The depletion of natural resources such as freshwater and cropland makes it necessary to find a new solution for sustainable food production. Aquaponic systems seem to be a great alternative to traditional agriculture, however, there are still many unknowns that need to be explored. It is already known how fish stocking affects water quality in aquaponic systems, but not how it affects the plants’ growth, and especially on chlorophyll fluorescence. In this study, we examined how the density of 0, 2, 4, 8, and 16 stocking fish in five aquaria affects lettuce growth. The first tank was only a hydroponic system with plants but without fish (control). In the remaining four aquaria – 2, 4, 8 and 12 specimens of common carp fry with an average weight of 20 grams (average 8.5–33.2 g) were placed in the aquaponic growing system. Physicochemical analysis of water was conducted to determine the levels of pH, electrical conductivity ( EC), N-NO 3, N-NO 2, N-NH 4, P-PO 4, O 2 and physiological parameters of plants (nitrogen balance index – NBI, chlorophyll content index – CCI, quantum yield – QY, flavonoid content – Flv) were analysed. The results showed that fish stocking density has different effects on plant physiological parameters, but in most cases, was insignificant. It seems that the greater number of fishes and higher density indirectly causes growth inhibition (lower photosynthetic efficiency) due to the increase of N-NO 3 and a decrease of O 2 in the water.

Winter oilseed rape (Brassica napus L.), Europe’s foremost oilseed crop, is significantly impacted by hailstorms, leading to substantial yield reductions that are difficult to predict and measure using conventional methods. This research aimed to assess the effectiveness of photosynthetic efficiency analysis for predicting yield loss in winter rapeseed subjected to hail exposure. The aim was to pinpoint the chlorophyll fluorescence parameters most affected by hail stress and identify those that could act as non-invasive biomarkers of yield loss. The study was conducted in partially controlled conditions (greenhouse). Stress was induced in the plants by firing plastic balls with a 6 mm diameter at them using a pneumatic device, which launched the projectiles at speeds of several tens of meters per second. Measurements of both continuous-excitation and pulse-modulated-amplitude chlorophyll fluorescence were engaged to highlight the sensitivity of the induction curve and related parameters to hail stress. Our research uncovered that some parameters such as F_s, F_m’, Φ_PSII, ETR, F_o, F_v/F_m, and F_v/F_o measured eight days after the application of stress had a strong correlation with final yield, thus laying the groundwork for the creation of new practical protocols in agriculture and the insurance industry to accurately forecast damage to rapeseed crops due to hail stress.

Nutrient deficiency (ND) stands as a prominent environmental factor that significantly impacts global plant growth and productivity. While numerous methods have been employed for detecting nutrient deficiencies in plants, many of them are invasive, time-consuming, and costly. In contrast, chlorophyll fluorescence (ChlF) signals have emerged as a non-destructive tool for the identification of specific nutrient deficiencies, such as nitrogen (N), phosphorus (P), and potassium (K), across various plant species. In this pioneering study, ChlF measurements were employed for the first time to detect a combination of nutrient deficiencies, including deficiencies in nitrogen and phosphorus (–NP), nitrogen and potassium (–NK), potassium and phosphorus (–KP), and a complete NPK deficiency (–NPK). The experiment was conducted using wheat (Triticum aestivum) and maize ( Zea mays) plants, which were grown under controlled laboratory conditions. An optimal hydroponic system was established to facilitate eight experimental conditions, namely: control, –N, –P, –K, –NP, –NK, –KP, and –NPK. Measurements were systematically collected at two-day intervals over a span of 24 days. Our findings demonstrate that chlorophyll fluorescence signals can enable the differentiation of various nutrient deficiencies even prior to the onset of observable symptoms. Furthermore, the examination of chlorophyll fluorescence parameters enables us not only to identify a singular macronutrient deficiency but also to detect multiple macronutrient deficiencies concurrently in a plant.