Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Key Laboratory of Crop Physiology Ecology and Production Management of Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
Photosynth Res. 2021 Dec;150(1-3):295-311. doi: 10.1007/s11120-021-00847-x. Epub 2021 May 25.
In this work, we sought to understand how breeding has affected photosynthesis and to identify key photosynthetic indices that are important for increasing maize yield in the field. Our 2-year (2017-2018) field experiment used five high-yielding hybrid maize cultivars (generated in the 1970s, 2000s, and 2010s) and was conducted in the Xinjiang Autonomous Region of China. We investigated the effects of planting density on maize grain yield, photosynthetic parameters, respiration, and chlorophyll content, under three planting density regimens: 75,000, 105,000, and 135,000 plants ha. Our results showed that increasing planting density to the medium level (105,000 plants ha) significantly increased grain yield (Y) up to 20.32% compared to the low level (75,000 plants ha). However, further increasing planting density to 135,000 plants ha did not lead to an additional increase in yield, with some cultivars actually exhibiting an opposite trend. Interestingly, no significant changes in photosynthetic rate, dark respiration, stomatal density, and aperture were observed upon increasing planting density. Moreover, our experiments revealed a positive correlation between grain yield and the net photosynthetic rate (P) upon the hybrid release year. Compared to other cultivars, the higher grain yield obtained in DH618 resulted from a higher 1000-kernel weight (TKW), which can be explained by a longer photosynthetic duration, a higher chlorophyll content, and a lower ratio of chlorophyll a/b. Moreover, we found that a higher leaf area per plant and the leaf area index (HI) do not necessarily result in an improvement in maize yield. Taken together, we demonstrated that higher photosynthetic capacity, longer photosynthetic duration, suitable LAI, and higher chlorophyll content with lower chlorophyll a/b ratio are important factors for obtaining high-yielding maize cultivars and can be used for the improvement of maize crop yield.
在这项工作中，我们试图了解杂交种的选育对光合作用的影响，并确定提高田间玉米产量的关键光合作用指标。我们进行了为期两年（2017-2018 年）的田间试验，使用了五个高产杂交玉米品种（分别于 20 世纪 70 年代、2000 年代和 2010 年代选育），试验地点位于中国新疆维吾尔自治区。我们在三种种植密度（75000、105000 和 135000 株/公顷）下，研究了种植密度对玉米籽粒产量、光合作用参数、呼吸作用和叶绿素含量的影响。结果表明，与低密度（75000 株/公顷）相比，中密度（105000 株/公顷）种植显著提高了籽粒产量（Y），最高可达 20.32%。然而，进一步增加种植密度至 135000 株/公顷并没有导致产量的进一步增加，一些品种甚至出现了相反的趋势。有趣的是，随着种植密度的增加，光合速率、暗呼吸速率、气孔密度和孔径均没有明显变化。此外，我们的实验还揭示了杂种释放年份与籽粒产量和净光合速率（P）之间的正相关关系。与其他品种相比，DH618 获得更高的籽粒产量是由于更高的千粒重（TKW），这可以通过更长的光合时间、更高的叶绿素含量和更低的叶绿素 a/b 比来解释。此外，我们发现每株植物的叶面积和叶面积指数（HI）的增加并不一定会导致玉米产量的提高。综上所述，我们证明了更高的光合能力、更长的光合时间、合适的叶面积指数、更高的叶绿素含量和更低的叶绿素 a/b 比是获得高产玉米品种的重要因素，可以用于提高玉米作物的产量。
