Diurnal changes in Sorghum leaf starch molecular structure

• Published in: Plant science (Limerick) Vol. 239; pp. 147 - 154
• Main Authors: Li, Cheng, Godwin, Ian D., Gilbert, Robert G.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.10.2015
• Subjects: Amylopectin - chemistry; Amylose - chemistry; chain-length distribution; Chromatography, Gel; Circadian Rhythm; CLD; degree of polymerization; dimethyl sulfoxide; Diurnal change; DMSO; Leaf starch; Molecular size distribution; Molecular Structure; Plant Leaves - chemistry; SEC; size-exclusion chromatography; Sorghum - chemistry; Structural characterization; SEC; Leaf starch; Diurnal change; DMSO; Structural characterization; Molecular size distribution; CLD; DP; dimethyl sulfoxide; size-exclusion chromatography; degree of polymerization; chain-length distribution
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2015.07.026

•Leaf starch is important for plant growth; Sorghum leaf starch is used here.•The diurnal changes in starch molecular structure were characterized.•Leaf starch granule: hierarchical molecular structure from inner to outer parts. [Display omitted] Control of the fine structure of transitory starch synthesized during the day in leaves is required for its normal degradation during the subsequent night. In this study, the molecular structure of transitory starch from Sorghum leaves over the diurnal cycle was characterized using size-exclusion chromatography. This is the first study of diurnal changes in the chain-length distribution (CLD) of amylopectin and amylose over the entire range of chain lengths, and in the size distribution of whole starch molecules. It was found that the outer layers of leaf starch granules, which were synthesized during the daytime and degraded during the night, contained more large molecules, including amylopectin with more short chains and more branching, than those in the inner layers. The outer layers also had lower amylose content. Starch molecular sizes in leaves are much smaller than in grain starch. The starch structures observed are likely to give optimal energy control during plant growth. Lack of this control may contribute to poor plant growth.