Abstract: An analysis of the photosyntic physiological characteristics is conducted between two ecotypes of indigenous Leymus chinensis of the Songnen plain—-one ecotype of yellowish green colour,the other of greyish green colour.The result shows that under high concentration of CO ₂,the latter tops the former in light quantum utilization efficiency,thus boasting higher photosynthetic capacity than the former.Under dim light,the greyish-green L.chinensis exhibits higher photosynthetic rate than the other,though both register similar photosynthetic rate under intense light.The greyish-green ecotype needs intense light before its stomatal conductance starts to work,for it is blunter to light than the yellowish green type,whose stomatal conductance starts to work under dim light and increases its capacity with the intensifying of light.Under intense light when the CO₂ concentration reaches 700μmolmol^-1 ,its stomatal concluctance capacity exceeds that of the greyish-green type.The differences of stomatal conductance capacity and light quantum utilization efficiency between the two lead to their varient photosynthelic curves.It is the enzyme activity in the L.chinensis that induces the photosynthetic rate of the plant to decrease in high CO₂ concentration.

Key words: Leymus chinensis, Ecotype, Grey-green type, Yellow-green type, CO₂ doubling, Photosy-nthetic physiological response

摘要： 对松嫩草原黄绿型和灰绿型两个生态型羊草,进行光合生理特性测定。结果表明,在高CO₂浓度条件下灰绿型羊草的光量子利用率高于黄绿型,光合能力较强。在弱光条件下,前者光合速率高于后者,在强光下二者相差不大。随着CO₂浓度的升高,二者光补偿点和饱和点均升高。与灰绿型相比,黄绿型羊草呼吸较弱而光饱和点和水分利用率高,因此比前者更适应向阳、干旱的生境条件。二者气孔导度差异显著,灰绿型羊草的气孔导度起点较高,对光钝感,黄绿型起点较低,随着光照强度的增加,气孔导度随之增加,甚至在CO₂浓度等于700μmolmol^-1时的强光条件下高于前者。气孔导度和光量子利用率的差异是导致二者光合作用曲线不同的原因。酶系统活性是导致高CO2浓度时光合速率降低的主要因素。

关键词: 羊草, 生态型, 黄绿型, 灰绿型, CO2浓度倍增, 光合生理响应