Effects of Pb and Cr Accumulation on the Growth Performance of Some Local Rice Varieties from North-Eastern Nigeria

Abstract

Rice is an important cereal crop and foods for many population which utilizes certain concentration of heavy metals as source of nutrient. Heavy metals contamination and food safety are global issues that requires attention. Nigeria local rice varieties; Mai-kaya, Jamila and Mai-kwalli were evaluated for effective agronomic response and phyto-extraction of Pb and Cr. The rice seeds grown in paddy farm for three weeks and transplanted to pots for heavy metals accumulation studies. 500 ppm of Cr and Pb were prepared and use to water the rice at its different concentrations (100mL, 200mL, 300mL, 400mL and 500mL). Growth parameters including root and leaf development were determine both in the field and after transplanting at 2-weeks intervals. The concentration of the heavy metals in dried sample of both rice organs and soil was determined by acid digestion and analyze using atomic absorption spectrophotometry (AAS). The growing plant in various Pb and Cr concentrations was found to produced root number at a range of 60.00 ± 2.00 to 38.33 ± 2.51, root length range of 11.43 ± 0.35 to 5.06 ± 0.20, fresh weight of 0.99 ± 0.01 to 0.40 ± 0.00 and dry weight of 0.85±0.17 to 0.13±0.00. Jamila was recorded with optimum plant height of 43.33, followed by Mai-kwalli with 38.33 after two weeks of treatment with Cr 100mg/Kg. For the phyto-extraction, Jamila and Mai-kaya demonstrate optimal Cr accumulation in their seeds and soil across all the concentrations. Jamila rice was found to be highly adaptive to various heavy metals concentration than Maikaya and Maikwalli. However, the the Pb and Cr values detected in the present study are beyond permissible limit. The maximum allowable limit for Pb is 300 µg/kg, while for the Cr is 0.2mg/kg.