C.W. Fennell

Biotechnology of southern African bulbs

The greatest diversity of bulbs, including petaloid monocotyledons with corms, rhizomes and tubers, can be found in the Cape Floral Kingdom in southern Africa. Biotechnological approaches are used to meet the growing demand for bulbs and to conserve those over-exploited by the herbal medicine trade. This review outlines the principles and practices of micropropagation, flower bulb improvement, in vitro conservation, molecular marker applications and secondary metabolite production for southern African bulbs and discusses the future role of bulbs and biotechnology in the development of the region.

The regulation of plant growth and development in liquid culture

Plant liquid culture offers many benefits over solidified media. Growth and multiplication rate of shoots, roots, bulblets and somatic embryos is enhanced in liquid culture, as a consequence of better availability of water and nutrients resulting from a lower resistance to diffusion and closer contact between the explant and the medium. Morphogenic development, such as meriste- moid production and somatic embryogenesis, is influenced by the physical environment provided by the liquid culture, and benefits from reduced gradients within the medium and dilution of exuded toxins. Chemical growth regulating factors, including plant hormones, growth retardants and other bioregulators are also discussed in terms of their influence on growth and development. Automation and scaling up for bioreactor production of propagules requires optimisation before becoming commercially viable. Considerable potential exists for future research into the molecular aspects regulating developmental pathways such as somatic embryogenesis, storage organ formation and meristemoid induction.

Acetylcholinesterase inhibition of Crinum sp.

Leaf, bulb and root materials of Crinum campanulatum, C. graminicola, C. macowanii, C. moorei and C. variabile were tested for acetylcholinesterase inhibitory activity in TLC- and microtitre plate assays. Leaves were not very active, whereas bulbs and roots contained several compounds with inhibitory activity. All species contained a band corresponding to galanthamine on the TLC plate.