title: Diurnal changes in Sorghum leaf starch molecular structure.
abstract: 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.
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agricultural and Food Innovation, Brisbane, QLD 4072, Australia.
authors.forename: Cheng
authors.initials: C
authors.lastname: Li
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, Brisbane, QLD 4072, Australia.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Godwin
authors.affiliation: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agricultural and Food Innovation, Brisbane, QLD 4072, Australia. Electronic address: b.gilbert@uq.edu.au.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gilbert
mesh_terms: D000687:Amylopectin / Q000737:chemistry*; D000688:Amylose / Q000737:chemistry*; D002850:Chromatography, Gel; D002940:Circadian Rhythm; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry; D045868:Sorghum / Q000737:chemistry*
chemical_list: D000688:Amylose; D000687:Amylopectin
keywords: CLD; DMSO; DP; Diurnal change; Leaf starch; Molecular size distribution; SEC; Structural characterization; chain-length distribution; degree of polymerization; dimethyl sulfoxide; size-exclusion chromatography