Whole-Plant Trait Integration Underpins High Leaf Biomass Productivity in a Modern Mulberry (Morus alba L.) Cultivar

Understanding yield improvement in horticultural systems depends on elucidating how multiple plant traits operate in concert to sustain productivity. Mulberry (Morus alba L.) provides a suitable model for examining such whole-plant integration. Under cold-region field conditions, a modern high-yield cultivar (‘Nongsang 14’) was compared with a traditional cultivar (‘Lusang 1’). Measurements encompassed canopy architecture, biomass allocation between roots and shoots, leaf economic traits, and gas-exchange parameters, allowing trait coordination to be evaluated across structural and physiological dimensions. Multivariate profiling—Principal Component Analysis (PCA) and correlation networks—was used to characterise phenotypic integration. The modern cultivar’s superior productivity emerged as a coordinated “acquisitive” trait syndrome. This strategy couples a larger canopy (higher LAI) and nitrogen-rich foliage (higher LNC) with greater stomatal conductance (Gs), operating together with reduced root-to-shoot allocation. These features form a tightly connected network where structural investment and physiological upregulation are synchronised to maximise carbon gain. These findings provide a whole-plant framework for interpreting high productivity, offering guidance for breeding programmes that target trait integration rather than single-trait optimisation.