Scaling law links plant growth variation to grain yield in wheat stands.

Growth rate, a fundamental trait associated with plant resource use, scales with plant mass, following consistent allometric power laws shaped by biophysical constraints and natural selection captured in metabolic scaling theory (MST). Although well-established in wild plants, MST has been overlooked in crop improvement. We quantified the relationship between individual plant mass and growth rate in 195 European winter wheat cultivars under glasshouse conditions and examined how variation in growth allometry relates to stand-level grain yield across eight field environments and to its underlying genetic, developmental, and physiological mechanisms. Variation in allometry was linked to plant size, in which increased leaf allocation and faster development elevated allometric exponents. Phenotypic and genetic analyses revealed adaptive strategies, ranging from large, slow-developing genotypes that support reproductive initiation to small, fast-developing genotypes that enhance floret survival and reproductive effort. A shared genetic basis associated with Photoperiod-1 linked growth allometry in the glasshouse to genotype-by-environment interactions for grain yield in the field. Our findings demonstrate that growth allometry is biologically robust and agronomically relevant. While phenology is associated with adaptive variation in allometry, the allometric framework integrates developmental and physiological processes that jointly shape cultivar performance across environments, providing a basis for environment-specific crop improvement.