Abstract: The needles of two superior provenances, with different cold tolerance, of Pinus massoniana were used as the materials to measure photosynthetic metabolism, nitrogen metabolism, endogenous protective enzyme system and membrane lipid reaction, and to examine relationships between these physiological and biochemical indices and the cold resistance. Chlorophyll content generally increased with the decrease of temperature, indicating a highly cold-resistant P. massoniana trees associated with high capability of photosynthesis. The changing trend of soluble sugar and proline contents at 0℃ and 4℃ temperatures could be used to estimate the cold resistance of P. massoniana. Their positive and negative values respectively represented strong and poor cold-resistance. Soluble protein content was inversely correlated with the cold resistance, and the higher content associated with poorer cold-resistance. Superoxide dismutase (SOD) was a chilling-sensitive regulating enzyme and peroxidase (POD) was a freezing-sensitive regulating enzyme. Trees had stronger resistance to cold when their SOD as well as POD activities increased and could remain at high level for longer time under the stress of low temperature. Under the stress, the activity of SOD started earlier than that of POD. However, trees with a stronger cold-resistance had lower content of malondialdehyde (MDA) and their MDA peak level arrived later. The six indices measured in the current study interacted with each other under the stress of low temperature.

Key words: Pinus massoniana, provenance, cold resistance, protected enzyme