Mannitol utilisation by celery (Apium graveolens) plants grown under different conditions in vitro

Celery plants produce sucrose and mannitol as primary photosynthetic products and translocate both carbohydrates in the phloem and metabolise them in sinks. In vitro cultivation allows the supply of plants with different exogenous carbon and energy sources, thus influencing the endogenous equilibrium of carbohydrates and allowing study of resulting changes on growth and developmental processes. We investigated the growth and metabolic responses of celery (Apium graveolens, var. dulce, cv. Afina) to the supply of carbohydrates under in vitro conditions. No differences in biomass accumulation were observed in sucrose or mannitol supported plants at lower carbohydrate concentrations in the media (1 and 3%). Higher concentrations of mannitol, however, did not support the growth as well as media supplemented with equivalent sucrose concentrations. Differences in the degree of responses of particular organs to changes in type and concentration of media carbohydrates occurred. HPLC analysis of the soluble carbohydrate contents revealed that celery grown on mannitol accumulated very high concentrations of mannitol (65-91% of total soluble carbohydrate content). The accumulated mannitol was utilised when exogenous carbohydrates were withdrawn by transferring the plants to media without carbohydrates and the osmotic potential of the media increased. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.