Three-dimensional architecture of axile roots of field-grown maize

The framework of root system architecture is shaped by the three-dimensional (3D) trajectory of the axile roots. However, methods for characterising root trajectory in the field are lacking. Our aim was to develop a new method for quantifying the spatial distribution of axile roots of maturing plants. The trajectory of axile roots of two maize cultivars was measured using a 3D digitiser in situ in the field, in parallel with diameter measurements along the same roots based on scanned images. The measured diameters were then mapped onto the digitised trajectory. We show that inter-plant distances did not influence root trajectory in either cultivar. The two cultivars had different initial angles from the vertical and presented slightly different patterns of root angle distribution. The reorientation of an axile root downwards was related to its angle and diameter, which can serve as a valuable resource for the parameterisation of root architecture models. The method is suitable for accurate determination of the 3D architecture of axile roots of mature maize plants under field conditions. The value of acquiring a relative complete root trajectory is highlighted.