3.5. SPAD value, Fv/Fm and pigments
The plants were slightly greener in aquaponics compared with hydroponics. In the control treatments, the chlorophyll index in young leaves, determined as SPAD readings, was higher in aquaponics as compared to hydroponics (Table 4). Foliar spraying of Mg or Fe increased the SPAD value of young leaves in hydroponics grown plants, while SPAD value of young leaves in aquaponics grown plants was not affected by foliar application of any elements(Table 4). There was no difference in maximal quantum yield of PSII photochemistry (Fv/Fm) of young and old leaves of plants among different treatments (Table 4). The content of chlorophyll a was higher in aquaponics than in hydroponics grown control plants,and foliar spraying of elements did not affect it in aquaponic grown plants (Table 4). Greener color and higher chlorophyll content of leaves in aquaponics grown plants could be partly due to higher but non-toxic level of ammonium absorption by tomato plants in aquaponics (Roosta and Schjoerring, 2007; Roosta et al., 2009). Ammonia is the main end product of the breaking down of proteins in fish. Fish digest the protein in their feed and excrete ammonia through their gills and in their feces (Durborow et al., 1997a). Although, most of this ammonia is then converted to nitrite (NO2−)which is also quickly converted to non-toxic nitrate (NO3−) by naturally
occurring bacteria under normal conditions, plants uptake some ammonia before its conversion to NO2− and NO3− (Durborow et al., 1997b).
3.5. SPAD value, Fv/Fm and pigments
The plants were slightly greener in aquaponics compared with hydroponics. In the control treatments, the chlorophyll index in young leaves, determined as SPAD readings, was higher in aquaponics as compared to hydroponics (Table 4). Foliar spraying of Mg or Fe increased the SPAD value of young leaves in hydroponics grown plants, while SPAD value of young leaves in aquaponics grown plants was not affected by foliar application of any elements(Table 4). There was no difference in maximal quantum yield of PSII photochemistry (Fv/Fm) of young and old leaves of plants among different treatments (Table 4). The content of chlorophyll a was higher in aquaponics than in hydroponics grown control plants,and foliar spraying of elements did not affect it in aquaponic grown plants (Table 4). Greener color and higher chlorophyll content of leaves in aquaponics grown plants could be partly due to higher but non-toxic level of ammonium absorption by tomato plants in aquaponics (Roosta and Schjoerring, 2007; Roosta et al., 2009). Ammonia is the main end product of the breaking down of proteins in fish. Fish digest the protein in their feed and excrete ammonia through their gills and in their feces (Durborow et al., 1997a). Although, most of this ammonia is then converted to nitrite (NO2−)which is also quickly converted to non-toxic nitrate (NO3−) by naturally
occurring bacteria under normal conditions, plants uptake some ammonia before its conversion to NO2− and NO3− (Durborow et al., 1997b).
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