Organic molecules make up what percentage of the dry weight of a plant?

96%

A mineral deficiency is likely to affect older leaves more than younger leaves if

the mineral is very mobile within the plant

What should be added to soil to prevent minerals from leaching away?

humus

You are weeding your garden when you accidentally expose some roots. You notice swellings (root nodules) on the roots. Most likely your plant

is benefiting from a mutualistic bacterium

For this pair of items, choose the option that best describes their relationship:

A) suffers from a mineral deficiency

B) is infected with a parasite

Item A is less than item B

Which of the following is not a function of rhizobacteria?

supply growing roots with glucose

Why is nitrogen fixation such an important process?

fixed nitrogen is most often the limiting factor in plant growth

What is the major function of sodium in plants?

required to regenerate phospophenolpryuvate in C4 and CAM plants

What are epiphytes?

plants that grow on other plants but do not obtain nutrients from hosts

The earliest vascular plants on land had underground stems (rhizomes) but no roots. Water and mineral nutrients were most likely obtained by

absorption by mycorrhizae

What soil(s) is(are) the most fertile?

both humus and loam

In hydroponic culture, what is the purpose of bubbling air into the solute?

to provide oxygen to the root cells

The bulk of a plant's dry weight is derived from

CO2

Two groups of tomatoes were grown under laboratory conditions, one with humus added to the soil and one a control without the humus. The leaves of the plants grown without the humus were yellowish (less green) compared with those of the plants grown in humus-enriched soil. The best explanation for this difference is that

the humus contained minerals such as magnesium and iron, needed for the synthesis of chlorophyll

Which of the following best describes the general role of micronutrients in plants?

they are cofactors in enzymatic reactions

The data of Figure 37.1 indicate that the plant

grows best in soil air levels above 15% and grows the same in 15% and 20% soil air percent

There are several properties of a soil in which typical plants would grow well. Of the following, which would be the least conducive to plant growth?

compacted soil

Reddish-purple coloring of leaves, especially along the margins of young leaves, is a typical symptom of deficiency of which element?

P

We would expect the greatest difference in plant health between two groups of plants of the same species, one group with mycorrhizae and one group without, in an environment

in which soil is relatively deficient in mineral nutrients

A woodlot was sprayed with a fungicide. What would be the most serious effect of such spraying?

a decrease in tree growth due to the death of mycorrhizae

You are conducting an experiment on plant growth. You take a plant fresh from the soil that weighs 5 kg. Then, you dry the plant overnight and determine the dry weight to be 1 kg. Of this dry weight, how much would you expect to be made up of organic molecules?

960 grams

Which of the following is a true statement about nitrogen fixation in root nodules?

leghemoglobin helps maintain a low O2 concentration within the nodule

Which of the following is not true of micronutrients in plants?

They are the essential elements of small size and molecular weight

The enzyme complex nitrogenous catalyzes the reaction that reduces atmospheric nitrogen to

NH3

For this pair of items, choose the best that describes their relationship:

A) the amount of nitrogen in a fertilizer marked "15-10-15"

B) the amount of nitrogen in a fertilizer marked "15-5-5"

Item A is exactly or very approximately equal to item B

Which of the following best describes the fate of most of the water taken up by a plant?

it is lost during transpiration

When performing a mineral nutrition experiment, researchers use water from a glass still. Why is it not a good idea to use regular distilled water from a stainless steel still?

metal ions dissolving off the steel may serve as micronutrients

Some of the problems associated with intensive irrigation include all but

overfertilization

Most of the mass of organic material of a plant comes from

carbon dioxide

A farming commitment that embraces a variety of methods that are conservation-minded, environmentally safe, and profitable is called

sustainable agriculture

The rhizosphere would best be described as

soil that is bound to roots and differs from the surrounding soil in containing many more microbes

Among important crop plants, nitrogen-fixing nodules are most commonly an attribute of

legumes

What is the mutualistic association between roots and fungi called?

mycorrhizae

Dwarf mistletoe grows on many pine trees in the Rockies. Although the mistletoe is green, it is probably not sufficiently active in photosynthesis to produce all the sugar it needs. The mistletoe also produces haustoria. Thus, dwarf mistletoe growing on pine trees is best defined as

parasite

Micronutrients are needed in very small amounts because

most serve mainly as cofactors of enzymes

A young farmer purchases some land in a relatively arid area and is interested in earning a reasonable profit for many years. Which of the following strategies would best allow such a goal to be achieved?

selecting crops adapted to arid areas

Most of the dry weight of a plant is the result of uptake of

CO2 through stoma

For this pair of items, choose the best that describes their relationship:

A) the percent of plant species that form ectomycorrhizae

B) the percent of plant species that form mycorrhizae

Item A is less than item B

What is the major function of nitrogen in plants?

component of DNA and RNA

Which of the following is a primary difference between ectomycorrhizae and mycorrhizae?

Ectomycorrhizae do not penetrate root cells, whereas endomycorrhizae grow into invaginations of the root cell membranes

Mycorrhizae enhance plant nutrition mainly by

absorbing water and minerals through the fungal hypae

Which soil mineral is most likely leached away during a hard rain?

NO3

Which of the following elements is incorrectly paired with its function in a plant?

sulfur - component of DNA; activates some enzymes

Hyphae form a covering over roots. Altogether, these hyphae create a large surface area that helps do which of the following?

aid in absorbing minerals and ions

In a root nodule, the gene coding for nitrogenase

is part of the Rhizobium chromosome

Based on the information provided above, what is the most likely cause of the decline in productivity?

the soil water potential has become more negative due to salination

Nitrogen fixation is a process that

converts nitrogen gas into ammonia

The best conclusion from the data in Figure 37.1 is that the plant

grows fastest in 5 to 10% air

What is the function of a root nodules leghemoglobin?

regulate the supply of oxygen to Rhizobium

Which of the following is of least concern to a researcher in a mineral nutrition experiment?

ability of a laboratory balance to weigh very small quantities of chemicals

For this pair of items, choose the option that best describes their relationship:

A) the amount of molybdenum in a gram of dried plant material

B)the amount of sulfur in a gram of dried plant material

Item A is less than item B

If you wanted to increase the cation exchange and water retention capacity of a loamy soil, what should you do?

add clay to the soil

The best explanation for the shape of the growth response curve in Figure 37.1 is that

the roots require oxygen for respiration and growth

For this pair of items, choose the option that best describes their relationship:

A) the number of essential macronutrients required by plants

B) he number of essential micronutrients required by plants

Item A is greater than item B

Carnivorous plants have evolved mechanisms that trap and digest small animals. The products of this digestion are used to supplement the plant's supply of

minerals

The most efficient way to increase the essential amino acids in crop plants for human consumption is to

breed for higher yield of deficient amino acids

Which element is important in the formation and stability of cell walls?

calcium

Which of the following essential nutrients plays an essential role in the opening and closing of the stomatal aperture?

K

If you were the country agricultural agent, what would be the best advice you could give the farmer who owns the field under a study in Figure 37.2?

plant variety of cotton that requirers less water and can tolerate salinitiy

Some plants extract and concentrate heavy metals from the soil. A current use for such plants is

photoremediation of pollutes sites

All of the following contributed to the dust bowl in the American southwest during the 1930s except

clear cutting of forest trees

A growing plant exhibits chlorosis of the leaves of the entire plant. The chlorosis is probably due to a deficiency of which of the following macronutrients?

nitrogen

If a plant is infected with Rhizobium, what is the probably effect on the plant?

it probably will grow faster

Iron deficiency is often indicated by yellowing in newly formed leaves. This suggest that iron

is a relatively immobile nutrient in plants

What is meant by the term chlorosis?

the yellowing of leaves due to decreased chlorophyll production

The N-P-K percentages on a package of fertilizer refer to the

percentages of three important mineral nutrients

If an African violet has chlorosis, which of the following elements might be a useful addition to the soil?

magnesium

In what way do nitrogen compounds differ from other minerals needed by plants?

only nitrogen requires the action of bacteria to be made available to plants

A soil well suited for the growth of most plants would have all of the following properties except

a high pH

Which two elements make up more than 90% of the dry weight of plants?

oxygen and carbon

Most crops acquire their nitrogen mainly in the form of

NO3

What are the three main elements of which plant growth and development depend?

oxygen; carbon; hydorgen

In the 1640s, Jan Baptista van Helmont planted a small willow in a pot that contained 90.9 kg of soil. After five years, the plant weighed 76.8 kg, but only 0.06 kg of soil had disappeared from the pot. What did van Helmont conclude from this experiment?

the increase in the mass of the tree was from the water that he added over the five years