Abstract: Using an LI-6400 portable photosynthesis analyzer,we measured the net rate of photosynthesis,the photosynthesis availability radiation,the transpiration rate, and some other related eco-physiological factors of four Elytrigia varieties.The net photosynthetic rates and transpiration rates of all four Elytrigia showed two peaks on the curves of diurnal changes, and all witnessed obvious phenomena in midday depression of the two afore-mentioned rates.What leading to the phenomena exhibited in E.intermedia and E.repens was the decrease of photosynthetic capacity of the leaves, while that causing the midday depression of E.elongata and E.trichophora was the reduction of leaf stomatal conductance.Midday depression of transpiration was due to the high radiation, high leave temperature, low relative humidity, water scarcity in leaves, and the partial closure of stomata.E.elongata which boasts high light and low water use efficiency would enhance yield when it grows in areas with rich water resources, while E.repens is a preferable choice for water deficient areas.Appropriate thick planting of E.trichophora and E.intermedia could multiply yield.

Key words: Elytrigia Desv., Net rate of photosynthesis, Water use efficiency, Light use efficiency, Stomatal conductance

摘要： 用LI-6400型便携式光合测定仪观测4种偃麦草光合特性。结果表明:供试材料净光合、蒸腾作用日变化均为双峰型,有明显的光合“午休”现象,其中中间偃麦草(Elytrigia intermedia)和偃麦草(E.repes)的“午休”是叶肉细胞光合能力下降所改^[5-7],而长穗偃麦草(E.elongcata)和毛偃麦草(E.trihophora)则因气孔导度下降所致;蒸腾速率“午休”主要由于光辐射强、叶温高、湿度低、叶片缺水和气孔部分关闭所致;长穗偃麦草具有较高的光能利用率和较低水分利用率,因此在灌溉地区可以获得高产;在少水地区偃麦草则是理想的高产草种;通过合理密植毛偃麦草和中间偃麦草也有望获得高产。

关键词: 偃麦草属, 净光合速率, 水分利用效率, 光能利用效率, 气孔导度