Corn Seeds Were Germinated on Two Petri Dishes of Agar

Corn seeds were germinated on two petri dishes of agar containing a colored pH indicator. The dishes were placed on edge with the seedling oriented either vertically (A) or horizontally (B) . After 24-hours growth, the plates appeared as in C and D. Dark areas in D indicate lower pH. Which of the following statements is supported using the data?

A) During gravitropism, the concentration of auxin is higher on the topside of a coleoptile and the bottom side of a root.
B) During gravitropism, the pH is higher on the topside of the coleoptile and the bottom side of the root.
C) The higher the concentration of auxin in a tissue, the lower will be the pH around that tissue.
D) Phototropism affects only stems causing them to bend up; gravitropism affects only roots causing them to bend down