The effects of 2,4-Dichlorophenoxyacetic acid and leaf surface orientation on callus induction of black betel (Piper betle L. var. nigra)

Black betel (Piper betle L. var. nigra), which has pharmacological properties against a number of infectious disorders, contains secondary metabolites like alkaloids, terpenoids/steroids, flavonoids, and tannins. While preserving plant availability, callus culture can quickly enhance the production of these secondary metabolites. This study aims to determine the combination of the concentration of growth regulator 2,4-Dichlorophenoxyacetic acid (2,4-D) and the optimal position of leaf explants for the induction of black betel callus. This study is an experimental study using a complete randomized design with combinations of treatments between concentrations of 2.4-D growth regulators (0.0 mg/l; 1.5 mg/l; 2.5 mg/l; 3.5 mg/l) and leaf explant position (abaxial contact with media and adaxial contact with media). Quantitative data obtained were analyzed using the Kruskal-Wallis test and Mann-Whitney test on the SPSS program. Meanwhile, qualitative data in callus morphology were analyzed descriptively. The treatment of 1.5 mg/l 2,4-D using abaxial leaf position can be chosen as optimal combination of treatment. The results showed no significant difference (P>0.05) for many of the observed variables between this treatment compared to treatment with higher concentration of 2,4-D. MS media with 1.5 mg/l 2,4-D and abaxial leaf position can induce callus at 2.4 weeks after planting, caused 100 % percentage of explants forming callus, browning score of 2.1, 10% explant contamination, callus growth score of 2.6 and callus morphology in the form of yellowish-white callus color and compact callus texture.