Results and discussion Owing to callus itself had the ability to produce secondary metabolic compounds, plant tissue culturists use this capacity to gain many useful chemicals via callus culture in vitro such as flavor and fragrance, pigment and pharmaceutical compounds [16]-[19]. In the present research, lemon basil callus could be induced only on the MS medium containing all concentrations of 2,4-D not the basal one. This result indicated that plant growth regulator was necessary for callus production of lemon basil. Callus derived from leaf of lemon basil came out around the cutting edge of explant on 3-4 days after cultured. However, there had been the small amount of callus produced in the first week (Figure 1). So, fresh weight of callus was started detecting on the second weeks (Figure 2). At 0.25 mg/l 2,4-D on week 2, callus was mostly light-green and compact and this color apparently disappeared during the time course. The other two concentrations (0.5 and 1 mg/l 2,4-D) also gave non-friable calli but whitish from the beginning and browning of those calli obviously seen at the final week.