Effect of Hg stress in Larix olgensis on the growth, antioxidant and detoxifying enzymes of the Lymantria dispar

To understand the physiological response mechanisms of Lymantria dispar larvae to heavy metal stress, their host, 2-year-old Larix olgensis seedlings grown in pots, were treated with three different concentrations of HgCl2 (Hg). Hg accumulation and tannin content in larch needles were measured. The growth and detoxification ability of the larvae were analyzed after being fed on the Hg-stressed needles. The results showed that Hg concentration in larch needles increased with Hg treatment concentration increase, while the tannin content decreased. The larval body mass was significantly decreased. The responses of the larval antioxidant and detoxifying enzymes to Hg stress appeared to differ, with the superoxide dismutase (SOD) and peroxidase (POD) activities in 4th instar larvae were significantly higher than CK. In contrast, the acid phosphatase (ACP), alkaline phosphatase (AKP) and glutathione S-transferase (GST) activities in 4th instar larvae were significantly lower than CK. This result indicated that Hg could inhibit the growth of larvae along the food chain. The larval antioxidant and detoxification enzymes produced adaptive responses to the Hg stress, which might partially alleviate the oxidative damages caused by Hg.