Biosynthesis of sucrose and mannitol as a function of leaf age in celery (Apium graveolens L. )
In celery (Apium graveolens L.), the two major translocated carbohydrates are sucrose and the acyclic polyol mannitol. Their metabolism, however, is different and their specific functions are uncertain. To compare their roles in carbon partitioning and sink-source transitions, developmental changes in /sup 14/CO/sub 2/ labeling, pool sizes, and key enzyme activities in leaf tissues were examined. The proportion of label in mannitol increased dramatically with leaf maturation whereas that in sucrose remained fairly constant. Mannitol content, however, was high in all leaves and sucrose content increased as leaves developed. Activities of mannose-6-P reductase, cytoplasmic and chloroplastic fructose-1,6-bis-phosphatases, sucrose phosphate synthase, and sucrose synthase increased with leaf maturation and decreased as leaves senesced. Ribulose bisphosphate carboxylase and nonreversible glyceraldehyde-3-P dehydrogenase activities rose as leaves developed but did not decrease. Thus, sucrose is produced in all photosynthetically active leaves whereas mannitol is synthesized primarily in mature leaves and stored in all leaves. Onset of sucrose export in celery may result from sucrose accumulation in expanding leaves, but mannitol export is clearly unrelated to mannitol concentration. Mannitol export, however, appears to coincide with increased mannitol biosynthesis. Although mannitol and sucrose arise from a common precursor in celery, subsequent metabolism and transport must be regulated separately.
- Research Organization:
- Washington State Univ., Pullman (USA)
- OSTI ID:
- 7164423
- Journal Information:
- Plant Physiol.; (United States), Vol. 86:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Partitioning and transport of the translocates mannitol and sucrose in the light and dark in celery (Apium Graveolens L. )
Unusual carbon partitioning during phosphate deficiency in celery, a mannitol-synthesizing species
Related Subjects
LEAVES
METABOLISM
SACCHAROSE
BIOSYNTHESIS
AGE DEPENDENCE
BIOCHEMICAL REACTION KINETICS
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBOXYLASE
ENZYME ACTIVITY
OXIDOREDUCTASES
PHOSPHATASES
PRECURSOR
TRACER TECHNIQUES
VEGETABLES
CARBON-CARBON LYASES
CARBOXY-LYASES
DISACCHARIDES
ENZYMES
ESTERASES
FOOD
HYDROLASES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LYASES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
PLANTS
REACTION KINETICS
SACCHARIDES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques