Auxins and Shoot Growth

Question 1

1.

Answer 1

Auxins are synthesised in meristem cells (in shaded side of the plant), diffuse away from tip and bind to receptor sites of cells in zone of elongation.

Question 2

2.

Answer 2

This stimulates a protein pump so pH decreases. This is optimum for wall-loosening enzymes called expansins, which break bonds in cellulose so walls are less rigid.

Question 3

3.

Answer 3

Cells develop large vacuoles and expand as they take in more water by osmosis.

Question 4

4.

Answer 4

Auxins are destroyed by enzymes, causing pH increase to normal. This means expansins can’t work in those conditions so bonds within cellulose reform and the cell can no longer expand.