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.

The application of the bioelectric recognition assay for the detection of human and plant viruses: definition of operational parameters

The bioelectric recognition assay (BERA) is a novel biosensory method based on a unique combination of a group of cells, their immobilization in a matrix that preserves their physiological functions and the expression of the cell interaction with viruses as a change in electrical properties. A BERA sensor consists of an electroconductive, tube-like probe containing components of immobilized cells in a gel matrix. Cells are selected to specifically interact with the virus under detection. In this way, when a positive sample is added to the probe, a characteristic, 'signature-like' change in electrical potential occurs upon contact between the virus and the gel matrix. In the present study, we demonstrate that BERA can be used for the detection of viruses in humans (hepatitis C virus) and plants (tobacco and cucumber viruses) in a remarkably specific, rapid (1-2 min), reproducible and cost-efficient fashion. The sensitivity of the virus detection with BERA (0.1 ng) is equal or even better than with advanced immunological, cytological and molecular techniques, such as the reverse transcription polymerase chain reaction. Moreover, a good storability of the sensors can be achieved without affecting their performance. The potential use of portable BERA biosensors in medicine, for mass screening purposes, as well as for the detection of biological warfare agents without prior knowledge of a specific receptor-molecule interaction is discussed.