Tolerance and Concentrations of Nickel in Mustard (Brassica juncea L.) as Influenced by Nickel Application in Soil with Respect to Growth, Pigments Content and Activity of Antioxidative Enzymes

Abstract

To study the effect of nickel (Ni) levels in soil on growth and biochemical constituents in mustard a bulk composite alluvial soil was collected and analyzed for their physicochemical properties (sandy loam texture, pH 7.8, EC 4.6 dS m-1, organic carbon 0.34 g kg-1, Fe 8.5, Mn 5.2, Cu 0.56, Zn 0.62 and Ni <0.01 mg kg-1 (DTPA extractable). Various levels of nickel (Ni) viz. 0.0, 0.05, 0.25 and 2.5 mg kg-1 (Ni as NiSO4) were applied in soil before filling in the earthen pots (12 kg capacity) and mustard variety Pusa Mustard 24 (NPJ- 345) was sown. The growth parameters (length and dry weight), pigments content (chlorophyll a, b, total chlorophyll and carotenoids content) and activity of antioxidative enzymes (catalase and peroxidase) were observed after 45 days of sowing. The experiment was conducted in completely randomized design (CRD) and replicated thrice. The maximum concentration of Ni (15.2 µg g-1 dry weight) was recorded in root followed by shoot (11.6 µg g-1 dry weight) on dry weight basis at application of 2.5 mg kg-1 Ni in soil. At this level (2.5 mg kg-1 Ni application), mustard showed maximum reduction in dry weight, chlorophyll a, and chlorophyll b contents by 20, 24 and 40%, respectively. All applied levels of nickel inhibited growth and pigments content in mustard, whereas activity of antioxidative enzymes viz. catalase and peroxidase was enhanced with increasing nickel concentrations in soil and plants.