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2 Journal of Water and Land Development

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Does fish stocking rate affect the photosynthesis of Lactuca sativa grown in an aquaponic system?

100%

Jaszczuk Z. M. , Brysiewicz A. , Kozioł A. , Auriga A. , Brestic M. , Kalaji H. M.

tom no. 58

243--252

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-NO3, N-NO2, N-NH4, P-PO4, O2 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-NO3 and a decrease of O2 in the water.

Early detection of phosphorus deficiency stress in cucumber at the cellular level using chlorophyll fluorescence signals

84%

Sieczko L. , Dąbrowski P. , Kowalczyk K. , Gajc-Wolska J. , Borucki W. , Janaszek-Mańkowska M. , Kowalczyk W. , Farci D. , Kalaji H. M.

tom Special Issue

176--186

Abiotic stressors contribute to growth restriction and developmental disorders in plants. Early detection of the first signs of changes in plant functioning is very important. The objective of this study was to identify chlorophyll fluorescence parameters that change under phosphorus deficiency stress in cucumber. In this work, a trail to study the early changes caused by phosphorus deficiency in cucumber plants by analysing their photosynthetic performance is presented. Chlorophyll-a fluorescence (ChF) parameters were measured every 7 days for a period of 28 days. Measurements were made separately on young and old leaves and on cucumber fruit. Parameters that decreased during the stress were: p2G, PIabs, PItotal, REo/CSo, and TRo/CSo. P deficiency decreased total electron carriers per RC (ECo/RC), yields (TRo/ABS (Fv/Fm), ETo/TRo, REo/ETo, ETo/ABS and REo/ABS), fluxes (REo/RC and REo/CSo) and fractional reduction of PSI end electron acceptors, and damaged all photochemical and non-photochemical redox reactions. Principal component analysis revealed a group of ChF parameters that may indicate early phosphorus deficiency in cucumber plants. Our results are used in the discovery of sensitive bioindicators of phosphorus deficiency in cucumber plants. Most JIP test parameters are linked to mathematical equations, so we recommend using of advanced statistical tools, such as principal component analysis, which should be considered very useful for stress identification. It has also been shown to be more effective in multivariate methods compared to univariate statistical methods was demonstrated.