Abstract:

A fast chlorophyll fluorescence parameters were measured in two varieties of eggplants, Duanbahei with colder tolerance and Heishuai with higher temperature tolerance by Plant Efficiency Analyzer (PEA). Also the thermodynamics analyse of PSⅡ cold shock stability were studied by using the standard stade denaturalization Gibbs free energy variation △GD of the maximal photochemical efficiency of photosystem Ⅱ (Fv/Fm) and reaction centers RC/CSo . With the temperature decreasedand time extended, The Fv/Fm of PSII, factual photochemistry efficiency ΔF/Fm′ and RC/CSo were "S" downtrend.The exhibition of the energy dissipation DIo/RC and the nonphotochemical quenching coefficient qN were "S" ascends.The generalized analysis reflected the dual mechanism under the cold shock, the reversible deactivation of PSⅡ reaction centers and the energy dissipation which depended on lutein circulation were important in protecting PSⅡ for preventing photoprohibition. Moreover, two groups of new parameters were introduced as index for comparing cold shock easily through the different PSⅡ action of two varieties. Semi-attenuation temperature T_1/2 and t_1/2 of Heishuai were 1.4 ℃ and 0.8 ℃ higher than that of Duanbahei. The △GD of the Fv/Fm and RC/CSo in the leaves of eggplant were "waterfall" downtrend with the cold shock temperature decreased.The △GD and the denaturalization midpoint temperature Tm of Heibei were lower than Duanbahei. The result showed the cold tolerance of Heishuai is lower than Duanbahei.

Key words: eggplant (Solanum melongena L), cold shock stress, chlorophyll fluorescence parameter, photosystem Ⅱ, Gibbs free energy