Modulation of TDZ-induced morphogenetic responses by anti-auxin TIBA in bud-bearing foliar explants of Kalanchoe pinnata

This investigation was conducted to study the range of TDZ-induced morphogenetic responses displayed by foliar explants of Kalanchoe pinnata with or without an epiphyllous bud and to assess their possible auxin mediation by using potent anti-auxin TIBA. Each epiphyllous bud developed into a healthy plantlet when cultured in vitro without nutrient/hormonal supplements. The bud on 10⁻⁶ M TDZ-treated leaf disc produced a compact, dwarf and rootless plantlet having achlorophyllous leaves with increased number of marginal notches. TDZ also caused a significant enlargement of the leaf disc as well as induced an organized hypertrophic growth at a specific site, with either effect being more pronounced in discs without an epiphyllous bud. Treatment with 10⁻⁴ M TIBA completely checked the plantlet growth. In combined dispensations, the TDZ-induced responses were modified by the anti-auxin TIBA in more than one way. Whereas it caused a complete reversal of hypertrophic growth on leaf discs and partially restored pigmentation of plantlet leaves, it could not annul the leaf disc enlargement. The diverse morphogenetic modulations were tissue and response specific. A complete reversal of TDZ-induced leaf disc hypertrophy by TIBA indicated an auxin mediation, whereas a complete non-reversal of the induced leaf disc enlargement pointed to the non-involvement of auxin, for the respective responses. The latter response could probably be manifested through cytokinin-activity of TDZ, while still others may not be interpreted exclusively through either one of the two hormonal options.