Possible roles of methyl glucoside and myo-inositol in the opening of cut rose flowers

Methyl glucoside and myo-inositol are present in all organs of rose (Rosa hybrida L.). To investigate the possible role of these carbohydrates in the opening of cut roses, flowers with a 10, 20 or 40-cm-long stem and a single flower bud (about 1.5 cm in diameter) were placed in water and flower opening and changes in sugar content in flowers and stems examined for 7 d. The longer the stem of the cut flower, the larger was the flower diameter. In stems, the concentration of carbohydrates, including methyl glucoside and myo-inositol markedly decreased before flower opening. In petals, contents of glucose, methyl glucoside and myo-inositol also decreased before flower opening, but those of fructose, sucrose and xylose did not. When glucose and methyl glucoside were added to the vase water (4 %) flower opening was clearly promoted; this was accompanied by an increase in methyl glucoside and fructose concentrations in petals. On the contrary, myo-inositol inhibited flower opening, and this was accompanied by an increase in myo-inositol and xylose concentrations in petals. These results suggest that methyl glucoside and/or its metabolites are transported into the petal cells, thereby lowering the osmotic water potential and promoting flower opening. Myo-inositol is not readily metabolized, and exogenous myo-inositol given at a high concentration may act as an extracellular osmolyte, which inhibits water uptake and flower opening. (C) 1999 Annals of Botany Company.