Abstract: Calorific value reflects the utilization efficiency of solar energy by plants, and also, is an important parameter about the conversion of solar energy into biomass and for energy flow analysis. In the meanwhile, it is an important basis in explaining the adaptability of plant populations. The change patterns of the calorific values of eight dominant plant species on Xilin River fluvial wetlands were studied by oxygen bomb calorimeter, with the causes of the change patterns analyzed. The results showed that the calorific values of the test plant species had no unified change pattern, which was possibly related to the partitioning ratio of calorific value in different plant organs and the timing when the reproductive period appeared. In general, spike had a higher calorific value than leaf and stem, and aquatic plants had obviously lower calorific value than mesophytes and wet mesophytes. Within a species, the change pattern of calorific value had certain relations to the phenophase, with approximately two lowest values and two highest values. Among the species, the differences in the calorific value were decided by the nature of the species themselves. Under the same habitat and climatic conditions, the species that contained more materials rich in energy could more easily accumulate calorific, and thus, more adaptable to grow under this environment.

Key words: Strawberry, Strong light stress, Photoinhibition, Chlorophyll fluorescence, Xanthophyll cycle