The "dustbowl" of the 1930s resulted from _____.
the removal of the native grasses that held the soil in place and planting of agricultural crops
Soil can easily become deficient in _____, because these ions are negatively charged and do not stick to negatively charged soil particles.
The particles in soil are important because they _____.
are charged and hold ions needed by plants
Fertilizers are usually enriched in _____.
nitrogen, phosphorus, and potassium
Which of the following would be considered a sustainable agricultural practice?
What is the goal of phytoremediation?
to clean contaminated sites by using plants that have the ability to extract and store soil pollutants
Why do farmers need to be concerned with the pH level of soil?
The pH level of soil affects cation exchange and influences the chemical form of minerals.
At low soil pH levels (5 or less), what can happen?
Toxic aluminum ions become more available, stunting the plant's growth.
Phytoremediation is showing promise as a sustainable, cost-effective way to decontaminate soil and water. In the case of a hyperaccumulater such as Thlaspi caerulescens, however, what might be a drawback of the technology?
Herbivores that eat the plant may be poisoned.
Carnivores that eat the herbivores that eat the plant may be poisoned.
The third and fourth responses are correct.
The biological process that produces 96% of the dry mass of a plant is called _____.
Which of the following substances does a plant obtain from the air?
A botanist claims to have discovered a new macronutrient required for plant growth. Most of this scientist's colleagues are skeptical of her claim. Why might they consider it unlikely?
Any nutrient needed in large amounts (macronutrient) has probably been noted already.
If a plant's leaves are yellowing, it may be that the plant is deficient in the elements needed to make chlorophyll, one of which is _____.
If a plant is deficient in _____, it will not be able to make DNA.
Soil could be deficient in any of the following nutrients. If you had to supply one of them, which would be needed in the smallest amount?
Which is true regarding mineral deficiency symptoms in plants?
Growing tissues would show signs of mineral deficiency of mobile nutrients after older tissues.
When you add "plant food" to your potted geraniums, you are actually providing the plant with _____.
How did the addition of a gene for citrate synthesis increase the tolerance of tobacco and papaya plants to high aluminum concentrations in the soil?
The citric acid produced by the plants bound the free aluminum in the soil, making it less available to be taken up by the plants.
What is the main benefit of the Sub1A-1 gene?
What supplies the energy for most of the microorganisms in the rhizosphere?
The most abundant gas in our atmosphere cannot be used by plants directly in its atmospheric form and is, therefore, captured by certain bacteria that live symbiotically in their roots. What is this gas?
Nitrogen fixation is _____.
converting nitrogen in the air to a form usable by plants
the enzyme that catalyzes the conversion of atmospheric nitrogen to ammonia is _____.
Which of the following organisms can fix nitrogen?
Legumes (members of the pea family) have roots with swellings called nodules that _____.
contain nitrogen-fixing bacteria
Which of these describes the initial interaction between Rhizobium and a soybean root?
Soybeans secrete chemical signals that are detected by Rhizobium.
In root nodules, the mutualistic association between legumes and bacteria, the plants provide _____, and the bacteria provide _____.
carbohydrates ... fixed nitrogen
Mycorrhizae develop _____.
between roots and beneficial fungi
Which of the following is true of mycorrhizae?
Arbuscular mycorrhizae do not have a dense mantle ensheathing roots.
By trapping insects, carnivorous plants obtain _____, which they need _____.
nitrogen ... to make protein