INDUCED DIFFERENTIATION OF GERANIUM PLANTS FROM UNDIFFERENTIATED CALLUS IN VITRO

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Abstract
Geranium callus produced from explants of stem tip, internode pith with vascular tissue on synthetic media with or without coconut milk and 2,4‐dichlorophenoxyacetic acid grew well for many generations, but only tracheids were induced in them. If callus produced on these media was subcultured immediately on Murashige and Skoog medium with 0.1 mg/liter/α‐naphthalene acetic acid (NAA) and 10.0 mg/liter kinetin (K) and incubated at 16/8‐hr light/dark cycle, shoots were induced in 8‐10 weeks and roots in another 8‐10 weeks. Callus produced on the MS medium with the same supplements of NAA and K, subcultured on the same medium and incubated in 16/8‐hr light/dark cycle, produced shoots in 6‐8 weeks. However, on callus subcultured more than three times, shoots differentiated with greater difficulty and none differentiated after six subcultures. Some abnormal shoot‐like structures were also produced, the cells of which showed virus‐like inclusion bodies. Requirements of the different varieties for differentiating organs differed. Among 12/12‐, 15/9‐, 16/8‐, and 20/4‐hr light/dark photoperiods that induced differentiation, 15/9‐ and 16/8‐hr were more effective than the others. Continuous illumination did not induce differentiation. Differentiated shoots formed roots more readily on a medium with reversed proportions of auxin and kinetin. On agar roots were devoid of root hairs. Root hairs were formed when the shoots and plantlets were cultured on filter‐paper bridges. Many “mother” stock plants were produced. These are being studied for their growth qualities and for possible viruses and other pathogens.