Growth, /sup 14/C-sucrose uptake, and metabolites of starch synthesis in apical and basal kernels of corn (Zea mays L. )
Developing field-grown kernels of corn (Zea mays L. cv. Cornell 175) from the base and apex of the ear were sampled from seven to 70 days after pollination (DAP) an compared with respect to dry weight, ability to take up /sup 14/C-sucrose from solution in vitro, and content of sucrose, glucose, starch, glucose-1-P (G1P), glucose-6-P (G6P), fructose-6-P (F6P), ADP-glucose (ADPG), and UDP-glucose (UDPG). ADPG and UDPG were analyzed by HPLC. All other metabolites were analyzed enzymatically. Simultaneous hand-pollination of all ovaries in an ear did not reduce the difference between apical and basal kernels in dry weight, indicating that the latter fertilization of apical kernels was not responsible for their lesser mature dry weight. Detached kernels took up /sup 14/C-sucrose (0.3-400 mM) and glucose (5-100 mM) at rates linearly proportional to the sugar concentration. Glucose, fructose, and sorbitol did not inhibit uptake of /sup 14/C-sucrose. Uptake was not stimulated by 5 mM CaCl/sup 2/ or the addition of buffers (pH 4.5-6.7) to the medium. Sulfhydryl reagents (PCMBS, NEM) and metabolic inhibitors (TNBS, DNP, NaF) did not reduce uptake. These observations suggest that sucrose is taken up by a non-saturable, non-energy-requiring mechanism. Sucrose uptake increased throughout development, especially at the stage when basal kernels began to accumulate more dry weight than apical kernels (10-20 DAP in freely pollinated ears; 25 DAP in synchronously pollinated ears). Hydrolysis of incorporated sucrose increased from 87% at 14 DAP to 99% by 57 DAP.
- Research Organization:
- Cornell Univ., Ithaca, NY (USA)
- OSTI ID:
- 6026045
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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SACCHAROSE
UPTAKE
SEEDS
CHEMICAL COMPOSITION
CALCIUM CHLORIDES
CARBON 14 COMPOUNDS
FRUCTOSE
GLUCOSE
IN VITRO
LIQUID COLUMN CHROMATOGRAPHY
MAIZE
METABOLITES
REAGENTS
SORBITOL
ALDEHYDES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CARBOHYDRATES
CEREALS
CHLORIDES
CHLORINE COMPOUNDS
CHROMATOGRAPHY
DISACCHARIDES
DIURETICS
DRUGS
GRASS
HALIDES
HALOGEN COMPOUNDS
HEXOSES
KETONES
LABELLED COMPOUNDS
MONOSACCHARIDES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
PLANTS
SACCHARIDES
SEPARATION PROCESSES
550201* - Biochemistry- Tracer Techniques