Chlorophyll fluorescence characteristics of Ilex latifolia
The diurnal changes of chlorophyll fluorescence parameters of Ilex latifolia in different seasons were studied in this paper. As results, the daily change range of every chlorophyll fluorescence measured in spring and autumn was smaller than that in summer and winter. In summer, the values of Fm(maximal fluorescence), Fm′(actual maximal fluorescence), Fv(variable fluorescence), Fv/Fm(optimal/maximal photochemical efficiency of PSⅡ), Fm/F0(electron transfer rate), and Fv/F0(potential activity of PSⅡ) from 8:00 to 18:00 obviously showed a descending-ascending trend with the lowest value occurred at about 14:00, but the value of NPQ(non- photochemical quenching) from 8:00 to 18:00 in summer obviously presented a ascending-descending trend and the highest value was detected at about 12:00. The daily change of Fm, Fm′, Fv, Fv/Fm, Fm/F0, and Fv/F0 in winter appeared to be a single peak and the highest value appeared at about 14:00. The daily change trend of NPQ in winter, however, was contrary to those parameters mentioned above and the lowest value appeared at about 14:00. The value of Fv/Fm, Fm/F0, and Fv/ F0 in spring and autumn were obviously higher than those in summer and winter, indicating that the electron transfer rate and potential activity of PSⅡ in spring and autumn were higher than those in summer and winter. On the contrary, the value of NPQ in winter and summer was obviously higher than that in spring and autumn, which showed that higher proportion of light energy absorbed from the sun in winter and summer were used for avoiding the destruction of photosynthetic tissue through hot dissipation. In spring, summer, and autumn, a closely positive and negative correlation was found between the value of NPQ and the value of illumination and air moisture, respectively. In summer, there was a close negative correlation between the value of Fm/F0, Fv/F0, and Fv/Fm and the value of air temperature and illumination, respectively. However, the correlation between the value of Fm/F0, Fv/F0, and Fv/Fm and the value of air moisture was distinctly positive in summer season.