【作者】 王丽；

【导师】 胡田田；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2017， 硕士

【摘要】 近年来,随着水肥资源供需矛盾的加剧,局部灌水施肥的研究越来越受到重视。前人对局部恢复供应、尤其是局部复水条件下作物的生长生理响应研究较多,但考虑前期胁迫状况的研究很少。而农业生产中,灌水或施肥往往是作物在遭受一定时间的水分或养分胁迫之后进行。因此,亟需开展预胁迫时长对局部恢复水氮作物根系生长和吸收功能的影响研究,以期为充分发挥作物对水分养分逆境的适应潜力,提高水肥资源管理水平提供理论依据。为此,本论文通过玉米幼苗分根水培试验,以PEG 6000模拟水分胁迫,设置不同氮素供应模拟氮素胁迫水平,试验分为前期均匀胁迫和后期局部恢复供应两阶段。在预胁迫阶段,玉米幼苗两侧根系均经受-0.4MPa的水分或1m M的氮素胁迫,设置0d、1d、3d和6d共4个预胁迫时间;之后进入局部恢复供应阶段,即1/2根区恢复正常供应,以15N标记的Ca（15NO3）2为氮源,另1/2根区维持原来的胁迫水平,供应非标记Ca（NO3）2;以两侧根系持续正常供应水分和氮素为对照（CK）。分别在局部恢复供应后0、0.25d、0.5d、1d、3d、5d、7d和9 d,动态监测作物各根区根系的生长及水分与氮素吸收状况,探究玉米根系经受不同预胁迫时长的水分或氮素胁迫后,根系生长和吸收功能的响应及其与解剖结构间的关系。取得以下主要结果:（1）根系水分吸收的研究表明,局部复水时,预胁迫0d、1d、3d和6d各处理复水侧根系总导水率分别在局部恢复0.25d、0.5d、3d和5d后快速增大,各处理两侧根区之间总导水率、单位根长导水率和单位根面积导水率分别在局部复水0.5d、1d、3d、7d时,0.5d、3d、5d、7d时和0.5d、5d、5d,7d时表现出显著性差异,即复水侧显著大于持续胁迫侧,表明预胁迫时间延长使复水侧根系吸水恢复速度变慢。局部恢复供氮时,各处理恢复侧根系总导水率分别在局部恢复0.5d、1d、3d、5d后快速增大,单位根长和根面积导水率分别在局部恢复3d、5d、5d、5d时和3d、3d、3d、5d时与持续胁迫侧表现出显著性差异。可见,恢复侧根系导水率开始明显增长及其与胁迫侧间出现差异的时间随预胁迫时长增大而延迟。水分或氮素预胁迫后,局部恢复供应可使叶片水分状况恢复。预胁迫0d始终与CK持平;水分预胁迫1d、3d、6d时,分别在局部恢复供应3d、7d、7d时接近对照水平,氮素预胁迫分别在局部恢复供应3d、7d、9d时达到CK水平。预胁迫时间越长,后期恢复速度越慢。（2）利用¹⁵N同位素示踪技术对各根区氮素吸收的研究表明,玉米幼苗经受-0.4 MPa、1m M的水分或氮素胁迫,局部恢复供应条件下,复水侧根系氮素吸收速率表现为,预胁迫0d和1d分别在局部复水0d和5d后显著大于CK;预胁迫3d在局部复水5d后恢复到CK水平;预胁迫6d始终小于CK。恢复供氮侧氮素吸收速率表现为,预胁迫0d和1d始终显著大于CK;预胁迫3d和6d局部恢复供氮0¹d内显著大于CK,预胁迫3d在局部恢复1d后与对照差异不明显;预胁迫6d在1d后显著小于对照。胁迫侧表现为,水分和氮素预胁迫0d的胁迫侧分别在局部供应1d和5d后显著小于CK,预胁迫1、3、6d始终显著小于CK。预胁迫时长明显影响恢复侧根系氮素吸收的恢复程度,两侧根系氮素吸收出现差异的时间随预胁迫时长增大而延迟。水分预胁迫0、1、3和6d的两侧根系含氮量和氮素累积量分别在局部复水9、5、1、5d和9、9、1、1d时表现出显著性差异。氮素预胁迫后,两侧根系含氮量和氮素累积量分别在局部恢复5d、5d、9d、9d时和1d、5d、5d、5d时表现出显著性差异。（3）根系生长响应的研究表明,预胁迫后局部复水,预胁迫0d的复水侧根长、根面积和根干物质量始终与CK无显著差异,两侧根长和根干物质量分别在局部复水1d和5d时差异显著,根面积始终差异不显著;预胁迫1,3,6d条件下,根长、根面积和根干物质量分别在局部复水1d、1d、3d时、3d、3d、5d时和1d,3d,7d时表现出显著差异。预胁迫0d的复水侧根长及根面积增长速率,分别在局部复水0.5d和3d后显著大于胁迫侧,预胁迫1、3、6d的各处理,除预胁迫1d时的根面积在0.25⁰.5d时差异不显著外,其他各处理两侧根系差异显著。预胁迫后局部恢复供氮,预胁迫0d的两侧根长、根面积平均增长速率均在5⁹d内差异不显著,根干物重平均增速在5⁷d时差异不显著;预胁迫1d时,根面积和根干物重增速分别在局部恢复供应0.25⁰.5d和1³d时差异不显著,其他时间与预胁迫3d和6d的两侧根系均表现为供应侧显著大于胁迫侧,表明随预胁迫时间延长,恢复供应侧根系生长的恢复时间延迟且程度降低。（4）玉米根系解剖结构的研究表明,水分、氮素或水氮同时预胁迫6d后,根系和导管直径显著小于对照,皮层厚度占根直径的比例显著大于对照。不同的是,水分胁迫对皮层厚度无显著影响,而氮素胁迫及水氮双重胁迫使皮层厚度明显增大。局部恢复供应后,各处理恢复侧根系导管直径、根系直径很快恢复,1d时达到甚至超过CK,之后趋于稳定,且始终大于预胁迫结束时;皮层厚度占根系直径的比例在1⁵d内均显著小于预胁迫结束时。局部复水后,皮层厚度恢复供应5d时与对照差异不显著,皮层厚度占比1d后显著小于预胁迫结束时;局部恢复供氮后,皮层厚度在恢复供应9d时达到对照水平;局部恢复水氮供应1d后,皮层厚度在局部恢复1⁵d内增幅减缓,9d时显著小于对照。恢复供应侧表现出一定的恢复与适应性。各处理持续胁迫侧的根系和导管直径,除氮素胁迫在局部恢复1d时与CK差异不显著外,均显著小于CK,皮层厚度和其占根系直径的比例受局部胁迫影响持续增加。更多还原

【Abstract】 With the contradiction between the supply and demand of water and fertilizer increasing,the study of local irrigation and fertilization has been paid more and more attention.Many studies have been done on the growth and physiological responses of crops under partial resupply,especially under partial rewatering.However,few studies have been conducted to consider the stress status of early crops.In agricultural production,irrigation or fertilization is often carried out by crops after a certain time of water or nutrient stress.Therefore,in order to develop water and nutrient stress adaptation potential and provide a theoretical basis for improve water resource management level,research of function of previous stress time on partial resupply of water and nitrogen on crop root growth and absorption need to be carried out.Therefore,Maize seedling was prepared using split-root hydroponic technique,with PEG 6000 simulating water stress,setting different nitrogen supply for nitrogen stress level,the test was divided into two stages.In the previous stress stage,-0.4MPa water stress or 1mM nitrogen stress were subjected to maize seedling root.With the time of 0,1,3,6d previous stress,then partial resupply,the 1/2 root zone with normal supply,labeled with 15 N Ca(15NO3)2 as nitrogen source,The other 1/2 root zone supplied with normal level,with no labeled Ca(NO3)2.Then monitor the crop growth status of absorption of root water and nitrogen dynamically,at the resumption time of 0,0.25,0.5,1,3,5,7 and 9 d,exploring the dynamic changes of root growth and absorption function after partial re supply.At the same time,the changes of root anatomical structure were observed,investigating the internal relationship between root structure and root absorption function.The main results are as follows:(1)Study on root water uptake showed that the rewatering root hydraulic conductance increase rapidly at 0.25 d,0.5d,3d and 5d respectively,with the previous stress time of 0d,1d,3d and 6d.both sides of the root zone total hydraulic conductance、unit root length and area hydraulic conductance conductivity showed significant difference at the resupply time of 0.5d,1d,3d,7d、 0.5d,3d,5d,7d and 0.5d,5d,5d,7d,rewatering zone was significantly higher than that of stress zone,showed that the longer previous stress time the slower hydraulic conductance recovery.After water or nitrogen previous stress,the resupply root zone hydraulic conductance increase rapidly at 0.5d,1d,3d and 5d respectively.Both sides of the root zone unit root length and area hydraulic conductance showed significant difference at the resupply time of 3d,5d,5d,5d、3d,3d,3d,5d and 0.5d,5d,5d,7d.Thus the time of resupply zone increase obviously and significant difference between two roots delayed with the increase of the previous stress time.The partial resupply can restore leaf water status.The leaf water content with presvious tress 0d keeps the same with CK;Water previous stress 1d,3d,6d,the leaf water content keeps close to CK respectively at the partial resupply of 3d,7d,7d.Nitrogen previous stress level at the resupply time of 3d,7d,and 9d reached CK.The longer previous stress time,the slower rate of recovery.(2)Study on the nitrogen absorption of the root zone using 15 N isotope tracer technique showed that maize seedlings subjected to-0.4 MPa,1mM of water or nitrogen stress,rewatering root zone nitrogen uptake rate showed that the previous stress time of 0d and 1d was significantly greater than CK at the partial resupply time of 0d and 5d;The nitrogen uptake rate of previous stress 3d at the partial resupply time of 5d reached CK;The nitrogen uptake rate of previous stress 6d always lower than CK.The nitrogen absorption rate of nitrogen supply side,after the previous stress 0d and 1d was significantly greater than CK;Previous stress 3d reached CK after resupply 1d;Previous stress 6d higher than CK after resupply 1d.Stress side showed that water and nitrogen previous stress 0d,stress sides less than CK after the resupply time of 1d and 5d.The previous stress 1d,3d,6d,always less than CK significantly.The duration of stress time significantly affect the recovery of nitrogen uptake in resupply roots,and the difference in nitrogen uptake between the two roots was delayed with the increase of previous stress.The nitrogen content and nitrogen accumulation of both roots of water stress 0,1,3 and 6d showed significant differences at partial rewatering time of 9,5,1,5d and 9,9,1,and 1d,respectively.After nitrogen stress,the nitrogen content and nitrogen accumulation of both roots showed significant differences in the resupply time of 5d,5d,9d,9d,and 1d,5d,5d and 5d.(3)Study on the root growth response showed that root length,root area and root dry weight of previous stress 0d has no significant difference with CK after resupply,both root length and root dry weight had significant difference at resupply time of 1d and 5d,the root area had no significant differences.The root length,root dry weight and root area with previous stress 1d,3d,6d,showed significant difference at 1d,1d,3d、3d,3d,5d and 1d,3d,7d.The root length and root growth rate with previous stress 0d were significantly greater than the stress side at the resupply time of 0.5d and 3d.The root length and root growth rate,with previous stress 1d,3d,6d,had significant difference on both sides of the root,except the root area at 0.25~0.5d with previous stress 1d had no significant difference.After partial resupply of nitrogen stress,the two sides of the root length and root area of the average growth rate in 5~9d had no significant difference and root dry weight average growth rate of no significant difference in 5~7d with previous stress 0d;root area and root dry weight growth rate at resupply time of 0.25~0.5d and 1~3d,had no significant difference with previous stress 1D.Other time and previous stress on both sides of the root of 3D and 6D were significantly greater than the supply side.With previous stress time prolonged,the resupply root growth restore degree reduce and recovery time delay.(4)The anatomical structure of maize roots showed that the diameter of roots and tubes were significantly smaller than that of CK,and the proportion of cortex thickness to root diameter was significantly higher than that of CK after water 、nitrogen stress 6d.The difference was that water stress had no significant effect on cortical thickness,while nitrogen stress 、water and nitrogen stress increased the cortical thickness.The diameter of roots and tubes recovered quickly and even more than CK at the resupply time of 1d,then tended to be stable,it is larger than resupply 0d;the thickness of cortex accounted for the proportion of root diameter in 1~5d was significantly lower than resupply 0d.After water resupply,the thickness had no significant difference with CK,cortical thickness proportion less than stress side significantly at resupply 5d.After nitrogen resupply,the thickness of cortex reached CK level at the recovery of 9d;The thickness of cortex less than CK at the recovery of 9d The restored supply side showed recovery and adaptation.The continued stress side of diameter of root tube less than CK significantly,except nitrogen stress resupply at 1d had not difference significantly,the thickness of cortex and the root diameter ratio accounted for stress continues to increase.更多还原