烤烟伸根期对低温胁迫的生理响应

【目的】研究低温胁迫对伸根期的烤烟生理特性的影响。【方法】采用盆栽方式，在人工培养箱中对耐冷性不同的烤烟品种红花大金元（低温不敏感型）和K326（低温敏感型）进行低温胁迫处理，研究不同低温胁迫时间烤烟的渗透调节物质、保护酶活性、多酚代谢、光合速率和光合色素等的变化情况，筛选出适用于烤烟耐冷性鉴定的指标。【结果】随低温胁迫时间的延长，烤烟的净光合速率和叶绿素耐冷系数呈下降趋势，下降速率与低温胁迫程度呈正相关，与品种的耐低温能力呈负相关；丙二醛和相对电导率耐冷系数在低温胁迫的前3 d随胁迫时间的延长呈上升趋势，上升速率与品种耐低温能力呈负相关；过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、多酚氧化酶（PPO）和苯丙氨酸解氨酶（PAL）活性和可溶性蛋白、可溶性糖及总酚耐冷系数随低温胁迫时间的延长先升高后下降，低温不敏感型材料上升速度高于低温敏感型材料。相关分析表明，低温胁迫下，烟叶相对电导率耐冷系数与叶绿素、净光合速率、SOD活性的耐冷系数呈极显著负相关，与可溶性蛋白、POD活性、PAL活性的耐冷系数呈显著负相关，与丙二醛、叶绿素a/b的耐冷系数呈显著正相关。主成分分...

Physiological responses of flue-cured tobacco to low temperature stress at root-extending stage

  Objective  This study aims to study the effect of low temperature stress on physiological characteristics of tobacco during root extension stage.  Methods  The changes of associated physiological indicators including osmotic regulators, protective enzyme activities, polyphenol metabolism and photosynthesis of tobacco were studied using two different cold resistance tobacco varieties (Honghuadajinyuan with high cold resistance and K326 with low cold resistance) at root extension stage under low temperature stress in artificial incubator. On this basis, the suitable indexes for the identification of cold tolerance of flue-cured tobacco were screened.  Results  With the extension of low temperature stress time, the cold tolerance coefficient of the net photosynthetic rate and chlorophyll (a+b) of tobacco leaves showed a downward trend, and the downward rate was positively correlated with the degree of low temperature stress and negatively correlated with the cold resistance of varieties. The cold tolerance coefficient of malondialdehyde and relative conductivity were increased with the extension of low temperature stress time in the first 3 d, and the rising rate was negative correlated with the cold resistance of varieties. The cold tolerance coefficients of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), phenylalnine ammonialyase (PAL) and the soluble protein, soluble sugar and total phenol increased first and then decreased with the extension of low temperature stress time, and the rising speed of cold insensitive variety was higher than that of cold sensitive variety. Correlation analysis showed that the cold tolerance coefficient of relative conductivity was in extremely significant negative correlation with chlorophyll (a+b), net photosynthetic rate and SOD activity, in significant negative correlation with soluble protein, POD activity, PAL activity, and in significant positive correlation with malondialdehyde and chlorophyll a/b under low temperature stress. Principal component analysis showed that the first principal components determining the cold tolerance of tobacco mainly included the cold tolerance coefficient of relative conductivity, malondialdehyde, soluble sugar, soluble protein, chlorophyll (a+b), chlorophyll a/b, SOD activity, POD activity, total phenol and net photosynthetic rate. The second principal components mainly included the cold tolerance coefficient of the activity of CAT, PPO and PAL.  Conclusion  The cold tolerance coefficient of leaf relative conductivity, chlorophyll (a+b), net photosynthetic rate and SOD activity can be used as the basis for screening cold tolerant tobacco germplasm under continuous low temperature stress. The cold tolerance coefficient of osmotic adjustment factors, antioxidant factors and photosynthetic factors can be used as the main screen indexes, and the cold tolerance coefficient of polyphenol metabolism factors can be used as the secondary screen indexes in the evaluation of tobacco cold tolerance.