[Campbell Biology P.856] Which of the following statements correctly describes a step in the... | Practice Question
Which of the following statements correctly describes a step in the process of cation exchange in soil as illustrated in Figure 37.3?
A: Roots directly absorb mineral cations from the soil solution without any prior exchange.
B: Carbon dioxide released by roots reacts with water to form carbonic acid, which then dissociates, releasing H+ ions.
C: H+ ions released by soil particles directly bind to mineral cations, making them unavailable for plant uptake.
D: Soil particles become positively charged, attracting and binding mineral cations.
Explanation
Figure 37.3, step 2, clearly shows that CO2 released by roots reacts with H2O to form H2CO3, which then dissociates into HCO3- and H+. These H+ ions are crucial for the cation exchange process.