Effect of Rice and Quinoa Straws on Reducing Lead Uptake in Lettuce (Lactuca sativa)
Two soil samples were obtained from a Farm on the roadway of Qalyub district (QF soil) and Farm of Faculty of Agriculture, Ain Shams Univ., Qalyubia Governorate (AS soil). Lead concentration was determined in the two soil samples. It was found that QF soil has more concentration of lead (300 mg Kg soil) 1 than AS soil (35.57 mg Kg soil). In a pot experiment, lettuce seedlings were transplanted in two sources of 1 lead contaminated soils during the seasons of 2013/2014 and 2014/2015 to study the effects of Pb on growth parameters, some biochemical constituents in lettuce and the efficiency of rice or quinoa straw in reducing Pb uptake from the contaminated soils. Increasing Pb level in soils caused a gradual decrease in plant fresh and dry weights, average leaves number, stem diameter and head circumference. Ascorbate peroxidase (ASP) activity and total soluble phenols, N, P, K and Ca concentrations were decreased. Whereas, hydrogen peroxide (H O ), malondialdehyde (MDA), glutathione (GSH), oxalic acid and Pb concentrations and the activities of 2 2 guaicol peroxidase (POD) and polyphenol oxidase (PPO) were increased. Adding rice or quinoa straws as an agricultural residue to both Pb contaminated soils enhanced plants tolerance under lead stress by improving the growth vigor, increased uptake of N, P, K, Ca ions and soluble phenols concentration and reduced proline, H O , MDA, GSH, oxalic acid, Pb concentrations and activities of ASP, POD and PPO enzymes. The results 2 2 concluded that rice straw is more effective than quinoa straw in most morphological and biochemical components.