The Effects of Night Chilling on Chlorophyll Fluorescence in Seedlings of Two Tropical Rain Forest Tree Species

In this study, the effect of night chilling (5℃±1℃, 12 hours at night, for three consecutive nights) on chlorophyll fluorescence in leaves of two tropical rain forest tree species was examined. Seedlings of Pometia tomentosa (Sapindaceae), a canopy species,and Horsfieldia tetratepala (Myristicaceae), a middle layer species, were nursed under three light regimes (full, 25% and 8% daylight) in the Xishuangbanna Tropical Botanical Garden. More severe photoinhibition at noon resulted from the night chilling was observed in P. tomentosa seedlings grown under full daylight. However, this photoinhibition was recovered rapidly after termination of the chilling treatment, indicating that no irreversible photooxidation damage occurred. In addition, heat dissipation, as indicated by non-photochemical quenching (NPQ), in the seedlings of both species grown under 25% and full daylight conditions were suppressed by night chilling, but there was no increase in Fo(Initial fluorescence) value in both species, suggesting no inactivation of PSII reaction centers. Our results support the observations in the field that native tropical rain forest plants are usually not injured when severe cold wind affects the region. Resistance of native tropical plants to chilling is consistent with their geographical distribution.