A cell suspension of grape, Vitis vinifera L. cv Gamay Fréaux, was grown under different conditions of water stress (high external osmotic potential) induced by an increase of sucrose concentration or by the addition of mannitol to the culture medium. Best growth (cell density) was achieved in the low osmotic potential medium. Increasing the osmotic potential of the medium from -0.5 MPa to -0.9 MPa medium resulted in a significant increase in accumulation of anthocyanins in pigmented cells. Regulation of the osmotic potential of culture medium may be useful in controlling anthocyanin production.

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A cell suspension of Vitis vinifera L. cv. Gamay Frédaux var. teinturier composed of 50% pigmented cells was grown in Gamborg B5 medium supplemented with (per litre) 250 mg casein hydrolysate, 0.1 mg α-naphthalenacetic acid, 0.2 mg kinetin, and either 20, 30, 50, or 60 g sucrose. In the presence of 20 and 30 g sucrose/L, growth of cells was characterized by a typical sigmoid pattern and maximum cell density was obtained in 30 g sucrose/L. In both media, the anthocyanin content of pigmented cells did not change significantly throughout the growth cycle. In the presence of 50 g sucrose/L, cell growth was characterized by an extended lag phase. During this period, there was a significant (P < 0.05) accumulation of anthocyanins in the pigmented cells. Browning of the medium and premature cell death was observed in medium with 60 g sucrose/L. Microscopic observation of the suspension revealed the occurrence of anthocyanoplasts, especially in anthocyanin-containing cells cultured in 50 g sucrose/L. In some instances anthocyanoplasts were observed in cells with nonpigmented vacuoles, thus supporting the thesis according to which anthocyanoplasts would be the site of anthocyanin synthesis. Key words: anthocyanins, anthocyanoplasts, cell culture, metabolism, sucrose, Vitis vinifera.

Cell cultures of grapes, Vitis v&ifera L. cv Gamay Fr6aux were grown under different conditions of external osmotic potential induced by an increase of sucrose concentration or by the addition of mannitol to the culture medium. Addition of 82 mM mannitol or increasing sucrose concentration to 132 mM had similar effects on repressing growth. Cyanidin 3-glucoside, peonidin 3-glucoside and peonidin 3-p-coumaroylglucoside are three main anthocyanins of Vitis cells. Increasing osmotic potential from -0.43 MPa to -0.8 MPa in the medium resulted in a significant intracellular accumulation of anthocyanin especially peonidin 3-glucoside in the pigmented cells. High osmotic potential appears to stimulate the methylation of anthocyanins. Osmotic potential is an important culture factor and may be useful in the controlling of anthocyanin production and composition.

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