Abstract:
Rhizoboxes are soil-root compartments
that may well provide the closest naturalistic conditions for studying root systems architectures (RSAs)
in controlled environments. Rhizobox-based studies
can however lead to mis-estimation of root traits
due to poor recovery of roots and loss of fine root
features during washing of roots. We used a novel
scanner-based rhizobox system to evaluate: (i)
RSA traits of Brassica rapa genotypes; (ii) the relationship between root traits recorded from rhizoboxes and those of harvested roots and (iii) genotypic
variation of seedlings in response to external P ([P]
ext) availability. Brassica rapa genotypes were grown
in soil-filled rhizoboxes abutting flatbed scanners
and were watered once with either deionised water
or a solution of 600 μM KH2PO4 to approximately
80% field capacity on a weight basis. Shoot and
root P concentrations ([P]shoot and [P]root) of the B.
rapa lines grown on different [P]ext were quantified.
Visible root length at the surface of rhizoboxes constituted 85% of the total root length recovered from
harvested root samples. High P supply induced a
strong increase in [P]shoot in all genotypes (P < 0.001)
whereas low P supply generally led to greater partitioning to roots. Seed P concentration and tissue P
concentration were correlated only at low [P]ext. Total
root length was strongly correlated with tissue P
content under both low [P]ext (r = 0.81, P < 0.05) and high [P]ext (r = 0.82, P < 0.05) conditions. The novel
scanner-based rhizobox system used addresses the
substantial limitations associated with current use of
rhizoboxes to study root growth dynamics
