Corn is the largest food crop on the mainland, accounting for about 35% of the total grain planting area, and plays an important role in ensuring national food security. Due to the limited area of available arable land, increasing planting density is a key cultivation measure to increase maize yield. Photosynthesis is the material basis for the formation of crop yield, but high-density planting usually leads to population canopy, insufficient photosynthetic production capacity and decreased seed setting rate, which limits the improvement of crop yield. Therefore, it is very important to study the response mode of photosynthetic capacity in maize canopy and its regulation mechanism on yield under high-density planting conditions to achieve density and yield increase. The team's previous research on multi-site field experiments showed that high leaf chlorophyll content, high photosynthesis rate, long photosynthetic duration and low chlorophyll a/b ratio were important physiological factors determining the high yield and high light efficiency of maize varieties under dense planting conditions (Photosynthesis Research, 2021, 150: 295-311). In addition, the dry matter accumulation and nitrogen distribution to grain in the population at the grain filling stage could be increased by optimizing nitrogen application measures, so as to compensate for the limitation of individual growth of maize by dense planting, and achieve a synergistic improvement of population yield and nitrogen efficiency (Field Crops Research, 2023, 294: 108874).
近日，中国农业科学院作物科学研究所周文彬研究员团队在Plant Physiology发表了题为“Photosynthetic capacity and assimilate transport of the lower canopy influence maize yield under high planting density”的研究论文。 该研究揭示了密植条件下调控玉米产量的光合生理机制，并提出了玉米耐密高产的理想株型。
In this study, the canopy was divided into four layers with the ear position of corn as the boundary, and the changes of yield and photosynthetically related traits of the whole canopy of three maize varieties under different planting densities were analyzed through a two-year field experiment system, so as to elucidate the physiological response of the canopy after densification and its role in regulating the formation of yield. The results showed that increasing planting density reduced the light transmittance of maize canopy, and reduced the chlorophyll content and net photosynthetic rate of leaves under the panicle, resulting in a significant decrease in the biomass accumulation per plant in the subcanopy. At the same time, increasing the planting density reduced the metabolic activity of female panicles, thereby limiting the development of female panicles, resulting in the decrease of panicle length and grain number per panicle. Therefore, densification caused yield loss through the effect on the development of leaves and female panicles under the panicle. In addition, it was found that yield traits were significantly positively correlated with the photosynthetic capacity and biomass accumulation of leaves under the canopy, indicating that the photosynthetic and material accumulation capacity of leaves under panicles under dense planting conditions played a key role in increasing maize yield.
The analysis of the morphological characteristics of maize canopy under different densities showed that the length and width of leaves on ears of dense-tolerant and high-yield maize varieties decreased after densification, while the length of leaves under ears increased, the leaf width decreased slightly, and the leaf area under ears did not change significantly. This plant structure can improve the light transmittance, so that more light can penetrate into the lower canopy, which is conducive to the photosynthesis of the lower canopy, so as to maintain the material accumulation capacity, and increase the dry matter accumulation of the group, so as to achieve high yield. Based on the above results, this study further proposed the ideal plant type with high yield and high light efficiency of maize.
In conclusion, maintaining high photosynthetic carbon assimilation and assimilate transport capacity of lower canopy leaves and promoting female ear development under dense planting conditions were the key strategies to improve maize yield. This study provides new ideas and insights for optimizing dense planting and high-yield cultivation practices and cultivating dense-tolerant crop varieties, and provides an important theoretical basis for further improving the yield potential of field crops.
Yan Yanyan, a doctoral student jointly trained by the Institute of Crop Science of the Chinese Academy of Agricultural Sciences and Nanjing Agricultural University, is the first author of the article, and Zhou Wenbin, a researcher from the Institute of Crop Science, Chinese Academy of Agricultural Sciences, is the corresponding author of the paper. In addition, Professor Dai Tingbo from the College of Agronomy of Nanjing Agricultural University and researcher Wang Yonghong from the Institute of Crop Research of Ningxia Academy of Agriculture and Forestry Sciences participated in the research work. The research was supported by the National Key R&D Program of China and other projects.
Paper link: https://doi.org/10.1093/plphys/kiae204
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