Phytotoxic effect of 2,4-D and dicamba on date palm (Phoenix dactylifera L.) tissue cultures at initiation stage

The phytotoxic effect of different concentrations of 2,4-D (2,4-dichlorophenoxyacetic acid) and Dicamba (3,6-dichloro-2-methoxybenzoic acid) on procallus growth of date palm (Phoenix dactylifera L.) Hillawii cultivar was investigated. Maximum fresh and dry weights of procallus were obtained in 2,4-D 50 mg/L and dicamba 10 mg/L. A delay in procallus initiation and severe browning responses were observed in cultured tissues at high concentration of 2,4-D (100 mg/L) compared to low ones. A biochemical analysis of date palm procallus revealed that the high concentration of 2,4-D (100 mg/L) led to a significant accumulation of total carbohydrates, free proline content, total phenolic compounds and high activity of peroxidase, as well as, a significant reduction in free amino acid and total soluble protein production, compared to low concentration of 2,4-D 50 mg/L and Dicamba 10 mg/L.