Chapter 35, Problem 3
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.
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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 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.