Identifying maize architectural ideotypes through 3D structural model validated in the field: Assessing the impact of plant architecture and sowing pattern to improve canopy light regime

This study explores the influence of in-field maize plant architectural parameters (leaf inclination, curvature, orientation) and sowing patterns (plant density from 6 to 12 plts m − 2 , row spacing from 0.4 to 0.8 m) on canopy light conditions. A new three-dimensional (3D) maize architectural model -CORNIBU, integrated with a canopy light regime computation model- was able to describe phenotypic space with a relatively low number of input parameters. The reliability of CORNIBU to describe the actual variability of daily f I P A R (fraction of Intercepted PAR) depending on the sowing pattern and plant architecture was evaluated by generating digital canopies of five actual maize hybrids from a field experiment. The predicted daily f I P A R from CORNIBU digital canopies and the field-measured f I P A R from hemispherical photographs on actual maize canopies exhibited a significant and positive correlation ( R 2 ∼ 0.6), when calibrating the leaf phyllotaxy parameter from nadir gap fraction. Then, an in silico experiment conducted with CORNIBU permitted to identify the architectural ideotypes maximizing canopy light interception ( f I P A R ) and canopy light distribution ( f I L A , the fraction of Illuminated Leaf Area). This analysis highlighted a trade-off between f I P A R and f I L A , therefore any architectural ideotype cannot maximize both variables. Deeper light distribution would be achieved with more erectophile leaves and leaves orientation following an almost distichous phyllotaxy, whereas greater light interception would be achieved with more pronounced planophile leaves and random leaf orientation. The incorporation of photosynthetic light-responsive curves to estimate canopy daily photosynthesis provided additional insights to understand the trade-off between f I P A R and f I L A . Our findings indicate that the form of the hyperbolic function, i.e of the light-response curve, determines the optimal balance between f I P A R , f I L A and the resulting architectural ideotypes. Plant architectures with a higher light interception -planophile leaves- maximize daily canopy photosynthesis when the light-response function is more linear, whereas a more asymptotic curve determines that ideotypes where incident light is more uniformly distributed through the foliage depth -erectophile leaves- are those that optimize daily canopy photonsynthesis. Finally, our analysis highlights that squared sowing patterns (plant spacing within rows is close to row distance) benefit canopy-level photosynthesis by decreasing mutual shading between plants within the same row, as compared to traditional rectangular patterns where row distance is 4 to 8 times higher than plant spacing. • A new 3D maize model that can efficiently model canopy light regime. • The trade-off between light interception and distribution drives canopy photosynthesis. • The optimal plant architecture is linked to the linearity of the light-response curve. • Canopy photosynthesis is enhanced by squared sowing patterns.