Variation of leaf traits with altitude in Lonicera caerulea var. Edulis (Caparifoliaceae) from northeastern China

摘要

Leaf structure, orientation and other properties along elevation gradients in seven populations of Lonicera caerulea var. edulis in the Changbai Mountains of China were studied to evaluate the relationship between the properties of adaptability to alpine environment. Leaf architecture was isolateral at low altitude, but dorsiventral at high altitudes, whereas the leaf orientation in space changed from upright to horizontal. Raised stomata were present in Lonicera caerulea var. edulis and their density increased with increasing elevation. Leaf thickness initially increased with altitude, but then decreased. Between 600 m and 1400 m, palisade parenchyma thickness increased but then decreased above 1600 m, reaching a minimum at 1800 m, a pattern also reflected by spongy parenchyma. The palisade parenchyma thickness/spongy parenchyma thickness ratio increased with increasing altitude. By contrast, the thickness of the upper epidermis decreased with increasing altitude, whereas there was no change in the lower epidermis. There were significant differences in the ecological indicators of L. caerulea var. edulis at seven altitudes. Leaf area (LA) and leaf biomass (LB) were highest at 1800 m, whereas the specific leaf area (SLA) was the highest at 1600 m. The leaf saturated weight (SW), LB and the specific leaf weight (LMA) were lowest at 1200 m. At 600 m, LA, SLA and SW/LB were the lowest, whereas LMA was highest at 800 m. The leaf saturated water content (SWC) and SW/LB were also highest at 600 m. Therefore, there was a significant correlation between leaf and environmental factors at different altitudes, indicating that Lonicera caerulea var. edulis modifies its structure and morphology to adapt to alpine environments with a thin atmosphere, lower oxygen levels, low temperatures, heavy rainfall and strong solar radiation.