Energy Survival as a Fundamental Constraint on Plant Biomass Formation

Plant biomass formation is the emergent outcome of a multistage physical–biological energy pathway in which radiant energy, atmospheric carbon dioxide, water, and mineral nutrients are absorbed, transported, transformed, and ultimately stored as chemical energy in organic matter. Although the biochemical mechanisms of photosynthesis have been characterized in great molecular detail, most existing plant growth and productivity models treat energy absorption, internal transport losses, photosynthetic conversion efficiency, and biomass accumulation as partially decoupled processes. This fragmentation obscures the physical constraints governing real-world plant productivity and limits the interpretability of observed discrepancies between theoretical photosynthetic efficiencies and ecosystem-scale biomass yields.

Here we present a unified plant energy–biomass framework that explicitly integrates absorption dynamics, thermodynamic energy survival, and photosynthetic conversion capacity within a single physically consistent formulation. Central to the framework is a dimensionless energy survival factor,

Ψ=AE/TE+ε

where AE denotes absorbed energy retained within the biological system boundary, TE represents transport and environmental dissipation losses (including optical reflection, thermal degradation, diffusive leakage, and metabolic overhead), and εε captures irreducible entropy-generating losses required by the second law of thermodynamics. Unlike classical efficiency ratios, ΨΨ quantifies the probability that absorbed energy survives successive loss pathways long enough to remain available for biochemical conversion.

When coupled with an internal photosynthetic conversion competency term Cint, representing enzymatic, transport, and structural throughput constraints, the framework yields a general and thermodynamically consistent expression for useful biological energy and biomass formation:

Euseful=Ein⋅Ψ⋅Cint

Using empirically established ranges for absorbed photosynthetically active radiation (APAR ≈ 45–70% of incident PAR), excitation transport survival (≈85–95%), biochemical fixation efficiency (≈4–7% under field conditions), and post-fixation respiratory survival (≈40–70%), the framework naturally predicts net ecosystem-scale biomass conversion efficiencies of approximately 1–3% of incident solar energy. These values are consistent with global measurements of net primary productivity across terrestrial ecosystems and arise without invoking biological inefficiency or suboptimal design.

The analysis demonstrates that plant productivity is fundamentally survival-limited rather than efficiency-limited: increasing incident energy alone does not proportionally increase biomass unless transport losses, entropy production, and internal conversion bottlenecks are simultaneously reduced. By explicitly separating energy survival from conversion capacity, the unified formulation reconciles molecular-scale photosynthetic performance with whole-plant and ecosystem-scale productivity constraints.

This framework provides a physically grounded bridge between absorption physics, photosynthetic energetics, and biomass accumulation, offering a scalable and falsifiable foundation for crop productivity modeling, ecosystem energy-balance analysis, and comparative bioenergetics across biological and engineered systems.

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