EFFECTS OF NICKEL EXPOSURE ON JUTE MALLOW (CORCHORUS OLITORIUS)

Nickel (Ni) is a naturally occurring heavy metal and an essential micronutrient for plants, playing a key role in nitrogen metabolism, enzymatic activities, and iron uptake. However, anthropogenic activities such as industrialization, fertilizer use, and chemical applications have elevated Ni concentrations in soils to potentially toxic levels. While beneficial at low concentrations, excess Ni can disrupt plant metabolism, inhibit growth, and reduce chlorophyll synthesis. Corchorus olitorius (jute mallow), a widely consumed leafy vegetable in Nigeria and Africa, is particularly prone to heavy metal accumulation. This study investigated the effects of Ni exposure on Corchorus olitorius grown under controlled conditions at varying concentrations (0, 5, 10, 15, and 20 µM). Growth parameters, chlorophyll content, and heavy metal accumulation were assessed. Metal concentrations, including Ni, chromium, iron, zinc, copper, cadmium, cobalt, and manganese, were determined using Atomic Absorption Spectroscopy (AAS). Results showed variable Ni uptake, with the highest accumulation in Sample A (5 µM) and lowest in Sample D (20 µM). Lead was absent in all samples, indicating minimal contamination. Chlorophyll content, measured via UV spectrophotometry, increased significantly at 10 µM Ni (4.64 mg/g), compared to the control (4.41 mg/g) and 5 µM (4.09 mg/g). However, higher concentrations (15–20 µM) reduced chlorophyll levels, with 15 µM showing the lowest value (3.39 mg/g). Carotenoid levels followed a similar trend, with moderate enhancement at 10 µM and decline at higher concentrations. These results indicate that Corchorus olitorius can tolerate and utilize low to moderate Ni exposure to enhance pigment synthesis, but excessive Ni disrupts chlorophyll metabolism and suppresses growth. The findings highlight the dual role of Ni in plant physiology and emphasize the health risks of consuming vegetables grown in Ni-contaminated soils. The study underscores the need for monitoring heavy metals in agricultural environments and adopting strategies to mitigate Ni pollution in food crops.