Medical College of Soochow University, 215123 Suzhou, People's Republic of China.
Biol Trace Elem Res. 2011 Oct;143(1):468-77. doi: 10.1007/s12011-010-8830-y. Epub 2010 Aug 27.
Lanthanoids (Ln) were demonstrated to improve chlorophyll formation and the growth of plants. But the mechanism of the fact that Ln promotes chlorophyll biosynthesis of plants is poorly understood. The main aim of the study was to determine Ln effects in chlorophyll formation of maize under magnesium (Mg) deficiency. Maize plants were cultivated in Hoagland's solution. They were subjected to Mg deficiency and to cerium administered in Mg-deficient Hoagland's media, and then the contents of various chlorophyll precursors and gen expressions of the key enzymes of chlorophyll biosynthesis were examined. The decrease of chlorophyll contents in maize leaves caused by Mg deficiency suggested an inhibition of chlorophyll synthesis that was inhibited by a reduction of the precursors as measured by analyzing the contents of δ-aminolevulinic acid, porphobilinogen, uroporphyrinogen III, Mg-protoporphyrin IX, and protochlorophyll, as well as the expression levels of magnesium chelatase, magnesium-protoporphyrin IX methyltransferase, and chlorophyll synthase; Mg deficiency significantly inhibited the transformation from coproporphyrinogen III or protoporphyrin IX to chlorophyll. However, cerium addition significantly relieved the inhibition of chlorophyll biosynthesis in maize caused by Mg deficiency and increased chlorophyll content and promoted a series of transformations from δ-aminolevulinic acid to chlorophyll and maize growth under Mg deficiency. It implied that cerium might partly substitute for the role of Mg.
镧系元素（Ln）被证明可以促进叶绿素的形成和植物的生长。但是，Ln 促进植物叶绿素生物合成的机制还不清楚。本研究的主要目的是确定 Ln 在镁（Mg）缺乏下对玉米叶绿素形成的影响。玉米植株在 Hoagland 溶液中培养。它们被置于 Mg 缺乏和 Ce 在 Mg 缺乏的 Hoagland 培养基中，然后检查各种叶绿素前体的含量和叶绿素生物合成关键酶的基因表达。Mg 缺乏导致玉米叶片中叶绿素含量下降表明叶绿素合成受到抑制，这是通过分析 δ-氨基酮戊酸、卟胆原、尿卟啉原 III、Mg-原卟啉 IX 和原叶绿素的含量以及镁螯合酶、镁-原卟啉 IX 甲基转移酶和叶绿素合酶的表达水平来衡量的，前体减少，以及叶绿素合成受到抑制。Mg 缺乏显著抑制了 coproporphyrinogen III 或 protoporphyrin IX 向叶绿素的转化。然而，铈的添加显著缓解了 Mg 缺乏对玉米叶绿素生物合成的抑制作用，增加了叶绿素含量，并促进了一系列从 δ-氨基酮戊酸到叶绿素的转化和玉米在 Mg 缺乏下的生长。这表明 Ce 可能部分替代了 Mg 的作用。
