Fig. 6.

Short (S) and long (L) adventitious roots of rice plants transferred into an O₂-free agar solution with methylene blue. Methylene blue is colourless when reduced and blue when oxidized. Arrow denotes the ‘blue halos’ adjacent to adventitious roots. Plants were raised for 3–4 weeks in aerated nutrient solution, prior to transfer to stagnant deoxygenated agar nutrient solution for 0, 6, 12, 24, 48 or 120 h (A). Scale bar = 10 mm. Percentage of roots with ‘blue halos’ along short and long adventitious roots (B). Lengths at the commencement of treatment were: short (65–90 mm) and long (105–130 mm) adventitious roots. Sample numbers and length of roots used in these measurements are given in Supplementary Data Table S1, available online. *Significant difference between short and long adventitious roots (P < 0·05, Fisher's exact test).