桑树斑叶突变体叶绿素合成特性的初步研究

Primary Investigation on Properties of Chlorophyll Synthesis of a Leaf-variegated Mutant in Mulberry(Morus L.)

以新发现的桑树斑状叶色突变体Cty—Sm为材料，分析叶片中3种光合色素与叶绿素合成中间产物δ－氨基酮戊酸、胆色素原含量的变化状况，探讨突变体叶色差异的生理原因及其调控机制。与正常生长的原始材料（对照桑）相比，突变体叶片黄化部分的叶绿素a、叶绿素b和类胡萝卜紊含量均有不同程度的下降，其中叶绿素a的减少最显著，仅为对照桑的5．43％－10．23％，这是导致突变体叶色黄化的直接原因。其次，突变体黄化部分的δ-氨基酮戊酸含量明显升高，而胆色素原含量明显降低，推测其叶绿素a的减少是由于δ-氨基酮戊酸与胆色素原之间合成代谢受阻的缘故。

Changes of contents of 3 photosynthetic pigments and 2 intermediates in chlorophyll biosynthesis, δ-aminolevulinic acid （ALA） and porphobilinogen （PBG）, were analyzed in the newly identified leaf-variegated mulberry mutant to explore their physiological basis and control mechanism. The results showed that the content of chlorophyll a, b and carotenoid were decreased obviously, especially the content of chlorophyll a dramatically declined to just about 5. 4% -- 10.2% of the control, which may result in the etiolation directly. Qn the other hand, the ALA content increased while the PBG content decreased obviously, suggesting that the reduction of chlorophyll a was due to a metabolic block between ALA and PBG synthesis pathway.