PLURONIC-F-68 STIMULATES GROWTH OF SOLANUM-DULCAMARA IN CULTURE

The effects have been studied of the non-ionic surfactant, Pluronic F-68, on the growth of transformed roots, callus and protoplasts of Solanum dulcamara L. Root growth was stimulated by addition of 0.001-0.05% (w/v) of freshly-prepared, commercial grade Pluronic to culture medium, with maximum increases in root fresh and dry weights at 0.01 %. Higher concentrations (0.5-1.0% w/v) of freshly-prepared Pluronic inhibited growth. A Pluronic fraction, prepared by passage through silica-Amberlite resin, retarded root growth even at concentrations that were stimulatory with the commercial preparation. Similarly, commercial grade Pluronic solutions stored at 4-degrees-C or 22-degrees-C for 5 d ('aged') also inhibited root growth. Roots grew faster on Pluronic F-68-treated membrane rafts compared with growth on commercially-available rafts; such growth enhancement was comparable to that seen in medium supplemented with 0.01% (w/v) freshly-prepared commercial Pluronic. Callus growth was also stimulated by the addition of freshly-prepared, commercial grade Pluronic F-68 to medium, with maximum increases at 0.1% (w/v); in contrast, 1.0% (w/v) Pluronic was inhibitory to callus growth. The mean plating efficiency (15 d after plating) of protoplasts cultured at densities of 0.1-2.0 x 10(5) cm-3 was increased up to 26% by 0.1 % (w/v) Pluronic, while 1.0% was inhibitory. Both root and callus soluble carbohydrates and proteins were increased by exposure to freshly-prepared, commercial Pluronic. Similarly, the specific activities of malate dehydrogenase and acid phosphatase were increased in Pluronic F-68-treated callus and roots. The biotechnological implications of these results are discussed in relation to the potential value of non-ionic surfactants as growth-stimulating additives to plant culture media.