随着气候变暖, 高寒草原分布面积逐步增加, 高寒草原植物如何适应高寒干旱环境的研究还比较缺乏。该研究通过分析高寒草原优势种紫花针茅(Stipa purpurea)不同地理种群叶片解剖结构特征差异及其与气候因子的相关性, 阐明紫花针茅叶片适应高寒环境的策略, 为理解高寒植物对高寒干旱胁迫环境的适应机制提供科学依据。在青藏高原不同地理位置选择8个紫花针茅种群, 选择成熟健康叶片用卡诺氏固定液固定, 将固定好的叶片带回实验室进行石蜡切片和染色, 用显微镜观察叶片结构, 并用数码相机拍摄, 然后用软件Image-pro plus 6对叶片结构进行测量。结果显示: 紫花针茅叶片普遍具有较厚的角质层, 可减少水分散失和抵御较强的辐射; 不同地理种群紫花针茅叶片解剖结构在厚壁细胞厚度、叶片厚度、导管直径、主脉导管腔面积/主脉维管束面积和维管束面积/叶横切面积等特征上存在较大差异, 以适应不同区域的生境。Pearson相关性和聚类分析结果表明紫花针茅叶片解剖结构与气候因子密切相关; 主成分和冗余分析结果表明在干旱区域紫花针茅叶片解剖结构主要受到蒸发量的影响, 而在相对湿润区域紫花针茅叶片解剖结构主要受生长季降水量、湿润系数和年降水量/年蒸发量影响。综上所述, 紫花针茅通过增加厚壁细胞减少水分散失, 同时增加导管直径、主脉导管面积/主脉维管束面积和维管束面积/叶横切面积等输水组织面积适应高寒干旱气候。

Aims The anatomical structure of plant leaves could be a direct reflection of the plant’s mechanism of response and adaptation to climate change. The distribution of alpine steppe has increased due to climatic warming over the Qingzang Plateau.Stipa purpurea is the dominant species of alpine steppe. However, few studies have been conducted on the adaptation mechanisms of alpine steppe plants. In this study, we analyzed the characteristics of leaf anatomical structure among different populations of S. purpurea and the relationship between these characteristics and climatic factors over the Qingzang Plateau. The ultimate aim was to identify the mechanism by which S. purpurea acclimatizes to alpine environments.
Methods Leaves of S. purpurea were collected from eight sites on the Qingzang Plateau and fixed using FAA fixative solution. Then, the leaves were paraffin wax sectioned and double-stained. Samples were then observed with a microscope and photographed with a digital camera. The area and thickness of leaf anatomical structure were measured with the soft (Image-pro plus 6.0).
Important findings Leaves of S. purpurea generally had thick cuticles, which were able to reduce water loss and radiation exposure. From the results of one-way analysis of variance, there were significant differences among the eight populations in collenchymatous cell thickness, vessel diameter, bundle catheter cavity area/bundle of the main vascular area, and vascular area/leaf cross-sectional area, which were beneficial characteristics for S. purpurea in adapting to the local environment. The characteristics of leaf anatomical structure were significantly correlated with environmental factors via Pearson’s analysis and cluster analysis. The results from principal component analysis and redundancy analysis showed that the anatomical structures in arid regions were mainly affected by annual evaporation, and those in semi-humid regions were mainly affected by the average precipitation humidity index and annual precipitation/annual evaporation during the growing season. In conclusion, to adapt to the alpine and arid environment,S. purpurea has reduced water loss by simultaneously increasing its collenchymatous cell thickness and water-conducting tissue area (vessel diameter, bundle catheter cavity area/bundle of main vascular area, and vascular bundle area/leaf cross-sectional area).