Data from: Cold adaptation drives variability in needle structure and anatomy in Pinus sylvestris L. along a 1,900 km temperate–boreal transect

1. Occupancy of cold habitats by evergreen species requires structural modification of photosynthetic organs for stress resistance and longevity. Such modifications have been described at inter-specific level while intra-specific variation has been underexplored.
2. To identify structural and anatomical traits that may be adaptive in cold environments, we studied intra-specific variability of needles of Scots pine (Pinus sylvestris L.), a wide-ranging tree, along a 1900 km temperate-boreal transect in Europe.
3. Needles from 20 sites representing mean minimum winter temperatures between -4.0°C and -19.9°C and mean annual temperatures between 8.3°C and -1.7°C were sampled for measurements of leaf mass per area (LMA, g m-2), leaf density (LD, g cm-3) and 30 other morpho-anatomical traits.
4. Needles from cold sites lived longer, were shorter, showed higher LMA and LD, had narrower and more collapse-resistant tracheids, thicker epidermal cells with thicker cell walls, and wider resin ducts occupying larger fraction of needle volume in comparison to needles from warmer sites.
5. Along the steep climatic gradient, needles presented a coordinated phenotypic spectrum of external and internal traits that are largely interpretable in functional, adaptive terms. This intra-specific pattern of co-varying traits provides insight into the adaptive syndrome associated with stress tolerance and extended needle longevity under cold conditions of high latitudes.

1. 常绿物种在寒冷生境中定植，需对光合器官进行结构改造以实现抗逆性与寿命延长。此类改造已在种间水平得到广泛阐释，但种内变异的相关研究仍有待深入挖掘。
2. 为识别寒冷环境下具备适应性潜力的结构与解剖学性状，我们针对分布范围广泛的树种——欧洲赤松（Pinus sylvestris L.），沿欧洲境内1900公里的温带-寒温带样带，对其针叶的种内变异展开了系统研究。
3. 我们从20个样点采集针叶样本，这些样点的冬季平均最低气温介于-4.0℃至-19.9℃之间，年平均气温介于8.3℃至-1.7℃之间；随后对叶面积干重（LMA, leaf mass per area, g·m⁻²）、叶片密度（LD, leaf density, g·cm⁻³）以及其余30项形态解剖学性状开展了测定。
4. 相较于温暖生境的针叶，寒冷生境的针叶寿命更长、长度更短，表现出更高的LMA与LD水平，管胞更窄且抗塌陷能力更强，表皮细胞更厚且细胞壁更厚，同时拥有更宽的树脂道，且树脂道占针叶体积的比例更高。
5. 沿着这一陡峭的气候梯度，针叶呈现出一套协调统一的外部与内部性状表型谱，该谱在功能与适应性层面均可得到合理解释。这种共变性状的种内格局，为理解高纬度寒冷环境下与抗逆性及针叶寿命延长相关的适应综合征提供了关键认知。