Epidermis with stomata of Arabidopsis leaves two or six days after exposure of the seedlings to an agar plaque without (control) or with
). Guard cells were visualized under the fluorescent microscope (450-520 nm) after stained with calcoflour white (the upper level). The lower panel shows the % closed stomata. Based on 3 independent biological experiments with 10 leaves from individual seedlings each. Bars represent SEs. Asterisks indicate significant differences, as determined by Student’s t-test (**P < 0.01).