Measurements
Five plants were randomly selected from each treatment. To scan root
traits of every plants, the roots were severed from the shoot at the
root collar and then were gently washed with running tap water over a
sieve with a mesh size of 0.2 mm. Each root sample was scanned in water
with a flatbed scanner (Epson Perfection V700 Photo, Seiko Epson
Corporation, Nagano, Japan). Subsequently, the images were analyzed
using the software winRHIZO (Regent Instruments
Canada Inc., Quebec, QC, Canada). Root traits analyzed were total root
length (calculated using a one pixel thinned image and multiplying the
number of pixels by pixel size), root surface area (calculated by
determining the root diameter and length), root volume (calculated using
the root surface area and length), an root tips (Wang and Zhang 2009).
After scanning, root samples were oven-dried at 65°C to constant weights
and weighed to determine root dry biomass. Root tissue density (RTD) was
determined by the ratio of root dry biomass to root volume. Specific
root length (SRL) was estimated by the ratio of total root length to
root dry biomass.