柳枝稷和白羊草苗期水分利用与根冠比的比较

Comparison of water use efficiency and root/shoot ratio in seedling stage of switchgrass(Panicum virgatum) and old world bluestems (Bothriochloa ischaemum)under different soil water conditions

室内生长箱内柳枝稷和白羊草苗期水分利用与根冠比的试验结果表明,低水下柳枝稷光合速率降低,蒸腾速率增大,叶片水分利用效率减小,根长增加,整体水分利用率降低,但生产力的根冠分配与高水相差较小。低水也造成白羊草光合降低,但蒸腾速率减小幅度更大,叶片水分利用效率反而提高,主要原因是白羊草叶片气孔具有较强的随水分条件变化的调节作用。白羊草的根系在低水下伸长速率减慢,根长/株高降低,水分条件好时根系也能够迅速生长,特别是加强根系的生产力分配。不同水分下白羊草消耗单位水分形成的生产力均大于柳枝稷,说明白羊草在苗期对土壤水分变化的适应能力比柳枝稷要强。

The results from comparing water use efficiency (WUE) and root/shoot ratio in seedling stage of switchgrass (Panicum virgatum) and old world grass (Bothriochloa ischaemum) planted in growth chamber showed that when soil water decreased, switchgrass's photosynthesis rate decreased, transpiration rate increased, WUEL decreased, root length increased and WUEy decreased, but the root biomass/shoot biomass changed a little. Old world grass's photosynthesis and transpiration rate decreased and WUEL increased under low soil water. Old world grass's root length grew slowly under low soil water, but aboveground height/root length ratio increased; when the water content was high, its root length grew quickly, especially the root biomass/shoot biomass ratio increased. The WUEy of old world grass was bigger than switchgrass under different soil water. According to the results obtained, it is considered that old world grass has better adaptability to soil water change than swichgrass at the seedling stage.