El-Nakhel, Christophe (2019) NUTRIENT DELIVERY AND WATER MANAGEMENT FOR PRODUCING LETTUCE (Lactuca sativa L.)FOR BIOREGENERATIVE LIFE SUPPORT SYSTEMS. [Tesi di dottorato]

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Tipologia del documento: Tesi di dottorato
Lingua: English
Titolo: NUTRIENT DELIVERY AND WATER MANAGEMENT FOR PRODUCING LETTUCE (Lactuca sativa L.)FOR BIOREGENERATIVE LIFE SUPPORT SYSTEMS
Autori:
AutoreEmail
El-Nakhel, Christophechristophe.elnakhel@unina.it
Data: 9 Giugno 2019
Numero di pagine: 206
Istituzione: Università degli Studi di Napoli Federico II
Dipartimento: Agraria
Dottorato: Scienze agrarie e agroalimentari
Ciclo di dottorato: 31
Coordinatore del Corso di dottorato:
nomeemail
D'Urso, Guidodurso@unina.it
Tutor:
nomeemail
Rouphael, Youssef[non definito]
Data: 9 Giugno 2019
Numero di pagine: 206
Parole chiave: Bioregenerative food systems bioactive compounds; carotenoids profile, light intensity; nitrates; phenolic acids, ascorbic acid, Space Life Support Systems, antioxidant molecules, HPLC-DAD, daily water uptake, functional quality, mineral profile, physiological parameters, relative growth rate, water use efficiency, chemical eustressor, nutrient strength, hydroponics, nutrient solution management, iron chelate EDDHA, sodium selenate.
Settori scientifico-disciplinari del MIUR: Area 07 - Scienze agrarie e veterinarie > AGR/04 - Orticoltura e floricoltura
Informazioni aggiuntive: All the chapters of this thesis will subsequently be published individually in adjusted versions
Depositato il: 18 Giu 2019 13:25
Ultima modifica: 16 Giu 2020 09:57
URI: http://www.fedoa.unina.it/id/eprint/12729

Abstract

Space farming for fresh food production is a key requirement for the success of long duration space missions through self-sufficiency and human life sustainment (physical and psychological well-being) in space colonies. Plant production contributes to atmosphere revitalizing, water purification and waste product recycling as well. However, several obstacles have to be overleaped including abnormal environmental conditions, space energy and resources limitations. Therefore choosing the appropriate cultivar is as important as the species selection, since such choice can influence the obtained fresh biomass, water use efficiency (WUE), growing cycle duration, qualitative features and more importantly quality conservation after harvest. So far, several studies have suggested various crop species highlighting the varied response to environmental constraints in a genotype and cultivar dependent manner. The aim of the present study was to evaluate six lettuce cultivars belonging to different groups and with different leaf colors under low and optimal light intensity in order to identify the most promising genotypes for incorporation in controlled life support systems. Then two differently pigmented butterhead Lactuca sativa L. (red and green Salanova) were chosen and assessed in term of morphometric, mineral, bioactive compounds and physiological parameters. Through precise control of the nutrient solution (NS), closed soilless systems effectuate targeted manipulation of plant secondary metabolites that constitute health-promoting components of human daily diet. An NFT system in a controlled-environement growth chamber was presently employed to grow these cultivars for 19 day, under optimal light and to assess the effect of NS macronutrient-based concentration, proportion (Ca/Mg/K) and biofortification (Iron and Selenium) effect on the bioactive profile of red and green-pigmented Salanova. In this study, morphometric analysis, mineral composition, antioxidant activitiy, phenolic acids and carotenoids content where studied for all treatments: (i) full, half- and quarter-strength corresponding to EC 1.5, 0.75 and 0.5 dS m-1 , (ii) Macrocations proportions, (iii) four Fe concentrations in the nutrient solution (0.015 control, 0.5, 1.0 or 2.0 mM Fe) and (iv) six Se concentrations (0, 8, 16, 24, 32, 40 μM as sodium selenite). Baby Romaine plants had a better agronomic performance than the rest of the tested cultivars under low light intensity conditions, indicating a more efficient light harvesting mechanism. As for intrinsic water use efficiency (WUEi), it was the highest for baby Romaine and red oak leaf cultivars, regardless of light regime. Chicoric acid was the major detected compound, followed by chlorogenic, caffeoyl-tartaric and caffeoyl-meso-tartaric acids. The major phenolic compound (chicoric acid) and total phenolic acids were not affected by light intensity, whereas the rest of the detected phenolic compounds showed a varied response to light intensity. Regarding cultivars response, red oak leaf was mostly affected by low light intensity showing the highest content in chicoric acid and consequently in total phenolic acids content, while under optimal light conditions red Salanova exhibited the highest phenolic profile. The main detected pigments were β-cryptoxanthin and violaxanthin + neoxanthin, followed by lutein and β-carotene. All the target carotenoids decreased significantly under low light intensity, with red Salanova having a distinct profile of carotenoids. Red Salanova registered a biomass of 130 g at harvesting (19 DAT), 22.1 % bigger than green Salanova, with a water uptake of 1.42 L during the full growing cycle and a WUE of 91.9 g L-1, 13.8 % higher than the green cultivar. The latter had accumulated more P, K, Ca, Mg and 37.2 % more nitrate than red Salanova that in its turn had higher relative water content, leaf total and osmotic potential and higher SPAD index. Red Salanova as well exhibited at harvest around two-fold greater lipophilic antioxidant activity and total phenols, and around six-fold greater ascorbic acid. On the other hand the half-strength nutrient solution reduced fresh yield of both cultivars by 14%, however, moderate nutrient stress (half-strength NS) boosted red Salanova concentrations of ascorbate, chlorogenic, chicoric, caffeoyl-meso-tartaric and total phenolic acids, and anthocyanins by 266%, 199%, 124%, 251%, 162% and 380%, respectively compared to control full-strength NS. Moreover, red Salanova plants treated with elevated Mg (Solution of high proportion of Mg) contained higher amounts of pigments. Chicoric and chlorogenic acid were the main phenolic compounds in SMg, and SCa and SMg red Salanova plants, respectively. As for the biofortification, thhe 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 cultivars, the addition of 1.0 mM and especially 2 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. However, 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 to the control treatment, respectively; moreover, increased 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 to the control (0.015 mM Fe) treatment. Whereas, leaf selenium content increased significantly with Se application in both cultivars, in particular, the red leaf lettuce accumulated 57% more Se than the green one. Regardless the cultivar, the addition of 16 μM Se in the nutrient solution improved the content of all detected phenolic acids, and at the same dose in red Salanova, a substantial increase in anthocyanins content (184%) was also recorded. In conclusion, cultivation of mixed lettuce cultivars is the most possible scenario for space farming where some cultivars could provide adequate amounts of fresh biomass while others could contribute to covering daily diet requirements in nutrients and health beneficial compounds. Moreover, the high phenolics and ascorbic acid contents of red Salanova represent natural sources of antioxidants to enrich human diet, and more convenient agronomic requirements make it an appropriate cultivar candidate for bio-regenerative life support systems, plus a nutritional eustress constitute effective means to increase phytochemical content and optimize year-round production of lettuce in closed soilless systems. In conclusion, nutrient solution management and biofortification could be used as an effective cultural practice to increase bioactive properties and quality of hydroponically grown lettuce.

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