外源褪黑素对烟草苗期低温胁迫的缓解作用研究OA

[Objective]To investigate the effects of exogenous melatonin spraying on the growth of tobacco seedlings under low-temperature stress and to analyze the physiological and molecular mechanisms underlying their cold adaptation.[Methods]Using the tobacco cultivar K326 as the experimental material,five treatment groups were set up:normal temperature+foliar spraying of distilled water(CK1,normal temperature control),8℃ low-temperature stress+foliar spraying of distilled water(CK2,low-temperature stress control),8℃ low-temperature stress+foliar spraying of 50 pmol/L melatonin solution(T1),8℃ low-temperature stress+foliar spraying of 100 pmol/L melatonin solution(T2),and 8℃ low-temperature stress+foliar spraying of 200 μmol/L melatonin solution(T3).The agronomic traits of tobacco seedlings under different treatments were compared.Stress physiological indicators were measured,and transcriptome sequencing was conducted on tobacco seedlings from CK1,CK2,and T2 treatments to explore the key metabolic pathways and core genes involved in exogenous melatonin alleviating low-temperature stress in tobacco seedlings.qRT-PCR technology was used for verification.[Results]Low-temperature stress(CK2)significantly inhibited the growth of tobacco seedlings,leading to a substantial decrease in agronomic indicators such as plant height and root length.Spraying exogenous melatonin alleviated the inhibitory effect of low-temperature stress on tobacco seedling growth,with the T2 treatment showing the best results.Compared with CK2,plant height,root length,maximum leaf area,above-ground fresh weight,underground fresh weight,above-ground dry weight,and underground dry weight of tobacco seedlings under T2 treatment increased by 45.78％,60.68％,83.97％,106.25％,68.09％,123.08％,and 125.00％,respectively.Additionally,indicators such as plant height and above-ground fresh weight in T2-treated seedlings showed no significant difference from CK1.At the physiological stress level,the activities of superoxide dismutase and catalase in T2-treated seedlings were significantly higher than in CK2-treated seedlings,increasing by 61.62％and 87.35％,respectively.The malondialdehyde content was significantly reduced by 53.1％.Chlorophyll content and photosynthetic parameters were close to those of CK1.Meanwhile,by optimizing the osmotic adjustment mode,soluble sugars became the main osmotic regulators.Transcriptome sequencing analysis revealed 6,035 differentially expressed genes(DEGs)between the T2 and CK2 treatments,11,440 DEGs between CK2 and CK1,and 6,623 DEGs between T2 and CK1.Among them,DEGs related to exogenous melatonin alleviating low-temperature stress in tobacco seedlings were mainly enriched in the Calvin cycle carbon fixation pathway,with core genes like ppc,MDH1/2,FBP,and GAPDH up-regulated.Correlation analysis showed that genes such as GPT were significantly correlated with tobacco seedling growth indicators,photosynthetic characteristics,and stress-resistance physiological indicators.qRT-PCR verification confirmed the reliability of the transcriptome data[Conclusion]Exogenous melatonin can alleviate the damage caused by low-temperature stress to tobacco seedlings by activating the Calvin cycle carbon fixation pathway,strengthening the antioxidant defense system,optimizing osmotic adjustment,and protecting photosynthetic performance.The optimal application concentration is 100 μmol/L.