The strips were incubated in the opening medium alone, or treated with 10 mM ABA for 30 min in the light.
After treatment, the strips were examined using an epifluorescence (excitation 470–480 nm, emission 515–550 nm) and a bright-field microscope (AX-80T; Olympus Optical Co. Ltd., Tokyo, Japan) with a digital camera (DP 70; Olympus Optical Co. Ltd.).
Fluorescence emission of guard cells was analysed using Adobe Photoshop 5.5