Physiological and Biochemical Responses of Rice (Oryza Sativa L.) to Phenanthrene and Pyrene

Abstract

Phenanthrene (Phe) and pyrene (Pyr) are two typical polycyclic aromatic hydrocarbons (PAHs) found in contaminated soil. This study investigated physiological and biochemical responses of rice (Oryza sativa L.) to PAH stress after they were planted in soils contaminated with Phe and Pyr, in the presence or absence of a PAH-degrading bacteria (Acinetobacteria sp.). A number of parameters including biomass and water, chlorophyll and chlorophyll a/b ratio, electrolyte leakage, activities of superoxide dismutase (SOD) and peroxidase, and soluble carbohydrate and soluble protein contents were monitored. Results show that rice plants have good resistance and tolerance to lower levels of PAHs stress, while adding high levels of PAHs to soils resulted in adverse effects on rice plants such as a reduction in biomass and damage to photosynthetic function. Water content and SOD activities were the most sensitive indicators of PAH stress among the observed parameters. Inoculation with PAH-degrading bacteria promoted growth and photosynthesis of rice.

KEY WORDS:

• stress
• polycyclic aromatic hydrocarbons (PAHs)
• polycyclic aromatic hydrocarbon (PAH)-degrading bacteria
• damage
• resistance

ACKNOWLEDGEMENTS

The authors would like to thank the Area of Excellence Project (CITYU/AoE/ 03–04/02) and the Group Research Project, Central Allocation (HKBU 1/03C), Research Grants Council of the University Grants Committee of Hong Kong, for financial support.

Notes

*p < 0.05 (n = 4);

**p < 0.01;

***p < 0.001.