Fig. 5
Time courses showing the effects of a range of KNO3 and NH4Cl concentrations on Arabidopsis root and shoot development. Images were captured robotically by the Microphenotron and quantitative data generated using fully automated image analysis software (AutoRoot). A suspension of Arabidopsis seed that had been surface-sterilised and soaked in water at 4o for 48 h was sown onto the gel surface of the Phytostrips as clusters of 5–6 seed per well. The initial N supply in the gel of the Phytostrips and in the 150 µl liquid medium in the microtitre plates was 0.05 mM KNO3. After 4 days in the growth room, when most roots were first visible, the nutrient solution in the microtitre wells was replaced with a fresh nutrient solution containing the appropriate concentration of either KNO3 or NH4Cl to give a final theoretical concentration of 0.5, 2, 11 or 44 mM of the respective N source after diffusion into the gel. The control treatments contained only 0.05 mM KNO3. Three replica 96-well plates were set up, each with a full set of all eight N treatments (one per Phytostrip) plus two control Phytostrips (the Phytostrips at either end serving as buffers against edge effects). Images of the developing seedlings were captured robotically from above and the side on the day of treatment and daily thereafter and analysed using the AutoRoot software [19]. Time-courses of the development of five of the software-generated traits have been plotted: a, b ‘root mass’, a likelihood estimate of the total root mass in each well; c, d ‘Q0-horizontal’, a trait that allows lateral root branching in the top quadrant of each well to be tracked; e, f ‘Q3-vertical’, a trait that allows the extent of primary root growth in the bottom quadrant of each well to be tracked; g, h ‘leaf area’, a measure of the total area of leaves as viewed from above (an underestimate of the actual leaf area at later time points because of overlap between leaves); i, j ‘leaf hue’, a measure of the greenness of the leaves (n = 24 ± SE). The scale for hue on the y axis is from 0 (red) to 120 (green)