Abstract: Aiming at the situation of frequent drought in late spring and early summer in southwest areas, this paper adopted the method of rain proof drought shed installation and carried out a pool-culture experiment with same irrigation quota but different irrigation times, taking Honghuadajinyuan (Hongda) with strong drought resistance and Yunyan 87 (Yun 87) with weak drought resistance as materials. The paper also analyzed the effects of different drought stress on tobacco characteristics, such as expression of drought resistant gene, physiological-biochemical traits of drought resistance, pigment content of tobacco leaf, photosynthetic of tobacco leaf, etc.. The results showed that chlorophyll a, chlorophyll b, chlorophyll a+b, chlorophyll a/b, carotenoid, leaf water content, transpiration rate, stomatal conductance and net photosynthetic rate tended to decrease under drought stress. And intercellular carbon dioxide concentration, proline, superoxide dismutase activity, soluble sugar, malondialdehyde content, and relative expressions of NtSOD, NtPOD, NtCAT, NtP5CS, NtLEA5, NtNCED1 tended to increase under drought stress. Membrane lipids of chloroplast was effected and photosynthetic pigment content of tobacco leaf was decreased under drought stress at root extending stage, which lead to net photosynthetic rate decreased by non-stomatal factors. The effects of drought stress on tobacco growth and development at root extending stage were mitigated by osmotic adjustment and free oxygen removal. The relative expressions of NtP5CS, NtLEA5, NtNCED1, which regulated ABA and proline, were up-regulated under drought stress by raising proline content in tobacco leaf, and decreasing vacuole osmotic potential and leaf water loss. Meanwhile, the relative expressions of NtP5CS, NtLEA5, NtNCED1 were up-regulated under drought stress by strengthening activities of antioxidant enzymes, and removing free oxygen produced by drought stress. Three major components were obtained by principal component analysis. The cumulative contribution rate reached 91.3%, of which proline, superoxide dismutase activity, soluble sugar, NtSOD, NtPOD, NtCAT, NtP5CS and NtLEA5 were divided into the first major component; chlorophyll a, chlorophyll b, chlorophyll a+b, chlorophyll a/b and carotenoid were divided into the second major component; Net photosynthetic rate and leaf water content were divided into the third major component. The major component of drought resistance in Hongda gained 4.608 score, which was 40.08% higher than that of Yun 87. These indicators could be used as the principal indicators to identify the drought resistance of tobacco at root extending stage when breeding drought-tolerant tobacco varieties. The second major component including photosynthetic pigment index and third major component including net photosynthetic rate and leaf water content could be used as the secondary indicators.

Key words: tobacco, root extending stage, drought stress, physiological characteristics, drought resistance

摘要： 针对西南地区春末夏初干旱频发的现状，以抗旱性不同的烤烟品种红花大金元（红大，抗旱性强）和云烟87（云87，抗旱性弱）为材料，采用防雨旱棚池栽的方式，对烤烟伸根期进行相同灌溉定额不同灌溉时间处理，分析不同干旱胁迫对烤烟抗逆基因表达、抗旱生理生化、烟叶色素含量、烟叶光合特征等的影响。结果表明：受干旱胁迫影响，烤烟叶绿素a、叶绿素b、叶绿素a+b、叶绿素a/b、类胡萝卜素、叶片含水量、蒸腾速率、气孔导度和净光合速率均呈下降趋势，SOD活性、胞间CO2浓度、脯氨酸含量、可溶性糖含量、丙二醛含量与NtSOD、NtPOD、NtCAT、NtP5CS、NtLEA5、NtNCED1相对表达量呈上升趋势。烤烟伸根期干旱胁迫破坏叶绿体脂膜结构，降低烟叶光合色素含量，进而由非气孔因素限制导致烤烟净光合速率下降。烤烟通过渗透调节和自由氧清除两种方式减缓干旱胁迫对烤烟伸根期生长发育的影响。干旱胁迫下NtP5CS、NtLEA5和NtNCED1等控制ABA、脯氨酸合成的基因上调表达，增加烟叶脯氨酸含量，降低液泡渗透势，减少烟叶失水。同时干旱胁迫使NtSOD、NtPOD、NtCAT基因上调表达，增强抗氧化酶活性，消除烤烟体内因干旱胁迫产生的自由氧。主成分分析得到三个主成分，累计贡献率达到91.3%，其中脯氨酸、SOD活性、可溶性糖、NtSOD、NtPOD、NtCAT、NtP5CS和NtLEA5被划分为第一主成分，叶绿素a、叶绿素b、叶绿素a+b、叶绿素a/b和类胡萝卜素被划分为第二主成分，净光合速率和叶片含水量被划分为第三主成分。红大抗旱性主成分得分4.608，比云87高40.8%。第一主成分“烤烟抗旱生理生化与基因表达因子”的变化与烤烟品种抗旱性密切相关，在烤烟抗旱育种时可作为烤烟伸根期抗旱性鉴定的主要鉴选指标，第二主成分“烟叶光合色素因子”和第三主成分“烤烟光合速率与叶片水势因子”可作为次要鉴选指标。

关键词: 烤烟, 伸根期, 干旱胁迫, 生理特性, 抗旱性