Fig. 2

Pictures visualizing poplar plant development in hydroponic cultivation. About 7 days after the start of the rooting phase, the buds began to swell (a) and the first roots emerged (b). A few days after bud break, fully functional shoots with intact leaves developed (c). The highest number of roots per stem cutting was typically achieved within 14 days (d) and only a very limited number of roots emerged afterwards (e). When plants were harvested after 5 weeks of hydroponic cultivation, the shoots were about 11 cm tall and had eight leaves, whereas eight to ten roots had developed having mean lengths of 13 cm (f). Scale bar = 5 cm, only for picture (f)