Fig. 6

Transmitted light imaging quantified changes in vacuolar pH. Red onion epidermal cells were incubated on 40 mM MES at pH 7, or on this buffer containing 25 mM methylamine (MA), and were imaged with 6 different wavelengths (405, 456, 488, 514, 561 and 633 nm). a Colour transmitted light imaging after incubation of buffer alone. b Colour transmitted light imaging after treatment for 10 min with 25 mM methylamine. c–e For each of the wavelengths and for each cell, a vacuolar absorbance value was calculated. This was defined as 1 minus the background-corrected transmission of the laser, relative to a cell-free reading. Absorbance values for cells at 405 nm (c), 488 nm (d) and 633 nm (e) correlated to absorbance measured at 561 nm. Each dot represents a different cell, and data were fitted with quadratic (c, d) and exponential equations (e). Absorbance of red light (e) was much stronger in the MA-treated cells, consistent with the change in colour