Effects of molybdenum on the precursors of chlorophyll biosynthesis in winter wheat cultivars under low temperature

صينى. 探讨低温缺钼条件下冬小麦叶绿素合成受阻位点。采用土培试验、微区试验、营养液培养试验,设不施钼(CK, 土壤有效钼0.112 mg/kg)和施钼（+Mo, 施钼水平为0.13 mg/kg）处理，及δ-氨基酮戊酸(ALA)转化抑制剂乙酰丙酸（LA）处理，研究了缺钼对冬小麦品种叶绿素几种重要合成前体的影响。低温时叶绿素a与叶绿素b的比值（Chla/Chlb）上升，而不施钼时比值不变，表明低温抑制Chla 向Chlb的转化，而缺钼不影响它们的转化。叶绿素合成前体原叶绿素酸(酯)(Pchl)、镁原卟啉Ⅸ(Mg-ProtoⅨ)、原卟啉Ⅸ(protoⅨ)、尿卟啉原Ⅲ(UroⅢ)不施钼时显著下降，其中UroⅢ急剧下降，ALA、谷氨酸（Glu）显著累积，表明从Glu或ALA向UroⅢ的转化可能受阻；加入ALA转化抑制剂LA后，ALA含量逆转为不施钼小于施钼，表明缺钼条件下ALA向UroⅢ的转化受阻。缺钼影响ALA向UroⅢ的转化，导致叶绿素合成受阻，含量下降。

إنجليزي. 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. 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 mgand#8226;kg-1) and Mo addition (+Mo, 0.13 mgand#8226;kg-1 Mo was added). Levulinic acid (LA), the analog ofδ-aminolevulinic acid (ALA) was also introduced in the experiment. 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 (P0.01), 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. 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.