MORPHOGENIC CONTROL OF PLANTS MICROPROPAGATED IN BIOREACTOR CULTURES AND ITS POSSIBLE IMPACT ON ACCLIMATIZATION

The potential use of micropropagation in vitro for mass-production of plants is currently limited by high costs due to intensive manual handling and low survival rate ex vitro. Scaled-up liquid cultures in bioreactors and automation provide an alternative method for mass-production. Bioreactor cultured plants in liquid media develop abnormal shoots, having vitreous leaves. Growth regulators including growth retardants control leaf expansion and induce meristemoid aggregates in bioreactor cultures.

Liquid cultured Philodendron buds require the presence of paclobutrazol or ancymidol (inhibitors of gibberrelin synthesis) to reduce leaf expansion and enhance bud cluster proliferation. In the agar hardening medium, the separated buds developed into normal plants which could be transplanted ex vitro. Gladiolus buds proliferated profusely to clusters in bioreactor cultures supplemented with either ancymidol, paclobutrazol or uniconazol (Majic). Mechanically separated meristemoid clusters were induced to form cormlets which could either be stored or transplanted ex vitro without acclimatization. In Nerine cultured in bioreactors the presence of paclobutrazol enhanced meristemoid clusters, which developed upon the removal of growth retardants, into somatic embryos, plantlets and bulblets.