TABLE 2.

Comparison of the three devices assessed: hydroponic tubes, 2D-rhizotron, and neutron tomography.

Characteristics		Hydroponic tubes	Rhizotron	Neutron tomography
Physical	Dimensions	3.3 × 11.5 cm	44 × 51.5 × 3 cm	3.5 × 10 cm
	Weight of one unit in use	65 g	6 kg	150 g
	Substratum (volume)	Liquid, solution (50 mL)	Membrane + Peat/ perlite (3/2, 2.8 L)	1 mm sand (50 mL)
Biological	Starting biological material	Unrooted herbaceous cutting (without unfolded leaf)	4 weeks pre-rooted herbaceous cutting (with 3 unfolded leaves)	3 weeks pre-rooted herbaceous cutting (with 2 unfolded leaves)
	Contact between roots and substrate	Yes	No	Yes
	Mortality during the experiment	5%	20%	Not evaluated
	Volume of irrigation	50 mL not renewed	300 mL per day	50 mL per day
Technical (for imaging)	Technique	Visible light	Visible light	Neutronic
	Sensor	Digital camera SONY- DSC-HX60	Scanner EPSON GT-15000	Camera CCD
	Resolution/ Level of precision	10 Mpixels (3648 x 2736)	300 dpi	6.8 mm/theoric pixel; 15.2 mm/pixel in the essay
	Type of data	2D imaging (pixel-based gray value images)	2D imaging (pixel-based gray value images)	180 2D images with a rotation of 1°
	Number of acquisition per plant	1 picture	2 scans	1 scan/ 1 3D reconstruction
	Field of view	Non-relevant	297 x 420 mm	8 x 80 mm
Phenotypic traits that could be determined	ARN	X	X	X
	ARL		X	X
	DIA		X	X
	LRN		X	X
	LLRL		X	X
	RSV			X
Logistic	Time required before mounting the test	10 min (cut of the mother plant)	4 weeks (time of pre-rooting)	3 weeks (time of pre-rooting)
	Time of assembly / disassembly of a unit	5–1 min	30 min–1 h	5–1 min
	Number of units available or manageable	60 manageable	12 available	As needed
	Occupied area for 10 units	0.02 m2	1.5 m2	0.05 m2
	Average acquisition time for a unit	10 s	15 min	4 h 40
	Maximum duration of an essay	4 weeks	5–6 weeks	Not evaluated
	Estimated average cost per unit per test	Less than 1 euro per tube	600 euros per unit	Zero*
	Specific remarks	–	–	3000 euros/day**

For each of the 3 devices, the table summarizes the main physical aspects, biological characteristics, technical parameters for image acquisition, logistic, and economic characteristics taken into consideration in this study.

*if official proposal selected by the large-scale infrastructure selection committee.

**if results are subject to confidentiality.

ARN: Adventitious Roots Number; ARL: Adventitious Root Length; DIA: Diameter of the Adventitious Root; LRN: Lateral Root Number; LLRL: Longest Lateral Root Length;

TNN: Total Number of Nodules; PNN: Primary Nodule Number; RSV: Root System Volume.