Abstract: By using solution culture, this paper studied the effects of 3 000 μmol·m^-2·s^-1 saturation pulse light of chlorophyll fluorescence apparatus on the leaf temperature of Citrus unshiu Marc. under different phosphorus supply and light intensity. The results showed that after treated with the saturation pulse light of chlorophyll fluorescence apparatus, the leaf temperature difference (△t) of C. unshiu increased in the sequence of phosphorus deficiency blaze group (-P₉₀₀), phosphorus deficiency midblaze group (-P₆₀₀), and phosphorus deficiency low-light group (-P₁₀₀). A wider rising scope was observed with the weaker intensity of culture light and longer processing time. On the contrary, there was no significant difference in △t among the phosphorus supply blaze group (+P₉₀₀), phosphorus supply midblaze group (+P₆₀₀), and phosphorus supply low-light group (+P₁₀₀). When 1,4-dithiothreitol (DTT) was applied, the difference of △t among the groups became remarkable whether phosphorus was supplied or not. The diurnal changes of △t increased with increasing light intensities. The contents of chlorophyll a, chlorophyll b and carotenoid of each group decreased with increasing light intensity, while the transpiration rate, stomatal conductance and intercellular CO₂ concentration had less difference among the groups. This study suggested that the leaf temperature difference of C. unshiu was related to light intensity, phosphorus supply, processing with DTT, and duration of phosphorus deficiency stress.

Key words: Black soil, Soil organic carbon, Simulation