Contrasting resource-use strategies under tropical stress: Linking leaf functional traits to fruit yield components in Camellia oleifera

Expanding economically important woody oil crops, such as Camellia oleifera , into tropical regions poses severe physiological challenges due to high irradiance and temperature. Understanding how plants balance stress tolerance and reproductive output under these conditions is critical for optimizing cultivar selection. In this study, we evaluated four elite C. oleifera cultivars in a tropical plantation (Hainan, China) to determine how leaf anatomical and physiological traits coordinate to drive yield components. A striking physiological hallmark across all cultivars was a severe depression in maximum photochemical efficiency ( Fv/Fm : 0.28–0.47), indicating chronic photoinhibition induced by tropical abiotic stress. Under this severe environmental pressure, we identified a distinct functional trade-off among the cultivars. The high-yielding cultivar HY3 exhibited an “acquisitive” trait profile, characterized by superior net photosynthetic rate, enhanced stomatal conductance, and a larger main vein cross-sectional area, prioritizing carbon assimilation for reproductive allocation. Conversely, cultivar HY4 displayed a “conservative” strategy, investing heavily in defensive structures such as a thickened upper cuticle and high non-photochemical quenching (NPQ), which favored survival and photoprotection over maximum carbon assimilation. Furthermore, partial least squares structural equation modeling (PLS-SEM) revealed cultivar-specific mechanistic pathways of resource coordination. In HY3, specific leaf anatomy was strongly coupled with yield components through the enhancement of photosynthetic gas exchange. In contrast, the conservative anatomical structure of HY4 constrained direct carbon allocation to yield, redirecting resources towards light-use efficiency and physical defense. These findings demonstrate that leaf anatomical traits are not merely structural descriptors, but functional mediators reflecting how plants balance survival and reproduction. This trait-based framework offers valuable insights into the ecological adaptation of woody crops under tropical stress, providing a theoretical basis for context-specific cultivar selection and precision management.