Senescence And Death Mechanism Study Of Heavy Metals Pollution On Aquatic Plants

The senescence and death process of aquatic plants under heavy metalspollution were studied. The floating plant-Trapella sinensis was treated withHg~2+ and Cu~2+and the emerged plant-Sagittaria trifolia was treated with Hg~2+.The methods and means of physiology, cytology, genetics and molecular biology were used. There are three structural systems in organisms. The structure of genetic message expression system is one of them. The protective enzymes system is the key factor in plant defense responses. The imposition of environmental stress leads to increased production of reactive oxygen species (ROS) in plant cells. Effects of heavy metals on the structure of genetic message expression system, the activities of protective enzymes , ROS contents and the relationships among them were studied. The results showed that Trapella sinensis had higher endurance to copper and Sagittaria trifolia to mercury. The results also indicated that the same defense mechanism of plants in heavy metals pollution: The low level of heavy metals pollution had the lest effects on the structure of genetic message expression system. When heavy metal pollution concentration enhanced , both heavy metals and ROS injured the structure of genetic message expression system. The decrease of CAT activity and the disruption of mitochondria inner membrane and nuclear envelope lead to programmed death on cell, tissue, even organ level, which would protect the whole plant. The different pathways involved the anti-pollution were also found: Sagittaria trifolia could excrete mercury particles out of root to reduce the mercury content and Trapella sinensis leaf abscise to avoid the death of the whole plant.