Developing a scale-up system for the micropropagation of cucumber (Cucumis sativus L.): the effect of growth retardants, liquid culture and vessel size.

We investigated the effect of the growth retardant flurprimidol, the phase of the culture medium (solid versus liquid) and the size of the liquid culture vessel (250-ml flask versus 2.5-l airlift bioreactor) on the micropropagation of cucumber (Cucumis sativus L.) from nodal explants. Flurprimidol at concentrations of 0.1-2 mg l(-1) caused considerable growth retardation but increased, albeit slightly, the number of branches and buds and stimulated (solid medium) or reduced (liquid medium) the accumulation of NO(3)-and PO(4)(3-). Flurprimidol had varying effects on the accumulation of soluble sugars and antioxidant compounds. Bioreactor-derived plants showed an increased fresh weight and size but a decreased content of macronutrients, solid sugars, ascorbic acid and free antioxidant phenolics. The majority (95%) of the plants were successfully acclimatized after being graft on squash. The perspective for an efficient, commercial-level use of bioreactors in combination with growth retardants of this commercially important vegetable species is discussed.