Which of the following statements best summarizes the acid growth hypothesis in an actively growing shoot?
A) Auxin stimulates proton pumps in the tonoplast to pump hydrogen ions out of the vacuole and allow water to enter.
B) Auxin-activated proton pumps lower the pH of the cell wall, which breaks hydrogen bonds and makes the walls more flexible.
C) Auxins and gibberellins together act as a lubricant to allow cellulose microfibrils to slide past each other.
D) Auxins activate aquaporins that increase turgor pressure in the cells forcing them to expand.

Question

Quizplus · Accepted Answer

The acid growth hypothesis suggests that auxin (a plant hormone) stimulates proton pumps in the plasma membrane, not the tonoplast, to pump hydrogen ions (H+) into the cell wall. This acidification of the cell wall region lowers the pH, which activates expansins and other enzymes that break hydrogen bonds between cellulose fibers, making the cell walls more flexible and allowing for cell expansion.

Which of the Following Statements Best Summarizes the Acid Growth