Should the root tubes be installed vertically, horizontally or at an angle?

The angle the root tubes are installed will depend on the species, type of study (i.e. agriculture, forestry). Often, root tubes are installed at a 45° angle, especially when looking at fine root growth. However, a study by Villordon et al. (2011) , found vertically installed root tubes gave the best estimate of root growth and storage roots development in sweet potato, Ipomoea batatas.