# Insights on the Adaptation of _Foericulum vulgar_ Mill to Iron Deficiency
## 3 Results and Discussion
### Effect of HCO\({}_{3}\)-Induced Fe Deficiency on Antioxidant Abilities  
Plants need a balanced uptake, consumption and storage of mineral elements for proper ion homeostasis, this being distressed by nutritional imbalances in soils. Under Fe deficiency conditions, both leaf and root organs are subjected to ROS attack, partially due to the reduction of photosynthetic activity, which shows an over-reduction of the photosynthetic electron transport chain in leaves [33; 43]. After the reduction of Fe (III) to Fe (II) by ferric chelate reductase, Fe(II) is re-oxidized in Fe-deprived root cells, generating a complex with citrate, Fe(III)-dicitrate. The occurrence of these two stable and interconvertible forms of Fe accelerates potential electron transfer (or captured) to (or from) other species, to form free radicals. Accordingly, plant resistance to various stresses is associated with their antioxidant capacity and increased levels of antioxidants [24; 43]. On the other hand, considering the multiple aspects of antioxidants and their reactivity, the application of a single method is, in general, considered to be a very limited approach to estimate the antioxidant properties of plant extracts, while the use of simultaneous tests is more appropriate for a real perspective [44]. In our study, the hydromethanolic extracts, obtained from leaves and from roots, were evaluated regarding their ability to trap free radicals, namely, 2,2-diphenyl-1-picrylhydrazyl (DPPH\(\bullet\)), nitric oxide (NO\(\bullet\)) and peroxyl (RO\({}_{2}\)\(\bullet\)), along with the capacity to reduce ferric Fe to ferrous form (FRAP assay) and to inhibit the malondialdehydedehyde formation resulting from lipids oxidative damage, through TBARS assay. As shown in Figure 6, the antioxidant potencies varied significantly among the plant organs. Indeed, in control plants, excepting for ORAC, the extracts obtained from leaves were more active than those from roots (as reflected by lower IC\({}_{50}\) and EC\({}_{50}\) values), possibly because of their richness in phenolic compounds. In general, bicarbonate supply did not affect the antioxidant potential of leaf extracts toward DPPH\(\bullet\), NO\(\bullet\) and RO\({}_{2}\)\(\bullet\) radicals. The only exception was observed in TBARS, for which the ability to hamper lipid peroxidation was even decreased in bicarbonate-treated plants, compared to those of the control condition. In turn, root extracts of fennel grown under iron deficiency conditions exerted higher scavenging ability towards the radicals DPPH and NO, as well as a higher potency to reduce ferric Fe and to inhibit lipid peroxidation. The application of linear regression analysis to establish relationships between the phenolic amounts with the antioxidant activities resulted in a high significant negative correlation between the IC\({}_{50}\) values of DPPH (\(r=-0.95\); \(r=-0.98\)) and the EC\({}_{50}\) values of FRAP (\(r=-0.88\); \(r=-0.93\)) with TPC/TFC, while lower or no correlation were observed in the case of NO\(\bullet\) quenching activity (\(r=-0.54\) for TPC; \(r=-0.64\) for TFC) and TBARS (\(r\) values \(<0.5\)), respectively ( Supplementary Materials Table S2). In general, these results suggest that both phenolic compounds and flavonoids are key contributors in DPPH and FRAP assays, while non-phenolic compounds may also have an important contribution on the remaining tests. Changes in the antioxidant activities of plants subjected to Fe-deficiency have been investigated [24; 43], with variable results being reported. Recently, [PERSON] et al. [24] highlighted that, when grown under Fe deficiency, _Anethum graveolens_ was able to increase the antioxidant capacity of the overall plant. In another study, [PERSON] et al. [45] described that _Abelmoscus esculentus_ root extracts from the Fe-deficiency tolerant variety had higher DPPH scavenging ability than the control plants, which was significantly correlated with the levels of phenolic compounds.