Sugar contents and 14C-photosynthates distribution in early luxuriant stage of asparagus roots

One-year-old asparagus plants (Asparagus officinalis L.) were grown in pots for 45d before 14C-feeding. In order to clarify the sugar metabolism of roots, carbohydrate contents and 14C distribution in each root region and its sugar form were determined. The following results were obtained: 1) The total sugar content was in the order of new storage roots base of old storage roots tip of old storage roots rhizomes sucking roots. In storage roots, the content of sucrose and 3-4 degrees of polymerization fructans were high. The content of higher degrees of polymerization fructans was the highest in new storage roots. In sucking roots, contents of sucrose and monosaccharide were high, but the content of higher degrees of polymerization fructans was very low. In rhizomes, the content of sucrose was high. 2) At 18 h after 14C-feeding, 14C-assimilates remained mainly in leaves and main stems and 20% of 14C-assimilates had moved into roots. Distribution of the 14C rate in the roots was high in old storage roots and sucking roots. 3) The relative strength as a sink (RSS) was the greatest in leaves as an assimilatory organ and small (about 40) in whole roots. It was more than 100 in new storage roots and sucking roots. These data suggest that photosynthates move into those new organs preferentially. 4) The distribution rate of chemical forms in the roots was represented mostly by sugar, but the rate was different in each region. The distribution rates of the alcohol-insoluble fraction and organic acid were high in sucking roots and new storage roots. However, in old storage roots, the most of distribution rate was of sugar. Therefore, old storage roots function as a sugar-storage organ. 5) Although the fructan content was very low, the change rate into more than 3 degrees of polymerization was high in sucking roots. It is assumed that those fructans translocate from storage roots