MORPHOGENIC PATTERNS OF PLANTS MICROPROPAGATED IN LIQUID MEDIUM IN SHAKEN FLASKS OR LARGE-SCALE BIOREACTOR CULTURES

ABSTRACT

Plant propagation in vitro through axillary and/or adventitious buds is at present labor intensive, which contributes to the high cost of plant production. Liquid cultures used to scale up mass propagation often affect adversely shoot morphogenesis. Abnormal shoot morphogenesis due to continuous submergence and vigorous aeration in the liquid medium results in vitreous shoots which poorly survive transplanting ex vitro. Nephrolepis, Philodendron, and Gladiolus bud explants were cultured in liquid medium in shaken cultures or bioreactors. Ferns propagated in liquid medium in shaken cultures produced meristemoid clusters, while leafy shoots developed in agar. In bioreactors the biomass was two to three times higher than in shaken cultures. Meristemoid clusters separated and inoculated to pretransplanting hardening agar medium developed normal shoots. In Gladiolus, shoot morphogenesis was controlled by the use of growth retardants, which also enhanced bud and protocorm production. In the presence of benzyladenine, naphthaleneacetic acid, high sucrose levels, and either ancymidol or paclobutrazol, protocorms reached a diameter of 4–6 mm. Protocorms separated from the clusters and subcultured to a hardening medium produced plantlets or nondormant corms, which were either planted directly in the soil or stored. In liquid-cultured Philodendron explants, proliferation was enhanced by the presence of paclobutrazol in the medium, while leaf development was almost completely inhibited. Bud aggregates separated and inoculated to a hardening agar medium developed normal shoots. The induction of meristemoid aggregates or protocorms in liquid cultures provided a rapid micropropagation method and obviated abnormal shoot morphogenesis in foliage plants and geophytes.