Interaction of lead and cadmium on growth and leaf morphophysiological characteristics of European hackberry (Celtis australis) seedlings

Background In the present study, different concentrations of lead (factor A; 0, 15, and 30 mg L (-1)) and cadmium (factor B; 0 and 5 mg L (-1)) were applied via irrigation water during 6 months to evaluate their effects on growth of European hackberry (Celtis australis L.) plants. The experiment was arranged in factorial with completely randomized design and four replications under greenhouse conditions. Results Application of 5 mg L (-1) Cd or the lead levels (15 and 30 mg L (-1)) significantly reduced new shoot growth, plant leaf area, SPAD value, leaf water conductance and leaf photosynthesis, whereas significant increase in number of chlorotic and necrotic leaves, leaf transpiration rate, leaf proline and soluble sugars was observed. Higher reduction in new shoot growth and leaf water conductance and higher increase in leaf soluble sugars and proline was observed over the interaction of 5 mg L (-1) Cd and 30 mg L (-1) Pb. The highest soluble sugars and proline were in Pb30Cd5 (a3b2) treatment. Leaf Pb or Cd concentration was increased following their treatment. Application of cadmium significantly reduced leaf Pb, and similarly leaf Cd was significantly reduced by application of lead at both levels compared to untreated plants. Conclusion The results showed that the hackberry growth was influenced by positive and negative interactions of Pb and Cd applied in irrigation water. The extent of growth reduction indicates that hackberry represents a relatively tolerant ornamental tree to high Pb and Cd levels.