Responses of Niger [Guizotia abyssinica (L.f.) Cass.] to cadmium and nickel stress

Niger (Guizotia abyssinica (L.f.) Cass) is an incredibly useful but underutilized oil crop commonly grown in East Africa, mainly in Ethiopia, and the Indian subcontinent. Various abiotic stresses of the present-day environment significantly reduce crop productivity. Of them, heavy-metal stress is one of the major causes of osmotic stress that leads to oxidative stress. The present study aims to elucidate and understand the influence of nickel and cadmium chloride stress on seed germination, chlorophyll content, protein content, hydrogen peroxide production, proline accumulation, and antioxidant enzyme activity in niger. The germination rate of sterilized seeds exposed to 0, 25, 50, 75, 100, and 150 ppm of nickel and cadmium chloride was recorded 24 h after treatments. Four-week-old seedlings were also treated with heavy metals and biochemical observations were recorded on the 15th day after treatment. A direct relationship was noted between heavy metal stress and the hydrogen peroxide and proline content of niger. The extent of oxidative stress was significantly higher, as compared to the control, in all the treatments. The majority of the antioxidants exhibited a significantly negative relationship with chlorophyll and protein content of niger. Furthermore, a higher concentration of heavy metal stress results in decreased germination rate, chlorophyll content and triggers antioxidant enzyme activity. Thus, oxidative stress in niger caused by a high level of nickel and cadmium, which could result in membrane damage via the production of reactive oxygen species was compensated by the active defense mechanism via high proline accumulation and antioxidant enzyme activity. © The Author(s) under exclusive licence to Society for Plant Research 2023.