紫花苜蓿苗期根系生长的水分胁迫损伤及氮磷的修复生长作用

土壤水分胁迫对牧草根系生长有重要影响。为明确土壤水分胁迫对紫花苜蓿根系生长的损伤以及胁迫解除后根系修复生长过程中土壤养分的作用和利用率,以赛迪-7(Sadie-7)和标杆(Icon)两个品种进行盆栽试验,分析了土壤渍水和低水分条件下生长的紫花苜蓿小苗的根系形态;并在解除土壤水分胁迫后施氮(尿素:0.336 g/盆)或磷(过磷酸钙:1.51 g/盆),分析了氮、磷对根系生长的影响。结果表明,土壤渍水显著抑制紫花苜蓿小苗主根的伸长生长,主根直径、根表面积以及根体积均小于对照;土壤低水分处理促进主根伸长生长,但显著抑制侧根生长。胁迫解除后,前期渍水处理的植株主根生长加快,但侧根生长则比前低水分处理的植株和对照缓慢;施氮、磷肥可显著促进根系的生长。土壤水分胁迫造成的根系生长伤害及胁迫去除后侧根生长缓慢导致氮、磷吸收利用率显著降低。试验结果说明,保持适宜的土壤水分或在土壤水分胁迫后适当施用氮、磷肥,将是促进紫花苜蓿根系生长,提高饲草产量的重要栽培措施。

Effect of water stress on root growth of alfalfa seedling sand on nitrogen- and phosphorus-use efficiencies after waters tress

A pot experiment was conducted to assess the effects of soil moisture on the root growth of alfalfa (Medicagosativa)and its nutrient-use efficiency after water stress.Two alfalfa cultivars (Sadie 7 and Icon) were grown under low- (deficiency),appropriate- (CK),or high- (water logging)soil moisture treatments for 20 days before restoring soil moisture to the CK level.The nitrogen- and phosphorus-use efficiencies of the plants were determined by applying nitrogen (urea:0.336 g/pot)or phosphorus (superphosphate:1.51 g/pot) at the end of the soil moisture treatment.Root growth differed significantly (P<0.05)among the three soil moisture treatments.Taproot elongation was significantly inhibited by water logging.The taproot diameter, surface area,and volume were lower in water-stressed plants than in CK plants.The taproot was significantly shorter under low soil moisture conditions than in the CK.The growth rate of the root system was significantly lower in the low- and high-soil-moisture treatments than in the CK,and the root system in the high-soil-mois-ture treatment showed the poorest recovery after removal of water stress.Root growth was inhibited under wa-ter stress conditions,and the absorption and utilization of nitrogen and phosphorus were significantly (P<0.05)lower after low- and high-soil-water stress than in CK because of slow recovery of the root system.In-creasing the nitrogen and phosphorus supply significantly improved root growth.Together,these results sug-gested that maintaining soil moisture at an appropriate level and fertilizing with nitrogen and phosphate after soil stress are important to promote the growth of alfalfa roots and increase the forage yield.