Plant materials, conditions and TCDD-treatment

Seeds of date palm (Phoenix dactylifera L.), variety Khalas were washed, air-dried, and stored in plastic bags at room temperature. Seeds were germinated in vitro as described previously (Hanano et al., 2016). Seedlings were obtained 15 days after sowing. Seedlings with a radicle length of 0.5, 2.5, or 5 cm were referred as stage I, II, and III, respectively. Non-germinated seeds (stage 0). The 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD dissolved in toluene at 10 μg mL⁻¹, purity 99%) was purchased from Supelco Inc., USA. To test the effect of TCDD, seeds were daily watered by the prepared solutions at various concentrations of TCDD (0, 10, 50 ng L⁻¹) as described previously (Hanano et al., 2016).