Abstract:

【Objective】 To explore the effects of salt, alkali and complex salt alkali stress on the photosynthetic characteristics and antioxidant enzyme activity of tomato seedlings.【Methods】 In this study, the salt-tolerant tomato IL7-5-5 and the salt-sensitive tomato M82 were selected as materials, and the seedlings were subjected to the same concentration of salt, alkali and complex salt alkali stress. The photosynthetic characteristics, contents of MDA, ${\text{O}}_2^{-}$, H₂O₂ and activities of SOD, POD, CAT, APX and GR of tomato seedlings under different stress conditions were studied.【Results】 The results showed that: Compared with the control, under salt stress, photosynthetic gas exchange parameters of M82 tomato seedlings significantly decreased, Pn decreased by 48.10%, WUE increased by 95.81%, POD and CAT activities significantly decreased, and GR activity significantly increased. The contents of ${\text{O}}_2^{-}$ and H₂O₂ were significantly reduced by 15.75% and 25.85%. Leaf Pn, Ci and WUE of IL7-5-5 varieties were significantly decreased by 34.72%, 32.78% and 51.02%, respectively. SOD activity was significantly increased, GR activity was significantly increased, CAT and APX activities were significantly decreased. The contents of MDA, ${\text{O}}_2^{-}$ and H₂O₂ were significantly reduced by 29.48%, 34.47% and 18.66%. Under alkali stress, photosynthetic gas exchange parameters Pn, Gs, Tr and CE of M82 tomato seedlings significantly decreased by 56.40%, 71.02%, 61.93% and 41.73%, Ci significantly decreased by 25.49%, POD and CAT activities significantly increased, and APX activities significantly decreased. MDA content was significantly increased by 40.55%, while ${\text{O}}_2^{-}$ and H₂O₂ contents were significantly decreased by 25.80% and 20.48%. Photosynthetic gas exchange parameters Pn, Gs and Ci of IL7-5-5 tomato seedlings significantly decreased by 68.75%, 74.65% and 59.49%, Tr and CE significantly decreased by 63.69% and 21.54%, SOD activity significantly increased, CAT and GR activities significantly decreased. The production rate of ${\text{O}}_2^{-}$ decreased by 10.18%. Under salt-alkali stress, photosynthetic gas exchange parameters Pn, Gs, Ci, Tr and CE of M82 tomato seedlings significantly decreased by 44.64%, 67.05%, 37.46%, 56.56% and 11.58%, POD activity significantly decreased, APX activity significantly decreased, ${\text{O}}_2^{-}$ significantly decreased by 34.06%. MDA content was significantly increased by 37.44%; Photosynthetic gas exchange parameters Pn and Gs of IL7-5-5 tomato seedlings significantly decreased by 27.78% and 78.87%, Tr significantly decreased by 69.05%, WUE significantly increased by 128.17%, GR and SOD activity significantly increased, and ${\text{O}}_2^{-}$ production rate significantly decreased by 25.30%.【Conclusion】 Both tomato varieties can achieve the effect of eliminating ${\text{O}}_2^{-}$ and H₂O₂ by adjusting the activity of antioxidant enzymes. The content of MDA of IL7-5-5 tomato seedlings is maintained at the control level, and the degree of membrane lipid peroxidation is lighter than that of M82 tomato varieties. Under the three stress conditions, the photosynthetic rate of tomato seedlings decrease, and the alkali stress is the lowest in both varieties. Both alkali and saline-alkali stress causes membrane lipid peroxidation damage to M82 tomato seedlings to a certain extent. Stress can regulate the activity of antioxidant enzymes and the contents of ${\text{O}}_2^{-}$ and H₂O₂ in the leaves of the two tomato varieties to different degrees. The contents of H₂O₂ are the lowest in both tomato varieties under salt stress, followed by alkali stress and saline-alkali stress.

Key words: tomato; salt stress; alkali stress; compound saline-alkali stress; photosynthetic characteristics; enzyme activity

摘要：

【目的】研究盐、碱及复合盐碱胁迫对番茄幼苗光合特性及抗氧化酶活性的影响。【方法】以前期筛选的耐盐渐渗系番茄品种IL7-5-5及盐敏感栽培番茄品种M82为材料,通过对幼苗进行相同浓度的盐、碱及复合盐碱胁迫处理,研究不同胁迫条件下番茄幼苗光合特性、MDA、${\text{O}}_2^{-}$、H₂O₂含量以及SOD、POD、CAT、APX、GR活性的影响。【结果】与对照相比,盐胁迫条件下,番茄品种M82幼苗叶片光合气体交换参数显著降低,Pn降低了48.10%,WUE极显著增加了95.81%,POD和CAT活性极显著降低,GR活性显著增加,从而使${\text{O}}_2^{-}$和H₂O₂含量极显著降低了15.75%、25.85%;IL7-5-5番茄品种幼苗叶片Pn、Ci、WUE极显著降低,分别降低了34.72%、32.78%、51.02%,SOD活性极显著增加,GR活性显著增加,CAT和APX活性极显著降低,使MDA、${\text{O}}_2^{-}$和H₂O₂含量极显著降低了29.48%、34.47%和18.66%。碱胁迫条件下,番茄品种M82幼苗叶片光合气体交换参数Pn、Gs、Tr、CE极显著降低56.40%、71.02%、61.93%和41.73%,Ci显著降低了25.49%,POD和CAT活性极显著增加,APX活性极显著降低,使MDA含量极显著增加了40.55%,${\text{O}}_2^{-}$和H₂O₂含量极显著降低了25.80%、20.48%;番茄品种IL7-5-5幼苗叶片光合气体交换参数Pn、Gs和Ci极显著降低68.75%、74.65%和59.49%,Tr、CE显著降低63.69%、21.54%,SOD活性极显著增加,CAT和GR活性极显著降低,使${\text{O}}_2^{-}$产生速率显著下降10.18%。盐碱胁迫条件下,番茄品种M82幼苗叶片光合气体交换参数Pn、Gs、Ci、Tr和CE极显著下降44.64%、67.05%、37.46%、56.56%和11.58%,POD活性极显著下降,APX活性显著下降,使${\text{O}}_2^{-}$极显著下降34.06%,MDA含量极显著增加37.44%;番茄品种IL7-5-5幼苗叶片光合气体交换参数Pn、Gs极显著下降27.78%、78.87%,Tr显著下降69.05%,WUE极显著增加128.17%,GR和SOD活性极显著增加,使${\text{O}}_2^{-}$产生速率极显著下降25.30%。【结论】2个番茄品种均能够通过调节抗氧化酶活性,达到清除${\text{O}}_2^{-}$和H₂O₂的效果,番茄品种IL7-5-5幼苗能够维持MDA含量在对照水平,比番茄品种M82膜脂过氧化程度轻。3种胁迫条件下,番茄幼苗的光合速率下降,2个番茄品种均以碱胁迫最低;碱胁迫和盐碱胁迫均对番茄品种M82幼苗造成了一定程度的膜脂过氧化损伤;胁迫不同程度的调节了2个番茄品种幼苗叶片抗氧化酶的活性、${\text{O}}_2^{-}$和H₂O₂的含量,其中2个番茄品种均以盐胁迫条件下H₂O₂的含量最低,其次是碱胁迫、盐碱胁迫。

关键词: 番茄, 盐胁迫, 碱胁迫, 复合盐碱胁迫, 光合特性, 酶活性