A Illustrations depicting the traditional notion of reaction wood. Top: a single stem bent away from the vertical, Bottom: a transverse section showing the tension wood region more darkly shaded. B Images displaying reaction wood in field-grown willow. Top: Photograph of mature willow stems grown in a UK field trial. Bottom: Midpoint 20-μm transverse section of a single stem from a mature field-grown willow tree. Stained in 1% Chlorazol Black E in methoxyethanol (black – binds specifically to the gelatinous layer within the G-fibres of tension wood ) and 1% aqueous Safranin O (red – binds to the secondary cell wall in a non-specific manner). Scale bar = 5 mm.