The effects of lead and manganese in soil on males and females of the dioecious herb Spinacia oleracea

• Females of S. oleracea were larger than males. • No detrimental effect was seen as a result of addition of metals (Pb and Mn) as nitrates. • Males accumulated more Pb in their tissues, suggesting greater tolerance to this heavy metal. Males and females of dioecious plant species commonly differ in their morphology, physiology or life-history traits, and also in their response to environmental stress, which may lead to sex biases and eventually to population declines. Metal toxicity is an extreme case of environmental stress, where differences in tolerance between males and females have been reported before, but mainly in woody species (trees from the genus Populus ) . Here, we aimed to increase our understanding of the response of the sexes of dioecious species to metal stress by investigating the individual and combined effects of added Pb and Mn to the soil on the growth and physiological performance of male and female plants of the wind-pollinated herb spinach ( Spinacia oleracea L). We carried out a glasshouse experiment, where male and female plants of S. oleracea were grown in soils without and with added Pb, Mn and combined Pb + Mn (added as nitrates), and with different nutrient levels (‘low’ or ‘high’ nutrients). The addition of Pb and Mn as nitrates did not have any detrimental effects on the growth, chlorophyll content, % N, %C and C/N in spinach plants. Moreover, the addition of Pb (NO 3 ) 2 and Mn (NO 3 ) 2 appears to have increased the nitrates in the soil, as shown by the improved nitrogen content found in plants growing under low nutrients. Male plants accumulated more Pb and Mn in their aboveground tissues than females, but this was not followed by greater detrimental effects on growth. Overall, this study highlights the relevance of the metal species added in causing toxic effects and points to a greater tolerance to metal stress in males of S. oleracea .