Fatty acids in germinating seeds of sunflower (Helianthus annuus) and cotton (Gossypium barbadense)

Abdalla, Ahmed El-Sayed Mohamed (1986) Fatty acids in germinating seeds of sunflower (Helianthus annuus) and cotton (Gossypium barbadense). PhD thesis, University of Glasgow.

Abstract

Analyses of long-chain and short-chain fatty acids were carried out on sunflower (Helianthus annuus L.) and cotton (Gossypium barbadense L.) seeds and seedlings under optimum conditions of temperature and water availability. The total lipid content and the levels of the three lipid subfractions (neutral, phospholipid and glycolipid) were determined in the cotyledons, radicles and seed coats of both species. A major proportion of the total lipid in the cotyledons was neutral lipid which decreased gradually during the germination period, but the levels of the two other subfractions increased. No significant changes in the amounts of the three lipid subfractions were noted in extracts of the pericarp and testa, although slight changes were noted in extracts of radicles. Long-chain fatty acid composition of total lipid and the lipid subfractions was determined using gas-liquid chromatography with flame-ionization detection (GLC-FID) for quantification and combined gas-chromatography-mass spectrometry (GC-MS) for characterisation. Linoleic (C18:2) was the most abundant fatty acid and palmitic (C16:0), stearic (C 18:0), oleic (C 18:1) were the other major fatty acids. Of the fatty acids from the neutral lipid subfraction, decreased slightly in Gossypium cotyledons, decreased in the cotyledons of both species, and C18:2 decreased gradually in Gossypium cotyledons. Only slight changes were detected in the levels of fatty acids from the phospholipid and glycolipid subfractions during the three-day germination period. Short-chain fatty acids in both species were determined using GC-FID and GC-MS. Laurie (C12) was most abundant fatty acid and caprylic (C8), pelargonic (C9), capric (C10) were the other major fatty acids. C8 and C9 levels decreased in the whole seeds as well as in cotyledons but C10 and C12 increased in the whole seeds, and increased sharply in the cotyledons of both species. The quantities of these short-chain fatty acids changed in radicles and seed coats during the 72 h germination period. Investigations of the spherosomal preparation (lipid- storage organelles) from the cotyledons of both species during germination included morphological studies using electron microscopy and lipid-chemistry studies using GC-FID and GC-MS. The ultrastructural appearance of the spherosomal preparations were in agreement with previous publications. Spherosome diameter varied between 0.5 - 1.0 mum in Helianthus and 0.3 - 2. 0 mum in Gossypium, and spherosomes were bounded by a half-unit membrane. The total lipid content and lipid subfractions, and their fatty acid composition were studied in the spherosomal preparations from the cotyledons of both species during germination. Neutral lipid was the most abundant lipid in the spherosomal preparation, and its levels decreased during germination. The major fatty acids of spherosomal preparations were the same for those of intact seeds. C16 and C18 from spherosomal neutral lipid increased about three-fold but C18:1 and C18:2 decreased to less than half the original level in both species during the three-day germination period. Mitochondria from the cotyledons of both species were isolated, and the constituent lipid and fatty acid composition studied during germination. The mitochondria showed enrichment in the enzyme marker succinate dehydrogenase. Phospholipid was the most abundant lipid in the mitochondria-rich fraction, and its levels increased during germination. C16 and C18 from the mitochondrial phospholipid subfraction increased about three-fold in Helianthus but C18 decreased to about half content in Gossypium; C18:1 decreased to about one-third in Helianthus, but increased in Gossypium during the germination period.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Plant sciences
• Date of Award: 1986
• Depositing User: Enlighten Team
• Unique ID: glathesis:1986-76570
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 14:08
• Last Modified: 19 Nov 2019 14:08
• URI: https://theses.gla.ac.uk/id/eprint/76570