Abstract:

To analyze the photosynthetic physiological mechanism that exogenous salicylic acid（SA）relieves harm of tomato seedlings under the salt stress，‘Qinfeng Baoguan’tomato seedlings were taken as the testing material. Under hydroponic conditions，the chlorophyll fluorescence dynamics technology was used to research the effects of nutrient solution（1/4 Hoagland）applied with SA（200 μmol · L^-1）on PSⅡ photochemistry activities of tomato seedlings and excitation energy distribution and antenna pigments absorb light energy utilization under stress of 100 mmol · L^-1 NaCl. The results indicate that under the stress of NaCl in 15 d，there are PSⅡpotential photochemical activity（F_v/F_o），maximal photochemistry efficiency（F_v/F_m），antenna conversion efficiency（F_v′/F_m′），practical photochemical efficiency（Φ_PSⅡ），photochemical fluorescence quenching coefficient（q_P），quotient of absorbed luminous energy used for photochemical action（P）and chlorophyll fluorescence decay rate（R_fd）of seedling leaves applied with SA which increase in different degree. While there are also PSⅡnon-photochemical fluorescence quenching coefficient（NPQ），excitation pressure（1–q_P），quotient of absorbed luminous energy used for antenna heat dissipation（D），photosynthetic function relative limit value（L_PFD）and unbalanced distribution of coefficient deviation on excitation energy between two photosystems（β/α–1）which decrease evidently. But there is no obvious regularity on quotient of absorbed luminous energy used for non-photochemical dissipation（E_x）in reaction center of PSⅡ. These results above show that exogenous SA can decrease photoinhibition caused by salt stress through increasing PSⅡ photochemical activity，and then promote the growth and development of tomato seedlings.

Key words: tomato, salicylic acid（SA）, NaCl stress, seedlings, PSⅡ photochemical efficiency, distribution of luminous energy