喷施外源EBR和H2O2对低温胁迫烟苗恢复生长期生理特性的影响

  目的  探讨表油菜素内酯（EBR）和过氧化氢（H₂O₂）对低温胁迫后烟草幼苗生理和生长特性的影响。  方法  以烤烟品种K326为材料，研究低温胁迫后喷施外源表油菜素内酯（EBR，0.01 mg/L）和过氧化氢（H₂O₂，340 mg/L）对烤烟苗期抗氧化酶（SOD、POD、CAT）活性、渗透调节物质、丙二醛（MDA）和生物量的影响。  结果  （1）烟草苗期低温胁迫（CK1）4 d与正常生长（CK2）烟株相比SOD活性降低，POD、CAT活性升高，MDA、可溶性糖和脯氨酸含量上升，可溶性蛋白含量下降，生物量降低；（2）低温胁迫结束后，喷施外源EBR（T1）和H₂O₂（T2）相比低温对照（CK1），恢复生长12 d烟苗SOD、POD、CAT活性分别提高61.87%和47.37%、239.06%和193.11%、168.07%和139.63%，MDA含量分别降低60.00%和50.00%，渗透调节物质含量和生物量显著增加；（3）喷施外源EBR（T1）和H₂O₂（T2）与正常生长（CK2）烟株相比，在恢复生长8 d和12 d时SOD、POD、CAT活性与可溶性糖含量无显著差异，MDA含量降低，脯氨酸含量显著上升。  结论  喷施外源EBR（0.01 mg/L）和H₂O₂（340 mg/L）能加快低温胁迫后烤烟K326幼苗的生理和生长恢复进程。 

Effects of spraying exogenous EBR and H2O2 on the physiological characteristics of tobacco seedlings in the recovery period under low temperature stress

  Objective  This study aims to explore the effects of epibrassinolide and hydrogen peroxide on physiological and growth characteristics of tobacco seedlings under low temperature stress.  Methods  Using flue-cured tobacco variety K326 as material, the effects of exogenous epibrassinolide (EBR, 0.01 mg/L) and hydrogen peroxide (H₂O₂, 340 mg/L) on antioxidant enzymes activity (SOD, POD, CAT), osmotic regulation substances, malondialdehyde (MDA) and biomass of flue-cured tobacco at seedling stage were studied.  Results  (1) Compared with normal growth (CK2), SOD activity decreased, POD and CAT activity increased, MDA, soluble sugar and proline content increased, soluble protein content decreased, and biomass decreased in tobacco seedlings under low temperature stress (CK1) at 4 d. (2) After the end of low temperature stress, the SOD, POD and CAT activities of tobacco seedlings sprayed with exogenous EBR (T1) and H₂O₂ (T2) increased by 61.87% and 47.37%, 239.06% and 193.11%, 168.07% and 139.63%, respectively as compared with the control (CK1). MDA content decreased by 60.00% and 50.00%, respectively, while osmoregulation substances contents and biomass increased significantly. (3) Compared with normal growth (CK2), the tobacco plants sprayed with exogenous EBR (T1) and H₂O₂ (T2) had no significant differences in SOD, POD, CAT activity and soluble sugar content at 8 days and 12 days after resuming growth, but exhibited decreased MDA content and significantly increased proline content.  Conclusion  Spraying exogenous EBR (0.01 mg/L) and H₂O₂ (340 mg/L) can accelerate the physiological and growth recovery process of flue-cured tobacco K326 seedlings under low temperature stress.