中文摘要：

通过对烟草幼苗喷施不同浓度的CaCl2、赤霉素（GA3）、水杨酸（SA）和多效唑（PP333）进行预处理,比较分析4种化学调控剂处理对10℃低温胁迫下烟草幼苗耐冷性及其光合生理特性的影响。结果表明：（1）与喷施蒸馏水对照相比,4种化学调控剂预处理均可提高烟草幼苗的干物质积累量、根系活力、脯氨酸含量及光合效率,降低丙二醛（MDA）含量,总体上提高了烟草幼苗素质。（2）在10℃低温胁迫下,4种化学调控剂预处理可使烟草幼苗保持比对照更高的单株干重、相对生长速率、干物质积累速率、根系活力、脯氨酸含量、叶绿素含量、净光合速率、胞间CO2浓度、气孔导度和蒸腾速率,并减缓了低温诱导的MDA积累和相应的膜脂过氧化作用,最终提高烟草幼苗的耐冷性。（3）4种化学调控剂处理提高烟草幼苗耐冷性的程度不同,在该研究中以SA综合效果最好。

英文摘要：

By spraying different concentration of CaCl2,gibberellin（GA3）,salicylic acid（SA）and paclobutrazol（PP333）,we studied and compared the effects of the pretreatments with four chemical regulators on chilling tolerance and photosynthetic characteristics in tobacco（Nicotiana tabacum L.）seedlings.The results showed that：（1）As compared with the control spraying distilled water,the pretreated seedlings with the four chemical regulators generally had higher dry weight,root vigor,proline content and net photosynthetic rate,and lower malondialdehyde（MDA）content,which totally enhanced the quality of tobacco seedlings.（2）When transferred to chilling stress at 10 ℃ for 20 d,as compared with the control,the pretreated seedlings with the four chemical regulators could maintain higher dry weight,relative growth rate,dry matter accumulation rate,root vigor,proline and chlorophyll content,net photosynthetic rate,intercellular CO2 concentration,stomatal conductance and transpiration rate,reduced MDA content and lipid perioxidation,which finally enhanced chilling tolerance of the tobacco seedlings.（3）The pretreatments with thefour chemical regulators all could increase chilling tolerance in tobacco seedlings to different contents,in general,SA pretreatment displayed the best effect.