National Science and Technology Basic Survey Project(2019FY101300) ；The National Natural Science Foundation of China (31872683,31988102,31961143022)
气孔是植物与大气进行水气交换的阀门,调节着植物的蒸腾与光合作用。 因此,气孔性状的变异影响着植物功能,并能够反映植物对环境的适应。目前,内蒙古高原草地植物气孔性状的空间变异及其对环境的响应尚未被探究。于2018年在内蒙古高原草原区沿降水梯度设置了10个受人为干扰较少的天然草地样地,采集每个样地及周围的植物,并对每个物种叶片上、下表皮的气孔性状进行了测量和计算。结果表明:(1)气孔密度(SD)、气孔大小(SS)和气孔相对面积(SRA)的均值分别为262.29个/mm2、378.84 μm2和8.10%;下表皮与上表皮的气孔密度比(R.SD)、大小比(R.SS)和相对面积比(R.SRA)的均值分别为1.54、1.04和1.61。(2)由于草地生境开阔,气孔形态性状在不同生活型(草本与木本植物、一二年生与多年生草本)间没有显著差异(P>0.05)。(3)从草甸草原到荒漠草原,叶片SD和SRA减小,SS增大,气孔性状变异的主要驱动因素是年降水。(4)气孔综合指标SRA主要受SD驱动,降低叶片SD是内蒙古高原草地植物提高耐旱性的重要机制之一。(5)植物还可以通过降低气孔比来适应干旱胁迫,下表皮气孔是内蒙古高原植物气孔比降低的主要贡献者。研究结果有助于进一步了解草地植物叶片气孔独特的气候适应机制,还可为生态预测模型提供基础数据。
Stomata are the valves for water and CO2 exchange between plants and the surrounding environment, regulating plant transpiration as well as photosynthesis to some extent. Therefore, the spatial variation of stomatal traits affects plant functions and reflects the adaptation of plants to their environments. The stomatal traits have attracted scientists' attention for a long time. However, spatial variation in the stomatal traits of grassland plants on the Inner Mongolia Plateau and their responses to the environment has not yet been explored. In this study, we set up 10 study sites, with low levels of human disturbance, along the precipitation gradient on the Inner Mongolian Plateau. In 2018, we collected nearly all the plant species that were present within a 1 km×1 km area of each site. The stomatal density (SD), stomatal size (SS), and the stomatal relative area (SRA) of the adaxial and abaxial epidermis of each species were measured. Meanwhile, the ratio of stomatal traits between the abaxial and adaxial epidermis was calculated. Results showed that the mean SD, SS, and the SRA were 262.29 stomata/mm2, 378.84 μm2, and 8.10%, respectively. The mean stomatal density ratio (R.SD), the stomatal size ratio (R.SS), and the stomatal relative area ratio (R.SRA) were 1.54, 1.04, and 1.61, respectively. Due to the open grassland habitat, there were no significant differences in leaf stomatal morphological traits among the different life forms, namely herbs vs woody plants and annual or biennial herbs vs perennial herbs (P>0.05). With the increase in the degree of drought, the leaf SD and SRA decreased, and the SS increased. The mean annual precipitation was the main driving factor of stomatal variation, and the mean annual temperature and photosynthetically active radiation had no significant effect on stomatal traits. The SRA was mainly driven by the SD, and it was one of the most important mechanisms of reducing leaf SD to improve the drought tolerance of grassland plants on the Inner Mongolian Plateau. Plants can also adapt to drought by reducing the stomatal ratio. The stomata in the abaxial epidermic were the main contributor to the decrease in the stomatal ratio on the Inner Mongolian Plateau. These new findings help us further understand the unique climate adaptation mechanisms of plant stomata in natural grassland communities and provide these ecological process models as baseline data.