Variability in cadmium and zinc shoot concentration in 14 cultivars of sunflower (Helianthus annuus L.) as related to metal uptake and partitioning

• Cd and Zn shoots concentrations differed by around 2-fold between 14 sunflower genotypes.
• Differences in shoot Cd content were explained by differences in uptake and translocation.
• Differences in shoot Zn content were mainly explained by differences in uptake.
• Differences in metal uptake were not related to the branching density of roots.

AimsCadmium (Cd) is a very toxic metal in soils, contaminating agricultural crops due to its absorption by roots. Among crops, sunflower (Helianthus annuus L.) accumulates relatively high amounts of Cd. This work examined the variability of Cd and zinc (Zn) in shoots of sunflower cultivars and investigated if the variability was linked to the shoot growth, to the metal uptake and to the metal partitioning aboveground.MethodsFourteen cultivars of sunflower were cultivated in a nutrient solution containing 20 nM of Cd(NO3)2 and 760 nM ZnSO4. The between-cultivar variability for the total Cd and Zn content in root and shoot biomass was determined at the 6–8 leaf stage and possible correlations with the biomass and root architecture were investigated.ResultsCd and Zn concentrations in shoots differed between cultivars by a factor of 2.3 and 2.2, respectively. Metal uptake was more positively correlated with shoot biomass than with root biomass and was not correlated with root architecture. The between cultivar differences for metal concentration in shoots was explained by differences in uptake relative to shoot growth and for Cd, by the partitioning of the metal between roots and shoots.ConclusionsThis study suggests that Cd root uptake relative to shoot growth and Cd partitioning to shoots could be targets for selecting cultivars having a low (for crop quality) or a high (for phytoextraction) Cd content aboveground.