Abstract: 【Objective】 To study the effects of salt stress on the growth, photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of pepper seedlings under the same amount of different nitrogen form culture conditions. 【Method】 Nutrient solution culture was adopted and 6 treatments were set: nitrate nitrogen (A1), ammonium nitrogen (A2), organic nitrogen (A3), nitrate nitrogen + 100 mmol/L NaCl (A1T), ammonium nitrogen + 100 mmol/L NaCl (A2T), organic nitrogen + 100 mmol/L NaCl (A3T), and the growth index, root-crown ratio, photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of 3d pepper seedlings were measured after salt stress. 【Result】 The results showed that Photosynthetic gas exchange parameters (Pn, Gs, Ci, Tr) of pepper seedlings treated with nitrate and ammonium nitrogen were significantly decreased under NaCl stress,and in addition, the significant increase of stomatal limit value (Ls) indicated that stomatal limit was the main reason for the decrease of photosynthetic rate. The significant increase of F0 and qP indicated that the stability of PS II may be damaged. However, the photosynthetic activity of pepper seedlings treated with nitrate nitrogen increased by increasing the proportion of oxidized QA in PSII reaction center, and finally increased the seedling index and root-shoot ratio of pepper seedlings by 47.21% and 22.68% respectively. Although the oxygen complexes (OEC) activity was enhanced treated with ammonium nitrogen, the decrease of its ability to dissipate excess light energy leads to the decrease of self-protection ability, which led to a significant decrease in the actual photochemical efficiency (φ PS II). Finally, the seedling index decreased by 17.58%.Pn and Ls increased significantly and C i decreased significantly in pepper seedlings treated with organic nitrogen, which indicated that pepper seedlings could reduce leaf transpiration and increase leaf water use efficiency, so that leaves could maintain higher carboxylation efficiency, thus increasing the net photosynthetic rate, but its Fm and NPQ increased significantly, F0 and ΦPSⅡ and qP reduced significantly, indicating that although the OEC activity was enhanced in PSⅡ, the proportion of the oxidation QA decreased, coupled with excessive light energy dissipation the blade assimilatory power was reduced. However, the increase of strong seedling index and root-crown ratio combined with the test results before salt stress indicated that single organic nitrogen supply poisoned pepper seedlings.【Conclusion】 To sum up, after salt stress by nitrate nitrogen treatment, the photosynthetic activity and photosynthetic rate of pepper seedlings leaf PSⅡ were still maintained, and the seedling index and root-crown ratio were increased. The results showed that nitrate nitrogen could be used as a source of nitrogen for pepper planting in greenhouse under salt stress

Key words: pepper seedling; NaCl stress; N form; photosynthetic rate; chlorophyll fluorescence
 ;  ;  

摘要： 【目的】在等量不同氮素形态培养条件下,研究盐胁迫对辣椒幼苗生长、光合气体交换参数及叶绿素荧光参数的影响差异。【方法】采用营养液培养,设置6个处理:硝态氮(A1)、铵态氮(A2)、有机态氮(A3)、硝态氮+ 100 mmol/L NaCl 胁迫(A1T)、铵态氮+ 100 mmol/L NaCl 胁迫(A2T)、有机态氮+ 100 mmol/L NaCl 胁迫(A3T),测定盐胁迫后3 d辣椒幼苗的壮苗指数、根冠比、光合气体交换参数和叶绿素荧光参数的变化。【结果】NaCl 胁迫下硝态氮和铵态氮处理辣椒幼苗的光合气体交换参数(Pn、Gs、Ci、Tr)均显著下降,气孔限制值(Ls)显著增加,二者光合速率下降的主要原因是气孔限制。F0和qP的显著增加说明光系统Ⅱ稳定性可能遭到破坏,但硝态氮处理的辣椒幼苗叶片能够通过增加PSⅡ反应中心氧化态QA 的比例使光合活性增加,最终增加了辣椒幼苗的壮苗指数47.21%和根冠比22.68%。铵态氮处理虽然能够增强放氧复合体(OEC)活性,但其耗散过剩光能的能力降低导致自我保护能力下降,从而导致实际光化学效率(ΦPSⅡ)显著降低,最终导致壮苗指数显著降低17.58%。有机态氮处理辣椒幼苗Pn和Ls显著增加,Ci显著降低,说明辣椒幼苗能够减少叶片蒸腾增加叶片水分利用率,使叶片保持较高的羧化效率,进而增加了辣椒幼苗叶片的净光合速率,但其Fm和NPQ显著增加、F0、ΦPSⅡ和qP显著降低,PSⅡ反应中心虽放氧复合体活性增强,但氧化态QA的比例减小,加上光能的过度耗散使叶片同化力降低,但其壮苗指数和根冠比的增加结合盐胁迫前试验结果则说明单一有机态氮供应使辣椒幼苗受到毒害。【结论】硝态氮处理盐胁迫后,辣椒幼苗叶片光系统Ⅱ仍可维持较高的光合活性,保持较高的光合速率,使壮苗指数和根冠比增加。硝态氮可以作为温室内盐胁迫土壤种植辣椒的供应氮源。

关键词: 辣椒幼苗, NaCl 胁迫, 氮素形态, 光合速率, 叶绿素荧光