Comparative Morphology and Biochemical Analysis of Nickel Toxicity in Minor Fruit Species (Grewia asiatica L., Syzgium cumini (L.) Skeels and Tamarindus indica L.)

Abstract

We evaluated the growth potential of three minor fruit species (Grewia asiatica L., Syzgium cummini and Tamarindus indica L.) after exposure to increasing Ni levels (0, 10, 20 and 40 µg kg−1 soil). The growth attributes, lipid peroxidation, photosynthetic machinery, macro nutrients and capacity of enzymatic antioxidants; Superoxide dismutase (SOD), Catalase (CAT) and Peroxidase (POD) in both leaves and roots were investigated under Ni exposure. A significant reduction in the biomass elongation of tissues (root and shoot) and enhanced oxidative damage via malondialdehyde (MDA) were noticed in all three species. Ni exposure triggered an induction of antioxidant enzyme response in a concurrent manner. Simultaneous increases in the antioxidant activities in the roots of G. asiatica and in the leaves of S. cumini suggest the existence of a sequence response against tissue damage. However, the activities of antioxidant enzymes in the tissues of T. indica were insufficient to counteract the elevated MDA levels. G. asiatica exhibited its resilience through the restricted transfer of Ni to aerial tissue, adequate uptake of nutrients, robust chloroplasts with lesser biodegradation of chlorophyll molecules and enhanced capacity of antioxidant enzyme biosynthesis. Thus, lesser modulations of morpho-biochemical expressions and the activity of antioxidants seem to contribute important defense mechanisms against Ni stress in the species.