Iron Biofortification of Red and Green Pigmented Lettuce in Closed Soilless Cultivation Impacts Crop Performance and Modulates Mineral and Bioactive Composition

Abstract

Consumer demand for vegetables of fortified mineral and bioactive content is on the rise, driven by the growing interest of society in fresh products of premium nutritional and functional quality. Biofortification of leafy vegetables with essential micronutrients such as iron (Fe) is an efficient means to address the human micronutrient deficiency known as hidden hunger. Morphometric analysis, lipophilic and hydrophilic antioxidant capacities of green and red butterhead lettuce cultivars in response to Fe concentration in the nutrient solution (0.015 control, 0.5, 1.0 or 2.0 mM Fe) were assessed. The experiment was carried out in a controlled-environment growth chamber using a closed soilless system (nutrient film technique). The percentage of yield reduction in comparison to the control treatment was 5.7%, 13.5% and 25.3% at 0.5, 1.0 and 2.0 mM Fe, respectively. Irrespective of the cultivar, the addition of 1.0 mM or 2.0 mM Fe in the nutrient solution induced an increase in the Fe concentration of lettuce leaves by 20.5% and 53.7%, respectively. No significant effects of Fe application on phenolic acids and carotenoid profiles were observed in green Salanova. Increasing Fe concentration in the nutrient solution to 0.5 mM triggered a spike in chlorogenic acid and total phenolics in red Salanova lettuce by 110.1% and 29.1% compared with the control treatment, respectively; moreover, higher accumulation of caffeoyl meso tartaric phenolic acid by 31.4% at 1.0 mM Fe and of carotenoids violaxanthin, neoxanthin and β-carotene by 37.0% at 2.0 mM Fe were also observed in red Salanova compared with the control (0.015 mM Fe) treatment. Red Salanova exhibited higher yield, P and K contents, ascorbic acid, phenolic acids and carotenoid compounds than green Salanova. The wok shows how nutrient solution management in soilless culture could serve as effective cultural practices for producing Fe-enriched lettuce of premium quality, notwithstanding cultivar selection being a critical underlying factor for obtaining high quality products.

Zinc and Iron Agronomic Biofortification of Brassicaceae Microgreens

“…Such difference, although it could be partially due to a difference in terms of growth cycle length between sprouts and microgreens, further highlights the importance of examining a larger variety of species to identify the ones that are more suitable to Fe biofortification. Differences in Fe content have been also reported between biofortified green and red pigmented lettuce leaves by Giordano et al and cowpea by Márquez-Quiroz et al, while other factors may also affect the biofortification efficiency including growing conditions and farming practices [28,41,79,80,87]. Considering that the RDA for Fe is estimated at 8-18 mg per day for adults older than 18 years old [14,77], the consumption of even small amounts of these three microgreens could help to cover the total daily requirements and they could be considered as useful dietary supplements, especially in the case of pregnant women where RDA of Fe increases to 27 mg per day.…”

“…As expected, Fe content in the plant tissues increased with increasing application rates and up to 11.07 mg L −1 , 44.85 mg L −1 , and 32.33 mg L −1 for arugula, red cabbbage, and red mustard, respectively. In the study of Giordano et al, the addition of 2 mM of Fe in the nutrient solution resulted in increased Fe content in the leaves of lettuce, regardless of the genotype [79]. However, in the same study, a negative effect of high Fe levels was observed on Ca, K, and Mg content in lettuce leaves, which was attributed to competition effects among the cations as well as to root injury and oxidative stress [79].…”

“…In the study of Giordano et al, the addition of 2 mM of Fe in the nutrient solution resulted in increased Fe content in the leaves of lettuce, regardless of the genotype [79]. However, in the same study, a negative effect of high Fe levels was observed on Ca, K, and Mg content in lettuce leaves, which was attributed to competition effects among the cations as well as to root injury and oxidative stress [79]. In contrast to the current study, Przybysz et al did not observe a significant effect of Fe enrichment (up to 36 mg L −1 ) on Mg, Ca, K, Zn, and Mn content in broccoli sprouts, while a varied effect was recorded on Zn content in radish sprouts [41].…”

“…Similarly, Przybysz et al [41] reported a negative impact on fresh yield of broccoli and radish sprouts enriched with Fe at concentrations of 24 and 36 mg L −1 , while no negative effects were observed on alfalfa and mung bean sprouts, suggesting that the response to increasing levels of Fe may vary significantly between species. Giordano et al have also reported negative effects of high levels of Fe (2 mM Fe) in nutrient solution on plant growth and yield parameters of hydroponically grown lettuce [79]. According to Fihlo et al, Fe levels higher than 25 mg L −1 caused toxicity symptoms in hydroponically grown common chicory (Cichorium intybus), although the toxicity threshold may vary among species [80,81].…”

Appraisal of Biodegradable Mulching Films and Vegetal-Derived Biostimulant Application as Eco-Sustainable Practices for Enhancing Lettuce Crop Performance and Nutritive Value

“…These macronutrients help against certain diseases, such as blood pressure imbalances, hypertension (K), and osteoporosis (P, Ca, and Mg) [15]. For lettuce, several authors reported a potassium content between 48-72 mg g −1 , phosphorus 4-6 mg g −1 , magnesium 1.4-2.8 mg g −1 , and calcium 4-10 mg −1 on a dry weight basis [15,16,47]. In our work, the use of biodegradable films influenced the biofortification of macronutrinets in lettuce leaves.…”