Fig. 2.

Root hair surface pH oscillations lag growth oscillations. (A) Simultaneous measurement of pH-dependent fluorescence and tip growth showed that surface pH at the root hair tip and growth rate oscillate with the same periodicity but out of phase. Fluorescence intensity (F.I.) was measured in an ROI close to the apex of the growing root hair (see Fig. 1). Note that peaks in alkalinization follow peaks in growth. Data are representative of n = 10 root hairs. (B) Cross-correlation analysis showed that pH oscillations lag growth oscillations by 7.0 ± 0.3 s (means ± SD of n = 10 root hairs).