Copper-induced changes in growth and antioxidative mechanisms of tea plant (Camellia sinensis (L.) O. Kuntze)

Abstract

Tea is the oldest, most popular, non-alcoholic caffeine containing beverage in the world. Tea plants are prone to the attack of many diseases which can be controlled by the treatment of pesticides. These pesticides contain heavy metal which prolonged accumulation can lead to the damage of crop yield both in quantity and quality. In the present study, we observed the effects of high concentration of Cu stress on physiological and biochemical parameters. The tea cultivars (S₃A₃ and TS-491) were collected from the Rosekandi Tea Estate, Silchar, Assam. The accumulation of Cu in the different parts of the tea plants had a positive correlation with the Cu stress. The accumulation of Cu was higher in roots than in leaves and also the new stems. The results show gradual decrease in the photosynthetic activity with the increase in the concentration of the Cu stress in both the cultivars. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased with the increase in the Cu concentration but remarkably in different manner in both the cultivars. The activities of antioxidants ascorbate peroxidase (APX), CAT, SOD and POD in cultivar S₃A₃ increased up to 500 µM and at 600 µM showed a low rate of increase whereas TS-491was tolerant up to 400 µM. The responses in the oxidative stress were characterized by an accumulation of malondialdehyde (MDA). Phenol content has also positive correlation with increase in the concentration in both the cultivars up to 500 µM. Finally it was concluded that Cu is tolerant to the cultivars of tea plant to some extent (specifically at lower concentration), but at higher concentration (beyond 400 µM) of Cu with exposure time, tea plant had a strong inhibition of growth by damaging the normal metabolism.

Keywords: Tea plants, copper stress, physiological characters, lipid peroxidation, reactive oxygen species.

Abbreviation: ROS, Oxygen species; POD, peroxidase; APX, ascorbate peroxidase; CAT, catalase; SOD, superoxide dismutase; PVP, polyvinylpyrrolidone; NBT, nitrobluetetrazolium; MDA, malondialdehyde