Levels of induced free proline in chelated and unchelated hydroponically grown lettuce (Lactuca sativa L.)

Abstract

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.