Heavy metal salts and osmotic pressure affect shoot regeneration from leaf explants of Dendranthema grandiflora

Shoot organogenesis was induced in two recalcitrant varieties of Dendranthema grandiflora Tzvelev 'Adorn' and 'Goldmine'. Regeneration of shoots from 'Goldmine' leaf explants was obtained on the following media; Murashige and Skoog (1962) (MS) medium amended with 0.1 μM BA, 11.5 μM lAA and 4.2 μM CoCI₂ and transferred after 5 weeks to medium with the same concentration of BA and CoCI₂, but without lAA. Schenk and Hildebrandt (SH) medium also was suitable for shoot induction in this variety when amended with 5% sucrose and 0.1 μM BA and 11.5 μM lAA. Explants were incubated for 2 weeks before being transferred to medium without growth regulators and the same concentration of sucrose. Poor shoot regeneration was obtained from leaf explants of 'Adorn' initially cultured on MS medium amended with 0.1 μM BA, 11.5 μM lAA and 0.58 μM AgNO₃ and subsequently transferred after 7 weeks to medium with the same concentration of AgNO₃, but without growth regulators. Mannitol was used to evaluate the osmotic effects on shoot organogenesis of 'Iridon'. Shoot organogenesis was inhibited by all concentrations of mannitol-sucrose relative to similar concentrations of sucrose. High concentrations of sucrose (greater than 6%), significantly inhibited the organogenic response from leaf explants of 'Iridon' and 15% sucrose completely inhibited shoot formation.