无机氮处理对矿山生态型水蓼氮积累及根系形态的影响

氮肥的过量施用,导致土壤中过量的氮易随渗漏、径流等方式进入水体,造成水体的富营养化加剧。矿山生态型水蓼为前期试验筛选的氮磷修复植物,明确根系形态变化对无机氮处理的响应特征可以为矿山生态型水蓼对氮素的吸收积累机理提供一定理论基础。采用砂培试验,以氮磷富集植物矿山生态型水蓼为研究对象,设置不同铵态氮浓度(25、50、75 mg·L^-1)和硝态氮浓度(25、50、75 mg·L^-1),研究了矿山生态型水蓼植株氮积累以及根系形态各参数的变化。结果表明,矿山生态型水蓼生物量和氮积累量均在供氮50 mg·L^-1时达到最大值。供氮浓度为50和75 mg·L^-1时,矿山生态型水蓼生物量表现为硝态氮处理显著高于铵态氮处理。矿山生态型水蓼氮含量和氮积累量均表现为铵态氮处理高于硝态氮处理。随着铵态氮浓度的增加,矿山生态型水蓼的根长、根表面积和根体积均显著减小;随着硝态氮浓度的增加,矿山生态型水蓼根长、根表面积、根体积均在供氮50 mg·L^-1时最大。在供氮为25 mg·L^-1时,矿山生态型水蓼根系形态各参数表现为铵态氮处理大于硝态氮处理,在供氮50和75 mg·L^-1时则表现为硝态氮处理显著大于铵态氮处理。适宜浓度硝态氮能促进矿山生态型水蓼的生长和侧根发育,从而促进对氮素的吸收。而铵态氮浓度过高会抑制矿山生态型水蓼的根系生长,但并不抑制其对氮素的吸收积累能力,这可能与矿山生态型水蓼根系的抗逆性有关。

Effects of inorganic N on the N accumulation and root morphology of a mining ecotype of Polygonum hydropiper

Excessive application of nitrogen(N) fertilizers increases the loss of N via runoff and leaching, resulting in a more serious eutrophication. In a previous study, we screened out a nitrogen-phosphorus enriched plant, the mining ecotype(ME) of Polygonum hydropiper. Studying the root morphology response to inorganic nitrogen addition could be expected to provide a theoretical basis for understanding the absorption and accumulation mechanism of nitrogen in the ME of P. hydropiper. Sand culture experiments were conducted to analyse the N accumulation and root morphology of the P. hydropiper ME supplied with different ammonium nitrogen(NH4-N) concentrations(25, 50, 75 mg N·L^-1) and different nitrate nitrogen(NO3-N) concentrations(25, 50, 75 mg N·L^-1). The P. hydropiper ME showed the greatest biomass and N accumulation at 50 mg N·L^-1. The biomass values of the P. hydropiper ME grown in 50 and 75 mg·L^-1 NO3-N treatments were significantly higher than those in NH4-N treatments;however, the P. hydropiper ME accumulated more N when grown in the NH4-N than when grown in the NO3-N treatments. The root growth of the P. hydropiper ME was greatly inhibited with increasing NH4-N concentrations in solution. The root system of the P. hydropiper ME showed the greatest length, surface area, and volume when grown in 50 mg·L^-1 NO3-N. The root growth of the P. hydropiper ME was greater in NH4-N than in NO3-N at 25 mg N·L^-1, but this difference was reversed at 50 and 75 mg N·L^-1. In summary, he appropriate NO3-N concentration promoted the growth of the P. hydropiper ME and the development of lateral roots, resulting in enhanced absorption of N. High concentration of NH4-N inhibited root growth, but did not reduce N accumulation in the plant.