利用叶绿素荧光评估草原植物羊草缺磷缺氮状况

羊草(Leymus chinensis)是北方草原的重要牧草。准确评估其营养状况,对维护羊草草原的生产力具有重要意义。以羊草幼苗为材料,利用能同时表征2个光系统光化学活性的叶绿素荧光检测技术,对缺氮和缺磷处理下的叶片光化学活性进行分析。结果表明,缺氮处理20天后羊草叶片叶绿素含量降低近50%。同期缺磷及缺氮处理对PSⅡ功能的影响总体大于PSⅠ。与对照相比,缺氮叶片的Φ(Ⅱ)和Φ(Ⅰ)分别比对照降低了30.3%与38.5%;ETR(Ⅱ)与ETR(Ⅰ)分别降低30.8%和28.9%。缺磷处理组Φ(Ⅱ)和ETR(Ⅱ)的降低幅度约为缺氮的1/2。这些定量研究结果对及时有效地诊断和区分羊草植物氮磷缺乏状况具有重要的参考价值。

Assessment of Phosphate and Nitrogen Deficiency in Sheepgrass by Chlorophyll Fluorescence Spectroscopy

Sheepgrass (Leymus chinensis) is a forage plant species dominant in the north steppes. Accurate assessment of nutritional status of L. chinensis is essential to rational management of the grassland. For accurate assessment, we characterized and compared the photochemical activity of PSII and PSI in L. chinensis under Pi and N deprivation by using chlorophyll fluorescence spectroscopy. The effect of N deficiency on L. chinensis seedlings was greater than Pi deprivation. After 20 days of N-deprivation, chlorophyll content decreased nearly 50%. The activity of PSII was more affected than was PSI on the basis of in situ steady chlorophyll fluorescence measurements and light responsive curves. As compared with control plants, N-deprivated plants showed reduced Φ(II) and Φ(I) by 30.3% and 38.5%, and ETR(II) and ETR(I) were reduced 30.8% and 28.9%. Under Pi deprivation, the decreased values of Φ(II) and ETR(II) were about 1/2 those detected in N-deprivated plants. These quantitative results of chlorophyll fluorescence analysis provide new insights into photochemical characteristics of L. chinensis under N- and Pi-deficiency and also a valuable approach for efficient assessment of the nutritional status of L. chinensis plants.