Relevance of nitrogen availability on the phytochemical properties of Chenopodium quinoa cultivated in marine hydroponics as a functional food

Chenopodium quinoa is a salt tolerant plant species of high nutritional value with potential to act as an extractive species under marine integrated multi-trophic aquaculture (IMTA). This study aimed to assess the growth performance and antioxidant content and activity of C. quinoa cultivated in saline hydroponics under contrasting nitrogen concentrations mimicking different aquaculture effluents described in literature. Seedlings were cultivated under greenhouse conditions in a modified Hoagland solution with a salinity of 20 g l- 1 artificial sea salt and four nitrogen concentrations: 20 mg l- 1 (N20); 40 mg l- 1 (N40); 100 mg l- 1 (N100) and 200 mg l- 1 (N200). After 4 weeks, leaf chlorophyll content and biomass gain were determined. Total flavonoids, total phenols and contents of elements were analyzed in C. quinoa leaves and shoot tips. Antioxidant capacity was quantified using oxygen radical absorbance capacity assay (ORAC). In treatments N100 and N200, C. quinoa presented higher biomass gain and lower antioxidant content and activity in its leaves and shoot tips. In contrast, in treatment N20 higher antioxidant content and activity were recorded, revealing the existence of stress inducing conditions during the experimental period. Shoot tips of these plants contained higher nitrogen and mineral contents than leaves. This approach may set the stage to develop a sustainable methodology to modulate the secondary metabolism of C. quinoa and enhance its value as functional food when cultured using marine aquaponics in IMTA systems.

Automated summary

This study evaluated the growth performance and antioxidant content of Chenopodium quinoa cultivated in saline hydroponics under contrasting nitrogen concentrations, showing that the plant exhibited higher antioxidant capacity and content under lower nitrogen concentrations.