Yield and quality responses, plant metabolism and metal distribution pattern in aromatic rice under lead (Pb) toxicity.

Present study was planned to assess the yield and quality responses, plant physio-biochemical characters and Pb distribution pattern in two aromatic rice cultivars viz., Guixiangzhan (GXZ) and Nongxiang-18 (NX-18) under four different Pb-levels viz., control (0), low (400), medium (800) and high (1200) mg kg(-1)of soil. Results revealed that Pb toxicity increased H2O2, lipid peroxidation and electrolyte leakage while inhibited photosynthetic pigments production, but such increment was higher in NX-18 than GXZ. Furthermore, Pb toxicity variably affected protein, proline and soluble sugars and the activities of enzymatic antioxidants viz., superoxide dismutase (SOD), peroxidases (POD), catalases (CAT) and ascorbate peroxidases (APX) and non-enzymatic anti-oxidants viz., reduced glutathione (GSH) and oxidized glutathione (GSSG) in both rice cultivars. The reductions in osmolyte accumulation and antioxidant activities were more severe in NX-18 than GXZ. Pb toxicity severely reduced yield and quality related attributes and plant biomass accumulation; however the reductions were more apparent NX-18 than GXZ. Furthermore, NX-18 accumulated less Pb proportions in roots (∼84%), and transferred more towards shoot, leaves, ears (at panicle heading (PH)) and grains (at maturity (MAT)) than GXZ (∼91% root Pb proportions). Hence, the ability of GXZ to retain higher Pb contents in roots and less towards upper plant parts, higher osmolyte accumulation and antioxidant activities and less yield reduction as compare to NX-18 might be an adaptive response of GXZ under Pb toxicity.