Except Mn, foliar spraying of all elements increased the content
of chlorophyll a in hydroponics grown plants (Table 4). Foliar application
ofMgand Fe increased chlorophyll b contents of plant leaves
in both hydroponic and aquaponic systems compared to the control
treatments (Table 4). Foliar application of Mg also significantly
increased the content of carotenoids in aquaponics grown plants
(Table 4). This pigment was increased by Zn or Cu in hydroponic
treatments (Table 4). Magnesium is a component of the chlorophyll
molecule and 15–30% of the total Mg in plants is associated with
the chlorophyll molecule (Marschner, 1995). On the other hand,
although Fe is not a constituent of chlorophyll, it is essential for
chlorophyll biosynthesis (conversion of Mg proporphyrin to protochlorophyllide)
(Marschner, 1995). Thus, the effects of these two
elements on chlorophyll b were due to their role in chlorophyll
biosynthesis.