| Abstract | Uzgoj hrane postaje sve zahtjevniji zbog klimatskih promjena koje negativno utječu na poljoprivredne prinose, ali i na kvalitetu i nutritivnu vrijednost namirnica. Uvođenje zanemarenih biljnih vrsta u proizvodnju s ciljem očuvanja bioraznolikosti i sigurnosti hrane jedno je od održivih rješenja za sve veće izazove s kojima se današnja poljoprivreda susreće. Kopriva je višegodišnja biljna vrsta bogata specijaliziranim metabolitima prepoznata po brojnim biološkim i funkcionalnim svojstvima značajnim za zdravlje ljudi. Iako raste samoniklo u prirodi, teži se uvođenju koprive u poljoprivrednu proizvodnju u svrhu dobivanja proizvoda ujednačene kvalitete. Hidroponski uzgoj koprive u zaštićenom prostoru još uvijek nije raširen, unatoč brojnim prednostima koje ima u odnosu na uzgoj na tlu, uključujući smanjenje mnogih rizika povezanih s proizvodnjom na otvorenom. Takav način uzgoja pruža mogućnost upravljanja abiotskim čimbenicima zraka (temperatura i relativna vlaga zraka) i hranive otopine (pH, elektroprovodljivost, koncentracija otopljenog kisika i temperatura), dok se odabranim agrotehničkim mjerama, poput balansirane gnojidbe i upravljanja režimom navodnjavanja, može utjecati na prinose i sadržaj specijaliziranih metabolita u biljnom materijalu. Ovaj način uzgoja također pruža mogućnost cjelogodišnje proizvodnje tijekom mjeseci kada to na otvorenom ne bi bilo moguće. Cilj ovog doktorskog rada bio je istražiti utjecaj četiri hranive otopine različitog sastava i dva režima navodnjavanja na agronomske karakteristike, količinu nitrata i sadržaj specijaliziranih metabolita te antioksidacijski kapacitet svježeg lista koprive. Biljke koprive uzgajane su u hidroponskom sustavu koristeći tehnike plutajući hidropon (FH) te dotjecanje i otjecanje (EF). Dva jednofaktorijalna pokusa provedena su s hranivom otopinom i režimom navodnjavanja kao faktorima u proljetno-ljetnom roku uzgoja, a postavljeni su po metodi slučajnog bloknog rasporeda u 3 ponavljanja. Pri uzgoju koprive tehnikom FH ostvarene su tri košnje, dok je pri uzgoju tehnikom EF ostvareno osam košnji od kojih je šest košnji uključeno u ovo istraživanje. Uzgoj koprive tehnikom FH u hranivoj otopini EC vrijednosti 1,7 mS/cm rezultirao je biljnim materijalom prosječno viših vrijednosti suhe tvari (19,92 % ST), sadržaja askorbinske kiseline (91,73 mg/100 g sv.t.) i ukupnih fenola (309,59 mg GAE/100 g), dok je uzgoj u hranivoj otopini EC vrijednosti 1,5 mS/cm rezultirao najvećim kumulativnim prinosom (4,2 kg/m2) uz najnižu prosječnu količinu nitrata u svježem listu koprive (5069 mg/kg NO3-). Antioksidacijski kapacitet listova koprive prema FRAP metodi iznosio je od 963,27 do 3237,62 μmol TE/L tijekom uzgoja tehnikom FH. Uzgoj koprive tehnikom EF uz režim navodnjavanja svaka 72 h rezultirao je višim vrijednostima svih agronomskih karakteristika koprive tijekom cijelog razdoblja uzgoja, osim u petom vegetacijskom periodu. Režim navodnjavanja svakih 48 h pozitivno je utjecao na sadržaj askorbinske kiseline, ukupnih fenola, neflavonoida i flavonoida (prosječno 98,80 mg/100 g sv.t., 245,73 mg GAE/100 g, 128,33 mg GAE/100 g, 117,40 mg GAE/100 g) te je rezultirao nižim količinama nitrata u listu koprive (prosječno 3570 mg/kg NO3-). Vrijednostiantioksidacijskog kapaciteta tijekom uzgoja tehnikom EF bile su više od onih utvrđenih pri uzgoju tehnikom FH, što potvrđuje kako je list koprive uzgajane tehnikom EF izvrstan izvor antioksidansa. Ovo istraživanje pokazalo je kako su obje istraživane tehnike hidroponskog uzgoja (FH i EF) perspektivne za uzgoj koprive. Međutim, tehnika EF, u kombinaciji s optimiziranim režimom navodnjavanja i sastavom hranive otopine, može značajno povećati prinos i kvalitetu lista koprive. Za postizanje optimalnog prinosa listova koprive visoke nutritivne vrijednosti u hidroponskom uzgoju, preporučuje se korištenje hranive otopine EC vrijednosti 1,5 mS/cm i tehnike EF uz režim navodnjavanja svaka 72 h. |
| Abstract (english) | Growing food is becoming more challenging due to climate change, which has a
negative impact on food quality, nutritional value and yields. A sustainable solution to the
challenges of modern agriculture is to adopt agricultural practices with a low environmental
footprint while preserving biodiversity and ensuring food security by introducing foods with
high nutritional value. At the same time, today's consumers are looking for novel, highly
nutritious foods that enhance their overall health and well-being. Stinging nettle (Urtica dioica
L.) is recognized not only as a medicinal plant, but also as a desirable green leafy vegetable
rich in phytonutrients, demonstrating its significant potential for human nutrition. Stinging nettle
is a perennial plant species with a high content of specialized metabolites and known for their
numerous biological and functional properties that benefit human health. Although it grows
wild, efforts are being made to introduce stinging nettle into agricultural production in order to
obtain uniform quality and safe plant material. Hydroponic cultivation of nettle, although not
yet widespread, offers numerous advantages over soil cultivation, including reduced risks
associated with outdoor production. This method allows the management of abiotic factors
such as air temperature and relative humidity, as well as nutrient solution parameters such as
pH, electrical conductivity, dissolved oxygen and temperature. In addition, selected
agrotechnical measures such as balanced fertilization and controlled irrigation regimes can
influence the morphological characteristics and yield but also the content of specialized
metabolites in the plant material. Hydroponic cultivation also enables year-round production
in a completely closed system that maximizes the use of resources and energy, creating a
circular system and thus greater sustainability and resilience of the entire cultivation system.
The aim of this PhD thesis was to investigate the possibilities of nettle cultivation in a
hydroponic system, respectively in floating system and ebb and flow system, and to investigate
the influence of four nutrient solutions with different compositions of macro and micronutrients
and two irrigation regimes on the agronomic properties, nitrate quantity and content of
specialized metabolites as well as the antioxidant capacity of fresh nettle leaves.
The nettle was grown in a hydroponic system using Floating Hydroponic (FH) and Ebb
and Flow (EF) techniques. Two monofactorial experiments were conducted in the springsummer
growing period, with nutrient solution and irrigation regime as factors, laid out in 3
replicates using the randomized block design method. During the cultivation period, the abiotic
factors of the greenhouse and the nutrient solution were continuously monitored and adjusted
if necessary. In the cultivation of stinging nettle using the FH technique, 3 consecutive cuts
were obtained, while in the cultivation using the EF technique, 8 consecutive cuts were
obtained, 6 of which were analyzed for the purposes of this study. Morphological and chemical
analyses of the plant material were carried out after each consecutive cut.
Cultivation of stinging nettle using the FH technique in a nutrient solution with an EC
value of 1.7 mS/cm resulted in plant material with higher average values for dry matter
(19.92% DM), ascorbic acid content (91.73 mg/100 g fw) and total phenols (309.59 mg
GAE/100 g), while cultivation in a nutrient solution with an EC value of 1.5 mS/cm resulted in
the highest cumulative yield (4.2 kg/m2) with the lowest average amount of nitrate in fresh
nettle leaves (5069 mg/kg NO3-). The antioxidant capacity of nettle leaves using the FRAP
method ranged from 963.27 to 3237.62 μmol TE/L using the FH technique. Cultivation of nettle
using the EF technique with irrigation every 72 h resulted in higher values of all nettle
agronomic traits in all six vegetation periods, except in the fifth vegetation period. Irrigation
every 48 h had a positive effect on the content of ascorbic acid, total phenols, non-flavonoids
and flavonoids (average 98.80 mg/100 g fw, 245.73 mg GAE/100 g, 128.33 mg GAE/100 g,
117.40 mg GAE/100 g) and resulted in lower nitrate levels in the nettle leaves (average 3570
mg/kg NO3 -). The antioxidant capacity value was higher when cultivated using the EF
technique than when cultivated using the FH technique, confirming that nettle leaves obtained
by cultivation in the EF hydroponic system are an excellent source of antioxidants.
This study has shown that both hydroponic cultivation techniques investigated (FH and
EF) prove to be promising hydroponic techniques for the cultivation of nettle. However, the EF
technique, in combination with an optimized irrigation regime and nutrient solution content,
can significantly improve the yield and quality of nettle leaves. To achieve an optimal yield of
nettle leaves with high nutritional value in hydroponic cultivation, it is recommended to use a
nutrient solution with an EC value of 1.5 mS/cm and an EF technique with an irrigation regime
every 72 h.
The results of this research will expand the existing knowledge on the possibilities of
growing nettle with modern hydroponic techniques and provide recommendations for the
composition of the nutrient solution and the irrigation regime that will lead to an optimal yield
and high nutritional quality of the fresh plant material. This research also provides an important
scientific contribution on the role and effect of water stress on the increase in the content of
specialized metabolites in the fresh nettle leaf with the aim of obtaining nutrient-rich plant
material. These results will serve as a basis for further research in the field of growing
vegetable, medicinal and aromatic plants using modern hydroponic techniques. |
