Abstract:
The experiments were conducted to explore the chelant-assisted lead (Pb) phyto-extraction and
subsequent antioxidative responses in spinach and turnip plants under both controlled (Growth
Incubator) environment and filed (natural) conditions. The seeds of turnip (Brassica Rapa L. cv.
Purple Top) and spinach (Spinacea oleracea L. cv. Desi) were surface sterilized and sown in
plastic pots filled with thoroughly washed sand. Later on, the same experiment was conducted in
the field under natural conditions. In controlled experiment, after germination, 10 d old spinach
and turnip seedlings were exposed to different Pb regimes (0, 2.42 and 4.83 mM). While in case
of field experiment, 20 d old plants were expose to Pb regimes where the control plot exhibited
0.0218 mM Pb concentration. After 10 days of Pb application, 2.4 mM concentrations of
different chelating agents viz., ethylenediamine tetra acetic acid (EDTA), citric acid (CA), oxalic
acid (OA), tartaric acid (TA) and malic acid (MA) were applied to the plants both under
controlled and field conditions. Different Pb regimes altered biomass and different physiobiochemical
attributes in both crop species. On the other hand, the application of chelates,
especially CA increased growth in both crop species. However, of the chelates, TA was much
more effective in increasing tissue specific Pb concentrations in both crops. The beneficial
effects of chelates attributed to the capacity to increase photosynthetic pigments, antioxidative
enzymes and nutrient uptake under different Pb regimes. Both crop species were able to tolerate
Pb levels applied. Furthermore, some chelates were able to reduce tissue specific toxic
concentration of Pb leading to hormesis. Overall, the results elaborated the potential of chelates
in increasing growth, biomass, and thus suggested their use for phytoextraction of Pb. Based on
the effectiveness of TA in increasing root Pb concentrations in case of turnip and shoot Pb
concentrations in case of spinach suggested its use for phytoextraction of Pb in Pb-polluted
environments.
