低磷胁迫对黄花苜蓿生理特性的影响

我国绝大部分土壤缺乏有效磷,严重限制了作物产量的提高。黄花苜蓿耐寒、耐旱、耐贫瘠,但其对磷缺乏的响应和适应机制尚未见报道。以呼盟黄花苜蓿与锡盟黄花苜蓿为材料,研究了不同供磷水平对黄花苜蓿生长、根系形态、柠檬酸分泌和光合特性的影响,探讨了黄花苜蓿适应低磷胁迫的机制。结果表明,低磷(5 μmol/L H₂PO₄^-)胁迫显著降低了黄花苜蓿的生物量、根系表面积、总根长、根系体积、地上部磷含量、净光合速率、气孔导度与蒸腾速率,但增加了黄花苜蓿柠檬酸释放速率。常磷(500 μmol/L H₂PO₄^-)处理下,呼盟黄花苜蓿与锡盟黄花苜蓿的各项指标之间没有显著差异,但低磷处理下,锡盟黄花苜蓿干重、鲜重、株高、地上部磷含量、净光合速率、气孔导度与蒸腾速率等下降幅度明显较小,而主根长与柠檬酸释放速率的增加幅度明显较大,表明锡盟黄花苜蓿较呼盟黄花苜蓿更耐低磷。

Effect of phosphorus deficiency on physiological properties of Medicago falcata

The deficiency of available phosphorous(P) in most of the soils in China restricts increases of crop production.There have been many studies on the responses and adaptation to phosphorus deficiency of different plant species in the literature,but there is little information on the effect of phosphorus deficiency on physiological properties of pasture plants,especially native legumes of temperate grassland.In this study,the effect of phosphorus deficiency was studied on two ecotypes(Ximeng and Humeng) of Medicago falcata,which is an important legume in temperate grasslands of northern China and which has good tolerance to cold,drought and infertile soils.The two ecotypes differed in their responses to phosphorus deficiency.There were no significant differences in biomass,area,length and volume of root system,phosphorus content in shoots,or net photosynthetic rate between the two ecotypes under phosphorus-sufficient(500 μmol/L H2PO4-) conditions.However,there were greater reductions in biomass,area,length and volume of root system,shoot phosphorus content and net photosynthesis rate in Humeng than Ximeng ecotypes after low phosphorus treatment(5 μmol/L H2PO4-).Further,there was more exudation of citrate from Ximeng than Humeng ecotypes under phosphorus-deficient conditions.Taken together,the tolerance to phosphorus deficiency of Ximeng is greater than that of Humeng.