Auxin activates proton pumps that acidify the apoplast and loosen cell walls. This allows cell expansion in IB Biology HL C3.1.21.
Plants have cell walls composed of cellulose.
When a plant cell grows, the cell wall must expand. Explain the role of auxin in cell wall expansion.
a. auxin causes (specific) genes to be transcribed/expressed;
b. stimulates proton pumps/causes movement of hydrogen ions into cell wall/through plasma membrane;
c. hydrogen ions/low pH/acidity loosens connections between cellulose (microfibrils/fibers)
OR
hydrogen ions/acidity activates expansin / expansin breaks/reforms connections between cellulose;
d. loosened cellulose can move apart/separate so wall becomes weaker/can expand;