Effect of nickel on physiological characteristics of castor plant (Riccinus communis L.)

A green house study was conducted to analyse the effect of Ni treatment on physiological characteristics of castor plant (Ricinus communis L.). Different levels of Ni (0, 10, 40, 80, 120, 160, 180, 200, 250 mg Ni kg⁻¹ soil) were applied in the soil. The findings of the study showed that photosynthesis and chlorophyll content decreased with increasing concentration of Ni and to combat the Ni-induced stress, respiration rate of castor plant increased with increasing level of Ni applied. The activities of various metabolic enzymes like NRA (nitrate reductase), POD (peroxidase) and SD (succinate dehydrogenase) decreased with increase in Ni concentration applied. Leaf protein content decreased at the level of 80 mg kg⁻¹, Ni applied while at higher dose of Ni (>80 mg kg⁻¹) phenol and O-dihydric phenols activity showed increasing trend. The study concluded that at lower level of Ni in soil may improve plant growth, but higher level will severely affect the photosynthesis rate as well as enzymatic activities.