Abstract: This study describes seasonal changes of photosynthetic characteristics during the strong growth period (July, August and September) of dominant plants in alpine grassland. Seven dominant plants(Kobresia humilis, Elymus nutans, Leymus secalinus, Melissitus rutenica, Oxytropis ochrocephala, Potentilla bifurca, Gentiana straminea)were selected from the alpine grassland experiment station of Gansu agricultural university located at eastern Qilian Mountains, Zhuaxixiulong. Species were selected to observe their photosynthetic-light response curves using a non-rectangular hyperbolic model with the GFS-3000 portable photosynthesis analyzer. Results showed that photosynthetic capacities of these plants decreased during an August drought. The adaptability of all tested plants to bright light and their ability to use low light were reduced. The photosynthetic capacity and adaptability to bright light in early growth stages of Elymus nutans, Leymus secalinus, Kobresia humilis and Potentilla bifurca were higher than that in late growth stages.However, the photosynthetic capacity and adaptability to bright light in late growth stages of Oxytropis ochrocephala, Melissitus rutenica and Gentiana straminea were higher than that in early growth stages. Elymus nutans, Oxytropis ochrocephala, Gentiana straminea and Potentilla bifurca were very sensitive to drought and susceptible to drought stress. In contrast, Leymus secalinus, Melissitus rutenica and Kobresia humilis were not as sensitive to drought.

Key words: Alpine grassland, Dominant plants, Photosynthesis-light response curves, Seasonal changes

摘要： 为研究高寒地区草地优势植物旺盛生长期光合特征,选取位于祁连山东段天祝藏族自治县抓喜秀龙乡的甘肃农业大学高山草原试验站围栏禁牧草地的矮嵩草(Kobresia humilis)、垂穗披碱草(Elymus nutans)、赖草(Leymus secalinus)、扁蓿豆(Melissitus rutenica)、黄花棘豆(Oxytropis ochrocephala)、二裂委陵菜(Potentilla bifurca)和麻花艽(Gentiana straminea)7种优势植物,利用GFS-3000便携式光合测定仪拟合了7-9月的光合-光响应曲线。结果显示:由于8月份的干旱,草地植物的光合能力受到严重影响,对弱光的利用能力和对强光的适应能力都降低。垂穗披碱草、赖草、矮嵩草和二裂委陵菜在7月份的光合能力,对强光的适应能力都高于9月份,而黄花棘豆、扁蓿豆和麻花艽则相反。垂穗披碱草、黄花棘豆、麻花艽和二裂委陵菜4种植物对干旱很敏感,容易受到干旱胁迫;而赖草、扁蓿豆和矮嵩草3种植物对干旱胁迫不敏感。

关键词: 东祁连山, 优势植物, 旺盛生长期, 光响应曲线