Compositional changes in seeds influenced by their positions in different whorls of mature sunflower head

The physicochemical characteristics of seeds located in different whorls of the sunflower (Helianthus annuus L) head at maturity have been studied. The proportion of filled seeds decreased from the peripheral to the central whorl, with a 10-fold decrease in filled/unfilled seed ratio. The dry weight of seeds and kernels and the oil content of kernels decreased from the peripheral towards the middle and central whorls. However, the dry weight of seeds and kernels in the seed crop was significantly higher and the oil content lower than in the oil crop. The contents of starch, total soluble sugars and reducing sugars were lower in the oil crop than in the seed crop. The starch content of peripheral whorls in the seed crop was much lower than that of central whorls, with accumulation of total soluble sugars and reducing sugars, whereas much less variability was observed with respect to the position of seeds on the sunflower head in the oil crop. The mean proportion of membrane lipids was higher and that of triacylglycerols lower in the seed crop than in the oil crop. The proportions of 16:0 and 18:1 were higher in the seed crop, while that of 18:2 was higher in the oil crop.