外源硝态氮对高铵胁迫下小麦幼苗生长的影响

为明确外源硝态氮对高铵胁迫下小麦幼苗生长的影响及其生化机理,采用温室水培的方式,以豫麦49(耐高铵品种)和鲁麦15(高铵敏感型品种)为材料,研究了外源硝态氮对高铵胁迫下小麦幼苗形态、激素含量和抗氧化系统的影响。结果表明,高铵胁迫条件下,外源硝态氮显著增加两个小麦品种株高、根长、干重,其中鲁麦15的地上部干重增加量高于豫麦49,而根系干重增加量则表现为豫麦49高于鲁麦15。高铵胁迫下,两个小麦品种植株的IAA、CTK含量、IAA/CTK显著低于对照;外源硝态氮处理5 d后,豫麦49地上部和根系IAA含量、根系CTK含量显著增加,恢复至对照水平;鲁麦15植株虽亦表现显著增加,但仍低于对照。另外,外源硝态氮对高铵胁迫下两个小麦品种地上部和根系的O■释放速率、SOD和POD活性及MDA含量没有显著影响。综上,外源硝态氮缓解小麦幼苗生长高铵胁迫的原因可能是通过增加IAA和CTK合成和转运,影响IAA和CTK之间的平衡,进而达到缓解效果。品种间比较,耐铵型品种豫麦49缓解作用可能源于对地上部和根系IAA含量以及根系CTK含量的协同调控;而高铵敏感型品种鲁麦15的缓解作用可能主要源于对地上部IAA含量的调控。

Effect of Exogenous Substances on Seed Germination and SeedlingGrowth under Elevated Ammonium Stress in Wheat

To elucidate effects of exogenous nitrate(NO^-₃) on seedling growth under elevated ammonium stress in wheat,two cultivars,Yumai 49(NH⁺₄- tolerant) and Lumai 15(NH⁺₄- sensitive) were treated with 5.0 mmol·L^-1 NH⁺₄- N(LEAN) or 5.0 mmol·L^-1 NO^-₃- N(CON) under hydroponic condition. The results showed that exogenous NO^-₃ increased shoot and root length,and plant biomass of both cultivars at the EAN-fed seedling growth stage. Yumai 49 had the greater change in root growth than Lumai 15,while for the changes in shoot growth,the opposite was true for the two cultivars. Furthermore,the content of IAA,CTK and IAA/CTK in the EAN-fed plants were lower than those in CON treatment. Exogenous NO^-₃ treatment(LEAN+R) increased the level of those traits in EAN-fed plants of both cultivars,and the IAA content in shoot and root, and CTK content in LEAN+R -treated root of Yumai 49 were recovered to the level in CON,while the increased in Lumai 15 in the LEAN+R treatment was lower than the level in CON. Further,there was no significant differences on content of O^·₂ production rate,SOD and POD activities,and MDA content between exogenous NO^-₃ treatment(LEAN+R) and LEAN. In summary,exogenous NO^-₃ has positive effects on increasing hormones synthesis and transport to recover the negative effects of LEAN on seedling growth. Yumai 49,being an ammonium tolerant cultivar,maintain higher level of IAA and CTK,resulting into better root growth performance than those in Lumai 15,while Lumai 15,being an ammonium sensitive cultivar maintain higher level of IAA,leading to a better shoot growth performance than that in Yumai 49.