Abstract: 【Objective】 The objective was to probe the site where the biosynthesis of chlorophyll was blocked under Mo deficiency at low temperature which led to the decrease of chlorophyll in winter wheat cutivars. 【Method】The precursors of chlorophyll synthesis were analyzed in winter wheat cultivars in soil culture, miniblock culture, solution culture in order to study the effects of Mo on chlorophyll biosynthesis without Mo addition (CK, soil available Mo 0.112 mg·kg-1) and Mo addition (+Mo, 0.13 mg·kg-1 Mo was added). Levulinic acid (LA), the analog ofδ-aminolevulinic acid (ALA) was also introduced in the experiment. 【Result】The ratios of Chla/Chlb was constant between CK and Mo treatment while it increased at low temperature which indicated that Mo deficiency did not inhibited the transformation of Chl a to Chl b at low temperature. Under Mo deficiency, the contents of protochlorophyll (Pchl), Mg-ProtoporphyrinⅨ (Mg-ProtoⅨ), protoporphyrinⅨ (protoⅨ), uroorphyrinogenⅢ (UroⅢ) decreased, and that of UroⅢ decreased significantly (P<0.01), while ALA and glutamate increased significantly compared to Mo treatment, which suggested that the transformation from glutamate (Glu) or ALA to UroⅢ was inhibited. The content of ALA reversed after addition of LA, it was higher in Mo treatment than in CK, thus disclosed that the transformation from ALA to UroⅢ was blocked under Mo deficiency. 【Conclusion】 The results indicated that the transformation from ALA to UroⅢ was blocked under Mo deficiency, thus inhibited the biosynthesis of chlorophyll and led to the decrease of chlorophyll of winter wheat cultivars.

Key words: Chlorophyll, δ-aminolevulinic acid, UroorphyrinogenⅢ, Glutamate, Levulinic acid, Winter wheat cultivars