| Summary: | The common trait of all auxins is a stimulation of cell elongation and also cell division in the presence of cytokinin; both are essential for callus induction and its multiplication. The response of plant tissues to various compounds with auxin activity may be quite different. In this study, the effectiveness of a synthetic auxin, 2,4-dichlorofenoxyacetic acid (2,4-D), instead of the generally applied natural auxin, indole-3-acetic acid (IAA), was tested for the proliferation of Nicotiana tabacum callus. The following concentrations of 2,4-D were tested: 0.1, 0.5, 1.0, 1.5, and 2.0 mg dm−3. Callus was derived from stem pith and its proliferation allowed on MS medium through five subcultures at 25°C and in darkness. After each passage, the fresh weight and morphological features of the callus were determined. The 0.5 mg dm−3 2,4-D treatment was the most favorable for producing the greatest increase in fresh weight in each of five subsequent subcultures as well as maintaining normal morphological features for proliferation. However, the 1.0 mg dm−3 2,4-D treatment in comparison with the lowest, 0.1 mg dm−3, was more beneficial when considering regular increases of fresh weight and a better cell cohesion for callus growth.
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