The Dual Role of Mannitol as Osmoprotectant and Photoassimilate in Celery

Inositols and methylinositols in sea buckthorn (Hippophaë rhamnoides) berries

“…The presence of methylinositols and other sugar alcohols has been shown to be related to an insufficient water supply to the plants [38,53]. Sea buckthorn is a hardy plant which grows well under dry conditions.…”

The effect of abiotic stresses on carbohydrate status of olive shoots (Olea europaea L.) under in vitro conditions

“…Although the amount of starch is relatively low, it may be of some importance during plant regeneration. The difference in starch deposition may be related to the fact that mannitol degradation is, from energy point of view, more effective (Pharr et al, 1995).…”

“…Apart from other potential advantages of mannitol as an osmoprotectant, polyols serve as storage compounds and redox agents (Bieleski, 1982;Loescher, 1987). From an energy utilisation point of view, degradation of mannitol should be even more efficient than that of sucrose, as NADH originates in the initial step of mannitol catabolism, and oxidation of NADH in mitochondria means a theoretical yield of up to three molecules of ATP (Pharr et al, 1995). Raffinose family oligosaccharides (RFO) are another group of soluble carbohydrates that are thought to participate in the defence reaction of plants exposed to abiotic stress.…”

Mannitol-producing tobacco exposed to varying levels of water, light, temperature and paraquat

“…Furthermore, in celery, mannitol would represent another carbon sink in addition to sucrose (as it accounts for 50% of the photosynthetically-fixed carbon), thus increasing the outlets in the cytosol for the carbon exported from the chloroplasts and ultimately from the leaf (Pharr et al, 1995). However, our +mtlD tobacco plants produced relatively little mannitol, both in terms of accumulated amounts and rates of synthesis.…”

“…In celery, for example, where mannitol represents 50% of the photoassimilate (sucrose represents the other 50%), relatively high photosynthetic rates, similar to those in C 4 species, have been observed (Pharr et al, 1995). This has been hypothesised to result both from increased turnover of NADP-NADPH compared to plants that form sugars, exclusively, and from the additional cytosolic sink for photosynthetically-fixed CO 2 provided by mannitol synthesis (Pharr et al, 1995).…”