Abstract:

The features of changes in chlorophyll fluorescence in response to the water status of four woody species of Sophora japonica, Populus×canadensis, Gingkgo biloba and Pinus thunbergii were analysed in terms of their drought resistance. The analysis was carried out with the fast-induction kinetics associated with chlorophyll fluorescence and changes of relevant parameters in leaves of detached twigs during desiccation stress with a Handy PEA chlorophyll fluorometer. The results showed that with the progression of dehydration, the fast-induction kinetics of chlorophyll fluorescence in the four species changed significantly. The maximum primary yield of photochemistry of photosystem Ⅱ (F_v/F_o), maximum quantum yield for primary photochemistry (F_v/F_m), performance index (PI) all declined, with S. japonica having the fastest decrease, followed by P. ×canadensis, G. biloba and P. thunbergii, suggesting that their toleration to dehydration was in the same order accordingly. However, the threshold of relative water content (RWC) for the fast-induction kinetics associated with chlorophyll fluorescence was 60%~70%, 40%~50%, 30%~40% and 10%~20% for P. thunbergii, G. biloba, P. ×canadensis and S. japonica, respectively, indicating that the resistance of photosystem to dehydration of the plants was in a reversed order. It is concluded that S. japonica and P. ×canadensis have had a higher tolerance to dehydration, but higher rate of water use, suggesting they are not suitable for arid environments; whereas P. thunbergii has had a higher resistance to dehydration, but their inner tissues have had lower tolerance, suggesting it is suitable for semi-arid or dry sub-humid environment; However, G. biloba is intermediate between the above two types of plants in terms of the adaptability to water regimes.

Key words: chlorophyll fluorescence parameter, drought tolerance, Sophora japonica, Populus×, canadensis, Gingkgo biloba, Pinus thunbergii