plants, the cohesive property of water is most important in the

xylem