紫花苜蓿叶片和根系膜脂过氧化及C、N特征对水分和N添加的响应北大核心CSCD

为研究紫花苜蓿叶片和根系对水分和外源氮(N)添加的响应规律,在温室条件下设置水分胁迫处理(WS)(35%±5%)田间持水量(field water capacity,FWC)和充分灌溉且未渍水(WW)(70%±5%)FWC两个水分梯度,每个水分梯度下设置0、5和10 mmol·L^(-1)3个N添加水平(Nn、Nm和Nh),研究了紫花苜蓿叶片和根系膜脂过氧化的程度及C、N特征对不同水分条件和外源N添加的响应规律。结果表明:WS和外源N提高了紫花苜蓿叶片丙二醛(MDA)含量,但对根系没有显著影响。WS和N添加未影响紫花苜蓿叶片C含量,但N添加提高了根系C含量。WS未改变紫花苜蓿叶片N含量,但提高了根系N含量。外源N添加不但提高了叶片N含量,还增加了根系N含量,但叶片N含量在WW处理下对外源N添加较为敏感,而根系N含量在WS处理下对外源N的添加较为敏感,这说明紫花苜蓿叶片和根系C、N状态对N添加的响应受土壤水分条件的调控。紫花苜蓿根系C/N较叶片更高,且对水分和外源N添加的响应更为敏感。WS处理显著提高了根系δ^(13)C,对叶片δ^(13)C无显著影响。外源N添加降低了叶片和根系δ^(15)N,且在WS处理下根系δ^(15)N显著降低,叶片中δ^(15)N在WW处理下显著降低。总之,相比叶片,紫花苜蓿根系生理参数及C、N特征对水分和外源N添加采取了更为积极的策略,在生长中发挥着更重要的作用。该研究结果有助于全面掌握紫花苜蓿各器官对水分和外源N添加的响应策略,为我国旱作农业区紫花苜蓿制定精准的水肥管理制度提供了理论依据。

Lipid peroxidation and carbon and nitrogen characteristics in leaves and roots of alfalfa(Medicago sativa)in response to water and nitrogen addition

In order to study the response of alfalfa （Medicago sativa） leaves and roots to water and N addition， two contrasting water availability regimes were set up under greenhouse conditions： water stress （WS） with soil maintained at 35%±5% field water capacity （FWC） and well-watered （WW， 70%±5% FWC）. Treatments of 0， 5 and 10 mmol·L^-1 N （Nn， Nm and Nh， respectively） were established under each watering regime. The responses of physiological parameters of alfalfa leaves and roots and their C and N characteristics to different water conditions and exogenous N addition were then studied at the three N levels. It was found that WS and exogenous N increased malondialdehyde content in alfalfa leaves， but had no significant effect on the root system. WS and N addition did not affect C content in alfalfa leaves， but N addition increased C content in roots. The content of N in alfalfa leaves did not differ between water treatments， but root N content was increased under the WS treatment. Exogenous N addition not only increased leaf N content， but also increased root N content. However， leaf N content was more sensitive to exogenous N addition under the WW treatment， while root N content was more sensitive to exogenous N addition under the WS treatment， which indicates that the response of alfalfa leaf and root C and N status to N addition was regulated by soil moisture conditions. The C∶N of alfalfa roots was higher than that of leaves， and was more sensitive to soil water status and exogenous N addition. The WS treatment resulted in significantly less negative root δ¹³C， but had no significant effect on leaf δ¹³C. δ¹⁵N tended to be reduced with exogenous N addition， but this effect was statistically significant in roots under WS treatment and in leaves under WW treatment. In conclusion， compared with leaves， alfalfa root physiological parameters and C and N characteristics displayed more active responses to water and exogenous N addition， and played a more important role in growth. The results are helpful to fully understand the response strategies of alfalfa organs to water and exogenous N addition， and provide a theoretical basis for formulation of water and fertilizer management systems that more precisely meet alfalfa requirements in dry farming areas of China.