Agronomic Traits and Photosynthetic Characteristics of Chlorophyll-Deficient Wheat Mutant Induced by Spaceflight Environment

Chlorophyll deficient mutants are ideal materials to study photosynthetic mechanism, pathways of chlorophyll biosynthesis and degradation, and the genes related to photosynthesis. A chlorophyll-deficient mutant of wheat (Triticum aestivum L.), Mt135, was obtained by space mutagenesis. The main agronomic traits and photosynthetic characteristics of this mutant were compared with its wild type in field experiment. The leaf color of Mt135 showed albino, striped, and green phenotypes. The albino plants with entire albino leaves died at seedling stage. The plants with green-and-white striped leaves usually matured 5–7 d later than the wild type, and had lower plant height, shorter spike length, fewer grain number, and smaller grain weight per plant and 1000-grain weight. In contrast, the green plants of the mutant had similar agronomic traits to the wild type. Preliminary genetic analysis showed that the inheritance of leaf color in Mt135 was controlled by nucleocytoplasmic interaction. When exposed to photosynthetic active radiation (PAR) at 110 μmol m−2 s−1, the green tissue of striped plant (S-G) had a similar value of maximum photosystem II quantum yield to the wide plant, but a significantly lower potential activity of photosystem II; the photochemical quenching, nonphotochemical quenching, effective quantum yield, regulated nonphotochemical energy dissipation, and nonregulated energy dissipation varied differently at seeding, elongation, and heading stages. In addition, for electron transport rate, photochemical quenching, and effective quantum yield, the differences between S-G plant and the wild plant varied under different PAR conditions. Nevertheless, the other 2 types of the mutant, white tissue of striped plant and albino plant, showed complete losses of photosynthetic function. As a result, the photosynthesis of Mt135 was greatly restricted. High photosynthetic active radiation had tremendous impact on the mutant at elongation stage and relatively weak impact at heading stage. The changes of photosynthetic function of striped plants are in accordance with the reduction of their plant height, spike length, and yield related traits.

摘 要叶绿素缺失突变体对研究植物光合作用机制, 揭示叶绿素生物合成与降解途径, 发掘鉴定光合作用相关新基因以及了解基因间的相互作用有重要意义。空间诱变创制的小麦叶绿素缺失突变体Mt135的叶色表现为完全白化、条纹和绿3种类型, 其中完全白化株叶片完全白化, 于苗期死亡; 条纹株叶片呈绿白相间的条纹, 能够正常成穗结实, 但其株高、穗长、株粒数、株粒重、千粒重都显著低于原始亲本, 生育期比原始亲本延长5–7 d; 绿株与原始亲本没有显著差异。初步遗传分析表明, Mt135是一个由核质基因共同作用的突变材料。对突变体及其原始亲本叶绿素荧光动力学参数的分析表明, 当光照强度为110 μmol m−2 s−1, 时, 条纹株绿色组织光系统II的最大量子产量与原始亲本无显著差异, 光系统II的潜在活性显著低于原始亲本, 而光化学猝灭系数、非光化学猝灭系数、实际量子产量、调节性能量耗散的量子产量、非调节性能量耗散的量子产量在不同的生育期间变化不同。另外, 不同的光照强度下, 条纹株绿色组织的电子传递速率、光化学猝灭系数、实际量子产量的变化也不相同。条纹株白色组织和完全白化株则完全失去光合能力。上述结果证实, 小麦叶绿素缺失突变体Mt135的光合作用受到很大的影响, 光合特性发生了改变, 较高的光照强度在拔节期对突变体影响较大, 抽穗期影响相对较小。条纹株光合特性的改变与其株高、穗长和产量相关性状显著降低的结果相互印证。