This research work was carried out to investigate the effects of ethylene diamine disuccinate (EDDS) on the absorption of cadmium and lead by hydroponically grown lettuce (Lactuca sativa L.). Samples were prepared through digestion (dry ashing) method and the analytes quantitatively analyzed using Atomic Absorption Spectrophotometric (AAS) technique. The effects of EDDS on Pb2+ and Cd2+ uptake by lettuce (Lactuca sativa L.) seedlings replanted in hydroponic solutions for 72 hr in a greenhouse were investigated. Two months old seedlings were exposed to various doses of Pb2+ and Cd2+ at constant concentration of EDDS. For unchelated treatments, increase in concentrations of Pb2+ and Cd2+ in the solution increases the uptake by the plants relative to control. Pb2+ contents in the roots showed more accumulation than in shoots (p<0.05) while Cd2+ content in the shoots was higher than in roots. Addition of 0.0025M EDDS to the solutions of Pb2+ and Cd2+ inhibits the uptake of the metal ions at the following concentrations (0.0025, 0.005 and 0.0075 mg/L) when compared to unchelated treatments of same concentrations. At 0.025 mg/L of Pb2+ and Cd2+, chelation substantially enhances their uptakes in both shoot and root of the plant (p<0.05). Compared to the unchelated treatments, chelation suppresses the translocation of Pb2+ and Cd2+ to the shoots of the plant (p<0.05), but there was a better translocation of Pb2+ (1.257) and Cd2+ (0.953) at 0.025 mg/L, thus indicating that, at very high concentration of the metals the plant was hyper-accumulator. For hydroponic solutions containing the combination of both metals; Pb2+ + Cd2+, Pb2+ uptake was more in the roots than in the shoots while Cd2+ content in the shoots showed more absorption than the roots for both chelated and unchelated treatments. Also, it was observed that chelation suppresses the uptake of Pb2+ and Cd2+ in the presence of one another by both root and shoot. Furthermore, increasing the concentrations of Pb2+ + Cd2+ in chelated treatments of hydroponic solutions results to a better translocation of Pb2+ while the translocation of Cd2+ to the shoot was enhanced. Generally, addition of EDDS to the hydroponic mixtures affected to a large extent the availability of Pb2+ and Cd2+ to the growing seedlings.
Keywords: Ethylene diamine disuccinate, greenhouse, hydroponic solution, lettuce, metals.
It is well described that under stress conditions many plant species accumulates proline as adaptive response to adverse conditions. In this study, eight weeks old Lactuca sativa L. seedlings were transplanted in nutrient solution containing various doses (0.000, 0.0025, 0.005, 0.0075, and 0.025mg/L) of Pb2+ and Cd2+ and constant concentration of EDDS (0.0025M). The effects of these treatments of Pb2+, Cd2+, combination of Pb2+ + Cd2+and with or without EDDS (Ethylene diamine disuccinate) were compared based on the level of stress induced to the seedlings. Free proline contents induced due to stress by uptake of Pb2+and Cd2+ were investigated in both unchelated and chelated treatment. The results obtained showed that the effect of increasing concentration of Pb2+ in hydroponic solution leads to decrease in the level of stress induced to the seedlings by EDDS while the lower the Cd2+ concentration in the hydroponic solution the more the level of stress induced by EDDS to the plant. The highest level of stress caused to the seedlings by unchelated and chelated Pb2+ solution are 68.294±5.642; 72.681±14.740 µmolg-1 respectively while that of Cd2+ are 28.962±8.703; 48.263±2.455 µmolg-1 respectively. From this, it is evident that Pb2+induced more stress to the plants than Cd2+ in the presence and absence of EDDS (p<0.05).
Keywords: Proline, Ethylenediaminedisuccinic Acid (EDDS), Lead, Cadmium, Lettuce.
The aim of this work was to investigate the effects of acetyl acetone on Zinc (Zn) uptake and growth of Drumstick (Moringa oleifera) plants. Thirty seedlings were raised in hydroponic solution containing varied concentrations of Zn and acetyl acetone. The results showed a significant (p>0.05) change in weights of the plants when concentrations of Zn and acetyl acetone were added. Plants grown in treated hydroponics died before control plants. Zn uptake and accumulation were dose dependent with respect to addition of both Zn and acetyl acetone. The translocation factor decreased highly insignificantly (P>0.05) at lower concentration of Zn and significant at higher concentration in treated plants compared to control. The chlorophyll, carotenoid and proline content were severely decreased after addition of Zn and acetyl acetone, inducing toxicity symptoms. Thus, acetyl acetone did not play any significant role in alleviating Zn-induced toxicity.
The effects of Pb treatments on Pb uptake by three food crops were investigated in a growth chamber experiment. Pb was added as Pb-acetate at the rates of 0, 200, 1000 and 2000 mg/kg soil. Lead concentrations in some plant parts were influenced more dramatically by soil Pb treatments than levels in other plant sections. Lettuce and carrot roots accumulated markedly higher Pb concentrations than the other plant parts. Since excessive dietary intake of Pb is undesirable, growth of Pb-responsive crops in contaminated soils should be avoided.
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