不同氮吸收效率水稻品种的苗期铵吸收特性及生长差异分析

Analysis of Ammonium Uptake and Growth Differences of Rice Varieties with Different Nitrogen Recovery Efficiency at Seedling Stage

[目的]测定不同氮吸收效率品种对外界NH4+浓度的响应,解释水稻品种间氮吸收差异的机理。[方法]采用水培法栽培氮吸收高效的水稻品种齐粒丝苗(QL)和氮吸收低效的品种沪科3号(HK),通过分析水稻幼苗在0—0.80 mmol·L^(-1)低铵浓度和1.00-12.96 mmol·L^(-1)高铵浓度下的铵吸收速率,计算铵吸收动力学参数Vmax和Km值,比较不同氮吸收效率水稻品种的苗期铵吸收特性;通过比较不同NH4+浓度下的水稻苗期株高、分蘖数、叶绿素含量、以及地上和地下部的干物质和氮素积累量,用根系扫描法分析根系形态,包括总根长、根体积、根表面积、平均直径、根尖数等,用非损伤性扫描离子选择电极技术(scanning ion-selective electrode technique,SIET)测量根分生区和伸长区NH4+的跨细胞膜运输,用液相氧电极系统分析根系氧损耗,研究不同氮吸收效率水稻品种的苗期生长差异。[结果](1)在0—0.8 mmol·L^(-1)、低铵浓度下,2个水稻品种QL和HK幼苗对NH4+的吸收符合Michaelich-Menten方程,氮吸收高效品种QL的吸收动力学参数Vmax为氮吸收低效品种HK的1.66倍;当NH4+的浓度大于1 mmol·L^(-1)时,水稻幼苗对NH4+的吸收均随着外界NH4+浓度的增加而增大,但同一NH4+浓度下,氮吸收高效品种QL对NH4+的吸收速率大于氮吸收低效品种HK;(2)水稻根系分生区在外界不同NH4+浓度下均表现为NH4+的跨细胞膜净流入,且NH4+净流入速率随着外界NH4+浓度的升高而增加,氮吸收高效品种QL在低铵(LN)、中铵(MN)和高铵(HN)处理下根系分生区NH4+净流入速率分别比氮吸收低效品种HK高42.0%、71.8%和63.6%;根系伸长区NH4+的跨细胞膜流通品种间存在差异,氮吸收低效品种HK在LN和HN下均出现NH4+跨细胞膜净输出,而氮吸收高效的品种QL仅在HN下出现NH4+跨细胞膜净输出,且净输出速率比氮吸收低效的HK低34.30%。(3)在LN和MN浓度下,氮吸收高效品种QL的苗期形态和物质积累并不占优势;适量增铵可以增加水稻的株高、分蘖、叶绿素含量、干物质和氮素积累量,但过高的外界铵浓度对水稻生长特别是根系生长有抑制作用;HN下,氮吸收高效的品种QL显示出一定的生长优势,播种后10-20 d的分蘖增加速率和干物质增加速率分别比氮吸收低效的品种HK高65.7%和31.4%;虽然品种QL的根系氮浓度比品种HK低15.1%,但其地上部氮积累量比HK高23.5%,说明QL比HK能更快地将根系吸收的氮转运至地上部供其生长所需。[结论]与氮吸收低效品种相比,氮吸收高效品种根系细胞膜上有更多的NH4+运输载体,根系吸收的NH4+同化、转运速度快,苗期分蘖速率和干物重积累速率大。

[Objective]The aim of this study was to determine the response of different Nrecovery efficiency(NRE)varieties to external NH4+concentration,and to explain the mechanism of N uptake difference among rice varieties.[Method]A high-NRE(QL)and a low-NRE(HK)rice variety were cultivated hydroponically at different NH4+concentrations,and the varietal difference of NH4+absorption at seedling stage were compared by analysis of the root NH4+absorption rate at the low NH4+concentration of0-0.80 mmol·L^(-1) and the high NH4+concentration of 1.00-12.96 mmol·L^(-1),and by calculating the NH4+absorption kinetics parameter Vmax and Km;The difference of seedling growth between varieties were analyzed by comparing the plant height,tiller number,chlorophyll content,dry matter and N accumulation of aboveground and underground part of rice seedlings growing in different NH4+concentrations,root morphology including total root length,root volume,root surface area,average root diameter,and root tip number were analyzed using the root scanning instrument;The root net fluxes of NH4+were measured non-invasively using SIET(scanning ion-selective electrode technique),root respiration was measured using a Hansatech oxygen electrode and an oxygraph control system.[Result](1)In the low NH4+concentration range of 0-0.8 mmol·L^(-1),the uptake of NH4+by QL and HK seedlings stage were in accordance with Michaelich-Menten equation,and the Vmax of high-NRE variety QL was 1.66 times higher than that of low-NRE variety HK.In the NH4+concentration higher than 1 mmol·L^(-1),the uptake of NH4+by rice seedlings kept increasing with the increase of NH4+concentration,and the uptake rate of NH4+by QL was greater than that of HK at the same NH4+level.(2)The root meristematic zone of both varieties showed a net NH4+influx,while it increased with the increase of NH4+concentration,and the high-NRE variety QL had greater value than low-NRE variety HK by 42.0%,71.8%and 63.6%at LN,MN and HN,respectively;The net NH4+efflux in the root elongation zone was showed at LN and HN in the low-NRE variety HK,while it was only showed at HN in the high-NRE variety QL,and 34.30%lower than variety HK.(3)Although an appropriate increase of NH4+could increase the plant height,tiller number,leaf chlorophyll content,dry matter and N accumulations,while HN inhibited plant growth,especially root growth.The growth of high-NRE variety QL did not show an advantage compared with low-NRE variety HK in the treatment of LN and MN,however,QL had greater tillering rate and dry matter accumulation rate by65.7%and 31.4%compared with HK during 10-20 days after seeding in HN,respectively.Although the N concentration of root of variety QL was 15.1%lower than that of variety HK,it’s aboveground N accumulation was 23.5%greater,which indicated that QL was more efficient than HK in transporting the Nabsorbed by roots to the aboveground.[Conclusion]It was concluded that compared with the low-NRE variety,the high-NRE variety had more NH4+transport carriers on the cell membrane of the root system,and the NH4+absorbed by the root system had a fast assimilation and transport speed,as well as a high tiller rate and dry matter accumulation rate in the seedling stage.