Differences in PI of Quercus liaotungensis seedlings between provenance.

The performance index of overall photochemistry (PI) is widely used in photosynthesis research, but the PI interspecies differences are unclear. To this end, seeds of Quercus liaotungensis from 10 geographical provenances were planted in two different climate types. Two years later, leaf relative chlorophyll content (SPAD) and chlorophyll a fluorescence transient of seedlings were measured. Meanwhile, the environmental factors of provenance location, including temperature, precipitation, solar radiation, wind speed, transpiration pressure, and soil properties, were retrieved to analyze the trends of PI among geographic provenance. The results showed that, in each climate type, there was no significant difference in SPAD and electron transfer status between PSII and PSI, but PI was significantly different among geographic provenances. The major internal causes of PI interspecies differences were the efficiency of electronic transfer to final PSI acceptor and the number of active reaction centers per leaf cross-section. The main external causes of PI interspecies differences were precipitation of the warmest quarter, solar radiation intensity in July, and annual precipitation of provenance location. PI had the highest correlation with precipitation of the warmest quarter of origin and could be fitted by the Sine function. The peak location and fluctuating trend of precipitation-PI fitted curve were different in two climate types, largely due to the difference of precipitation and upper soil conductivity in the two test sites. Utilizing the interspecific variation and trends of PI might be a good strategy to screen high and stable photosynthetic efficiency of Q. liaotungensis provenance.