A study on the response of planting density to 3D plant shape plasticity and population light transmittance of maize

Traditional two-dimensional (2D) analyses of maize (Zea mays L.) plant shape plasticity and canopy transmission under varying planting densities have limitations in capturing spatial heterogeneity. This study used a three-dimensional (3D) phenotyping platform to investigate architectural plasticity across different maize varieties and planting densities. Seven novel 3D architectural parameters were developed, and 3D canopy models were constructed for light distribution simulation. At the vegetative stage 9 (V9) stage, medium planting density (67,500 plants ha^–1, MD) increased plant side width and convex hull volume by 7.2 and 11.4%, respectively, compared to low planting density (37,500 plants ha^–1, LD). High planting density (97,500 plants ha^–1, HD) increased the width and volume by 4.2 and 17.8%, respectively, compared with MD. Similar changes were maintained at the V13 stage. At the silking stage, the number of voxel volume plant (NVP) and projected area (PJA) decreased by 6.2 and 11.9%, respectively, under MD compared with LD, and by 4.9 and 3.6%, respectively, under HD compared with MD. Across all densities, PJA and NVP in both MC812 and JNK728 were consistently lower than in ZD958. A bottom light transmittance estimation model combining point cloud parameters with support vector regression achieved reliable predictions (R²=0.76, RMSE=2.89%). The 3D canopy model effectively simulated population light distribution (R²=0.83, RMSE=8.53%). NVP and PJA were identified as critical parameters affecting bottom canopy transmittance, suggesting their potential as 3D selection indices for maize density tolerance breeding. These findings provide insights into stage-specific architectural plasticity and light interception, supporting molecular design breeding of density-tolerant maize.