Physiological dominance of the scion in shaping root architecture under suboptimal temperature

Background Non-optimal temperatures have become a major constraint on plant development under rapidly changing climatic conditions. Both sub- and supra-optimal temperatures reduce physiological activity, alter plant morphology, lead to plant mortality, and ultimately decrease crop productivity. Temperature-tolerant plants employ physiological and morphological mechanisms to mitigate such stress. In this study, we aimed to identify the source of temperature tolerance in warm-climate adapted melon ( Cucumis melo L.). Results Suboptimal temperature–tolerant accession (Ananas Yoqne’am; AY) and susceptible accession ( PI414723 ) were reciprocally grafted and grown under controlled temperature regimes of 16 °C, 25 °C, and 35 °C. Physiological and morphological traits were measured to characterize tolerance mechanisms and whole-plant responses. Temperature emerged as the dominant factor governing plant performance. Whereas non-grafted parental lines maintained consistent differences across all temperature regimes, reciprocal graft combinations diverged mainly under suboptimal (16 °C) conditions. Under these temperatures, scion identity strongly determined whole-plant performance through biochemical limitations. Conclusion These results highlight the importance of scion-derived traits in abiotic stress tolerance and their downstream influence on root function.