Consider the following statements regarding limiting nutrients. Select True or False for each statement.

T/F Nitrogen (N), phosphorus (P), and potassium (K) are common examples.

T/F Their presence limits the availability of micronutrients.

T/F Their availability tends to limit plant growth.

T/F Certain macronutrients and micronutrients can be considered limiting nutrients.

Where does most nutrient uptake occur in roots?

a. At the root cap, where root tissue first encounters soil away from the zone of nutrient depletion

b. At the Casparian strip, where ions must enter the symplast before entering xylem cells

c. In the symplastic and apoplastic pathways

d. In root hairs, in the zone of maturation

Why are proton pumps in root-hair plasma membranes important?

a. They pump protons into cells, generating a membrane potential (voltage).

b. They allow toxins to be concentrated in vacuoles, so the toxins do not poison enzymes in the cytoplasm.

c. They set up an electrochemical gradient that makes it possible for roots to absorb cations and anions.

d. They set up the membrane voltage required for action potentials to occur.

Why is the presence of clay particles important in soil?

a. They provide macronutrients—particularly nitrogen, phosphorus, and potassium.

b. They bind metal ions, which would be toxic if absorbed by plants.

c. They allow water to percolate through the soil, making oxygen-rich air pockets available. d. The negative charges on clay bind to positively charged ions and prevent them from being leached out of the soil.

Suppose that certain root cells have an overall charge that is more negative than normal. What impact would this likely have on the uptake of anions such as NO3⁻?

a. Anions would be less likely to enter roots.

b. Anions would be more likely to enter roots.

c. This would have no impact on the ability of anions to enter roots.

d. This would make anions and cations equally likely to enter roots.

In a semester-long experiment tracking growth in plants, your lab partner—who often skips class—carefully records the mass of water added to a potted plant with the expectation that this addition will be fully accounted for in the mass gained by the plant. Is your lab partner right or wrong? Explain.

Your friend claims that all plants are autotrophs because they perform photosynthesis. Is that a correct statement? Explain.

Why is it important for plants to exclude certain ions?

Summarize the difference between active and passive exclusion mechanisms.

There is a conflict between van Helmont's data on willow tree growth and the data on essential nutrients listed in Table 36.1. According to the table, nutrients other than C, H, and O should make up about 4 percent of a willow tree's mass. Most or all of these nutrients should come from soil. But van Helmont claimed that the soil in his experiment lost just 60 g, while the tree gained 74,000 g. Calculate the percentage of the added mass accounted for by soil, and compare it to the predicted 4 percent. State at least one hypothesis to explain the conflict between expected and observed results. How would you test this hypothesis?

Design an experiment, using radioactive carbon and the heavy isotope of nitrogen (15N₂), that would test whether the Rhizobia–pea plant interaction is mutualistic.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship? Based only on the information provided here, make a prediction on the effect of diving ants on overall pitcher plant growth.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind.

What nutritional impact do the ants have on fanged pitcher plants?

Do the pitcher plants derive any nutritional benefit from this relationship?

Nitrogen is a key nutrient often obtained by carnivorous plants from the insects they digest. Are the results presented here what would be expected if nitrogen is a limiting nutrient? Explain.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind.

What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship?

Carnivorous plants and legumes (e.g., peas, soybeans) both absorb key nutrients directly from other organisms. How is nutrient acquisition in pitcher plants similar to that in legumes? How is it different?