# Effect of Sowing Dates on Fatty Acids and Phytosterols Patterns of _Carthamus tinctorius_ L.
## 4 Discussion
### Sterols Content and Repartition in Safflower Seeds  
The distribution of sterols among the seed compartments observed in safflower was quite similar to results reported in other Asteraceae and Brassicaceae [23; 27]. In coriander, pericarp contributes to 1/3 of the total sterols of whole fruits [28]. Sterols and their saturated form, phytostanols, represent important food constituents, which have a high impact on human health. These compounds are structurally similar to cholesterol and thus have beneficial biological functions when incorporated in diet [29]. The main sterol member in most oil seeds, \(\beta\)-sitosterol, was found as the dominant sterol during different ripening stages of safflower seeds (Figure 4) which is in agreement with results reported elsewhere [30; 31]. Similarly, the genotypic effect on sterol was analysed in a collection of varieties of safflower, [6; 22; 32] and reported that \(\beta\)-sitosterol is the dominant phytosterol. In sunflower, phytosterols content was found to be dependent on environmental factors [19], genotype and climatic conditions [10; 33]. [PERSON] et al. [6] have highlighted the importance of growing conditions on the phytosterol content determination in safflower. Different phytosterols and fatty acid profiles and contents were observed when the plants were cultivated under a late sowing date compared to a conventional one (Figures 3 and 4). These differences are related to contrasted amounts of rainfall, instead of temperatures, recorded for both sowing dates (Figure 1 and Table 1). Climatic conditions may influence the sterols composition and profile. The \(\beta\)-sitosterol+stigmaterol/campesterol ratio has been used as an indicator of plant reaction to weather conditions [10]. Indeed, stigmaterol and sitosterol result from the activity of Sterol methyltransferase 2 (_SMT-2_), which modifies gramisterol into sitosterol after several biochemical transformations (Figure 5). This activity is released instead of the transformation of gramisterol on campesterol instead of \(\beta\)-sitosterol and stigmasterol. In our study, this ratio was 5.82 and 6.75 in the conventional and late sowing dates, respectively, which was in agreement with [PERSON] et al. [10] in sunflower and [PERSON] et al. [6] in safflower. Indeed, this balance depends on SMT enzymes involved in sterol biosynthesis (Figure 5). Our results mirrored that the _SMT-2_ activity may have been probably more important under late sowing conditions than under the conventional date. [PERSON] et al. [34] have reported, in Arabidopsis mutants, that overexpressing _SMT-2_ results in higher accumulation of \(\beta\)-sitosterol highlighting the involvement of this enzyme in the regulation of sitosterol/campesterol balance. Through the activity of the _SMT-2_ enzyme, results on safflower indicated that it may be possible to modify the sterol and fatty acid contents and composition by cultural practices management [25; 26]. Figure 5: Simplified hypothetical relationships between sterol and fatty acid biosynthesis pathways in Asteraceae. CAS1: Cyclo-Artenol Synthase; CPI1: Cyclo-Propyl Isomerase; FK: C14 reductase; HYD1: C8,7 isomerase; DWF7/STE1: \(\Delta^{7}\) sterol C5 reductase; DWF5: \(\Delta^{7}\) sterol C-7 reductase; DWF1/DIM: C24 reductase; SMT1: Sterol-Methyl Transferase 1, SMT2: Sterol-Methyl Transferase 2, SS: Squalene synthetase; SQE: Squalene Epoxidase. In terms of the distribution of phytosterols in the seed, the stigmaterol was the only sterol that presented a higher concentration in the hull compared to the embryo. As described in sunflower seeds [27], this result suggested that this sterol may have a different function in the protection of the seed structures. The late sowing date affected positively the sterol content and negatively the fatty acid composition (Figures 3 and 4). The impact observed on sterols and fatty acid composition could be explained by the fact that cytoplasmic acetyl-CoA required in the synthesis of both fatty acid and phytosterols did not fit all the carbon demands.