不同叶位和离体失水时间对烤烟叶片保水能力的影响

为阐明叶位和离体时间对烤烟叶片保水能力的影响。以2个田间抗旱性不同的烤烟品种豫烟6号和农大202的离体叶片为材料，采用离体叶片自然失水法，研究了不同叶位和离体时间对叶片失水率、抗氧化酶活性、激素和抗逆胁迫响应基因表达的影响。结果表明:5个不同叶位的失水率为离体0~24 h较高，24 h后失水速率逐渐变缓，叶位间差异不显著，农大202失水率显著高于豫烟6号；离体叶片内抗氧化酶（SOD、POD、CAT）活性、可溶性蛋白含量、脱落酸（ABA）含量均在离体24 h时达到最高值，丙二醛（MDA）含量也在24 h后增速变缓；4个胁迫响应基因（AREB、CDPK2、ERD10C、LEA5）相对表达量也在24 h达到最高，说明烤烟叶片离体24 h生理代谢反应最强，2个品种在离体24 h各指标差异最大。因此，烤烟叶片保水力与取样叶位关系不大，离体叶片失水24 h为测定烟草保水力的合适时间。 

Effects of stalk positions and natural dehydration after priming on water retention capacity of flue-cured tobacco leaves

In order to elucidate the effect of stalk positions and natural dehydration after priming on water retention capacity of flue-cured tobacco leaves, evaluation index of drought resistance of tobacco leaves was investigated. Effects of different stalk positions and natural dehydration after priming on leaf water loss rate, antioxidant enzyme activity, hormone and stress resistance gene expression were studied through natural dehydration method with two flue-cured tobacco varieties, Yuyan 6 and Nongda 202 of different drought resistance. Results showed that the water loss rate of leaves of 5 different stalk positions was higher during 0-24h, and gradually slowed down after 24h, and there was no significant difference among different stalk positions, but water loss rate of Nongda 202 was significantly higher than that of Yuyan 6. Antioxidant enzyme (SOD, POD, CAT) activity, soluble protein content, abscisic acid (ABA) content in excised leaves reached the highest value 24 hours in vitro, and Malondialdehyde (MDA) content also slowed down after 24 hours. The relative expression of four stress responsive genes (AREB, CDPK2, ERD10C, LEA5) reached the highest level after 24 hours. Physiological metabolism of excised flue-cured tobacco leaves was the strongest 24 hours in vitro, and the difference between the indexes of the two varieties was the greatest 24 hours in vitro. There was little relationship between water retention capacity and leaf position in excised flue-cured tobacco leaves, and leaf water loss 24 hours in vitro was the appropriate time to determine water retention capacity of excised tobacco leaves.