Relation of days after flowering to chemical composition and physiological maturity of sunflower seed

Abstract

Hybrid sunflower seed (achene) were collected from plants at 7‐day intervals after the initiation of flowering which occurred 58 days after planting. The seed were analyzed for moisture, total oil, free fatty acids, lipid classes, and fatty acid composition. Seed dry weight, oil and triglyceride contents were maximum 35 days after the initiation of flowering (DAF) when the seed moisture content was about 36%. This point was defined as “physiological maturity” for sunflowers. The fatty acid composition of the oil extracted from the seed was determined at each stage of maturity. Total saturated fatty acids were 27% at 7 DAF and then decreased to a constant 9% by 35 DAF. At 7 DAF, linolenic acid content was 10.7% then decreased to less than 0.1% by 28 DAF. Oleic acid was about 12% at 7 DAF, increased to 59.6% at 14 DAF, and then gradually decreased to 31.4% by 56 DAF. On the other hand, linoleic acid was about 48% at 7 DAF, decreased to 23% by 14 DAF, but then gradually increased to 59.2% by 56 DAF. An analysis of variance of linoleic and oleic acid contents from 21 DAF to 70 DAF showed a highly significant change in composition with maturation time. The changes in the composition of these fatty acids from 21 DAF to 70 DAF appeared to be related to the environmental temperature which gradually decreased until 56 DAF. Increase in free fatty acids after physiological maturity indicated that deterioration of seed oil was beginning to occur.

Expression of sunflower low-molecular-weight heat-shock proteins during embryogenesis and persistence after germination: localization and possible functional implications

“…4B); but, in contrast to HSP17.9 ( Fig. 4A), HSP17.6 proteins did not appear until 25 DAF, about the stage when sunflower sygotic embryos desiccate faster in the seed [28]. Thus, for HSP17.6, the accumulation of homologeous mRNAs earlier (10-15 DAF) in embryogenesis [ 10] did not result in detectable LMW HSP synthesis before 25 DAF.…”

“…However, expression of HSP17.6 (Fig. 4B) occurs well after deposition of most reserve substances in sunflower seeds [26,28]. During germination, HSP17.9 and HSP17.6 disappear after the major storage proteins, which are degraded before 3 DPI (data not shown).…”

“…Preliminary observations in our laboratory (10) and other groups [15][16][17][18][19][20][21][22][23][24][25][26][27][28]29] indicated expression of LMW HSPs during zygotic embryogenesis and seed germination. The results presented in this paper demonstrate differential developmental expression of two distinct families of cytoplasmic proteins.…”

“…For example, expression of HSP17.9 during embryogenesis (Fig. 4A) parallels storage protein [26] and lipid [28] accumulation in developing sunflower seeds. However, expression of HSP17.6 (Fig.…”

“…6). Thus, expression of HSP17.9 proteins, at least, could be induced by the progressive water loss of the embryo during sunflower seed development [28].…”