Keywords: 
• cadmium /
• manganese /
• Brassica chinensis /
• interaction /
• low cadmium accumulating cultivar /
• root morphology

Abstract: A solution-culture experiment was conducted to investigate the effects of different manganese (Mn) treatments (0, 0.1, 1.0, 10.0 and 100.0 μmol·L^-1) on the biomass of two cultivars of Brassica chinenesis with different cadmium (Cd) accumulation, as well as the influence on Mn and Cd concentrations in Brassica chinenesis and the root morphological parameters under Cd treatment (10.0 μmol·L^-1). Results show that the biomass of shoots of the two cultivars and roots of the low Cd accumulating cultivar “Huajun” was significantly reduced under low and high Mn treatments when compared with normal Mn treatment (1 μmol·L^-1), but it was not significantly different for root biomass of the common cultivar “Hanlv”. The total Cd accumulation of the two cultivars and the Cd concentrations in shoots of Huajun under low Mn treatments were significantly lower than those under Mn1 treatment. Under high Mn treatments, Cd concentrations in roots and shoots of the two cultivars were increased, but the total Cd accumulation did not significantly change or decrease in comparison with Mn1 treatment. Mn concentrations in shoots and roots of the two cultivars significantly increased with the increasing Mn levels in the solution. Under low Mn treatments, the Mn concentrations in roots of the two cultivars were lower than the critical value of Mn deficiency. Under low Mn treatments, root length, surface area, volume, average diameter and root tip number of “Huajun” significantly decreased compared to those under Mn1 treatment. In contrast with Mn1 treatment, root length of “Hanlv”, root surface area and volume of “Huajun” decreased significantly under high Mn treatments. Under low Mn treatments, the percentage of root surface area of fine roots (≤0.4 mm) in the two cultivars increased, and the percentage of thick roots (≥1.0 mm) decreased, when compared to Mn1 treatment. Under high Mn treatments, the percentage of root surface area of thick roots in “Hanlv” increased and that of fine roots decreased, and the opposite trend was seen in “Huajun”. In general, under low Mn treatments, the growth in roots and shoots of the two cultivars was affected, Cd concentrations in shoots and total Cd accumulation decreased. Under high Mn treatments, the growth of the two cultivars was also inhibited, but Cd concentrations in shoots and roots increased. The root morphological parameters of the two cultivars exhibited different response strategies under different Mn treatments.