Thermal Time normalization.
Thermal time normalization makes it possible compare plant growth in terms off both organogenesis (organ numbering) and development (organ size) aspects.

Light interception: PAR, LAI and Beer-Lambert Law
Only part of light energy is used in plant crops. A limited fraction of the light spectrum is absorbed by leaves; this part is constrained by the upper leaf area and decreases in the canopy.

Photosynthesis. Light Use Efficiency.
The photosynthesis process converts absorbed light energy into biomass with a ratio proportional to the Light Use Efficiency.

Density effect
At individual plant level, density limits light absorption capabilities, and thus dynamically limits biomass production.

Biomass common pool
Assumption. Biomass produced by the source organs (leaves) builds a common storage pool, to be shared among all competing growing organs.

Organ competition. Sinks
Growing organs compete for biomass allocation. They are sinks.

Process-based models.
Process-based models or crop models are designed to model and simulate biomass production.