铵态氮和硝态氮调节盐胁迫豌豆幼苗生长和根系呼吸的作用

【目的】 土壤盐渍化在干旱和半干旱灌溉区是制约农业生产的非生物因素之一，合理的调控措施可以减轻盐渍化对植物的危害，本文探讨了氮源调节豆科植物盐胁迫的生理生态机制。 【方法】 采用砂培试验，以3个豌豆品种 (银豌1号、S5001-1和Ha) 为供试材料，设定三个盐分浓度(0、50、100 mmol/L)，分别供应铵态氮和硝态氮4 mmol/L，每个品种均设六个处理。培养29天后对豌豆幼苗生物量、根系生长参数、根系呼吸及植株盐分离子含量进行测定。 【结果】 1) 三个盐分浓度相比，50 mmol/L NaCl处理下的3个豌豆品种幼苗的地上生物量和根系生长指标(根干重、根长和根表面积)显著高于0和100 mmol/L NaCl处理，且硝态氮处理显著高于铵态氮；2) 与无NaCl处理相比，3个豌豆品种植株含水量在100 mmol/L NaCl处理下明显降低，且硝态氮处理的显著低于铵态氮处理；3)豌豆根系呼吸速率均随着盐分浓度的增加和培养时间的延长总体呈降低趋势。3个豌豆品种根系呼吸速率对硝态氮和铵态氮的反应不同，相同盐分水平下，银豌1号铵态氮处理的高于硝态氮，Ha品种则相反，而S5001-1品种在两种氮源间差异不大。在50 mmol/L NaCl胁迫下，豌豆品种S5001-1与Ha硝态氮处理的根系呼吸累积量明显高于铵态氮，而银豌1号则相反；100 mmol/L NaCl胁迫下，豌豆品种Ha硝态氮处理的根系呼吸累积量显著高于铵态氮，其他两个品种在不同氮源处理间无差异。相同盐分胁迫水平下，银碗1号铵态氮处理的根系呼吸累积量明显高于品种S5001-1和Ha，而硝态氮处理下，品种Ha的根系呼吸累积量最高。4) 3个豌豆品种幼苗地上部Na+和Cl–含量均随盐浓度的增加而增加，而不同氮源对Na+在豌豆体内累积的影响因豌豆品种而异。 【结论】 在中度盐分胁迫下，施氮肥可缓解盐分胁迫对豌豆幼苗生长的影响，硝态氮缓解能力高于铵态氮，但在重度盐分胁迫下，盐胁迫是影响植物生长和离子吸收的主导因子，氮源调节作用变弱。尽管不同豌豆品种的根系呼吸对NH₄+-N与NO₃–-N的反应不同，但NO₃–-N缓解盐胁迫的效果总体上好于NH₄+-N。

Effect of NH4+-N and NO3–-N on plant growth and root respiration of pea seedlings under salt stress

【Objectives】 Soil salinization is one of abiotic factors affecting agricultural production in arid and semi-arid irrigated areas, and the areas of salinization have been gradually expanded in recent years. Reasonable controlling measures can alleviate damage of salinization to plants. Therefore, this study researched the physiological and ecological mechanism of nitrogen sources regulating the salt stress of legume plants. 【Methods】 A sand culture experiment was conducted with three pea cultivars of ‘Yinwan No.1’, ‘S5001-1’ and ‘Ha’ as tested materials. Three salt stress levels of NaCl 0, 50 and 100 mmol/L were set up, NH₄+-N and NO₃–-N were supplied separately in the set of salt treatment. The biomass, root growth parameters, root respiration and salt ion contents of pea seedlings were measured at 29 days after transplanting. 【Results】 1) Among the three NaCl stress treatments, the biomass of pea seedlings, the root dry matter, root length and root surface area for the three cultivars were all highest under 50 mmol/L NaCl treatment. The effects of nitrate-N were significantly better than those of ammonium-N. 2) Compared with no salt stress, the water contents of pea seedlings for all three varieties were significantly lower under 100 mmol/L NaCl treatment, and those with nitrate-N supply were significantly lower than with NH₄+-N. 3) The root respiration rates of three varieties decreased with the increase of salt concentration and plant growth period. The root respiration rates of the pea cultivars responded differently to the two N forms. Those of ‘Yinwan No.1’ in NH₄+-N treatments were higher than in NO₃–-N treatments at the same salt concentration, ‘Ha’ was opposite, and ‘S5001-1’ was similar. Under 50 mmol/L NaCl stress, the cumulative root respiration of both ‘Ha’ and ‘S5001-1’ in the NO₃–-N treatments were significantly higher than those in the NH₄+-N treatments, and those of ‘Yinwan No.1’ were on the contrary. Under 100 mmol/L NaCl stress, the cumulative root respiration in ‘Ha’ were significantly higher in the NO₃–-N treatments than in NH₄+-N treatments, there was no significant differences in other two varieties. 4) The contents of Na+ and Cl– of pea seedlings were increased with increase of salt concentrations. The effect of nitrogen sources on Na+ accumulation in pea seedlings depended on different pea cultivars. 【Conclusions】 Under moderate salt stress, the alleviation ability of NO₃–-N on the growth of pea seedlings is higher than that of NH₄+-N. Under severe salinity stress, the alleviation of nitrogen sources becomes less effective. Although the response differences of root respiration to NH₄+-N and NO₃–-N among different pea cultivars, NO₃–-N performs better than NH₄+-N in alleviating salt stress in general.