Mannitol metabolism in cultured plant cells

Abstract

Uptake and metabolism of [U‐ 14 C]‐mannitol by suspension cultures of Damns carota L. cv. Kirodagosun and Nicotiana tabacum L. cv. Wisconsin 38, and by cotyledon cultures of Pinus radiata D. Don have been studied. Uptake of label ranged from 138 to 906 nmol (g FW) −1 h −1 , resulting in absorption of 3 to 22% of the mannitol supplied to the cultures, over a 14 h incubation period. Of the absorbed mannitol 33 to 75% was metabolized, with label appearing in lipid, insoluble, acidic, basic, neutral and CO, fractions. No adaptation to culture with mannitol prior to the experiments was observed, but tobacco showed a decreased ability to metabolize the compound after 8 days in its presence. Because of the rates of uptake observed, and the metabolism of this compound, it is concluded that mannitol is not an ideal osmoticum for long‐term studies with any of these species, though its use in the short‐term remains valid.