Singh Madhulika, Singh Vijay Pratap, Prasad Sheo Mohan
Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Allahabad, 211002, India.
Plant Physiol Biochem. 2016 Dec;109:72-83. doi: 10.1016/j.plaphy.2016.08.021. Epub 2016 Aug 31.
In the present study, effect of different levels of nitrogen (N, deprived; N, sub-optimum; N, optimum and N, supra-optimum) in Solanum lycopersicum L. seedlings under NaCl (NaCl, 0.3 g kg sand and NaCl, 0.5 g kgsand) stress was investigated. Biomass accumulation, pigments, K concentration, nitrate and nitrite contents were declined by NaCl in dose dependent manner. As compared to control (N without NaCl), fresh weight declined by 4% and 11%, and dry weight by 7 and 13% when seedlings were grown under N+NaCl and N+NaCl combinations, respectively. Furthermore, fluorescence parameters (JIP-test): the size and number of active reaction centres of photosynthetic apparatus (F/F), efficiency of water splitting complex (F/F), quantum yield of primary photochemistry (φP or Phi_P), yield of electron transport per trapped excitation (Ψ or Psi_0), the quantum yield of electron transport (φE), and performance index of PS II (PI) and parameters related to energy fluxes per reaction centre (ABS/RC, TR/RC, ET/RC and DI/RC) were also affected by NaCl. However, toxic effect of NaCl on photosystem II photochemistry was ameliorated by N. The lower dose (NaCl) of NaCl exerts damaging effect on oxidation side of PS II, while higher dose (NaCl) damages PS II reaction centre and its reduction side. Moreover, control seedlings (N without NaCl) when exposed to NaCl and NaCl exhibited a significant enhancement in respiration rate by 6 and 16%, Na accumulation by 111 and 169% in shoot, and 141 and 223% in root and ammonium contents by 19 and 34% respectively. Nitrate and ammonium assimilating enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase (GOGAT) were adversely affected by NaCl stress while glutamate dehydrogenase (GDH) showed reverse trend. N addition caused further enhancement in free proline, and activity of Δ-pyrroline-5-carboxylate synthetase (P5CS), while activity of proline dehydrogenase (ProDH) decreased. The results indicate that different levels of N significantly modulated NaCl-induced damaging effects in tomato seedlings. Furthermore, the results suggest that after N addition Na, nitrite, nitrate, ammonium contents, nitrogen metabolic enzymes, proline content, and activity of P5CS are favourably regulated, which might be associated with mitigation of NaCl stress and effect was more pronounced with supra-optimum level of N (N).
在本研究中，研究了氯化钠（0.3 g/kg沙和0.5 g/kg沙）胁迫下不同氮水平（缺氮、次适氮、适氮和超适氮）对番茄幼苗的影响。氯化钠使生物量积累、色素、钾浓度、硝酸盐和亚硝酸盐含量呈剂量依赖性下降。与对照（不添加氯化钠的氮处理）相比，在氮+氯化钠和氮+氯化钠组合条件下生长的幼苗，鲜重分别下降了4%和11%，干重分别下降了7%和13%。此外，荧光参数（JIP测试）：光合机构活性反应中心的大小和数量（F/F）、水裂解复合物的效率（F/F）、初级光化学量子产率（φP或Phi_P）、每捕获一个激发能的电子传递产率（Ψ或Psi_0）、电子传递量子产率（φE）、PS II性能指数（PI）以及与每个反应中心能量通量相关的参数（ABS/RC、TR/RC、ET/RC和DI/RC）也受到氯化钠的影响。然而，氮缓解了氯化钠对光系统II光化学的毒性作用。较低剂量（氯化钠）的氯化钠对PS II的氧化侧产生破坏作用，而较高剂量（氯化钠）则损害PS II反应中心及其还原侧。此外，对照幼苗（不添加氯化钠的氮处理）在暴露于氯化钠和氯化钠时，呼吸速率分别显著提高了6%和16%，地上部钠积累分别增加了111%和169%，根部增加了141%和223%，铵含量分别增加了19%和34%。硝酸盐和铵同化酶如硝酸还原酶（NR）、亚硝酸还原酶（NiR）、谷氨酰胺合成酶（GS）和谷氨酸合酶（GOGAT）受到氯化钠胁迫的不利影响，而谷氨酸脱氢酶（GDH）则呈现相反趋势。添加氮导致游离脯氨酸以及Δ-吡咯啉-5-羧酸合成酶（P5CS）活性进一步增加，而脯氨酸脱氢酶（ProDH）活性降低。结果表明，不同水平的氮显著调节了氯化钠对番茄幼苗的损害作用。此外，结果表明添加氮后，钠、亚硝酸盐、硝酸盐、铵含量、氮代谢酶、脯氨酸含量以及P5CS活性得到了有利调节，这可能与缓解氯化钠胁迫有关，且超适氮水平（N）的效果更显著。
