Elevational adaptation of morphological and anatomical traits by Sakhalin fir (Abies sachalinensis)

摘要

Key message In Sakhalin fir trees from nine different source elevation provenances, we found genetic differentiation of traits related to mechanical reinforcement, hydraulic efficiency, and photosynthetic capacity. Climatic conditions change with elevation and trees must cope with the resulting variation in stresses. Thus, trees may differentiate into elevational ecotypes with genetic-based variations in morphological and physiological traits. To explore genetically differentiated traits related to elevational adaptation, needles and stems were analyzed in 43-year-old Sakhalin fir [Abies sachalinensis (Fr. Schm.) Masters] trees which derived from nine source elevations (230-1250 m above sea level) and grown in a nursery plantation at 230 m above sea level. Trees from a high-elevation provenance showed greater mechanical reinforcement in needles and stems. Needles from high-elevation provenances were shorter and thicker, and developed more sclerenchyma in transfusion tissue. Shorter and thicker stems and larger reaction wood portions were also found. Moreover, needles and stems from high-elevation provenance trees also exhibited xylem traits associated with higher hydraulic efficiency and lower hydraulic safety. In the midrib xylem, the theoretical conductivity was greater due to higher number of tracheids. Pit architecture of stem-xylem tracheid indicated a higher hydraulic efficiency, but lower hydraulic safety due to larger pit apertures. Furthermore, high-elevation provenance trees exhibited a thicker bark, which may reduce water losses and act as a water reservoir in winter. Leaf nitrogen content and stomata number per needle were higher in high-elevation provenance trees, both of which were related to high photosynthetic capacity. Overall, the data suggested genetic differentiation of traits related to various trade-offs and optimization for mechanical resistance, hydraulic efficiency, and photosynthetic capacity at high elevation in Sakhalin fir.