外源一氧化氮对盐胁迫下高粱种子萌发及淀粉转化的影响

Effects of Exogenous Nitric Oxide on Seed Germination and Starch Transformation of Sorghum Seeds Under Salt Stress

【目的】探讨外源一氧化氮(NO)对盐胁迫下高粱种子萌发过程的生理生化调节作用,为揭示甜高粱种子的萌发生理及其化学调控提供理论依据。【方法】以晋甜08-1为试材,用NaCl浓度(mmol·L-1)为0、50、100、150、200、300和400的溶液培养高粱种子,通过萌发率确定高粱种子萌发期的耐盐适宜浓度、半致死浓度和极限浓度。用0.05、0.1、0.2、0.4、0.6和0.8 mmol·L-1硝普钠(SNP,NO供体)在25℃黑暗条件下浸种12 h,以150 mmol·L-1的NaCl模拟盐胁迫,在培养36 h统计发芽势,72 h统计发芽率,在5 d时取样测定脯氨酸、丙二醛含量及淀粉转化相关指标。采用二硝基水杨酸法测定淀粉酶活性和还原性糖,蒽酮法测定可溶性糖和淀粉含量,茚三酮显色法测定脯氨酸含量,硫代巴比妥酸显色法测定丙二醛含量。通过对高粱种子发芽率、发芽势及种子吸胀、淀粉酶活性、淀粉及糖含量、脯氨酸等指标进行测定分析,研究外源一氧化氮对盐胁迫下高粱种子萌发及淀粉转化的影响。【结果】NaCl胁迫下高粱种子的萌发受到明显抑制,NaCl浓度大于100 mmol·L-1时高粱种子的萌发率显著降低,150 mmol·L-1 NaCl处理时高粱种子的萌发率为63.17%,400 mmol·L-1 NaCl完全抑制高粱种子萌发。0.05 mmol·L-1的SNP处理能够缓解盐胁迫对种子萌发的抑制,种子发芽势、发芽率、发芽指数分别比对照高14.44%、12.22%和18.07%(P<0.05);SNP处理使高粱种子中脯氨酸和可溶性糖含量分别增加18.97%和41.43%,从而降低渗透势,促进种子吸水,缓解NaCl造成的渗透胁迫,丙二醛含量显著降低,较NaCl单独处理降低了17.79%。SNP处理还能迅速提高盐胁迫下种子淀粉酶活性,在处理后第1天时就比NaCl处理提高了17.20%,加速淀粉的降解,显著增加可溶性糖和还原性糖含量。在处理的第5天时,SNP+NaCl处理淀粉含量比NaCl处理降低19.17%,可溶性糖和还原性糖的含量分别提高了41.4%和41.0%,差异显著(P<0.05),这为种子萌发提供能量,提高高粱种子萌发期的抗盐性。【结论】外源NO可调节高粱种子萌发期的淀粉酶活性和渗透调节能力,提高其对盐胁迫的抵抗能力,促进种子的萌发。

【Objective】To discuss the physiological and biochemical regulation of exogenous Nitric Oxide (NO) on thegermination of sorghum seeds under salt stress, which provided a theoretical basis for revealing the germination physiology andchemical regulation of sorghum seeds. 【Method】Sorghum (variety: Jintian 08-1) seeds were cultivated with 0, 50, 100, 150, 200, 300, and 400 mmol·L-1 NaCl solution. According to the germination rate under different concentrations of NaCl, the suitable salttolerance concentration, semi-lethal concentration, and limiting concentration of sorghum seeds at the germination stage weredefined. Sorghum seeds pretreated with 0.05, 0.1, 0.2, 0.4, 0.6 and 0.8 mmol·L-1 sodium nitroprusside (SNP, NO donor) for 12 h at25℃ in dark, then were cultured in salt solution of 150 mmol·L-1 NaCl. The germination potential and germination rate werecounted at cultured 36 h and 72 h, respectively. Proline content, malondialdehyde content and starch transformation related indexeswere determined at cultured 5 days. Dinitrosalicylic acid is used in colorimetric determination of reducing sugars and to analyzeamylase activity by quantitation of enzymatically released reducing sugar. The content of soluble sugar and starch were determinedby anthrone method. Proline content and malondialdehyde (MDA) content were measured by acid-ninhydrin method andthiobarbituric acid method, respectively. The germination rate, germination energy, water absorption capacity of seeds, amylaseactivity, starch and sugar content, proline and other indexes were determined and analyzed to investigate the effects of exogenousNO on sorghum seed germination and starch transformation under salt stress. 【Result】The germination of sorghum seeds wasobviously inhibited by more than 100 mmol·L-1 NaCl. When NaCl concentration was 150 mmol·L-1, the germination rate of sorghumseeds was 63.17%. 400 mmol·L-1 NaCl completely inhibited sorghum seeds germination. Pretreatment with SNP greatly relieves theinhibitory effect of the following salt stress to sorghum seeds germination, especially during the early stage of germination (36 h).0.05 mmol·L-1 SNP alleviated the inhibition of salt stress on seed germination, seed germination potential, germination rate andgermination index were 14.44%, 12.22% and 18.07% higher than those of the control, respectively (P<0.05). SNP increased thecontent of proline and soluble sugar in sorghum seeds by 18.97% and 41.43% respectively, which reduced osmotic potential,promoted water absorption and alleviated osmotic stress caused by NaCl. At the same time, the content of MDA decreased by17.79% compared with NaCl treatment alone. Further investigations showed that pretreatment with NO donor dramaticallystimulated the activities of amylase under salt stress by 17.20% compared with NaCl on the first day after treatment, and acceleratedthe degradation of starch, increased the content of reducing sugar. By the 5th day of SNP+NaCl treatment, the starch contentdecreased by 19.17%, and the content of soluble sugar and reducing sugar increased by 41.4% and 41.0%, respectively, compared toNaCl treatment. These newly produced substances provided energy for seed germination, and improved the salt resistance ofsorghum seeds during germination period. 【Conclusion】According to our results, exogenous NO could regulate the amylase activityand osmotic regulation ability of sorghum seeds during germination period, improved their resistance to salt stress, and promotedseed germination.