百脉根无效根瘤突变体的生物量及无效根瘤的电镜观察分析

百脉根是研究豆科植物根瘤形成和共生固氮分子机理的一种重要模式植物.为探索百脉根根瘤的形成机制,以EMS诱导野生MG-20突变并筛选的No.1006,No.486和No.2568等3种无效根瘤突变体为材料,测定其突变体植株生物量、根瘤数及固氮能,并对无效根瘤中根瘤菌感染的细胞进行电镜观察.结果表明:No.1006是根瘤原基突变体,No.486是白色无效根瘤突变体,No.2568是绿色无效根瘤突变体;这3种无效根瘤突变体植株生长至30d时,根瘤数和固氮能以及株高、地上部干质量、根干质量和根长等生物量与MG-20野生株差异无统计学意义(p0.05),但生长至40d开始均显著低于野生株(p0.05).No.486的白色无效根瘤和No.2568的绿色无效根瘤,经切片后在电镜下观察,无效根瘤细胞均存在不同程度的破坏;其中No.2568的绿色无效根瘤的细胞和由根瘤菌转化来的类菌体的破坏程度远大于No.486的白色根瘤.

Biomass of Ineffective Nodule Mutants of Lotus japonicus and Electron Microscopic Observation of Their Ineffective Nodules

Lotus japonicus is one of the important model plants in exploring the mechanism of nodule formation and symbiotic nitrogen fixation of legumes. In order to elucidate the mechanism of nodule formation in L. japonicus and the early aging of its ineffective nodules, three kinds of ineffective nodule mutants (No.1006, No.486 and No.2568) obtained from EMS-treated MG-20 seeds were used as the experiment materials, and phenotypic analysis and determination of nitrogen fixation capacity of their ineffective nodules were carried out, and rhizobia-infected cells of the nodules were observed with an electron microscope. The results showed that No.1006 was a nodule primordium mutant, No.486 a white nodule mutant and No.2568 a green nodule mutant. The number of nodules and their nitrogen fixation capacity as well as plant height, shoot dry weight, root dry weight and root length for these mutants were not significantly different from those of the wild type plant in the first 30 days of growth (p>0.05), but were significantly lower than the wild type plant after 40 days of growth (p<0.05). Electron microscopic examination revealed that the cells of ineffective nodules of mutants No.486 and No.2568 were damaged to varying degrees; and that cells and bacterioids in the green ineffective nodules of No.2568 were more seriously damaged than those of the white ineffective nodules of No.486.