干旱胁迫对新疆三个优势牧草种的光合特性与水分利用效率的影响

通过盆栽试验,研究了不同土壤含水量条件下(田间持水量的80%、60%和30%)新疆地区天然草地3个优势牧草种(无芒雀麦、草地早熟禾和鸭茅)叶片的光合生理特性及叶片和单株水分利用效率,以探讨不同优势牧草种对干旱胁迫的适应机制。结果表明:随干旱胁迫加剧,3个牧草种的C_i日平均值呈上升趋势,G_s、P_n、T_r 、P_n/C_i日平均值和日平均耗水量呈下降趋势,但物种间各参数变幅存在差异;草地早熟禾日平均生物产量呈明显下降趋势(P<0.05),鸭茅和无芒雀麦无明显变化(P>0.05);鸭茅的WUE_i日平均值和WUE_ET无显著变化(P>0.05),无芒雀麦和草地早熟禾呈明显下降趋势(P<0.05)。3个牧草种的WUE_ET均与其日平均累积生物量显著正相关(P<0.05),草地早熟禾的WUE_ET与其T_r日平均值和日平均耗水量亦显著正相关(P<0.05)。3个牧草种的叶片和单株水分利用效率随土壤含水量下降具有不同的变化趋势,预示着3个物种对干旱生境的适应不仅取决于其水分利用效率的大小,还可能与其生物学特性和生活史策略有关。

Effect of drought stress on the photosynthetic characteristics and water use efficiency of three dominant forage grasses in Sinkiang

This paper explores the adaptive mechanisms of three forage grasses (Bromus inermis ,Dactylis glomerata and Poa pratensis )that are predominant in Sinkiang natural grasslands.Using pot experiment methods,drought stress was simulated to determine the effects of three different soil water contents levels (80%,60% and 30% of field water capacity)on leaf photo-physiological characteristics and water use efficien-cy (WUE).With decreasing soil water contents,the daily average value of intercellular CO2 (C i )in the three grasses increased.The daily average values of stomatal conductance (G s ),net photosynthetic rate (P n ),tran-spiration rate (T r ),the ratio of P n to C i and evapotranspiration decreased,but the variation ranges of these characteristics differed across the three grasses.As drought stress increased,the daily average accumulated bi-omass of P .pratensis significantly decreased (P <0.05),but there was no obvious change in the other two grasses (P >0.05).The net water use efficiency (WUEET )and the daily average value of instantaneous water use efficiency (WUEi )of D .glomerata changed very little (P >0.05 ),but in the other two grasses both WUEET and WUEi significantly decreased (P <0.05).The WUEET of P .pratensis was significantly positively correlated with its daily average values for T r and evapotranspiration (P <0.05).The WUEET of the three for-age grasses was significantly positively correlated with their daily average accumulated biomass (P <0.05 ). The WUEi and WUEET of the three grasses followed different change trends with the decrease in soil water con-tents.This study suggests that the adaptability of the three forage grasses to arid environments depends not only on their WUE but is also related to their biological characteristics and life history strategies.