# Insights on the Adaptation of _Foericulum vulgar_ Mill to Iron Deficiency
## 3 Results and Discussion  
Effect of HCO\({}_{3}\)-Induced Fe Deficiency on Plant Growth and Levels of Photosynthetic Pigments and Nutrients  
Fe is involved in crucial physiological and metabolic processes including growth, DNA synthesis, respiration and photosynthesis [1,2]. Fennel plants grown under bicarbonate treatment (i.e, indirect iron deficiency conditions) showed classical symptoms of Fe deficiency after 14 days of treatment. Indeed, the top leaves exhibited visible intercostal chlorosis (Figure 1) that indicates a survival strategy of the plant to such constraint. This is consistent with previous bibliographic data that describe interveinal chlorosis of young leaves as the most obvious visible symptom of Fe deficiency [30]. Moreover, a decrease in the total content of chlorophylls in leaves of plants grown under Fe deficiency conditions was registered, when compared to the control. This resulted from a decrease in the levels of Chl a (\(-29\%\)) and of Chl b (\(-39\%\)), as presented in Figure 2. This reduction suggests a major role of Fe\({}^{2+}\) in the biogenesis of chlorophyll precursors such as 5-aminobenz acid and protochlorophyllide [7]. Figure 1: Morphogenic changes in fennel plants cultivated (**A**) under Fe sufficiency (+Fe) or (**B**) under Fe deficiency (+Fe +Bic), after a period of cultivation of 14 days. Arrows indicate intercostal chlorosis. Figure 2: Plant yields (**A**) and levels of photosynthetic pigment in leaves (**B**) of fennel plants grown under Fe sufficiency (+Fe) or under Fe deficiency conditions (+Fe + Bic). DW, dry weight; FW, fresh weight. Data represent the mean \(\pm\) standard deviation of three independent assays. *represents significant differences at \(p<0.05\); NS represents no significant differences at \(p<0.05\). The mean whole plant and shoot dry weights of Fe-deficient fennel plants were also reduced in relation to the control plants, contrary to root organs, which were able to uphold their growth (Figure 2). As previously described in Parietaria, in plants grown in calcareous media, the decrease in shoot growth represents an adaptive strategy of the plant to keep suitable levels of Fe and chlorophyll, as well as to preserve the photosynthetic activity in leaf tissues [31]. In turn, [PERSON] et al. [32] noted that bicarbonate supply provoked the appearance of proteoid roots that are developed from secondary and tertiary lateral roots, to allow increasing the surface of contact between plant and soil (for the release of nutrient solubilizing compounds and for the uptake of nutrients from the rhizosphere). The authors commented that such cluster roots in plants grown in the presence of bicarbonate is not a specific response to Fe deficiency, but a reaction to the general condition of low nutrient availability [32]. In Sulla plants, when grown in a calcareous soil, a reduced shoot growth was found (but not that of roots), which confirms its strategy of increasing root uptake efficiency for nutrients that are not easily available under these conditions [33]. Fe starvation has been demonstrated to affect mineral element homeostasis [34]. As shown in Figure 3, Fe content was notably diminished under Fe deficiency conditions, in both treated organs (ca. \(-57\%\) and \(-29\%\), for shoots and roots, respectively), as compared to control plants. At the same line, potassium content was considerably reduced in deficient shoots (\(-51\%\)) and roots (\(-22\%\)). In turn, zinc and copper exhibited an opposing tendency, with levels increases of about 19, 27, 24 and 36%, respectively, in bicarbonate-treated shoots and roots. The reduced Fe content is explained as a primary reaction to the low amount of Fe to which the plants were exposed [34].