Winrhizo pro 2015

We measured seven aboveground and fine-root morphological traits related to drought responses and resource use strategies. For aboveground traits, before harvesting, we measured vegetative plant height (Height, cm) and collected one young and fully expanded leaf from three individuals in each pot. For fine-root traits, we collected a sample (10-50mg) of finest roots (<2 mm) from each pot. Leaves and roots were scanned (Epson Perfection 3200 and Epson V700 photo scanner, respectively) and then dried for 72h at 60°C to measure dry leaf and root biomass. Leaf scans were processed with ImageJ software to determine leaf area (LA, mm²). Root scans were processed with WinRHIZO Pro 2015 (Regent Instruments Inc., Canada) to calculate average root diameter (AvgD, mm) and root length (cm). With these measurements, we estimated specific leaf area (SLA, the ratio of fresh leaf area to leaf dry mass, mm² mg^-1) and leaf dry matter content (LDMC, the ratio of leaf dry mass to leaf fresh mass, mg g^-1) for each leaf and averaged the values for each species at the pot level. We also calculated specific root length (SRL, the ratio of root length to root dry mass, cm g^-1) and root dry matter content (RDMC, the ratio of root dry mass to root fresh mass, mg g^-1) for each species at the pot level, due to the complexity associated with disentangling individual roots within a pot.

Arabidopsis seedlings were allowed to germinate and grow for 14 days on MS medium as described above for the nematode bioassays. To determine the total root length and number of root tips of the seedlings, the complete plants were transferred from the media onto a plastic tray with water. Next, the leaves of the seedlings were removed and the roots were spread out over the surface of the tray. The total root length was measured using the WinRHIZO package for Arabidopsis (EPSON perfection V800, WinRHIZO pro2015, Regent Instruments Inc., Quebec, Canada). The number of root tips was counted manually based on the scan made using WinRHIZO. Differences in the total root length per seedling in centimetres and the number of root tips were statistically analysed with a two‐way ANOVA and post‐hoc Tukey’s HSD test in R (P < 0.05).

Arabidopsis seedlings were allowed to germinate and grow for 14 d on MS medium as described above. To determine the number of root tips and root length of the seedlings, the complete plants were transferred from the media onto a plastic tray with water. Next, the leaves of the seedlings were removed and the roots were spread out over the surface of the tray. A scan of the roots was made with a photo scanner (Epson Perfection V800). The scan was analysed to measure root length using WinRhizo package for Arabidopsis (WinRhizo pro2015; Regent Instruments Inc., Ville de Québec, Canada). The number of root tips was counted by visually inspecting the scan. Differences in the number of root tips and the root length per plant were statistically analysed for significance with a two‐way ANOVA and post‐hoc Tukey HSD test in R (P < 0.05).