开放式空气二氧化碳浓度增高(FACE)条件下水稻的根系活力和氮同化能力

Root activity and nitrogen assimilation of rice(Oryza sativa)under Free-Air CO_2 Enrichment

利用FACE(Free Air Carbon-dioxide Enrichment)平台技术,用伤流量法研究了低氮(LN150kg·hm-2)和常氮(NN250kg·hm-2)水平下,大气CO2浓度升高对水稻分蘖、抽穗期和穗后35d根系活力和根系N同化能力(氨基酸合成能力)的影响.结果表明,就整株水稻来看,CO2浓度升高和N处理对根系活力无显著影响;但由于FACE条件下水稻分蘖数增加14.5%(LN)和20.7%(NN),使每茎根系活力(伤流强度)降低1.4%～21.7%.在分蘖和抽穗期,虽然FACE处理促进了根系吸收的无机N向氨基酸转化,根系伤流液中氨基酸氮/无机氮提高11.1%～143.1%,但氨基酸浓度和合成总量和对照相比无明显差异.在穗后35d,FACE处理减弱了水稻根系的N同化能力,表现为根系伤流液中氨基酸/无机氮降低38.1%(LN)和29.2%(NN);同时氨基酸浓度降低34.0%(LN)和44.7%(NN),氨基酸合成总量降低50.8%(LN)和40.0%(NN).提高施氮水平促进了抽穗期水稻根系对无机氮的吸收,伤流液中无机氮含量增加51.1%(对照)和155.2%(FACE),但并未增加氨基酸合成量,由此导致抽穗期氨基酸氮/无机氮显著降低19.5%(对照)和36.8%(FACE);同时,氮处理在这个时期与FACE处理表现出明显的交互作用.

With Free-Air CO2 Enrichment（FACE）technique, this paper studied the root activity and amino acid（aa） synthesis of rice（Oryza sativa）at low N（LN, 150 kgN· hm^-2）and normal N（NN, 250 kgN· hm^-2）under ambient air and elevated atmospheric CO2（Ambient ＋ 200 μmol· mol ^- 1）. Under elevated CO2, the xylem exudates per hill changed little, while the xylem exudates per stem declined by 1.4% ～ 21.7 % as the result of greater tiller numbers. At tillering and heading stages, elevated CO2 increased aa N/inorganic N in xylem exudates by 11.1% 143.1%, but did not affect the aa concentration in xylem exudates and the total amount of aa in roots significandy. However, at 35 days after heading, the aa N/inorganic N ratio decreased by 38.1% （LN）and 29.2% （NN） under elevated CO2. FACE also declined the aa concentration in xylem exudates by 34.0% （LN）and 44.7 % （NN）, and the total amount of aa by 50.8 % （LN） and 40.0 % （NN）, which meant the retarded capability of aa synthesis in roots. N amendment led to a decrease of aa N/inorganic N in xylem exudates by 19.5 % （Ambient） and 36.8 % （FACE） at heading stage, as the result of unaffected aa and increased inorganic N concentration. There existed a significantly antagonistical CO2 × N interaction on aa N/inorganic N at heading stage.