真盐生植物盐角草对不同氮形态的响应

盐角草(Salicornia europaea L.)是一种喜盐植物,其最佳生长的实现需要200—400 mmol/L NaCl。为了解盐渍环境下盐角草氮素吸收利用特点,在水培添加200或400 mmol/L NaCl情况下,从生长指标,光合参数,根系体积和活力,硝酸还原酶与谷氨酰胺合成酶活力,蛋白、总氮、硝态氮及铵态氮含量等方面检测了硝态氮、铵态氮和尿素3种氮形态对盐角草生长的影响。研究发现以氮摩尔浓度(mmol/L)计,在0.1—400 mmol/L浓度范围进行测试,盐角草在0.1 mmol/L低氮条件下仍能维持生长,同时,抑制盐角草生长的氮浓度域值较高,其中铵态氮、尿素和硝态氮分别为50、50及400 mmol/L。研究结果表明盐角草吸收利用氮素的能力强,对氮素的浓度耐受范围宽,3种氮形态都可作为氮源满足其生长需要,但有效促进生长的效果存在差异,总体顺序从高到低依次为硝态氮、铵态氮和尿素。研究为揭示盐生植物氮吸收利用特点提供了基础数据,对提高盐生植物生产力,指导沿海滩涂生态建设具有一定的指导意义。

The response of euhalophyte Salicornia europaea L. to different nitrogen forms

Salicornia europaea L., a euhalophyte, needs moderate concentrations of NaCl (200-400 mmol/L) to maintain its optimal growth. The assimilation of nitrogen under salinity might be distinctive in this plant. In present study, S. europaea plants were hydroponically cultured in medium containing moderate Na . Nitrate, ammonium and urea with nitrogen concentrations ranged from 0.1 to 400 mmol/L were separately applied to S. europaea plants in culture medium, to investigate the characteristics of nitrogen assimilation. Measurements on growth and photosynthetic parameters, nitrogen metabolic enzymes activities, as well as the content of soluble and unsoluble protein, nitrate, ammonium and total nitrogen, were performed after treatments for 30 days. The results showed there was no significant difference in growth of S. europaea plants when supplied with the three nitrogen forms at nitrogen concentrations of 0.1 and 1 mmol/L. However, when the concentration of nitrogen reached to 10 mmol/L or higher, nitrate proved to be the best nitrogen nutrition for the growth of S. europaea, followed by ammonium and urea. When nitrogen concentration increased to 50 mmol/L, the growth of S. europaea supplied with ammonium and urea were significantly inhibited, while the plants maintained normal growth until high nitrate nitrogen concentration of 400 mmol/L under salinity of 400 mmol/L Na . Under all three forms of nitrogen, photosynthetic parameters were consistent with the plant growth trends. Root volume and activities were normally distributed and raised to the peak at the nitrogen concentration of 10 mmol/L with nitrate, 1 mmol/L with ammonium and 1 mmol/L with urea, respectively. The nitrogen metabolic enzymes activities in S. europaea were affected by exogenous nitrogen concentration. The nitrate reductase and glutamine synthetase activities were increased with nitrate supply. However, ammonium and urea did not affect nitrate reductase activities. The glutamine synthetase activities were normally distributed under ammonium and urea, which was highest at the concentration of 10 mmol/L nitrogen in ammonium and 50 mmol/L in urea, respectively. The content of total nitrogen, soluble and unsoluble protein of S. europaea was increased with the increasing supply of exogenous nitrogen. In summary, this study revealed that S. europaea has a strong ability on nitrogen absorption and utilization. All the three forms of nitrogen with a wide range of nitrogen concentration can be used as nitrogen supply for S. europaea, among them, however, nitrate with nitrogen concentrations from 0.1 to 400 mmol/L was proved to be the best, followed by ammonium and urea whose acceptable nitrogen concentration ranged from 0.1 to 50 mmol/L. These findings act as basis for revealing the mechanism of nitrogen absorption and assimilation in S. europaea, which will in turn be meaningful for developing the halophytes in coastal and other saline areas.