PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Mentha arvensis is a fast growing plant with high biomass production that is commonly growing in tropical areas. However, its ability to hyperaccumulation and tolerance to heavy metal stress has yet to be investigated. The present study is focused to examine the effect of mercury (Hg) stress on plant growth, antioxidative enzyme activities and DNA damage in Mentha arvensis. Initially seedlings were grown in hydroponics for 15 days. Then seedlings were treated with different concentrations of mercury (10, 20, and 40 mg/l) and had the ability to grow up to 40 mg/l Hg. It is observed that shoot and root length of the seedlings were gradually decreased with increasing the mercury concentration in growth medium. A coordinated increase in the antioxidative enzyme (APX and CAT) activities was noticed with increase the Hg concentration upto 20 mg/l. However, the activity was slightly decreased at higher concentration of Hg (40 mg/l). Scanning electron microscopy with energy dispersive X-ray analysis was showed the deposition of Hg in leaf and root tissue of seedlings. The changes occurring in RAPD profiles following Hg treatment showed variation in band intensity, loss of bands and appearance of new bands compared with the normal seedlings. The exposure of mercury ion to seedlings induced a dose of dependent physiological changes has evidenced by increased antioxidative enzyme level, appearance and disappearance of DNA bands in the RAPD profile suggesting that the possible mechanism of the Hg phytotoxicity tolerance in Mentha arvensis was conformed.