氮素形态对盐胁迫下菊芋幼苗PSⅡ光化学效率及抗氧化特性的影响

Effects of nitrogen form on the photochemical efficiency of PSⅡ and antioxidant characteristics of Jerusalem artichoke seedling under salt stress

采用沙培方法研究了不同铵硝配比(NH4+/NO3-分别为4/1,1/1,1/4)的氮素营养供应对菊芋耐盐生理的影响。结果表明,1)低浓度的盐胁迫对菊芋幼苗生长的抑制作用不大,而高浓度的盐胁迫却能明显抑制菊芋幼苗的生长。而在同一盐浓度下,提高硝态氮比例能够较好的缓解盐胁迫对菊芋幼苗生长的抑制,促进菊芋幼苗干物质的积累,提高含水量、株高和叶面积。2)随着盐浓度的增加,菊芋幼苗PSⅡ系统受到了明显伤害,提高硝态氮比例能够减轻盐胁迫对PSⅡ系统的伤害程度,提高ΦPSⅡ、Fv、Fv/Fm、Fv/Fo,Fm/Fo和qP,其中铵硝比1/4的氮素营养供应能相对较好的促进光能向化学能的转变,提高光能利用效率,在100mmol/L NaCl处理下其ΦPSⅡ、Fv、Fv/Fm、Fv/Fo、Fm/Fo和qP分别是铵硝比4/1氮素处理的1.03,1.15,1.05,1.26,1.20和1.05倍。3)盐浓度的升高会对植物体造成渗透胁迫,引起植物细胞渗透压失衡,而在同一盐浓度下,提高硝态氮比例能够显著促进具有渗透调节作用的可溶性糖和可溶性蛋白生成及向根部的转移,有效维持盐胁迫下菊芋细胞的渗透压平衡。4)盐胁迫下,植物细胞会发生膜脂过氧化作用,而提高硝态氮比例能够促进具有消除活性氧功能的SOD、POD、CAT和APX活性的增加,减轻细胞中活性氧过多积累引起的膜脂氧化伤害,其中在100mmol/L NaCl处理下,铵硝比1/4氮素处理的SOD、POD、CAT和APX活性分别是铵硝比4/1氮素处理的1.19,1.08,1.18和1.11倍。由此表明相对于铵态氮来说,氮素营养中硝态氮比例的增加有助于促进盐胁迫下菊芋幼苗干物质的积累及含水量的增加,维持盐胁迫下菊芋幼苗PSⅡ系统的稳定性和细胞渗透压平衡,以及提高细胞内保护酶活性,从而增强菊芋幼苗对盐胁迫的抗性。

In order to study the effect of different nitrogen form on the physiology of Jerusalem artichoke seedling under the salt stress,a sand cultural study was carried out under the nitrogen nutrition（NH4＋/NO3-as 4/1,1/1 and 1/4） and salt stress.1） The treatment of low concentration of salt stress had a little effect on the inhibition of plant growth,but high concentration of salt stress could remarkably inhibit Jerusalem artichoke growth.Under the same salt concentrations,the dry weights,relative moisture content,plant height and leaf area of Jerusalem artichoke increased with the proportions of NO3——N augment.2）With the increasing of salt concentration,PSⅡ system was significantly damaged,but the increasing of the proportions of NO3——N could reduce the damage degree of the PSⅡ system and improve ΦPSⅡ,Fv,Fv/Fm,Fv/Fo,Fm/Fo and qP.Especially,nitrogen nutrition had the highest light use efficiency at the ratio of NH4＋/NO3-as 1/4.For example,under 100 mmol/L NaCl stress,compared with the treatment at the ratio of NH4＋/NO3-as 4/1,ΦPSⅡ,Fv,Fv/Fm,Fv/Fo,Fm/Fo and qP of the treatment at the ratio of NH4＋/NO3-as 1/4 increased by 1.03,1.15,1.05,1.26,1.20 and 1.05 times,respectively.3）Too much salt supply could cause the imbalance of plant cell osmotic,however,under the same salt concentration,the increasing of the proportions of NO3——N could significantly promote soluble sugar and soluble protein production and the transfer to the roots,then maintained the balance cell osmotic effectively under salt stress.4）Under the salt stress,the membrane lipid peroxidation usually occurred in plants cells,but the proportions of NO3——N augment could promote the SOD,POD,CAT and APX activity which had a function of eliminating reactive oxygen species,then alleviated membrane damage which the excessive accumulation of reactive oxygen species caused in cell.For example,under 100 mmol/L NaCl stress,compared with the treatment at the ratio of NH4＋/NO3-as 4/1,SOD,POD,CAT and APX activities of the treatment with NH4＋/NO3-as 1/4 were improved by 1.19,1.08,1.18 and 1.11 times,respectively.So with respect to NH4＋-N,the increase of the proportions of NO3——N was more conducive to increase the accumulation of dry matter and water content,improve the activity of intracellular protection enzyme,maintain the stability of PSⅡ system and cell osmotic balance,then enhanced the resistance of Jerusalem artichoke to salt stress.