Abstract: To investigate the role of light intensity in the recovery of chilled plants, photosynthesis and chlorophyll fluorescence parameters were examined in tomato (Solanum lycopersicum L. cv. Zhefeng 202) plants with natural sunlight or shading during recovery period after chilling under low light. Chilling under low light (8℃/12℃, PFD 80 mol·m^-2·s^-1) significantly decreased the net photosynthetic rate (P_n), the relative quantum efficiency of PSⅡ photochemistry (Ф_PSⅡ), photochemical quenching (qP), and efficiency of energy capture by open PSⅡ reaction centres (F_v′/F_m′), but increased nonphotochemical quenching (NPQ) and did not induce PSⅡ photoinhibition (F_v/F_m). P_n, F_v/F_m, Ф_PSⅡ, qP, NPQ and F_v′/F_m′ further deceased when the chilled plants were recovered under natural sunlight at 1 and then increased to the values close to the control. However, decreases in these parameters were less significant for shaded plants. Compared with control plants, shaded plants maintained higher NPQ during recovery period. Our results suggested that chilling under low light inhibited photosynthesis, but induced photoinhibition until the plants were exposed to full natural sunlight during recovery period. The photoprotection by shading is associated with the increased photochemical activity of PSⅡ and the enhanced thermal dissipation from antenna in PSⅡ.

Key words: Solanum lycopersicum L, chilling under low light, light intensity, recovery, photosynthesis, chlorophyll fluorescence