缺氮对细胞质雄性不育玉米产量和光合特性的影响

Effect of Nitrogen Deficiency on Yield and Photosynthetic Traits of Cytoplasmic Male Sterility Maize

在露天池栽条件下,比较研究了玉米细胞质雄性不育系(CMS)与其同型可育系的产量构成及其光合特性对氮素亏缺的响应。结果表明,在相同氮素供应水平下,CMS的产量显著高于其同型可育系,平均增产达11.5%,缺氮条件下千粒重、收获指数显著提高,而穗粒数差异不显著。花后CMS玉米叶片具有较高的含氮量、叶面积指数、叶绿素含量和可溶性蛋白含量,且在生育后期降低缓慢,延长了有效光合持续期,延缓了植株衰老进程。不育植株生育后期的净光合速率(Pn)、细胞间隙CO2浓度(Ci)和气孔导度(Gs)均显著高于其可育系,且气体交换参数对缺氮反应不敏感。不育系的叶绿体荧光参数实际光化学效率(ΦPSⅡ)、电子传递速率(ETR)和最大光化学效率(Fv/Fo)在生育后期也保持较高水平。说明不育植株生育后期在光合能力、电子传递和光能转化方面均具有明显优势,其产量提高可能是籽粒充实期叶片生理质量和光合效率共同提高的结果。

Male sterility of higher plant is a common phenomena found in many species. Cytoplasmic male sterility （CMS） plays an important role in maize （Zea mays L.） breeding for its advantages of yield and reducing costs. It is reported that CMS maize has a positive effect on yield of single and double hybrids, as well as their homotype hybrids. Normal detasseling and CMS hybrid probably lead to higher yield under stresses, and the increase extent of yield varies with stress degree. Most grain yields of CMS lines are higher than those of their homotype lines, and male sterile plants have different effects with different genotypes. Plant photosynthesis traits have a direct influence to yield. However, the mechanism of increasing yield by male sterility is uncertain. To investigate the effects of low nitrogen after anthesis on grain yield and photosynthetic traits, we conducted a field experiment by low nitrogen treatment in 2004-2005 with two inbred lines, cytoplasmic male sterility （478CMS and Q319CMS） and homotype fertile lines（478 and Q319）. The fertilizer was applied at one time before sowing, we sampled at 0, 10, 20, 30, 40 d after anthesis to determine the nitrogen content and the photosynthesis traits at the same time. Grain yield and yield components were measured after maturity. The result showed that compared with their homotype lines （the maintainer lines）, CMS lines had higher grain yield with the increase by 11.5%, significantly greater kernel weight and harvest index, but no significant difference in numbers of kernels per panicle. Also, CMS lines maintained higher nitrogen, chlorophyll and.soluble protein contents, and larger leaf area index at late growth stage, indicating that CMS maize has a better green-maintaining character, prolonging effective photosynthesis duration and postponing the senescence course of plant. In CMS lines, photosynthetic rate （Jan）, intercellular CO2 concentration （Ci） and stomatal conductance （Gs） were higher at late growth stage obviously, and not sensitive to nitrogen deficiency in soil. Chlorophyll fluorescence parameters such as the actual photochemical efficiency （ФPS Ⅱ）, the apparent electron transfer rate （ETR） and the maximal photochemical efficiency （Fv/Fm） of CMS lines were higher than those of their homotype lines. These suggested that CMS lines have great advantages in photosynthesis ability, electron transfer, and light energy transform at late growth stage, and the higher grain yield of CMS lines comes from the common improvement of leaf physiological activity and photosynthetic efficiency in grain filling period.