Physiological and biochemical mechanisms of grain yield loss in fumitory (Fumaria parviflora Lam.) exposed to copper and drought stress

Soil contamination with heavy metals adversely affects plants growth, development and metabolism in many parts of the world including arid and semi-arid regions. The aim of this study was to investigate the single and combined effects of drought and copper (Cu) stresses on seed yield, and biochemical traits of Fumaria parviflora in a split – factorial experiment at Research Field of Payam-E-Noor university of Kerman during 2019. The collected seeds from two Cu contaminated regions were evaluated under drought and Cu (0, 50, 150, 300, and 400 mg/kg) stresses. Drought stress levels were depletion of 50% (D(1)), 70% (D(2)) and 85% (D(3)) soil available water. The individual effects of drought and copper stresses were similar to each other as both reduced seed yield. The highest seed yield was observed at Cu concentration of 50 mg/kg under non-drought stress conditions. The maximum values of malondialdehyde (0.47 µmol/g), proline (2.45 µmol/g FW), total phenolics (188.99 mg GAE/g DW) and total flavonoids (22.1 mg QE/g DW) were observed at 400 mg/kg Cu treatment. However, the strongest antioxidant activity (83.95%) through DPPH assay, and the highest total soluble carbohydrate (115.23 mg/g DW) content were observed at 300 and 150 mg/kg Cu concentration under severe drought stress, respectively. The highest amount of anthocyanin (2.18 µmol/g FW) was observed at 300 mg/kg Cu and moderate drought stress. The findings of this study showed a high tolerance of F. parviflora plant to moderate drought stress and Cu exposure up to 150 mg/kg by modulating defense mechanisms, where grain yield was slightly lower than that of control. The results could also provide a criterion for the selection of tolerance species like F. parviflora for better acclimatization under Cu mines and/or agricultural contaminated soils subjected to drought stress.